research paper about search engines

Reference management. Clean and simple.

The top list of academic search engines

1. Google Scholar

4. science.gov, 5. semantic scholar, 6. baidu scholar, get the most out of academic search engines, frequently asked questions about academic search engines, related articles.

Academic search engines have become the number one resource to turn to in order to find research papers and other scholarly sources. While classic academic databases like Web of Science and Scopus are locked behind paywalls, Google Scholar and others can be accessed free of charge. In order to help you get your research done fast, we have compiled the top list of free academic search engines.

Google Scholar is the clear number one when it comes to academic search engines. It's the power of Google searches applied to research papers and patents. It not only lets you find research papers for all academic disciplines for free but also often provides links to full-text PDF files.

• Coverage: approx. 200 million articles
• Abstracts: only a snippet of the abstract is available
• Related articles: ✔
• References: ✔
• Cited by: ✔
• Links to full text: ✔
• Export formats: APA, MLA, Chicago, Harvard, Vancouver, RIS, BibTeX

BASE is hosted at Bielefeld University in Germany. That is also where its name stems from (Bielefeld Academic Search Engine).

• Coverage: approx. 136 million articles (contains duplicates)
• Abstracts: ✔
• Related articles: ✘
• References: ✘
• Cited by: ✘
• Export formats: RIS, BibTeX

CORE is an academic search engine dedicated to open-access research papers. For each search result, a link to the full-text PDF or full-text web page is provided.

• Coverage: approx. 136 million articles
• Links to full text: ✔ (all articles in CORE are open access)
• Export formats: BibTeX

Science.gov is a fantastic resource as it bundles and offers free access to search results from more than 15 U.S. federal agencies. There is no need anymore to query all those resources separately!

• Coverage: approx. 200 million articles and reports
• Links to full text: ✔ (available for some databases)
• Export formats: APA, MLA, RIS, BibTeX (available for some databases)

Semantic Scholar is the new kid on the block. Its mission is to provide more relevant and impactful search results using AI-powered algorithms that find hidden connections and links between research topics.

• Coverage: approx. 40 million articles
• Export formats: APA, MLA, Chicago, BibTeX

Although Baidu Scholar's interface is in Chinese, its index contains research papers in English as well as Chinese.

• Coverage: no detailed statistics available, approx. 100 million articles
• Abstracts: only snippets of the abstract are available
• Export formats: APA, MLA, RIS, BibTeX

RefSeek searches more than one billion documents from academic and organizational websites. Its clean interface makes it especially easy to use for students and new researchers.

• Coverage: no detailed statistics available, approx. 1 billion documents
• Abstracts: only snippets of the article are available
• Export formats: not available

Consider using a reference manager like Paperpile to save, organize, and cite your references. Paperpile integrates with Google Scholar and many popular databases, so you can save references and PDFs directly to your library using the Paperpile buttons:

Google Scholar is an academic search engine, and it is the clear number one when it comes to academic search engines. It's the power of Google searches applied to research papers and patents. It not only let's you find research papers for all academic disciplines for free, but also often provides links to full text PDF file.

Semantic Scholar is a free, AI-powered research tool for scientific literature developed at the Allen Institute for AI. Sematic Scholar was publicly released in 2015 and uses advances in natural language processing to provide summaries for scholarly papers.

BASE , as its name suggest is an academic search engine. It is hosted at Bielefeld University in Germany and that's where it name stems from (Bielefeld Academic Search Engine).

CORE is an academic search engine dedicated to open access research papers. For each search result a link to the full text PDF or full text web page is provided.

Science.gov is a fantastic resource as it bundles and offers free access to search results from more than 15 U.S. federal agencies. There is no need any more to query all those resources separately!

AI science search engines are exploding in number — are they any good?

• Katharine Sanderson

You can also search for this author in PubMed   Google Scholar

As large language models (LLMs) gallop ever onwards — including GPT-4, OpenAI’s latest incarnation of the technology behind ChatGPT — scientists are beginning to make use of their power. The explosion of tools powered by artificial intelligence (AI) includes several search engines that aim to make it easier for researchers to grasp seminal scientific papers or summarize a field’s major findings. Their developers claim the apps will democratize and streamline access to research.

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Nature 616 , 639-640 (2023)

doi: https://doi.org/10.1038/d41586-023-01273-w

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28 Best Academic Search Engines That make your research easier

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If you’re a researcher or scholar, you know that conducting effective online research is a critical part of your job. And if you’re like most people, you’re always on the lookout for new and better ways to do it. 

I’m sure you are familiar with some research databases. But, top researchers keep an open mind and are always looking for inspiration in unexpected places. 

This article aims to give you an edge over researchers that rely mainly on Google for their entire research process.

Our list of 28 academic search engines will start with the more familiar to less.

Table of Contents

#1. Google Scholar

Google Scholar is an academic search engine that indexes the full text or metadata of scholarly literature across an array of publishing formats and disciplines.

Great for academic research, you can use Google Scholar to find articles from academic journals, conference proceedings, theses, and dissertations. The results returned by Google Scholar are typically more relevant and reliable than those from regular search engines like Google.

Tip: You can restrict your results to peer-reviewed articles only by clicking on the “Scholarly”

• Scholarly results are typically more relevant and reliable than those from regular search engines like Google.
• You can restrict your results to peer-reviewed articles only by clicking on the “Scholarly” tab.
• Google Scholar database Coverage is extensive, with approx. 200 million articles indexed.
• Abstracts are available for most articles.
• Related articles are shown, as well as the number of times an article has been cited.
• Links to full text are available for many articles.
• Abstracts are only a snippet of the full article, so you might need to do additional searching to get the full information you need.
• Not all articles are available in full text.

Google Scholar is completely free.

#2. ERIC (Education Resources Information Center) 

ERIC (short for educational resources information center) is a great academic search engine that focuses on education-related literature. It is sponsored by the U.S. Department of Education and produced by the Institute of Education Sciences. 

ERIC indexes over a million articles, reports, conference papers, and other resources on all aspects of education from early childhood to higher education. So, search results are more relevant to Education on ERIC. 

• Extensive coverage: ERIC indexes over a million articles, reports, and other resources on all aspects of education from early childhood to higher education.
• You can limit your results to peer-reviewed journals by clicking on the “Peer-Reviewed” tab.
• Great search engine for educators, as abstracts are available for most articles.

ERIC is a free online database of education-related literature. 

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#3. Wolfram Alpha

Wolfram Alpha is a “computational knowledge engine” that can answer factual questions posed in natural language. It can be a useful search tool. 

Type in a question like “What is the square root of 64?” or “What is the boiling point of water?” and Wolfram Alpha will give you an answer.

Wolfram Alpha can also be used to find academic articles. Just type in your keywords and Wolfram Alpha will generate a list of academic articles that match your query.

Tip: You can restrict your results to peer-reviewed journals by clicking on the “Scholarly” tab.

• Can answer factual questions posed in natural language.
• Can be used to find academic articles.
• Results are ranked by relevance.
• Results can be overwhelming, so it’s important to narrow down your search criteria as much as possible.
• The experience feels a bit more structured but it could also be a bit restrictive

Wolfram Alpha offers a few pricing options, including a “Pro” subscription that gives you access to additional features, such as the ability to create custom reports. You can also purchase individual articles or download them for offline use.

Pro costs $5.49 and Pro Premium costs $9.99

#4. iSEEK Education 

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• 15 Best Academic Research Trend Prediction Platforms
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iSEEK is a search engine targeting students, teachers, administrators, and caregiver. It’s designed to be safe with editor-reviewed content.

iSEEK Education also includes a “Cited by” feature which shows you how often an article has been cited by other researchers.

• Editor-reviewed content.
• “Cited by” feature shows how often an article has been cited by other researchers.
• Limited to academic content.
• Doesn’t have the breadth of coverage that some of the other academic search engines have.

iSEEK Education is free to use.

#5. BASE (Bielefeld Academic Search Engine)

BASE is hosted at Bielefeld University in Germany and that’s where it name stems from (Bielefeld Academic Search Engine). 

Known as “one of the most comprehensive academic web search engines,” it contains over 100 million documents from 4,000 different sources. 

Users can narrow their search using the advanced search option, so regardless of whether you need a book, a review, a lecture, a video or a thesis, BASE has what you need.

BASE indexes academic articles from a variety of disciplines, including the arts, humanities, social sciences, and natural sciences.

• One of the world’s most voluminous search engines, 
• Indexes academic articles from a variety of disciplines, especially for academic web resources
• Includes an “Advanced Search” feature that lets you restrict your results to peer-reviewed journals.
• Doesn’t include abstracts for most articles.
• Doesn’t have related articles, references, cited by

BASE is free to use.

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CORE is an academic search engine that focuses on open access research papers. A link to the full text PDF or complete text web page is supplied for each search result. It’s academic search engine dedicated to open access research papers.

• Focused on open access research papers.
• Links to full text PDF or complete text web page are supplied for each search result.
• Export formats include BibTeX, Endnote, RefWorks, Zotero.
• Coverage is limited to open access research papers.
• No abstracts are available for most articles.
• No related articles, references, or cited by features.

CORE is free to use.

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#7. Science.gov

Science.gov is a search engine developed and managed by the United States government. It includes results from a variety of scientific databases, including NASA, EPA, USGS, and NIST. 

US students are more likely to have early exposure to this tool for scholarly research. 

• Coverage from a variety of scientific databases (200 million articles and reports).
• Links to full text are available for some articles.

Science.gov is free to use.

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#8. Semantic Scholar

Semantic Scholar is a recent entrant to the field. Its goal is to provide more relevant and effective search results via artificial intelligence-powered methods that detect hidden relationships and connections between research topics.

• Powered by artificial intelligence, which enhances search results.
• Covers a large number of academic articles (approx. 40 million).
• Related articles, references, and cited by features are all included.
• Links to full text are available for most articles.

Semantic Scholar is free to use.

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#9. RefSeek

RefSeek searches more than five billion documents, including web pages, books, encyclopedias, journals, and newspapers.

This is one of the free search engines that feels like Yahoo with a massive directory. It could be good when you are just looking for research ideas from unexpected angles. It could lead you to some other database that you might not know such as the CIA The World Factbook, which is a great reference tool.

• Searches more than five billion documents.
• The Documents tab is very focused on research papers and easy to use.
• Results can be filtered by date, type of document, and language.
• Good source for free academic articles, open access journals, and technical reports.
• The navigation and user experience is very dated even to millenials…
• It requires more than 3 clicks to dig up interesting references (which is how it could lead to you something beyond the 1st page of Google)
• The top part of the results are ALL ads (well… it’s free to use)

RefSeek is free to use.

#10. ResearchGate 

A mixture of social networking site + forum + content databases where researchers can build their profile, share research papers, and interact with one another.

Although it is not an academic search engine that goes outside of its site, ResearchGate ‘s library of works offers an excellent choice for any curious scholar.

There are more than 100 million publications available on the site from over 11 million researchers. It is possible to search by publication, data, and author, as well as to ask the researchers questions. 

• A great place to find research papers and researchers.
• Can follow other researchers and get updates when they share new papers or make changes to their profile.
• The network effect can be helpful in finding people who have expertise in a particular topic.
• Interface is not as user friendly
• Can be overwhelming when trying to find relevant papers.
• Some papers are behind a paywall.

ResearchGate is free to use.

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#11. DataONE Search (formerly CiteULike) 

A social networking site for academics who want to share and discover academic articles and papers.

• A great place to find academic papers that have been shared by other academics.
• Some papers are behind a paywall

CiteULike is free to use.

#12. DataElixir 

DataElixir is deigned to help you find, understand and use data. It includes a curated list of the best open datasets, tools and resources for data science.

• Dedicated resource for finding open data sets, tools, and resources for data science.
• The website is easy to navigate.
• The content is updated regularly
• The resources are grouped by category.
• Not all of the resources are applicable to academic research.
• Some of the content is outdated.

DataElixir is free to use.

#13. LazyScholar – browser extension

LazyScholar is a free browser plugin that helps you discover free academic full texts, metrics, and instant citation and sharing links. Lazy Scholar is created Colby Vorland, a postdoctoral fellow at Indiana University.

• It can integrate with your library to find full texts even when you’re off-campus.
• Saves your history and provides an interface to find it.
• A pre-formed citation is availlable in over 900 citation styles.
• Can recommend you topics and scans new PubMed listings to suggest new papers
• Results can be a bit hit or miss

LazyScholar is free to use.

#14. CiteseerX – digital library from PenState

CiteseerX is a digital library stores and indexes research articles in Computer Science and related fields. The site has a robust search engine that allows you to filter results by date, author.

• Searches a large number of academic papers.
• Results can be filtered by date, author, and topic.
• The website is easy to use.
• You can create an account and save your searches for future reference.

CiteseerX is free to use.

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#15. The Lens – patents search 

The Lens or the Patent Lens is an online patent and scholarly literature search facility, provided by Cambia, an Australia-based non-profit organization.

• Searches for a large number of academic papers.

The price range can be free for non-profit use to $5,000 for commercial enterprise.

#16. Fatcat – wiki for bibliographic catalog 

Fatcat is an open bibliographic catalog of written works. The scope of works is somewhat flexible, with a focus on published research outputs like journal articles, pre-prints, and conference proceedings. Records are collaboratively editable, versioned, available in bulk form, and include URL-agnostic file-level metadata.

• Open source and collaborative
• You can be part of the community that is very focused on its mission
• The archival file-level metadata (verified digests and long-term copies) is a great feature.
• Could prove to be another rabbit hole
• People either love or hate the text-only interface

#17. Lexis Web – Legal database

Are you researching legal topics? You can turn to Lexis Web for any law-related questions you may have. The results are drawn from legal sites and can be filtered based on criteria such as news, blogs, government, and commercial. Additionally, users can filter results by jurisdiction, practice area, source and file format.

• Results are drawn from legal sites.
• Filters are available based on criteria such as news, blogs, government, and commercial.
• Users can filter results by jurisdiction, practice area, source and file format.
• Not all law-related questions will be answered by this search engine.
• Coverage is limited to legal sites only.

Lexis Web is free for up to three searches per day. After that, a subscription is required.

#18. Infotopia – part of the VLRC family

Infotopia touts itself as an “alternative to Google safe search.” Scholarly book results are curated by librarians, teachers, and other educational workers. Users can select from a range of topics such as art, health, and science and technology, and then see a list of resources pertaining to the topic. 

Consequently, if you aren’t able to find what you are looking for within Infotopia’s pages, you will probably find it on one of its many suggested websites.

#19. Virtual Learning Resources Center

Virtual Learning Resources Center (VLRC) is an academic search engine that features thousands of academic sites chosen by educators and librarians worldwide. Using an index generated from a research portal, university, and library internet subject guides, students and instructors can find current, authoritative information for school.

• Thousands of academic information websites indexed by it. You will also be able to get more refined results with custom Google search, which will speed up your research. 
• Many people consider VLRC as one of the best free search engines to start looking for research material. 
• TeachThought rated the Virtual LRC #3 in it’s list of 100 Search Engines For Academic Research
• More relevant to education 
• More relevant to students

Powered by Google Custom Search Engine (CSE), Jurn is a free online search engine for accessing and downloading free full-text scholarly papers. It was created by David Haden in a public open beta version in February 2009, initially for locating open access electronic journal articles in the arts and humanities.

After the indexing process was completed, a website containing additional public directories of web links to indexed publications was introduced in mid-2009. The Jurn search service and directory has been regularly modified and cleaned since then.

• A great resource for finding academic papers that are behind paywalls.
• The content is updated regularly.uren

Jurn is free to use.

#21. WorldWideScience

The Office of Scientific and Technical Information—a branch of the Office of Science within the U.S. Department of Energy—hosts the portal WorldWideScience , which has dubbed itself “The Global Science Gateway.”

Over 70 countries’ databases are used on the website. When a user enters a query, it contacts databases from all across the world and shows results in both English and translated journals and academic resources.

• Results can be filtered by language and type of resource
• Interface is easy to use
• Contains both academic journal articles and translated academic resources 
• The website can be difficult to navigate.

WorldWideScience is free to use.

#22. Google Books

A user can browse thousands of books on Google Books, from popular titles to old titles, to find pages that include their search terms. You can look through pages, read online reviews, and find out where to buy a hard copy once you find the book you are interested in.

#23. DOAJ (Directory of Open Access Journals)

DOAJ is a free search engine for scientific and scholarly materials. It is a searchable database with over 8,000 peer-reviewed research papers organized by subject. It’s one of the most comprehensive libraries of scientific and scholarly resources, with over 8,000 journals available on a variety of themes.

#24. Baidu Scholar

Baidu Xueshu (Academic) is the Chinese version for Google Scholar. IDU Scholar indexes academic papers from a variety of disciplines in both Chinese and English.

• Articles are available in full text PDF.
• Covers a variety of academic disciplines.
• No abstracts are available for most articles, but summaries are provided for some.
• A great portal that takes you to different specialized research platform
• You need to be able to read Chinese to use the site
• Since 2021 there is a rise of focus on China and the Chinese Communist Party

Baidu Scholar is free to use.

#25. PubMed Central

PubMed is a free search engine that provides references and abstracts for medical, life sciences, and biomedical topics.

If you’re studying anything related to healthcare or science, this site is perfect. PublicMed Central is operated by the National Center for Biotechnology Information, a division of the U.S. National Library of Medicine. It contains more than 3 million full-text journal articles. 

It’s similar to PubMed Health, which focuses on health-related research and includes abstracts and citations to over 26 million articles.

#26. MEDLINE®

MEDLINE® is a paid subscription database for life sciences and biomedicine that includes more than 28 million citations to journal articles. For finding reliable, carefully chosen health information, Medline Plus provides a powerful search tool and even a dictionary.

• A great database for life sciences and biomedicine.
• Contains more than 28 million references to journal articles.
• References can be filtered by date, type of document, and language.
• The database is expensive to access.
• Some people find it difficult to navigate and find what they are looking for.

MEDLINE is not free to use ( pricing information ).

Defunct Academic Search Engines 

#27. microsoft academic  .

Microsoft Academic

Microsoft Academic Search seemed to be a failure from the beginning. It ended in 2012, then re-launched in 2016 as Microsoft Academic. It provides the researcher with the opportunity to search academic publications,

Microsoft Academic used to be the second-largest academic search engine after Google Scholar. Microsoft Academic provides a wealth of data for free, but Microsoft has announced that it will shut Microsoft Academic down in by 2022. 

#28. Scizzle

Designed to help researchers stay on top of the literature by setting up email alerts, based on key terms, for newspapers.

Unfortunately, academic search engines come and go. These are two that are no longer available.

Final Thoughts

There are many academic search engines that can help researchers and scholars find the information they need. This list provides a variety of options, starting with more familiar engines and moving on to less well-known ones. 

Keeping an open mind and exploring different sources is essential for conducting effective online research. With so much information at our fingertips, it’s important to make sure we’re using the best tools available to us.

Tell us in the comment below which academic search engine have you not heard of? Which database do you think we should add? What database do your professional societies use? What are the most useful academic websites for research in your opinion?

There is more.

Check out our other articles on the Best Academic Tools Series for Research below.

• Learn how to get more done with these Academic Writing Tools  
• Learn how to proofread your work with these Proofreading Tools
• Learn how to broaden your research landscape with these Academic Search Engines
• Learn how to manage multiple research projects with these Project Management Tools
• Learn how to run effective survey research with these Survey Tools for Research
• Learn how get more insights from important conversations and interviews with Transcription Tools
• Learn how to manage the ever-growing list of references with these Reference Management Software
• Learn how to double your productivity with literature reviews with these AI-Based Summary Generators
• Learn how to build and develop your audience with these Academic Social Network Sites
• Learn how to make sure your content is original and trustworthy with these Plagiarism Checkers
• Learn how to talk about your work effectively with these Science Communication Tools

10 thoughts on “28 Best Academic Search Engines That make your research easier”

Thank you so much Joannah..I have found this information useful to me as librarian in an academic library

You are welcome! We are happy to hear that!

Thank You Team, for providing a comprehensive list of academic search engines that can help make research easier for students and scholars. The variety of search engines included offers a range of options for finding scholarly articles, journals, and other academic resources. The article also provides a brief summary of each search engine’s features, which helps in determining which one is the best fit for a specific research topic. Overall, this article is a valuable resource for anyone looking for a quick and easy way to access a wealth of academic information.

Thank you for taking the time to share your feedback with us. We are delighted to hear that you found our list of academic search engines helpful in making research easier for students and scholars. We understand the importance of having a variety of options when it comes to finding scholarly articles, journals, and other academic resources, and we strive to provide a comprehensive list of resources to meet those needs.

We are glad that you found the brief summary of each search engine’s features helpful in determining which one is the best fit for a specific research topic. Our goal is to make it easy for our readers to access valuable academic information and we’re glad that we were able to achieve that for you.

We appreciate your support and thank you for your kind words. We will continue to provide valuable resources for students and researchers in the future. Please let us know if you have any further questions or suggestions.

No more questions Thank You

I cannot thank you enough!!! thanks alot 🙂

Typography animation is a technique that combines text and motion to create visually engaging and dynamic animations. It involves animating individual letters, words, or phrases in various ways to convey a message, evoke emotions, or enhance the visual impact of a design or video. – Typography Animation Techniques Tools and Online Software {43}

Hi Joannah! Here’s another one you may want to add! Expontum ( https://www.expontum.com/ ) – Helps researchers quickly find knowledge gaps and identify what research projects have been completed before. Thanks!

Expontum – Helps researchers quickly find knowledge gaps and identify what research projects have been completed before. Expontum is free, open access, and available to all globally with no paid versions of the site. Automated processes scan research article information 24/7 so this website is constantly updating. By looking at over 35 million research publications (240 million by the end of 2023), the site has 146 million tagged research subjects and 122 million tagged research attributes. Learn more about methodology and sources on the Expontum About Page ( https://www.expontum.com/about.php )

Hey Ryan, I clicked and checked your site and thought it was very relevant to our reader. Thank you for sharing. And, we will be reviewing your site soon.

Sounds good! Thanks, Joannah!

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Evaluation of Web Search Engines

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Using the proper search engine is crucial for efficient and effective web search. The objective of this paper is to develop methodologies to evaluate search engines in a systematic and reliable manner. A new model for evaluation and comparison of search engines is proposed. This hierarchical model classifies the most common features found in search engines and search results into groups and subgroups.

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Luo XiaoLing & Xue he ru

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XiaoLing, L., he ru, X. (2011). Evaluation of Web Search Engines. In: Zhiguo, G., Luo, X., Chen, J., Wang, F.L., Lei, J. (eds) Emerging Research in Web Information Systems and Mining. WISM 2011. Communications in Computer and Information Science, vol 238. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-24273-1_61

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Comparison of Four Search Engines and their efficacy With Emphasis on Literature Research in Addiction (Prevention and Treatment)

Gholam reza samadzadeh.

1 Department of Library and Medical Information Sciences, Zahedan University of Medical Sciences and Health Services, Zahedan, IR Iran

Tahereh Rigi

2 Department of Library and Information Sciences, Zahedan Payame Noor University, Zahedan, IR Iran

Ali Reza Ganjali

3 Research Center of Children and Adolscents Health, Health Services, Zahedan University of Medical Sciences, Zahedan, IR Iran

Surveying valuable and most recent information from internet, has become vital for researchers and scholars, because every day, thousands and perhaps millions of scientific works are brought out as digital resources which represented by internet and researchers can’t ignore this great resource to find related documents for their literature search, which may not be found in any library. With regard to variety of documents presented on the internet, search engines are one of the most effective search tools for finding information.

The aim of this study is to evaluate the three criteria, recall, preciseness and importance of the four search engines which are PubMed, Science Direct, Google Scholar and federated search of Iranian National Medical Digital Library in addiction (prevention and treatment) to select the most effective search engine for offering the best literature research.

Materials and Methods

This research was a cross-sectional study by which four popular search engines in medical sciences were evaluated. To select keywords, medical subject heading (Mesh) was used. We entered given keywords in the search engines and after searching, 10 first entries were evaluated. Direct observation was used as a mean for data collection and they were analyzed by descriptive statistics (number, percent number and mean) and inferential statistics, One way analysis of variance (ANOVA) and post hoc Tukey in Spss. 15 statistical software. P Value < 0.05 was considered statistically significant.

Results have shown that the search engines had different operations with regard to the evaluated criteria. Since P Value was 0.004 < 0.05 for preciseness and was 0.002 < 0.05 for importance, it shows significant difference among search engines. PubMed, Science Direct and Google Scholar were the best in recall, preciseness and importance respectively.

Conclusions

As literature research is one of the most important stages of research, it's better for researchers, especially Substance-Related Disorders scholars to use different search engines with the best recall, preciseness and importance in that subject field to reach desirable results while searching and they don’t depend on just one search engine.

1. Background

Surveying the valuable and the most recent information has become vital for researchers and scholars, because every day, thousands and perhaps millions scientific works are bought out as digital resources that represented by internet and researchers can’t ignore this great resource for literature review and they find related documents for their literature searche that may not be found in any library ( 1 ). Developing new technologies, scholars have faced abundant variety of collection literature research review with regard to subject of presentation and information space. Web cyberspace attracts the researchers’ attention because of variety of data with different forms and simultaneity. Literature search review is one of the most important search stages. Revising the literature search detected by search station in the broader tissue off helps researcher to expand the research view and his/her landscape. On the other hand he/she limits the research title and reaches to an intensive research question ( 2 ). Web, a huge resource of data plays an important role as an information reference for scholars. Nowadays, the rate of network data growth caused inaccessibility of information that is more worse than lacking them ( 3 ). With the creation and development of internet network as the greatest, the most varied and the most widespread information resource, simultaneous and various types of search tools are appeared to help users find information they want, these tools include search engines, meta-search engines and subject directories ( 4 ). Information retrieval is a challenge for users since search tools are too complex to navigate ( 5 ). As one of the most effective searching tools, its role is distinct because those search engines use software facilities which can find information from different sites for users. On the other hand, during the past decades developed knowledge in Substance-Related Disorders caught everyone’s eyes enormously ( 6 ). This growth is as a result of discussing about addiction as a national, regional and multi-dimensional problem. The volume of produced information and up to date personal data necessitates to study hours in a day, even a small part of this subject. Therefore, persuading to use internet is essential for updating data literature review. Then we concluded that the mentioned four popular search engines in medical sciences include: PubMed, Science Direct, Google Scholar and federated search of Iran’s health, treatment and medical education ministry and indicated that whether the of above mention search engines offered the best literature search about addiction (prevention and treatment). In Tober’s study, the four most popular search engines; PubMed, Science Direct, Scopus and Google Scholar are investigated to evaluate which search engine is the most effective for literature research in laser medicine. He concludes that all in all, Scopus was the most effective search engine in the literature research ,in case of requiring only an overview of the topic, even for a widespread and in depth investigation in area of life sciences and closely related topics, PubMed was more appropriate. Google Scholar, Science Direct are the best in preciseness and importance criterion in laser medicine ( 7 ). Also Bajpaie and et investigated in a research and compared 18 search tools, their results showed that four tools could be better than the others; these tools include two of the full-text scanners (High wire press & Google Scholar) and two citation scanners (PubMed & Scopus). The results show that, use of a single search tool can lead to loss of up to 70 % of the relevant citations in some cases. Hence, use of multiple search tools is recommended ( 8 ). Anders & Ivans compared PubMed with Google Scholar literature search in respiratory care topics by cross-sectional study and their research results showed that PubMed and Google Scholar had similar recall, but at precision criterion PubMed was better than the other. According to researches, PubMed was more efficient and better than Google Scholar with regard to the patient's searches and educational purposes ( 9 ).

In research by Flagas et al. a Comparison was made to evaluate the strength and weaknesses of PubMed, Scopus, Web of Science, and Google Scholar. Results showed that all databases were practical and offered numerous search facilities. PubMed and Google Scholar were free access for users. PubMed had offered optimal update frequency and include recent online articles; other database had rated articles based on some criteria such importance. For citation analysis, Scopus offered about 20% more coverage than Web of science; and Scopus covers the wider range of journals. Google Scholar can help in the retrieval of even the most oblique information and less often update ( 10 ). In a descriptive research, Mohammad Esmaeil, Lafzghazi and Gilvari compared six search engines and six meta-search engines in pharmaceutics information retrieval, results showed that if users survey in several search engines, they access to the relevant documents among the vastly available sources on web. Their research showed that Yahoo retrieved the most pharmaceutics documents and AOL had 62% precision and 21% recall, it retrieved the most relevant pharmaceutics documents. Among meta-search engines Dogpile was better than others ( 4 ). Outline description from evaluated search engines is explained in in the following:

1.1. PubMed

In 1997, PubMed (http://www.ncbi.nlm.nih.gov/PubMed) was offered by the National Library of Medicine on internet. It is one of the most popular and the most responsible resources on the World Wide Web for physicians and scholars ( 10 ). PubMed is a free search engine to search about medicine and biomedical journal literature. It searches several databases and interfaces Medline, directly. This search engine maps user’s search terms to the Medical subject heading (Mesh) and text words in Medline records and then searching ( 9 ). The PubMed offers users numerous powerful searche filters to limit their searches and gives them desirable retrieval information ( 11 ).

1.2. Science Direct

Science Direct (http://www.science direct.com) is a full text scientific database which is a part of the science verse and is provided by Elsevier publication in 1997. The web portal of Science Direct opens with features which invites the users just to browse the word scientific publications ( 7 ). This search engine is one of the greatest bibliographic and full text electronic collections about science, technology and medicine. Also we can have an exact searching with regard to limitations and abilities that is offered by Science Direct ( 12 ).

1.3. Google Scholar

Google Scholar (http://scholar.google.com): it’s design and handling is similar to that of Google search engine. It provides a simple way to search broadly for scholarly literature. In a particular place you can search across many disciplines and sources such as articles, theses, books, abstract and etc. This search engine helps you to find relevant scientific works in all over the world of sceince ( 12 ). The search results in Google Scholar can be limited to title, author, publication source, publishing date and other filters ( 13 ).

1.4. Integrated Digital Library (IDL):

IDL is an advanced system which gives us simple and one step access to all electronic resources at the Iranian National Medical Digital Library. Also we can browse and search all databases, e-journals, e-books and references in digital library alphabetically or by subject. Federated search allows you to search multiple online databases. Federated search saves your time and provides your favorite results quickly ( 14 ).

2. Objectives

The aim of this study is to evaluate the three criteria such as recall, precision and importance in the four search engines: PubMed, Science Direct, Google Scholar and federated search of Iranian National Medical Digital Library in addiction (prevention and treatment) to select the most effective search engine for offering the best literature research.

3. Materials and Methods

This research was cross-sectional study and we evaluated four famous and popular search engines in medical sciences include: PubMed, Science Direct, Google Scholar and federated search in IDL. We limited search to “Substance-related disorders” keyword in all search engines because this was the most common key word that specialists used. Documents that search engines offer are listed as results according to relevant value of query search with descent sequence. Hence, document offered as the first record in the search results, is the most related document to query search, from vision of that search engine ( 3 ). With regard to what was mentioned above and what cited to Tober’s study, sample research selected 10 first results of retrieval documents of each search engines. To compare search engines, three criteria, recall, precision and importance were evaluated ( 7 ). The calculation method for each criterion is explained as follow:

3.1. Performance test: Criteria of evaluation

The aim of the performance test was to get an overview about article dealing with the addiction topic (prevention and treatment). Therefore, we consulted with psychiatrist and selected proper key word among prevalent terms, and then matched with web version of mesh ( 15 ), and “Substance-Related Disorders” keyword was chosen as the most relevant query search at search engines in addiction (prevention and treatment).

1. The criterion ‘‘recall’’ (or ‘‘hits’’) is the number of found articles and is related to the integrity of the evidence base.

2. The criterion ‘‘precision’’ determines how well the filtered articles cover the topic of the search term and influences the time and cost of screening and the results for the related articles. It is evaluated by counting the search term in the search fields ‘‘title’’ (n title) and ‘‘abstract’’ (n abstract). The appearance of the terms in the field ‘‘title’’ (a) is two times more than the field ‘‘abstract’’ (b). Additionally the appearance is rated by the rank i, the position of the filtered article in the results list. From this the precision P can be calculated as follows:

P = ( (n + 1) – i ) • (a × n title + b × n abstract)

3. The criterion ‘‘importance’’ is determined by the number of citations “n” citation by publications of other authors. For this articles, citations that were in Science Direct and Google Scholar had been considered and for articles, citations were offered by PubMed and IDL and the other articles without citation, Web of knowledge citation database was used. Number of citation was used for calculating importance criterion and the rank i as described before. From this, the importance I is calculated as follows:

I = ((n + 1) − i) • n citation

For this study, only English written abstract and title which contain the search term “Substance-Related Disorders” were analyzed, for collecting information and data, directly observation was used. We entered keyword in each search engine, and to evaluate criteria, number of all retrieval articles (hits), titles, abstracts, and citations of 10 first articles in the result list were considered. All searches were conducted on November 29th, 2011 on Windows seven environment with Microsoft Internet Explorer in the Central Library of Zahedan Medical Sciences University. We used statistical software Spss 15 for data analysis. One-way analysis of variance (ANOVA) and post hoc Tukey was performed to evaluate search engines. P < 0.05 was considered statistically significant.

Results showed that PubMed retrieved most of the documents, 213 articles (32%) and it was better than the other search engines on recall criterion. Results from recall criterion were similar in Science Direct with 188 hits (28%) and, Google Scholar with 184 hits (27%). And IDL with 91 hits (13%) offered the least articles in this subject ( Table 1 ).

After survey of titles and abstract precision and statistical indicators of each search engines were investigated. Investigation of means showed that “the most precision” has allocated to Science Direct search engine with mean 25.2 (33%) and after that was ILD with mean 17.9 (24%), and then were PubMed with mean 16.2 (22%) and Google Scholar with mean 16 (21%). For detecting precision among search engines, One-way analysis of variance (ANOVA) was used and P value earned (0.726) which was more than 0.05, and this explained there was not statistically significant difference among search engines for precision. Whereas assessed P value from article titles investigation was P = 0.004 which showed significant difference in precision among search engines. Post hoc Tukey showed that there was difference between Science Direct with PubMed ( Table 2 ).

For importance, results showed that Google Scholar was the best and its means was 510.3 (82%), and after that was Science Direct, with mean 115.6 (18%). IDL with mean 0.3 (0%) and PubMed were not scored. Results of One-way analysis of variance (ANOVA) showed P Value = 0.002 that was less than 0.05, so we used Post hoc Tukey. Finding from importance criterion showed statistically significant difference between Google Scholar with each of the others search engines ( Table 3 ).

5. Discussion

Literature search is one of the most important steps in the research process. We review literature to avoid heavy works, to ensure we have a thorough understanding of the topic, to identify similar work done within the area, to identify knowledge gaps that demand further investigation, to compare previous findings, to critique existing finding and suggest further studies ( 16 ), which this features increase the importance or the exact literature review. Review of literature accomplishes for literature search in medical sciences on the internet by different search engines that they were compared, evaluated and reviewed by the other researchers in different countries to identify their search’s features and abilities ( 5 - 10 ) ( 15 - 22 ). This research was done to select the most effective search engine for offering the best literature research in addiction (prevention and treatment).

Investigations showed that search engines in various subject fields with regard to unique abilities and facilities are done differently, which this affair supported by other researchers, too ( 16 , 18 ). Search engines cover just a limited part of accessible information on the web and neither of them don’t have total recall and precision. The scale of recall, precision ( 23 ), and importance of search engines are different with regard to purpose of researchers from search. Results of this study showed that evaluated criteria were different in search engines, whereas PubMed had the most recall criterion and then were Science Direct and Google Scholar with similar recall. Recall in PubMed was about two times more than ILD’s recall. The results of Tober study were different, whereas PubMed had least recall in laser medicine ( 7 ). At the other research was done in respiratory care, results showed that the function of two search engines (PubMed & Google Scholar) was similar in recall criterion ( 9 ), our study showed this similarity between Google Scholar and Science Direct.

Means investigation explained that Science Direct offered the best precision and related documents in addiction. Although Results of One - way analysis of variance (ANOVA) did not show significant difference in precision among search engines, results were different in investigation of retrieved articles titles which P - value was less than 0.05 that explanatory existence showed significant difference among search engines, post hoc Tukey showed that considerable difference exists between Science Direct and PubMed. Also, in Tober study, Science Direct after Scopus had the best precision 7. But in the other research, results were different whereas PubMed had above precession ( 9 ).

In this study, Google Scholar had maximum importance and the next was Science Direct. PubMed and IDL were not scored. In PubMed Tober’s study, results were similar to our study in this criterion. For importance, results of ANOVA showed significant difference, moreover post hoc Tukey and comparing means showed that the difference was remarkable among Google Scholar. Also, former researcher supported indication of Google Scholar for offering the citations which caused importance of articles ( 10 , 20 , 22 ). Reviews of this research showed that IDL did not offer acceptable results in any of three criteria, with regard to expensive cost that Iran’s health, treatment and medical education ministry pay for funding medical sciences universities and this will be revision to buy and use this database or be changed the operation of federated search.

We had local limitation for our searches in federated search of IDL and Science direct because this search engines were not available to the public. The other limitation to our study was that we only used the “Substance- related disorders” keyword in search engines and didn’t use the related keywords. Next limitation was that at first, we wanted to evaluate Scopus along with the other search engines, but Scopus was disconnecting in Iran and thus excluded from this study. Results showed that use of one search engine for literature review in addiction (prevention and treatment), neither proper nor search engines can’t give us the best results. Former studies, also recommended combined search and simultaneous use from several search engines to reach effective and related results ( 4 , 8 , 17 ). With regard to broad extent, multilateral addiction subject and new sights discussion, it is recommended that researchers must use different search engines with the best recall, precision and importance to reach the best results, they must continue their search with abilities and various services that search engines give.

Acknowledgments

We appreciate Mr. Dashipoor for statistical analysis.

Implication for health policy/practice/research/medical education:

The aim of this study is the evaluation of three criteria, recall, precision and importance in the four search engines: PubMed, Science Direct, Google Scholar and federated search of Iranian National Medical Digital Library in addiction (prevention and treatment) to select the most effective search engine for offering the best literature research.

Please cite this paper as:

Samadzadeh GR, Rigi T, Ganjali AR. Comparison of Four Search Engines and their efficacy With Emphasis on Literature Research in Addiction (Prevention and Treatment). Int J High Risk Behav Addict.2013; 1(4): 166-71. DOI: 10.5812/ijhrba.6551

Authors’ Contribution:

Reza Samadzadeh conceived of and designed the study. Tahereh Rigi analyzed and interpreted the data. Alireza Ganjali drafted the paper critically revised it for important intellectual content. All authors gave final approval of the version to be publish.

Financial Disclosure:

Who have no relevant financial interests are asked to provide a statement indicating that they have no financial interests related to the material in the manuscript.

Funding/Support:

This study was no supported by Health or teaching and research Institutes.

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