1. AGRICOLA (agricola.nal.usda.gov/) Agricultural Online Access The National Agricultural Library "houses one of the world's largest collections devoted to agriculture and related sciences." You can search for books or articles, which you can then purchase through publishers 'websites. 2. AGRIS (agris.fao.org/agris-search/index.do) The International System for Agricultural Science and Technology is a great tool for researchers in the field of agriculture. Although it primarily provides bibliographic information, it does provide links to data sources wherever possible, many of which are open access. 3. Analytical Sciences Digital Library (home.asdlib.org/) The Analytical Sciences Digital Library is an incredible resource. It "collects, catalogs, links and publishes peer-reviewed, web-based discovery materials pertinent to innovations in curricular development and supporting technical resources in the analytical sciences." 4. Astrophysics Data System (ui.adsabs.harvard.edu/) The Astrophysics Data System is run by the Smithsonian Astrophysical Observatory under a NASA grant. It offers three bibliographic databases with a total of more than 12.5 million records. 5. Bio line International (www.bioline.org.br/) Bio line International is a resource tool that provides access to open access research from developing countries. This is a great resource to find authoritative sources on health, biodiversity, environmental changes, conservation, and international development. 6. Bio Med Central (www.biomedcentral.com/) Bio Med Central provides open access research in more than290 peer-reviewed journals in the fields of biology, clinical medicine, and health. 7. Cancer Data (www.cancerdata.org/search/node) This repository of open access materials related to the study of cancer is run by the Medical Informatics and Knowledge Engineering team of Maastro Clinic in Maastricht,a city inthe Netherlands. The research provided includes clinical protocols, publications, and datasets. 8. CERN Document Server (cds.cern.ch/?ln=en) CERN is the European Organization for Nuclear Research, and their document server connects researchers with more than amillion authoritative scientific sources. 9. CHBD: Circumpolar Health Bibliographic Database (www.aina.ucalgary.ca/chbd/) This is an incredibly specific resource, but it’s useful nonetheless. The Circumpolar Health Bibliographic Database contains 6,800 records related to human health in the circumpolar region (i.e., the area around one of Earth's poles). Some journals and articles require an access fee. 11*Items highlighted in green offer exclusively free or open access content. 10. Chem Bio Finder (www.cambridgesoft.com/databases/login/?serviceid=128) Chem Bio Finder requires registration, but signing up for this free service will give you access to research related to chemistry and biology. 11. Dryad (datadryad.org/stash) Dryad is a digital repository of curated, open access, scientific research. It is run by a not-for-profit membership organization.If you would like to publish your data on Dryad, there is an associated publishing charge. 12. Elsevier Open Access Journals (www.elsevier.com/about/open-science/open-access/open-access-journals)This is an A–Z directory of open access journals published by Elsevier. Although there is no search function, you can view the titles and descriptions of each journal. 13. Europe PMC (europepmc.org/) The Europe PMC provides access to life science articles, books, patents, and clinical guidelines. Although some of the articles are behind a paywall, there are 3.9 million full texts available. 14. High Wire (portal.highwire.org/lists/freeart.dtl) An affiliate of Stanford University, High Wire works to "facilitate the digital dissemination of more than 3000 journals, books, reference works, and proceedings." The advanced search feature allows you to specify exactly what youarelooking for and check through all resources or only open access resources. 15. Hub Med (git.macropus.org/hubmed/?term=&filter=free+full+text%5Bfilter%5D) Hub Med is a database of medical journals and articles. The site is simple and straightforward, and it allows you to filter your results to free full texts only. 16. IARP (agingportfolio.org/) The International Aging Research Portfolio (IARP) is a system that organizes and allows users to browse research related to aging. It "incorporates databases of grants from multiple sources," as well as MEDLINE publication abstracts. 17. My Science Work (www.mysciencework.com/) In addition to allowing you to share your research with others, My Science Work provides access to over 60 millionarticles, 25 million of which are open access. 18. National Agricultural Library (www.nal.usda.gov/main/) Run by the U.S. Department of Agriculture, the National Agricultural Library is an incredible tool for research, allowing you to search by subject and view articles on the publisher's website. 19. Pub Chem (pubchem.ncbi.nlm.nih.gov/) Pub Chem is a unique tool for researchers, allowing you to search by bio assay, compound, or substance. 20. Pubget (www.copyright.com/business/document-delivery-with-rightfind/) Pubget allows you to browse by paper or journal, offering you the option of viewing the PDFs of free-access articles or buying the PDFs of articles behind a paywall. According to the site, 10,000 new papers are added each day. 21. Public Library of Science (plos.org/) PLOS is a non-profit organization committed to facilitating openness in academic research. According to the site, "all PLOS content is at the highest possible level of open access, meaning that scientific articles are immediately and freely available to anyone, anywhere." 22. PubMed(pubmed.ncbi.nlm.nih.gov/) PubMed offers access to "more than 26 million citations for biomedical literature from MEDLINE, life science journals, and online books." Some citations link to the full text on PubMed Central and publisher websites, while others are behind paywalls. You can filter your search to view full texts only 23. Retina (ww1.retinamedicalsearch.com/) Retina is "the world’s leading search engine for medical students, doctors and researchers to find the right document in [the]shortest possible time." The site also allows you to seek full texts only. 24. Science.gov (www.science.gov/) Science.gov offers 200 million pages of authoritative U.S. government science information. Some of the resources need to be purchased through other sites. 25. Science Open (www.scienceopen.com/) Science Open is an incredible research and publishing network offering open access content from more than 24,000 journals. 26. Sci Tech Connect (scitechconnect.elsevier.com/) The research on Sci Tech Connect comes from the U.S. Department of Energy and includes research from the 1940s to today. Of this research, over 400,000 articles are available as full-text PDFs. 27. Semantic Scholar (www.osti.gov/) This easy-to-use resource uses artificial intelligence to efficiently sort through millions of science-related papers based on your search terms. According to the site, although some articles are behind paywalls, "the data [they] have for those articles is limited 28. VADLO (vadlo.com/) VADLO is a life sciences search engine that allows you to search for methods, techniques, protocols, and more. Because it is powered by Google, some of the search results lead to resources behind paywalls.