Data from the Unpaywall database of open access journals and repositories is integrated into the MIT Libraries catalog, which means an OA version of an article will appear as an option in search results if one is available. Unpaywall is also integrated into Web of Science.

Searching for articles through Google Scholar will find them in well-indexed repositories. The repository versions are usually those deposited by the authors and may include versions prior to peer review. More information on Google Scholar & article searches.

Examples of repositories to search directly:

• DSpace@MIT
• PubMed Central
• arXiv
• Social Science Research Network
• CORE (aggregator of OA repositories & OA journals)
• List of other disciplinary repositories 

You can find open access articles through browser extensions. These tools find legally available manuscript versions as well as final published articles when the journal allows it or the journal is open access.

• Open Access Button: Enter an article’s URL, DOI, title, or other information on the OA Button website to find free, legal, open access versions. Or install the Chrome or Firefox extension, then click on it from a paywalled article to initiate a search for an open version and, when available, instantly get free access. When free access is not found, the service can contact the author directly to help them make the article available.
• Unpaywall: Directly search an open, legal database of millions of open access scholarly articles. Or install the Chrome or Firefox extension to connect to open access versions of paywalled articles. As noted above, Unpaywall data is integrated into the MIT Libraries catalog, as well as Web of Science.

Most publishers allow authors to responsibly share their own publications. You can contact the author and ask for a copy. The author’s name and institution are usually shown on the preview page of the article.

Some authors are open to receiving requests for articles via social networking sites for researchers, including Academia.edu, ResearchGate, Mendeley, and HumanitiesCommons.

You can also request via Twitter using the hashtag #icanhazpdf, along with a link to the article.