Unpaywall: find open-access versions of paywalled research papers, instantly!
Unpaywall is an open-source platform that makes science more open and reusable online. It makes it with the idea that humanity needs to access our collective knowledge and wants to help bring that open access content to the masses. It is supported by grants from the National Science Foundation and the Alfred P. Sloan Foundation.
Unpaywall finds the fulltext for 65-85% of articles, depending on their topic and year of publication. It gathers content from thousands of worldwide open-access repositories such as Pubmed Central, DOAJ, Crossref, Datacite, Google Scholar and BASE.
Also, it enables you to get free, legal fulltext of research papers as you browse. When you view a paywalled research article, Unpaywall automatically looks for a copy in their index of over 10 million free, legal fulltext PDFs. If it finds one, click the green tab to read the article.
Unpaywall is being showed as the legal alternative of Sci-Hub that finds fulltext PDFs for paywalled articles. The main difference is where those PDFs come from: Unpaywall finds PDFs legally uploaded by the authors themselves, while Sci-Hub uses PDFs that are obtained by other means, including automated web scraping of publisher sites.
To add Unpaywall button on your browser (free for Chrome and Firefox), please visit http://unpaywall.org/
Wish you an enjoyable legal research!