Open Access (OA) is the free, immediate, online availability of research articles coupled with the rights to use these articles fully in the digital environment.
Search for open access articles:
Unpaywall is a free browser plugin for Firefox and Google Chrome, and can help you locate freely accessible research articles. When you find an article you'd like to read, click the icon to be immediately redirected to freely available full text.
It's fast, free, and legal, powered by a database of millions of author-uploaded PDFs, thanks to open access policies.