These are "social networks for scientists." Many authors upload their full-text papers here. If a paper is locked, there is often a "Request full-text" button that notifies the author directly. 3. Use Your Local or Institutional Library
Similar to Unpaywall, this tool searches thousands of repositories for a legal copy. If one isn't found, it can even send a request to the author to share the paper. download locked research papers
If you are a student or alum, your university library likely pays millions in subscription fees. These are "social networks for scientists