====== Search Engines ======


  * [[https://www.refseek.com|refseek.com]] is a search engine for academic resources. More than a billion sources
  * [[https://www.worldcat.org|worldcat.org]] - search the content of 20,000 global libraries.
  * [[https://link.springer.com|link.springer.com]] - access to more than 10 million scientific documents: books, articles,
  * [[https://www.bioline.org.br|bioline.org.br]] is a library of published bioscientific journals
  * [[http://repec.org|repec.org]] - Volunteers from 102 countries collected nearly 4 million publications
  * [[https://www.science.gov|science.gov]] is a U.S. government search engine for more than 2200 scientific sites.
  * [[https://www.pdfdrive.com|pdfdrive.com]] is the largest website for free download of PDF books. Claim more than 225 million titles.
  * [[https://www.base-search.net|base-search.net]] is one of the most powerful search engines for academic research texts. More than 100 million scientific articles, 70% of which are free