Search Engines

refseek.com is a search engine for academic resources. More than a billion sources
worldcat.org - search the content of 20,000 global libraries.
link.springer.com - access to more than 10 million scientific documents: books, articles,
bioline.org.br is a library of published bioscientific journals
repec.org - Volunteers from 102 countries collected nearly 4 million publications
science.gov is a U.S. government search engine for more than 2200 scientific sites.
pdfdrive.com is the largest website for free download of PDF books. Claim more than 225 million titles.
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