List of Search Engines

A list of specialized search engines. — Academic resources. More than a billion sources – search the content of 20,000 global libraries. – access to more than 10 million scientific documents: books, articles, is a library of published bioscientific journals – Volunteers from 102 countries collected nearly 4 million publications is a U.S. government search engine for more than 2200 scientific sites. is the largest website for free download of PDF books. Claim more than 225 million titles. is one of the most powerful search engines for academic research texts. More than 100 million scientific articles, 70% of which are free.