#Google is so powerful that it hides other search engines from us. We simply do not know about the existence of most of them.
Meanwhile, there are still a large number of excellent search engines in the world that specialize in books, science, and other smart information.
Here a list of sites you’ve might never heard of.
www.refseek.com is a search engine for academic resources. More than a billion sources
www.worldcat.org – search the content of 20,000 global libraries.
https://link.springer.com – access to more than 10 million scientific documents: books, articles,
www.bioline.org.br is a library of published bioscientific journals
http://repec.org – Volunteers from 102 countries collected nearly 4 million publications
www.science.gov is a U.S. government search engine for more than 2200 scientific sites.
www.pdfdrive.com is the largest website for free download of PDF books. Claim more than 225 million titles.
www.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