Google is so influential that it “hides” other search systems from us, so much that we don’t even know their existence. Despite this, there are a lot of excellent searchers on the Internet, who specialize in books, sciences and other interesting information. Here’s a list of sites you’re not sure you’ve heard of yet.
http://www.refseek.com – seeking Academic Resources. More than a billion sources: encyclopedia, monographies, magazines.
http://www.worldcat.org – searching for the content of 20 thousand libraries worldwide. You can find out where the nearest rare book you need lies.
https://link.springer.com – access to more than 10 million scientific documents: books, articles, research
notebooks.
http://www.bioline.org.br – a library of scientific biological magazines published in developing countries.
http://repec.org – a collection of nearly 4 million volunteers from 102 countries on economic studies and related sciences.
http://www.science.gov – American state search engine 2200+ scientific site. Over 200 million articles are indexed.
http://www.pdfdrive.com – the largest website for free download of books in PDF format. Over 225 million volumes.
http://www.base-search.net – one of the largest researches related to texts in academic studies. More than 100 million scientific documents, 70% of them are free.