Google and Google-like search engines such as Bing, Yahoo, and Ask.com dominate web search with, collectively, more than 95% of the market share. There are of course hundreds (or maybe thousands) of search engines, but most are highly specific and cover some narrow content set. Google is very good, but it's not the only way to look at the web, and that's why broadly comprehensive search engines that do not work like Google are valuable. Two other search engines -- Science.gov and the National Science Digital Library (NSDL; nsdl.org) -- that hear significant and valuable resemblances to Scirus. They concentrate on STEM content, but also extend into other subjects. Most of their results are public domain or open educational resources. Science.gov describes itself as "a gateway to government science information and research results." NSDL is in Science.gov, but its stand-alone value for science research deserves individual mention.
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