Open access to 1,585,492 e-prints in the fields of physics, mathematics, computer science, quantitative biology, quantitative finance, statistics, electrical engineering and systems science, and economics.
This Google tool for research lets you easily find relevant scholarly literature, such as books, theses, abstracts, and articles. Scholar indicates when a free full-text version of the article is available. Note many of these results will not appear on a regular Google search.
Microsoft Academic is a semantic search engine so it uses natural language processing to understand information in each document. It indicates if there is a free downloadable version of the report or article.
Science.gov searches over 60 databases and over 2,200 scientific websites to provide users with access to more than 200 million pages of authoritative federal science information including research and development results.
A global science gateway comprised of national and international scientific databases and portals. This search engine accelerates scientific discovery and progress by providing one-stop searching of databases from around the world
This is the most interesting search engine on the web. You can compute expert-level answers using Wolfram’s breakthrough algorithms, knowledgebase and AI technology. There are lots of examples of computing you can do through this engine.