US Dept of Energy. E-Print Network - contains over 5.5 million e-prints in basic and applied sciences, primarily in physics but also in chemistry, biology and life sciences, materials science, nuclear sciences and engineering, energy research, computer and information technologies
Open access to 768,909 e-prints in Physics, Mathematics, Computer Science, Quantitative Biology, Quantitative Finance and Statistics
American Mathematical Society - Search for documents on the AMS website. Does not identify documents found in MathSciNet, AMS Journals, AMS Bookstore, or the Combined Membership List. Go directly to these services to search for information.
SSRN provides 800,000 research papers from 335,000 researchers across 30 disciplines