From Cornell University, this free, open access archive has 579,000+ ePrints in physics, mathematics, computer science, quantitative biology, quantitative finance and statistics.
ChemRxiv (pronounced 'chem-archive') is a free submission, distribution, and archive service for unpublished preprints in chemistry and related areas. ChemRxiv gives researchers across a broad range of fields related to the chemical sciences the opportunity to share early results with colleagues and receive recommendations for improvement, ahead of formal peer review and publication.
Operated by the International Atomic Energy Agency, the INIS Repository contains over three million bibliographic records covering nuclear science and technology.