The arXiv (pronounced "archive") is a repository of electronic preprints, known as e-prints, of scientific papers in the fields of mathematics, physics, astronomy, computer science, quantitative biology, statistics, and quantitative finance, which can be accessed online.

Open Source Databases
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bioRxiv (pronounced "bio-archive") is a free online archive and distribution service for unpublished preprints in the life sciences.

PLOS publishes a suite of influential Open Access journals across all areas of science and medicine