The arXiv is a free open-access archive that contains over 1.9 million scholarly articles. It contains articles from the following fields: fields of physics, mathematics, computer science, quantitative biology, quantitative finance, statistics, electrical engineering and systems science, and economics.
While the articles included in the arXiv are scholarly, they are pre-prints and have not been peer-reviewed by the arXiv. When using materials from the arXiv, be sure to critically analyze the author, methods, and bias to make sure the source is credible.
Unless you know the exact title or arXiv-id, it's best to use the advanced search function in the math section. This allows you to create a much more refined search.
In the Advanced Search, you can search by Orcid, author, title, keyword, and more.
You can also limit by specific publication dates, years, and ranges.
zbMATH Open is a reviewing and abstracting site for pure and applied math. While it isn't full-text, there are over 3 million links to full-text. If you find an article and aren't sure how to access it, contact a librarian or submit an interlibrary loan request.
Mathworld is a free online math reference source. It includes thousands of entries, which include basic background information, equations, and related concepts. You can use the site's simple search bar located in the upper right corner, or you can browse concepts by discipline on the left side of the screen. There are 11 themes: Algebra, Applied Math, Calculus and Analysis, Discrete Math, Geometry, History & Terminology, Number theory, Probability and Stats, Recreational Math, and Topology.