Academia
- Academic Earth
- MIT CrossLinks
- MIT OpenCourseWare
- OpenStax (Free Textbooks)
- Open Yale Courses
- UMass OpenCourseWare
- Noba (Textbook Modules)
Compendia
- Britannica
- Encyclopedia of Integer Sequences
- Encyclopedia of Mathematics
- MacTutor (History of Math)
- Scholarpedia
- Stanford Encyclopedia of Philosophy
- Wikipedia
- Wiktionary
Library
- Archive (Library of Old Books)
- ArXive (Scholarly Articles)
- Project Gutenberg (Free eBooks)
- Kupdf.net (Freed Pubs)
- Gravity Research Foundation
- Quanta Magazine
- The Feynman Lectures on Physics
- Anna’s Archive
Life Science
Mathematics
- Abstract Math
- Combinatorics & Graph Theory
- Euclid’s Geometry
- MathWorld
- PlanetMath (Alphabetical or by Subject)
- Quanta Map of Mathematics
- Real-Not-Complex (Textbooks and Videos)
- The Story of Math
Open Access
- Frontiers (Science Publisher)
- IntechOpen ( Books)
- IPL (Academic Essays & Research Papers)
- Openverse (Free Images and Audio)
Search
- BASE (Academic Search)
- Microsoft Academic
- Science.gov (Federal STEM search)
- Semantic Scholar (Find DOI & goto Sci-Hub)
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