Free Databases (all subjects): General

"Approximately 1 million freely accessible images, videos, documents, and audio files from library special collections, faculty research, and institutional history materials, as well as hundreds of thousands of open access images from the Metropolitan Museum of Art."

"DPLA brings together the riches of America’s libraries, archives, and museums, and makes them freely available to the world. It strives to contain the full breadth of human expression, from the written word, to works of art and culture, to records of America’s heritage, to the efforts and data of science."

eScholarships provides open-access publishing services to the University of California and delivers a dynamic research platfor to scholars worldwide.

"Google Scholar enables you to search specifically for scholarly literature, including peer-reviewed papers, theses, books, preprints, abstracts and technical reports from all broad areas of research. Use Google Scholar to find articles from a wide variety of academic publishers, professional societies, preprint repositories and universities, as well as scholarly articles available across the web."

Articles at this web site explain how ordinary "stuff" works, such as electricity, car engines, the human body, government organizations, tattoos, etc.

Free access to citations and abstracts to articles from over 20,000 journals in a variety of subject areas. Full text is available for purchase.

Answer questions; do math; instantly get facts, calculators, unit conversions, and real-time quantitative data and statistics; create plots and visualizations; and access vast scientific, technical, chemical, medical, health, business, financial, weather, geographic, dictionary, calendar, reference, and general knowledge—and much more.

Worldwide catalog of over 100 million books held in libraries across America and other countries.