The National Library of Medicine's Medline database that provides abstracts and indexing for over 5,000 biomedical journals published in the U.S. and 70 foreign countries, and includes additional older citations and out of scope citations from Medline journals.
Each user must register to set up an account here and keep track of their username & password. SciFinder is a research discovery tool that allows you to explore the CAS databases (American Chemical Society) that contain literature from many scientific disciplines, including biomedical sciences, chemistry, engineering, materials science, agricultural science, and more!
ScienceDirect's Freedom Collection includes extensive full-text journal coverage of the physical and biological sciences, as well as some coverage of the social sciences and humanities.
Academic Search Ultimate offers access to an unprecedented collection of resources including journals, magazines, reports, books, and videos. Many are peer-reviewed and full-text. Subjects range from astronomy to zoology.