HathiTrust is a partnership of academic & research institutions, offering a collection of millions of titles digitized from libraries around the world. Includes many sciences titles, especially foundational works in each discipline.
SciFinder Scholar: You must first create a free account (below) before you can use the database at this link. Use the “Research Topic” link; click the microscope icon to read Abstracts, and notice that some citations are links. Use Journal Finder and ILL to get actual articles.