There are so many, but for the most part, you will find Academic libraries to have books and not journal access thru the connect option. You can also use the Library of Congress for book title access. I noticed, for example that selecting either Amherst or the U of Chicago “connect” (online search) are open to public searching from endnote, for books.
Searching for science and medical topics, you should use Pubmed, which is a public database for journal contents. Pubmed also has links that may take you to open access publications, but many of the actual publications in journals, may be restricted to subscribers. You may be able to visit a library once you have literature that interest you, and you can ask if you can make photocopies of the papers you need.
For other fields, you will need to consult others, as I am not aware of which databases might be open access.