Open Access E-Resources

4. Google Scholar: Google Scholaris a freely accessible web search enginethat indexes the full text or metadata of scholarly literature across an array of publishing formats and disciplines. Released in beta in November 2004, the Google Scholar index includes peer-reviewed online academic journals and books, conference papers, theses and dissertations, preprints, abstracts, technical reports, and other scholarly literature, including court opinions and Google Scholar uses a web crawler, or web robot, to identify files for inclusion in the search results. For content to be indexed in Google Scholar, it must meet certain specified criteria. An earlier statistical estimate published in PLOS One using a mark and recapture method estimated approximately 79–90% coverage of all articles published in English with an estimate of 100 million. This estimate also determined how many documents were freely available on the internet. Google Scholar has been criticized for not vetting journals and for including predatory journals in its index.

https://scholar.google.com/

7. JSTOR: More than 10,000 open access (OA) books from 125+ publishers including Brill, Cornell University Press, University College of London, and University of California Press, are now available at no cost to  libraries or users. It is a digital library of academic journals, books, and primary sources founded in 1994.Originally containing digitized back issues of academic journals, it now encompasses books and other  primary  sources as well as current issues of journals in the humanities and social It provides full-text   searches of almost 2,000 journals. Most access is by subscription but some of the site is public domain, and open access content is available free of charge.

https://about.jstor.org/librarians/books/open-access-books-jstor/