This content links are available online to study for educational purpose. you can refer this to study purpose only.
https://ccsuniversity.ac.in/bridge-library/
https://www.open.edu/openlearn/free-courses/full-catalogue
https://pitt.libguides.com/openeducation/biglist
https://shodhganga.inflibnet.ac.in/
https://openknowledge.worldbank.org/
https://www.ncbi.nlm.nih.gov/pmc/
https://www.highwirepress.com/
https://libguides.southernct.edu/openaccess
https://agris.fao.org/agris-search/index.do
https://www.sciencedirect.com/#open-access
https://academic.oup.com/journals/pages/open_access
https://projecteuclid.org/librarians/lib_oa
https://www.springeropen.com/journals
https://www.tandfonline.com/openaccess/openjournals
https://www.cambridge.org/core/what-we-publish/open-access