Open Access Databases:-

SCIENCE DIRECT - ELSEVIER JOURNALS
Elsevier is one of the fastest-growing open access publishers in the world, nearly all of Elsevier's 2,800 journals now enable open access publishing, with more than 150k Gold open access articles published in 2022 and more than 760 fully open access journals across our portfolio.

SPRINGER JOURNALS

Springer’s portfolio of 200+ peer-reviewed fully open access journals across all areas of science. SpringerOpen journals and books are made freely and permanently available online immediately upon publication. They are subject to high-level peer review, author and production services ensuring quality and reliability of the work.

DIRECTORY OF OPEN ACCESS BOOKS (DOAB)

The primary aim of DOAB is to increase the discoverability of Open Access books. The directory is open to all publishers who publish academic, peer-reviewed books in Open Access and should contain as many books as possible, provided that these publications are in Open Access and meet academic standards. The subjects covered mainly Sociology, Political Studies, Urban Planning, Development Studies etc.

ARXIV.ORG 

arXiv.org has open access to more than a million scholarly articles in the fields of physics, mathematics, computer science, quantitative biology, quantitative finance, statistics, electrical engineering and systems science, and economics.

DIRECTORY OF OPEN ACCESS JOURNALS (DOAJ) 

The Directory of Open Access Journals (DOAJ) is an indexing service that provides access to high quality, peer reviewed, open access journals. DOAJ is completely free of charge and all the data it holds is freely accessible. DOAJ indexed 14,298 journals, with 11,331 of those being searchable at the article level.