Google Scholar – The platform contains more than two million records of books, articles and abstracts, sorted by field of knowledge.
Microsoft Academic Search – It provides access to academic journals in various fields of science.
Bulgarian Portal for Open Science – It contains dissertations, scientific publications and conference papers by Bulgarian researchers.
Oxford University Research Archive (ORA) – It contains periodicals, books, dissertations, conference papers, as well as other open-access scholarly works.
HighWire Press – Stanford University – It contains over two million open-access articles.
Arachne – Full-text resources in German.
ICOMOS (International Council on Monuments and Sites) Open Archive – A repository of the International Council on Monuments and Sites.
EconBiz – A full-text database that contains various resources for researchers and students.
Research Papers in Economics (RePEc) – A decentralized bibliographic database maintained by volunteers from nearly 100 countries. It contains information from more than 3,000 periodicals.
Social Science Open Access Repository (SSOAR) – It contains articles, books, dissertations, conference papers, book reviews, and other scholarly works added by the authors.
PhilPapers – It provides access to more than 2.4 million resources from journals, books, archives and private sites selected by researchers in philosophy.
European Patent Office – It contains more than 110 million patents from around the world.
SpringerOpen – It provides full-text access to peer-reviewed journals in various fields of science.
Journals for Free – It provides open access to more than 17,000 academic journals.
Directory of Open Access Journals – It contains nearly four million articles published in more than 13,251 journals from all over the world.
Digital Commons Network – It provides open access to more than three million scholarly articles from approximately 590 institutions.
Index Copernicus – It indexes more than 2,500 periodicals from around the world, selected according to certain criteria.
Научная электронная библиотека eLIBRARY.RU – It provides access to more than 15 million research papers. Over 59,000 academic journals have been indexed, of which more than 10,180 are full-text.
ERIC – Online digital library for educational resources.
Academia.edu – It contains more than 20 million open-access articles.
Paperity – It contains more than 1.5 million full-text articles, published in more than 4,200 periodicals. A full-text search is available for a great deal of the literature.
CiteSeerX – It contains more than 750,000 full-text resources.
SciELO – It provides access to more than 985 full-text periodicals.
arXiv – A repository of e-preprints of articles.
CogPrints: Cognitive Science Eprint Archives – An e-archive where authors can submit their scholarly works.
OMICS International – It provides access to more than 700 leading peer-reviewed journals.
MDPI – It indexes more than 240 peer-reviewed, open-access journals in all fields of knowledge.
Scientific Research Publishing (SCIRP) – It provides open access to more than 200 academic journals.
Russian Science Citation Index – A bibliographic database that offers reference search. Some of the resources are full-text.
SCIndeks – Serbian Citation Index – It provides open access to more than 250 journals published in the Republic of Serbia, as well as the opportunity for bibliometric reference.
Научная электронная библиотека „КиберЛенинка” – A scientific digital library that includes approximately two million articles in Russian.