Nomos eLibrary provides access to academic books and journals in the subject areas of law, political sciences, economics, media and communication sciences, history, sociology, education and cultural studies, European Union, health sciences. The book selection has been continuously extended through the acquisition of individual eBook packages by MPG libraries. From volume 2022 onwards, access is given to the complete Nomos eBook portfolio. Max Planck researchers can publish their scientific work with Nomos as a print and in parallel as an Open Access eBook in the Nomos eLibrary. Further details are available on the MPDL website.

O'Reilly is an electronic reference library by providing access to technical content from leading publishers, including books, videos, proven learning paths, case studies, interactive tutorials and audio books. The learning platform gives access to the latest titles from O'Reilly and from Pearson's collection of imprints which include: Addison-Wesley Professional, Adobe Press, Cisco Press, Macromedia Press, New Riders, Peachpit Press, Prentice Hall PTR, Sun Microsystems Press, Que, and Sams. Microsoft Press titles are also available in O'Reilly.

The goal of OAIster is to create a collection of previously difficult-to-access, academically-oriented digital resources that is easily searchable by anyone.

The OAPEN Library contains freely accessible academic books, mainly in the area of Humanities and Social Sciences. OAPEN works with publishers to build a quality controlled collection of Open Access books, and provides services for publishers, libraries and research funders in the areas of dissemination, quality assurance and digital preservation. OAPEN serves as delivery platform for various open access initiatives, including Knowledge Unlatched.

OECD iLibrary is the online library of the Organisation for Economic Cooperation and Development (OECD) featuring its books, papers and statistics and is the gateway to OECD’s analysis and data. It also contains content published by the International Energy Agency (IEA), the Nuclear Energy Agency (NEA), the OECD Development Centre, PISA (Programme for International Student Assessment), and the International Transport Forum (ITF).

Open Syllabus is a non-profit research organization that collects and analyzes millions of syllabi to support novel teaching and learning applications. Open Syllabus helps instructors develop classes, libraries manage collections, and presses develop books. It supports students and lifelong learners in their exploration of topics and fields. It creates incentives for faculty to improve teaching materials and to use open licenses. It supports work on aligning higher education with job market needs and on making student mobility easier. It also challenges faculty and universities to work together to steward this important data resource. Open Syllabus currently has a corpus of nine million English-language syllabi from 140 countries. It uses machine learning and other techniques to extract citations, dates, fields, and other metadata from these documents. The resulting data is made freely available via the Syllabus Explorer and for academic research. The project was founded at The American Assembly, a public policy institute associated with Columbia University. It has been independent since 2019. All of the syllabi in the current collection are English language documents – including from universities where English is not the primary teaching language.

The OSF Preprints search combines records from various preprint repositories, including arXiv, bioRxiv, Cogprints, PeerJ, PsyArXiv, RePEc and SocArXiv.

The Oxford English Dictionary is a guide to the meaning, history, and pronunciation of over half a million words and phrases, both present and past, from across the English-speaking world. It traces the usage of words through 3.5 million quotations from a wide range of international English language sources, from classic literature and specialist periodicals to film scripts, song lyrics and social media posts.

Including Oxford Scholarship Online (OSO), the University Press Scholarship Online (UPSO) publishes new books every month from an ever-growing roster of contributing presses, each adding to the variety of subjects covered on the platform. The MPG purchased the volumes 2003-2013/2014 of 16 OSO subject collections. This selection is continuously extended by single e-book acquisitions by MPG libraries.

This historic journal index enables the simultaneous search in millions of citations for articles published in the arts, humanities and social sciences, across more than 300 years. It enables researchers quickly and comprehensively to identify articles relevant to their field of study and reduces what could take years of research to a matter of minutes. Journals indexed span 37 key subject areas and multiple languages.

The Miras Maktoob collection of Persian e-books consists of 249 volumes (189 works) originally published by the Written Heritage Research Institute (Miras Maktoob), a non-governmental organization in Tehran. These e-books contain both Persian and Arabic works on Islamic history and culture in the broadest sense.

Preprint Citation Index is a multidisciplinary collection of preprints from a wide range of leading repositories, including arXiv, bioRxiv, chemRxiv, medRxiv, and Preprints.org. Currently, it provides more than 2 million articles ahead of the formal journal publication in the sciences, social sciences and arts & humanities. Papers from more than 20 repositories will be added in future. Within the Web of Science platform researchers can thus discover preprint records alongside peer-reviewed journal articles and other content sets. This simplifies the process of evaluating preprint quality and trustworthiness by connecting preprints to the versions of record or linking to other scholarly output from preprint authors and the citation network in Web of Science. Furthermore you can link directly to the preprint repositories to view each version of the preprint and download full texts.

The integration between ProQuest Dissertations & Theses Global with the Web of Science enables seamless discovery of early career, post-graduate research from all around the world, alongside records for journal articles, conference papers, book chapters, preprints, patents, and more. ProQuest Dissertations & Theses Citation Index makes more than 5.5 million multidisciplinary dissertations and theses searchable, from over 4,100 institutions and more than 60 countries, dating back to 1637. Researchers have simultaneous access to unpublished and published scholarship that helps them to discover emerging trends, identify new areas of research and find post-graduate programs engaged in cutting-edge research. For joint subscribers of the Web of Science and PQDT Global, direct full text linking from the Web of Science to the ProQuest platform is available, giving access to 3 million full-text works from thousands of universities. Additionally, cited reference indexing and linking helps to further connect dissertations and theses to related works and discover hard-to-find sources of research.

The PsycINFO databases cover the professional and academic literature in psychology and related disciplines including medicine, psychiatry, nursing, sociology, education, pharmacology, physiology, linguistics, and other areas. Coverage is worldwide, and includes references and abstracts to over 1300 journals and to dissertations in more than 30 languages, and to book chapters and books in the English language. Over 50,000 references are added annually. Popular literature is excluded.

"Psyndex - Literature & Audiovisual Media" contains records on psychology from researchers in Germany, Austria, and Switzerland. Compiled by the German Center for Documentation and Information in Psychology at the University of Trier (ZPID), this database covers German and English journal articles, books, chapters, reports, dissertations as well as audiovisual media. The database is bilingual: titles and descriptors are in German and English. German publications are abstracted in German; English publications in English. The database is indexed with the Thesaurus of Psychological Index Terms by permission of the American Psychological Association. A bilingual thesaurus is included with the database.

PubMed comprises over 29 million citations for biomedical literature from MEDLINE, life science journals, and online books. PubMed citations and abstracts include the fields of biomedicine and health, covering portions of the life sciences, behavioral sciences, chemical sciences, and bioengineering. PubMed also provides access to additional relevant web sites and links to the other NCBI molecular biology resources. PubMed is a free resource that is developed and maintained by the National Center for Biotechnology Information (NCBI), at the U.S. National Library of Medicine (NLM), located at the National Institutes of Health (NIH).

The RSC publishing platform provides access to electronic journals and books from the Royal Society of Chemistry. From this page, you can reach over 1 million chemical science articles and chapters. Users from the MPG have access to the entire journal collection, including the RSC journals archive covering articles published back to 1841. In addition, a collection of about 900 ebooks was purchased within the scope of the German national licenses program. The Max Planck Society also covers article-processing charges in line with the RSC "Read & Publish" agreement. Further details are available on the MPDL website.

The SAO/NASA Astrophysics Data System (ADS) is a digital library portal for researchers in astronomy and physics, operated by the Smithsonian Astrophysical Observatory (SAO) under a NASA grant. The ADS maintains three bibliographic databases containing more than 13 million records covering publications in Astronomy and Astrophysics, Physics, and the arXiv e-prints. Abstracts and full-text of major astronomy and physics publications are indexed and searchable through the new ADS modern search form as well as a classic search form.

SciELO (Scientific Electronic Library Online) is a program of the Sao Paulo Research Foundation for the cooperative publishing of open access journals on the internet. Content includes regional journals from Latin American and the Caribbean as well as titles from Spain, Portugal and South Africa. The index covers approximately 650 titles (over 350 adding content to journals already covered in the Web of Science) and contains several million cited references.

ScienceOpen is a networking platform for scholars to enhance their research in the open, make an impact, and receive credit for it. The site provides advanced search and discovery functions, combined with post-publication peer review, recommendation, social sharing, and collection-building features. The Max Planck Society covers article-processing charges for ScienceOpen Research and ScienceOpen Poster centrally. Further details are available on the MPDL website.