Europeana, or the European Digital Library, is a pan-European digital library that provides access to 2 million books, maps, audio recordings, photographs, archival documents, paintings and films, materials originating from national libraries and cultural institutions of the 27 member states of the European Union.

https://www.europeana.eu/

Persée is a digital library of open-access scientific journals, mainly in French, created by the French Ministry of National Education. It is one of the largest French-language portals dedicated to the humanities and social sciences, with approximately 600,000 documents freely available.

https://www.persee.fr/

PubMed® comprises over 35 million citations for biomedical literature from MEDLINE, life science journals, and online books. Citations may include links to full-text content from PubMed Central and publishers' websites based on site and library subscriptions.

https://pubmed.ncbi.nlm.nih.gov/

PubMed Central (PMC) is a free full-text digital archive of biomedical and life sciences journals that have published open access articles.

https://pubmed.ncbi.nlm.nih.gov/

Europe PMC is a repository that provides access to international articles, books, patents, and clinical guidelines in the life sciences. Europe PMC provides links to related records in databases such as Uniprot, the European Nucleotide Archive (ENA), the Protein Data Bank Europe (PDBE), and BioStudies.

http://europepmc.org/

PubChem is a database of chemical molecules and their activities in biological assays. The system is maintained by the National Center for Biotechnology Information, a part of the National Library of Medicine, which is part of the United States National Institutes of Health.

https://pubchem.ncbi.nlm.nih.gov/

Το ChEMBL είναι μια χειρωνακτικά επιμελημένη βάση δεδομένων βιοδραστικών μορίων με ιδιότητες που μοιάζουν με φάρμακα. Συγκεντρώνει χημικά, βιοδραστικά και γονιδιωματικά δεδομένα για να βοηθήσει τη μετάφραση των γονιδιωματικών πληροφοριών σε αποτελεσματικά νέα φάρμακα.

https://www.ebi.ac.uk/chembl/

The Clarivate platform contains bibliographic databases and provides the ability to perform bibliographic searches, access abstracts and article references/citations. There is the possibility to link to the full texts of the articles if there is a subscription.

The WoS Core collection includes the following databases:

• Science Citation Index Expanded (SCI-EXPANDED) --1900-present Social Sciences
• Citation Index (SSCI) --1900-present
• Arts & Humanities Citation Index (A&HCI) --1975-present
• Emerging Sources Citation Index (ESCI) --2015-present
• Journal Citation Reports (JCR) -- current edition

https://www.webofscience.com/wos/woscc/basic-search

Elsevier bibliographic database containing 53 million records, 22,000 titles, and 5,000 publishers.

https://www.scopus.com/search/form.uri?display=basic#basic

ChemRxiv is a free-access preprint platform dedicated to early research findings in a broad range of chemistry fields.

https://chemrxiv.org/engage/chemrxiv/public-dashboard

bioRxiv is an open-access preprint repository for the biological sciences. It is hosted by the Cold Spring Harbor Laboratory. As preprints, the works hosted on bioRxiv are not peer-reviewed, but they undergo a basic quality check and are screened for plagiarism.

https://www.biorxiv.org/

ASAPbio (Accelerating Science and Publication in biology) is a scientist-led non-profit organization working to promote open and innovative communication in the life sciences.

https://asapbio.org/