* JSTOR is a digital library of academic journals, books, and primary sources. JSTOR provides access to over 12 million academic articles from more than 2,000 journals, and it is a valuable resource for researchers in a variety of fields. JSTOR is available by subscription, but many institutions offer free access to their students and faculty.
* PubMed is a free online database of biomedical and life sciences literature. PubMed indexes over 30 million citations from over 5,000 journals, and it is a valuable resource for researchers in the health sciences. PubMed is also available by subscription, but many institutions offer free access to their students and faculty.
* Web of Science is a multidisciplinary database of academic journals, books, and conference proceedings. Web of Science indexes over 120 million records from over 12,000 journals, and it is a valuable resource for researchers in a variety of fields. Web of Science is available by subscription, but many institutions offer free access to their students and faculty.
* arXiv is a free online repository of scientific papers and preprints. arXiv is sponsored by Cornell University, and it provides access to over 1.5 million papers from a wide variety of scientific disciplines. arXiv is a valuable resource for researchers who want to stay up-to-date on the latest research findings.
* DOAJ is a free online directory of open access journals. DOAJ indexes over 10,000 journals from a wide variety of scientific disciplines. DOAJ is a valuable resource for researchers who want to find high-quality open access articles.
* OpenAIRE is a free online repository of open access research outputs. OpenAIRE indexes over 10 million articles, datasets, and other research outputs from a wide variety of scientific disciplines. OpenAIRE is a valuable resource for researchers who want to find high-quality open access research outputs.