• PubMed 
  PubMed is a free resource supporting the search and retrieval of biomedical and life sciences literature. The PubMed database contains more than 37 million citations and abstracts of biomedical literature. Links to the full text are often present when available from other sources, such as the publisher's website or PubMed Central (PMC).
• Google Scholar
  Google Scholar is a freely accessible web search engine for locating multidisciplinary scholarly literature from a broad range of sources, including articles, books, dissertations/theses, abstracts, and court opinions. Links to free full text are included as available. 
• PubMed Central (PMC)
  PubMed Central (PMC) is a free full-text archive of biomedical and life sciences journal literature.
• Directory of Open Access Journals (DOAJ)
  DOAJ, a searchable index of open access journals published around the globe, includes journals across a variety of disciplines and languages.
• Public Library of Science (PLOS) 
  PLOS aims to accelerate advances in science and medicine through open access publishing. As of 2024, PLOS offers 14 peer-reviewed OA journals across a range of subject areas.
• BioMed Central (BMC)
  BMC offers more than 300 peer-reviewed journals covering topics science, technology, engineering and medicine through the ‘gold’ open access model, which give readers free and immediate access to content, with no embargo periods.
• SpringerOpen - Journals
  SpringerOpen provides more than 200 peer-reviewed fully open access journals across all areas of science.
• Sage Gold Open Access Journals
  Sage publishes more than 200 gold open access journals on topics in medicine, engineering, life sciences, and the social sciences.

Please Note: Preprints are completed scientific manuscripts that have been made publicly available prior to peer-review and publication in a journal. Because they have not been peer-reviewed, preprints should be considered preliminary research and should not be cited as evidence or used to support clinical or public health decision-making.

• OSF Preprints
  Part of the Open Science Framework (OSF) initiative to promote open collaboration in science research, OSF Preprints is a multidisciplinary preprint repository that allows authors to submit supplemental information, including data and code, along with their preprint manuscript.
• medRxiv
  medRxiv (pronounced "med-archive") is a free online archive and distribution server for preprints in the medical, clinical, and related health sciences.
• bioRxiv Pharmacology and Toxicology
  bioRxiv (pronounced "bio-archive") is an open-access service for preprints in the life sciences.
• ChemRxiv
  ChemRxiv (pronounced 'chem-archive') is a open-access service for preprints in chemistry and related areas.
• PsyArXiv
  PsyArXiv is an open-access service for preprints in the psychological sciences.
• SportRxiv
  SportRxiv is an open-access service for preprints in sport, exercise, performance, and health research. 
• MedRN: The Medical Research Network
  MedRN, from the  Social Science Research Network (SSRN), is an open-access service for medical research preprints, as well as other research outputs, including preliminary or exploratory investigations, book chapters, PhD dissertations, course and teaching materials, presentations, and posters. 

• NCBI Bookshelf
  Bookshelf, from the National Center for Biotechnology Information, provides free online access to books and documents in life science and healthcare.
• Directory of Open Access Books (DOAB)
  DOAB provides access to scholarly, peer-reviewed open access books.
• Open Textbook Library
  This open-access library contains over 1500 multidisciplinary titles that authors and publishers have licensed for free use, sharing, distribution, and adaptation with appropriate attribution.
• LibreTexts
  LibreTexts allows educators to develop, adapt, and share interactive textbooks, adaptive homework, and ancillary materials.

• Trip Medical Database
  The Trip search engine allows health care providers to locate high-quality research evidence to support clinical care.
• Evidence-Based Practice Center (EBC) Reports
  From the Agency for Healthcare Research and Quality (AHRQ), EBC reports is a searchable collection of from reports from Evidence-based Practice Centers regarding effective strategies for treating and managing common or costly medical conditions. The reports include systematic reviews, evidence syntheses, and technical bulletins from the U.S. Preventive Services Task Force, ERQ's Effective Healthcare and Technology Assessment programs, and leading clinical research institutions. 
• U.S. Preventive Services Task Force (USPSTF) Recommendation Topics
  The USPSTF recommendations are based on the USPSTF systematic reviews of the evidence of effectiveness for clinical preventive services.
• PEDro: Physiotherapy Evidence Database
  The PEDro database contains randomized controlled trials, systematic reviews and clinical practice guidelines to support evidence-based practice in physical therapy. Each study is scored for methodological quality.

• DrugBank
  DrugBank is an open access database providing chemical, pharmacological and pharmaceutical data for 500,000+ drugs and drug products, as well as comprehensive drug target information.
• ECRI Guidelines Trust 
  The ECRI Guidelines Trust is a publicly available online repository of objective, evidence-based clinical practice guideline content.
• Open-i
  Open-i is an open-access biomedical image search engine from the National Library of Medicine (NLM) that retrieves and displays structured MEDLINE citations augmented by image-related text and concepts and linked to images based on image features.