Access to free scientific articles

• Unpaywall (Chrome - Firefox)

It notifies if there is an open and free version of the searched article.

• Open Access Button (Chrome - Firefox)

It searches for an open and free version of the article. If it does not find one, the system contacts the author to request a copy.

• Google Scholar Button (Chrome - Firefox)

It accesses Google Scholar from any web page.

Select the article title on any page and find it by clicking the button.

• EndNote Click (Chrome - Edge)

It searches for full-text PDF files and finds the best available version of an academic article.

Thematic repositories

• ArXiv.org: physics, mathematics and computer science, among other subjects
• Astrophysics data system: astronomy and physics
• BioRxiv: biology
• CERN: particle physics and high energy physics
• CiteSeerX: computer science and information sciences
• ERIC: education
• PubMed Central: biomedical sciences and life sciences
• RePEc: economy
• SSRN: social sciences and humanities

General resources

• BASE: more than 400 million academic documents from more than 11,000 sources (repositories, open access journals, etc.). Most of them in full text.
• CORE: it indexes more than 300 million academic documents from more than 12,000 sources (repositories, open access journals, etc.). It also offers an extension for the browser (Core Discovery).
• OCLC OAIster: OCLC catalog that includes more than 50 million open access digital resources.
• OpenAIRE: document search engine in European repositories. Access to 200 million publications.
• OpenAlex: bibliographic database of multidisciplinary scope and in open access.
• Recolecta: it aggregates academic documents collected from open access repositories throughout Spain. It currently collects more than 3 million documents from 188 repositories.
• ScienceOpen: academic article hosting service. It allows searching for articles hosted on its servers, but also for articles present in other repositories (Arxiv, Pubmed, Scielo…).

If you cannot find the article you need using the Library Service search engine and cannot find an open-access version using the widgets and consulting the resources mentioned above, please request it through the Interlibrary Loan Service and they will provide it to you as long as the license allows it.

If you need assistance, please contact the Interlibrary Loan Service through Pregunt@

• The email address that usually appears in the article itself.
• Academia.edu o ResearchGate – Academic social networks.
• Knowledge Commons - Knowledge commons is an open access and open source network for people working in the humanities.
• #Icanhazpdf - Hashtag used on social networks to request access to articles in academic journals that are behind paywalls.