Check Europe PMC for a linked full-text copy, then query Unpaywall for open-access locations using the paper's DOI, and read the methods and results before appraising the study. Europe PMC supports fielded searches across life-science literature and provides links to available full text, so a search there can surface a copy that the PubMed abstract record does not show.
- Search Europe PMC for the same paper. Run a fielded search using the title or the DOI. Expected result: a record that includes a link to available full text. If a full-text link appears, open it and confirm the title and authors match the PubMed record.
- Query Unpaywall with the DOI. Unpaywall records describe open-access locations associated with a DOI, including host type, version, license information when available, and a selected best open-access location. Expected result: one or more candidate locations, or no open-access location for that DOI.
- Check the version and host. Unpaywall's version field distinguishes what kind of copy a location holds, and host type tells you whether the copy sits in a repository or on a publisher site. Use these fields to decide which copy to open first.
- Try CORE if the earlier steps leave no usable copy. CORE aggregates open-access research outputs and offers discovery services and tools for finding repository copies of scholarly work. Expected result: a repository copy or a confirmation that none is indexed there.
- Read the methods and results before appraising the study. Once you have the full text, read the methods and results sections first so your appraisal rests on how the study was conducted and what it found, not on the abstract's summary.
If a step returns no full-text link, treat the availability as unresolved for that source and move to the next step rather than concluding the paper is closed access. A missing link in one service does not establish that no open-access copy exists elsewhere.