A primary source in the sciences is a work of original research, such as the results of an experiment, a clinical trial, or other studies. They may involve scientific findings, discoveries, and proof or disproof of a hypothesis.
Primary sources in the sciences generally take the form of a research article in a scientific scholarly journal.
To locate a scientific primary source in a scholarly journal, you can browse scientific databases, such as the ones listed in this guide.
To identify a scientific primary source, check the abstract for discussion of data collection and analysis. If it's still unclear, look for a methods section detailing how original data was collected and analyzed. If you see words like "meta-analysis," "literature review," or "systematic review" in the abstract or title, it's likely to not be a work of original research and therefore not a primary source. Note: a study will include a review of literature, but it will have data collection and data analysis as the focus of the work.