Biological information exists in different formats including: articles, books, and data. Sources can be primary, secondary, or tertiary. Authors of primary sources analyze data. Secondary and tertiary sources interpret and summarize other sources. Primary sources are often the most up-to-date, but can be difficult to read and understand. Secondary and tertiary sources are often easier to understand, but have undergone additional interpretation.
Original research, evidence, and analysis
Examples: Research articles, Patents, Research data, Lab notes, Conference presentations, Clinical trials, Original models
Search tip: Did the authors themselves collect or analyze data? If the answer is yes, it is probably primary research.
Summaries, evaluations, or interpretations of others' research
Examples: Review articles, Book reviews, Annotated bibliographies
Search tip: Scholarly review articles are usually easier to understand than the primary literature. Try adding the term "review" to your search strategy to find them.
Collections and summaries of primary and secondary sources
Examples: Reference books, Dictionaries, Encyclopedias
Search tip: Try searching in ESearch for reference materials
How to Identify a Research Article:
Research articles are primary sources. The authors of the article have conducted an original analysis of primary data (data they collected) or secondary data (data someone else collected). Research articles have section labels that are similar to lab reports such as: Introduction, Methods, Results, Discussion, and Conclusion. Research articles often include some data in the form of tables or some representation of data in the form of charts, graphs, or other visualizations. Here is an example of a research article: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0277535
How to Identify a Review Article:
Review articles are secondary sources. They summarize or reorganize information that was published in other articles. They often have section labels that are more specific to the topic. Here is an example of a review article: https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0011069