Within the sciences, primary sources report on the results of an original experiment or research study by those that performed it. They typically contain the following elements:
Secondary sources in the sciences encompass a group of articles known as review articles. These articles summarize and analyze the current scientific literature on a topic. Secondary sources also typically, compare, critique, and interpret the primary literature. Examples include specific types of review articles including literature reviews and systematic reviews as well as encyclopedias, commentaries, and magazine articles. In general, secondary sources tend to come second in the publication cycle.
A review article in a scientific publication can contain many of the same features as an original research article (abstract, introduction, methods, results, and conclusion) so it is important to determine if the article is discussing original research or reviewing research done by others.