In sciences, primary literature consists of articles that report on research studies and are actually written by the researchers. Example: Geng, F., Ma, R., Ebina, Y., Yamauchi, Y., Miyamoto, N., & Sasaki, T. (2014). Gigantic Swelling of Inorganic Layered Materials: A Bridge to Molecularly Thin Two-Dimensional Nanosheets. Journal Of The American Chemical Society,136(14), 5491-5500. doi:10.1021/ja501587y
Tips for identifying primary literature:
Secondary literature consists of articles that give an overview of studies that have been done in a research area. The authors did not do the laboratory research; the articles are based on literature research. Some types of secondary literature are review articles, review journal volumes, and topical journal volumes. Review article example: Klahn, M., & Beweries, T. (2014). Organometallic water splitting - from coordination chemistry to catalysis. Reviews In Inorganic Chemistry, 34(3), 177-198. doi:10.1515/revic-2013-0019
Tips for identifying secondary literature:
Primary literature can be located using journal article databases, such as SciFinder Scholar or Web of Science. The majority of articles in a database are usually research studies, so you don't have to do anything special to find them.
Secondary literature can also be located using journal article databases. When searching in a database, add the word "review" to the search terms to find review articles.