It is important to understand where in the cycle you are getting the information and the characteristics of each type of resource.
Primary sources present original research by those who carried it out.
Secondary sources summarize and synthesize information from primary sources.
Tertiary sources condense information from primary and secondary sources.
Research articles in scientific journals present the original data and findings of the researchers involved in the experiment or study (primary source).
They usually include sections for Introduction, Methods, Results, and Discussion (IMRaD format) to match the scientific method.
Review articles in scientific journals provide an overview of the field or the topic by summarizing and synthesizing the data and findings from many experiments or studies (secondary source).
Peer-reviewed (or refereed) journals contain articles written by experts that are reviewed by other experts in the field for quality before publication.