Primary Research articles are nearly always presented in academic journals. They report on the process and results of primary research. They contain sections on: literature review, methods and materials, results and conclusions. Sometimes the sections have slightly different names. Primary articles tend to be more complex than other types of literature, but the abstract can help give you a general understanding of what will follow in the article.
Below is an example of a journal article. (click on image for full article)
You can tell it is a journal article because you can see the title of the journal, the volume, the pages and the date. This information is in the top left hand corner in the above example, but it can be on the opposite side, or at the bottom depending on the journal.
Here is another example from an online Journal
Review articles are another type of article appearing in a scientific journal. Rather than reporting on original research, like a primary research article, a review article reports on the current state of knowledge about a topic, by presenting recent research about the topic.
An example of a review article is: Recent progress in understanding the role of ecdysteroids in adult insects: Germline development and circadian clock in the fruit fly Drosophila melanogaster.
You may choose to select a secondary source for one of your references. These sources are usually magazines or websites, and do not present original scientific research.
Secondary articles are great to get you started in your research but do not have the content that you need to fully inform your research. Secondary articles are generally shorter and much less in-depth than primary articles. They often do not have an author, so it is hard for you to determine the authority of the article. Many magazine articles do have authors, but the authors are journalists, rather than scientists.
The article below is from the magazine Science & Spirit and is a single page article.