• review of the most important literature in the field that relates to their topic
• detailed explanation of the experiment or study
• description of the findings or results of the study or experiment
• complete bibliography

Primary research should explain exactly what the researcher did in the study or experiment. You should be able to use this explanation to duplicate the experiment if you wanted to.

Primary research articles are almost always written by the researchers or scientists themselves. These articles should describe what the authors have done personally, not describe the work others have done. If an article summarizes the work done by others, it is not primary research.