Primary sources in biological, health, and natural science fields typically consist of reports/information on original research that is provided by the participating researchers/scientists.
Examples include:
Scientific articles that are original research typically contain the following sections:
1. Abstract: a paragraph in the beginning of the article that summarizes the article
2. Introduction/background: overview or summary of the article, experiment or study, background for why the authors did this research
3. Methods or methodology: how was the experiment/study conducted, who or what was studied, and how many participated
4. Results: what happened as a result of the study, what are the findings
5. Discussion/Conclusion: what did the researchers observe from the experiment or study, is further study needed, did the experiment prove or disprove the hypothesis
6. References: what sources did the researchers use in the article to support their findings
7. Graphs, Charts, Tables are generally found in these types of articles
The abstract below is from a research study on sustainable tourism that was published in the Journal of Environmental Health Science and Engineering.
In order to find print articles: 
How to search:
When you're searching the library databases to find scientific primary sources, you want to try specific keywords. You want to take your topic and add words like trial, study, experiment, method(s), methodology, trial group, trial, randomized trial, blind trial. So if you're trying to find a primary source on Diabetes you could search Diabetes and randomized trial.
Best bet databases:
One of the essential databases to your NCC research experience! Search for your topic here to find articles from scholarly journals, magazines, newspapers and other reference sources. Many articles are full text.