The Cumulative Index for Nursing & Allied Health Literature, CINAHL, provides a number of filters/limiters that will help you to locate original research articles authored by nurses.
After entering your search topic, scroll down under "Search Options" and select one of the following:
Similarly you can use the "journal subset" filter and limit to "core nursing journals". Make sure to remove the "any author is a nurse" limiter before applying the "Journal Subset" limiter.
Many of the databases you will be using to conduct your research have an option to search by "Affiliated Author" or "affiliation". Entering the search term nurs* in this field will result in articles authored by nurses. Using the asterisk (*) is a useful technique called truncation. Searching the term nurs* retrieves results including the words nursing, nurse, or nurses.