Generally, there is not an easy way to search only for articles containing original research. What you can do is search the UNL Libraries databases for an article that is of interest to you; then read through the article to see if the authors are writing about their own research, or only reporting on others' findings. Please contact your subject librarian if you are having trouble finding the resources you need.
For psychology-related research, you can search in APA PsycInfo - it is one database that allows users to limit results by methodology, making it much easier to locate original empirical research studies.
