Based on experience and observation, rather than systematic logic. (according to MedicineNet.com)
The articles contain original research (such as scientific experiments, surveys and research studies)
A list of references or sources is provided at the end of each article
An editorial board, composed of experts in the field, reviews articles to decide whether they should be accepted; this is also known as "refereed," "peer-reviewed," "professional," "scholarly", or "academic".
Uses a specialized vocabulary for that field.
Below are two websites that explain Empirical articles and research:
Empirical Research: How to Recognize and Locate - http://users.library.fullerton.edu/cbruns/empirical_research.htm
Finding Empirical Research Articles in Education and Psychology