Most article databases indicate whether sources are scholarly, or from non-scholarly sources. But evaluating sources, scholarly or not, is a complex task. Here is a short video that describes some variables you should take into account when evaluating sources. Even though a source may be be biased, or manipulative, or even false, it maybe a valuable source for your research, as long as you make clear its purpose. Important variables include:

• Author
• Audience
• Review Process
• Currency
• Perspective

An excellent overview of scholastic sources is Scholarly vs. Non-Scholarly Articles - Introduction to Library Resources - LibGuides at West Virginia State University

In short, a scholarly article is original research or intellectual inquiry that is written by experts, that contains citations for the sources used to make and support claims; and will usually have been cleared through a formal peer-reviewed process prior to publication (where it was scrutinized and vetted by other experts in the field). Ulrich's periodicals directory can be used to search journal titles- to quickly determine if that journal is a peer-reviewed, scholarly source (termed "refereed" in this database).