Scholarly journal articles are written by people knowledgable in the area. The quality and relevance of the article are monitored by a peer review process. That is, when a author submits an article to an editor, the editor sends the article to be reviewed by several (typically three) experts in the field. Depending on the reviewers' evaluations, the editor may tell the author that the article was 1) rejected, 2) accepted, or 3) accepted but requiring extensive changes. In contrast, an article in the popular press, e.g., Time, Newsweek and Reader's Digest, is written by a member of the magazine staff with a consequence that it is based on articles the staff member has read, opinions of people he or she phones as well as his or her own personal opinions.
How to find a scholarly article in the library? First, almost everything in the Reader's Guide to Periodic Literature is from the popular press and, therefore, should be avoided. Two exceptions are Scientific American and Science. Both of these journals are written by scientists for scientists in other fields.
All the journals published by ACM and IEEE are scholarly as well as journals published by other professional societies. A good reference of the scholarly material in Computer Science is the ACM Guide to Computing Literature available in the Library's Reference Room. Since the ACM Guide is published every year, you need to look through several years.