If the title of the periodical has "Journal" or "Review" as part of the title, it could be a scholarly journal, but you may need to check further. For example, The New England Journal of Medicine or Nutrition Review are scholarly publications, but not Ladies Home Journal.
Many databases have a way to "limited to scholarly journals". Check the 'advanced search' or 'refine search' screens.
The articles are specialized, relatively lengthy, and intended for those familiar with the subject.
The article may be organized into at least two of the following sections: Introduction or Literature Review, Theory or Background, Subjects, Methods/Methodology, Results, Discussion.
The article has footnotes, endnotes, and/or a bibliography or list of references.
The title of the article reflects its content.
The content of the article normally reports on original research or experimentation.
The author's credentials (e.g., title, institutional affiliation) are usually listed.
The article is based upon either original research or on authorities in the field (rather than personal opinion).
The article is normally plain in appearance with few, if any, illustrations. There may be supporting diagrams or charts, but few glossy color pictures.
Pages may be numbered consecutively throughout the volume/year.