If you're using OneSearch, use the gray left column to filter your results to Peer Reviewed Articles only. Under Show Only, choose Peer-reviewed Journals, and under Resource Type, choose Articles.
If you found your article elsewhere, you can use Ulrichsweb to determine if a journal (where the article is published) is peer reviewed.
(Other words for peer reviewed are scholarly, academic, or refereed.)
In general, try to remember the following about scholarly journals:
Authors are authorities in their fields.
Authors cite their sources in endnotes, footnotes, or bibliographies.
Individual issues have little or no advertising.
Articles must go through a peer-review or refereed process.
Articles are usually reports on scholarly research.
Illustrations usually take the form of charts and graphs.