Many periodicals are known for being partisan (biased) in their reporting - either liberal (left-leaning) or conservative (right-leaning) in their point of view. Other periodicals stay centrist or moderate in their viewpoints.
It is important to be aware of a periodical's bias when using it as a source. Try to determine a periodical's bias when using it in your paper and try to get articles that show many different viewpoints (liberal, centrist/moderate, conservative) so that your paper is balanced. Make sure to acknowledge the source's bias in your paper (mentioning the paper's partisan slant, the reporter's personal viewpoints, etc).
This guide will help you locate periodicals that have a particular point of view (bias). There are three pages of viewpoints - liberal, centrist/moderate, and conservative. Each page contains journals, magazines, and newspapers that are partisan.