You can find journal and magazine articles by subject by using a tool called a Periodical Index, or Database. Before there were journal databases, there were paper journal indexes. While they are harder to use than the journal databases, they index the journals and magazines of the past that could still be useful to find articles on your topic.
Databases contain large amounts of data. The data can be in the form of a listing of names, addresses, citations to journals and magazines, or many other kinds of information. Journal databases are the evolution of the print periodical indices into the digital world, where they are much easier to use.
(see the Journal & History Databases tabs for links to more individual databases)
These four websites contain digitized copies of many different magazines and journals, mainly from the 18th and 19th centuries. They are different from the journal databases in that they cannot be searched by topic, but you can browse individual issues.