HathiTrust is a more precise (though slower) search engine than Google Books.
HathiTrust features freely accessible government documents including many government documents published after 1927.
The Search by Field option allows you to search for keywords within the Full-Text of all books, magazines, and government documents.
Each search blank can be set to: “any of these words” or “all of these words” or “exact phrase”
Search by Field will also allow you to search the Full-Text of a specific book or multiple issues of a specific magazine by typing a topic in a Full-text box and then in the second line setting the box to Title and typing in the title of a book or magazine. (See example below of a search for articles from the magazine Collier’s that include the phrase “patent medicine”).
Note - Collier’s went by various names during its many years of publication - e.g., Collier’s Weekly, Collier’s: The National Weekly, and Collier’s - so use that portion of the magazine name “Collier’s” common to all.
Be sure to set the Publication date to the range of years under consideration.
If searching for primary sources after 1927 be sure to also check the box for Full view only which will return results for government documents and those few other publications that are no longer protected by copyright.
To create a search across multiple magazines and journals (serials/periodicals) type in the topic of interest in the first Full-Text blank and search. Then - on the left-hand column of the results page - click on the option Serial under “Original Format” and then click on the option Periodicals under the option “Subject”.