Options to limit the results are in the left margin. Selecting Subscribed Journals limits results to those articles that allow full access.
By including the term data in the search for articles on voter turnout, the hope is to generate articles which describe research based on data sets.
The image below depicts the first four of 2,881 search results that are in subscribed journals, and are therefore available in the full text:
Click on Data Availability in the article's outline on the left margin to see if there is access to the underlying data set used in the research.