In addition to the thousands of print media titles- almost all of which also publish on the web - Nexis Uni also gathers material from web-only publications. These include well-known web magazines like Slate, Salon and Politico, as well as blogs and other e-content from legacy publicers like The New York Times and The Washington Post.
The screen image below shows a search on the term "steel tariffs" with the results narrowed by date (1/1/2017 - 5/31/2018), language (English) and by publication type - in this case "Web-based Publications."
"Publication Type" is one of a number of useful modifiers that can be used to narrow and refine your results. These are configured as drop-downs and are located along the left margin of the screen.