There is an online filter in the left menu, and items will show you if there is an online option like the first item shows
How do I find digital resources?
NELSON will show you digital resources only, and not the books and journals on the shelves, by using some of the filters. You can find the filters by logging into NELSON, using the search box for your search and then using the filters that you can see on the left side of the results page. If there is an online version, you will see a green hyperlink that says 'Available Online.'