You can search for journals by title or ISSN number on iDiscover. You can also search for journals on iDiscover using the same search bar for book searches.
If the relevant year is covered, the link provided should take you to a list of issues for your journal of choice.
iDiscover allows you access to a number of ebooks and eresourses. You can narrow down your title searches by resource type using the drop-down list by the search box or search the A-Z for various online Databases. If you have any questions on searching for books and ebooks you should get in touch with your Subject Librarian or else use the Help pages on iDiscover. There is also a blog dedicated to Cambridge University's ejournals and eresources.