Back issues of most journals are on microfiche. Just look in the box near the bottom of the record. The back issues of some journals are also on microfilm. Just look in the box near the bottom of the record. Microfiche and microfilm are not the same.
Microfiche are small plastic cards.
Microfilm is stored on reels. Both require these specialized machines in order to read and copy them. All six machines will read and make copies from microfiche. However, only the three machines on the left in the picture at top will make copies from microfilm.