There are many research institutes and other libraries in Tsukuba City, and most of them are open to the public.
You can see the list from 「つくばの図書館案内」("Tsukuba Library Guide", in Japanese) on the website of Tsukuba Science City Network.

Some libraries require advance reservations, so please check the website of the library you would like to visit beforehand.
If you need a "図書資料共通利用券" , please borrow one from the Reference Desk of each library and bring it with you.