How can we find out who was nominated for Nobel Prizes? While the Nobel laureates are announced each year, are there any online resources that list who was nominated?

In particular, I am asking the Academic side of Nobel prizes, especially in Chemistry, Economics, Literature, Physics, or Physiology-Medicine. 

For example, Wikipedia says that Kazuhiko Nishijima (西島 和彦) was nominated for the Nobel Prize in Physics in 1960 and 1961, but it is not clear where can we find the official/secondary information about other "short-list" nominees.
The Nobel prize nominations are confidential for 50 years. An official online database that has most of the nominations (that aren't confidential) can be found at the website of the Nobel prize. As of today the site claims that it covers nominations up to 1963 for all prizes*, except for the physiology and medicine prize, which has data up to 1953 only. However, it does appear to list some more recent nominations. Perhaps it's best to consider lists for later years as incomplete for now.

In particular, for the case of Kazuhiko Nishijima you can find that he was nominated at least four times.

*The prize in Economic Sciences was instituted only in 1968, with the first prize awarded a year later. Thus, 50 years have not yet passed, so you won't find any of those nominations in the database.