I'm not sure why you would want to, since AI tech is an easy source of tech for you, if your diplomats/spies can steal them, or you have any wonders that enable you to trade them or acquire them by other means.
If you end up playing Test of Time (either the Fantasy or Lalande scenarios), there are some techs that you will not be able to research for yourself - they're only available by theft, trade, or acquisition due to a wonder or having reached a particular point in the game. That's why, in the Lalande game, you need to leave at least two of the three alien races alive until late in the game. If you don't, you won't be able to reach the final map level (the gas giant Nona).