It is usually enough to finish researching the current technology, and even boost another one! Use this if you need an immediate result. In Gods & Kings and Brave New World, this ability is replaced by the 'Boost Science' ability, which lets you immediately gain a large number of science points based on the science output of your civilization. In vanilla Civilization V, the Great Scientist can use 'Discover Technology' to grant you a free technology. The unit is expended after performing either of these actions.

Construct an Academy (Great tile improvement).A Great Person, specialized in science research.