There probably were similar systems in later games, but in RT you didn't research any given "tech". The research was a series of sliders and toggles. Firstly, there was the "scientist work-months" income, which was dependent on the amount of labs you had, but where it comes from isn't important. This pool of "scientist points" was then split in two by a master research slider - into "general sciences" and "applied fields". General sciences were only Physics, Mathematics, Biology, and Chemistry (the game didn't focus on non-combat aspects too much, nowadays Economics and Psychology could probably be added too), and each had a slider that allocated a fraction of the total General Sciences points to it. As points in General Sciences accumulated, Applied Fields became unlocked. Applied Fields number in the dozens, so having a slider for each would be silly - instead each field is "on" or "off", and the total Applied Fields points are split evenly between all actively researched fields. Accumulating points in specific Applied Fields, and sometimes General Sciences, is what makes specific technologies available.
Now, as for the individual technologies - each has two sets of requirements. The first set of requirements is usually fairly lax, and determines the state of accumulated research at which the player can see the second set of requirements, at which the technology actually unlocks. This allowed you to not so much "research a tech", but to more or less "steer the research towards that tech", unlocking related technologies as "collateral" on the way to the thing you wanted.
The technologies were actually arrayed in something of a "tree", as there was a rather clear progression from certain technologies to more powerful ones, but it happened naturally due to research progress instead of being a predetermined sequence. Also back then (1997) nobody thought to randomize the tech tree or at least the requirement sets, so on the whole it was pretty static, only appearing to work in different ways because of the different distributions of research allocations you were likely to have on different playthroughs. Still, on the overall it still seems to me like the most natural-feeling research system in 4X games to date. It was unpolished, and more than a little glitchy (you unlocked heavy graviton cannons before normal ones, though who knows? might have been intended), but it felt right.