Google galciv2 wiki then go to that site and look around. It will answer many questions.
On your specific Q, it is a little more complicated than you might think. First, Moosetek13 is quite correct that one can sometimes complete the research of multiple techs in the same line in one turn.
The number of research points generated on a planet is determined by an equation with several factors. One is the percentage of production you have allocated to research in the empire-wide sliders. For example, if you have the sliders set at zero research, it matters not how many research buildings you have on the planet.
Another factor is if you have selected an area with "focus". That is, if you have increased one sort of production at the decrease of the other two.
Another factor is the percentage of spending you have selected. Any empire-wide setting below 100% reduces all areas by the exact amount of the decrease, but sometimes that spending level cannot be sustained without ruinous tax levels, if it can be sustained at all.
IIRC, a research building will add to the planet's output its rated or "nameplate" amount of research points only if the spending setting is at 100% and the research slider is at 100%. Factory output is affected in a similar manner.
