You can look at the tech effect descriptions in techs.txt and translate these into readable english. The format is described on the wiki
effects page, though it's a bit out of date... but not so much as to be useless.
The part you're interested in in the tech description is the effects groups. For example, the description of effects for Mining Engineering is:
Code:
Bonuses depend on planet type:
Barren and Inferno recive +4 per 10 population of planet at mining focused worlds.
Desert, Radiated and Toxic recive +2.
Tundra and Terran recive +1.
Ocean and Swap receive no bonus.
(It's mentioned in the earlier part of the description that the bonus is to max mining, though it should probably be restated in the effects part, actually...)
The tech effectsgroups definitions that correspond to that description:
Code:
effectsgroups = [
EffectsGroup
scope = And [
OwnedExclusivelyBy TheEmpire Source.Owner
PopulationCenter
PrimaryFocus Mining
Planet type = [Barren Inferno]
]
activation = Source
effects = SetMaxMining value = Target.MaxMining + 4
EffectsGroup
scope = And [
OwnedExclusivelyBy TheEmpire Source.Owner
PopulationCenter
PrimaryFocus Mining
Planet type = [Desert Radiated Toxic]
]
activation = Source
effects = SetMaxMining value = Target.MaxMining + 2
EffectsGroup
scope = And [
OwnedExclusivelyBy TheEmpire Source.Owner
PopulationCenter
PrimaryFocus Mining
Planet type = [Tundra Terran]
]
activation = Source
effects = SetMaxMining value = Target.MaxMining + 1
]
A bit of information is assumed (omitted) from the description, like that the effects only work on planets that the player who researched the tech owns, but this is stylistic.
It probably looks a bit daunting, but after looking at a few effects groups, the meaning should be fairly easy to figure out.