trhat will change for the AI as well?
i did it and every civ was in future era when i was in industrial age
The problem is that whatever difficulty YOU play on, the AI is always playing on Chieftain. Or, in my mod, Prince. (You can change the AI handicap default fairly easily, but if you change it without fixing the imbalances in other areas, the AI will become pathetically easy to beat.) If you only changed ResearchPercent for the difficulty you play on, then you'll see the AI shoot past you. But if you change all of them at once, either through SQL or through a number of Update commands in XML, then it'll apply to the AIs as well.
So no, you do NOT have to change tech costs directly, although if you want a flat multiplier (say, x5) then a one-line SQL mod would do what you want.
In my own experience, the problem wasn't that the tech costs were all too low, it's that as you reached the later eras the cumulative bonuses of having Libraries, Universities, Public Schools, and Research Labs just became too much. Likewise, the science boosts of Rationalism policies were just too large. So, in my own mod I lowered the building bonuses by ~33% (Libraries become +1 per 3 population, Universities become +20% increasing to +30% with the Free Thought Policy, Secularism gives +1 science per specialist instead of +2, and so on. The cumulative effect of these changes was to cut research progress in half in the late eras, without much of an impact on the Ancient Era speeds.