yes, its possible.
How you do it.
Go to the followng directory.
(or where you installed the game if not default)
C:\Program Files\Firaxis Games\Sid Meier's Civilization 4\
Then go to Assets\XML\Technologies\
There are 2 files here, you want CIV4TechInfos.
DON'T EDIT THIS FILE HERE. It may be possible you'll have to reinstall if you don't remember how to fix it if you want later on. Instead, copy the file and put it in the following path. You will have to create a few of these directories.
Main game directory... \Mods\<your mod name here>\Assets\XML\Technologies\
Once you have created that path, paste the file into here. Now you can edit it. You can open that file with notepad and edit it (right click, open with / Notepad)
Now if you look at the structure of the XML there is a flag called Disabled
If you set that flag to 1 on any tech you don't want researchable, then you can lock down to a specific era by locking on gunpowder and education and such, or however you want to do it.
Let us know if you have more questions to get what you need.
Edit: BTW once you have edited your XML file. Launch the game, then go to Advanced / Load Mod. Select the name you gave your directory here and it will restart the app with your custom XML file. In mine I disabled horseback riding... horse archer's scare me!