I haven't found one, but I've started just manually editing the CIV5HandicapInfos.xml file in ...\Steam\steamapps\common\sid meier's civilization v\assets\Gameplay\XML\GameInfo .
What you're looking for, under the relevant difficulty level, is ResearchPercent (150 means it will take you 50% longer to research each tech). Note that the CPU plays on Chieftain difficulty, although you can change this in another XML file. You can modify how fast the AI takes to construct units (AITrainPercent) and buildings (AIConstructPercent), but I don't think there's a quick and dirty way to change it for yourself. You can always turn off Time victory and lengthen research times though.