I have came across the same problem today....after spending the last few days on building a space station
Good news is that I have found a solution!
It only works if you have this message(for every not working part/experiment) in the debug screen (alt+F12) just after starting the game:
The problem is that the mod in version 1.5 has a different folder structure (below):
Option 1 - You might fix it by moving all the folders from 'StationScience-1.5' directly into 'GameData', but I have not tried it, as other parts are working fine for me and I didn't want to break anything else (but feel free to backup your saves and give it a go )
Option 2 - What I have done is amend the file path in every part.cfg file for all the parts that KSP could not load(find).
Which are: StnSciExperiment1, 2, 3, 4, 5, 6 and also StnSciKib.
On the top of that the textures for StnSciExperiment3 could not load because of a typo somewhere in the file path (in the part.cfg file). I've just copied the path from the Windows window and everything loads fine.
I have not tested the contracts (I haven't seen any yet), but I think they are bounded to unlocking the experiments, so hopefully they will start showing up now.
If option 1 is not working and you are not happy with amending the folder paths in the config files you can download my (amended) files below. It is a 7-zipped 'Parts' folder only, so overwrite yours and you should be flying (I have amended 7 files in total) Remember to create backups before changing anything in your game folder!
https://www.mediafire.com/?qn5a0m1ad5m5kxm