I have an instance with various environment and some notebooks are compatible with different environment for e.g. notebook1 is for MXNet and notebook2 is for Tensorflow.
When you start a jupyter notebook within an environment, it will only have access to the modules installed in that particular enviroment. If you need two specific environments for two different notebooks, you will need to start a jupyter notebook within the two environments separately.
If you are using anaconda, you would do the following in a terminal:
source activate MXNET
jupyter notebook
Then in a second terminal:
source activate Tensorflow
jupyter notebook