Problem
After switching into different environment through anaconda by source activate myenv, then install new package by pip install package. However, this new package could not be imported through jupyter notebook. Also, when creating new notebook, I could not select kernel for the myenv kernel.
Solution
https://github.com/Anaconda-Platform/nb_conda_kernels/issues/57
Install Ipykernel in the conda virtual env.
conda install ipykernel
Then add the kernel to jupyter noteobok by
source activate myenv
python -m ipykernel install --user --name myenv --display-name "Python (myenv)"
Also you can switch between kernels using the following method.
https://qiita.com/yoppe/items/38005f415a5b8b884c7d