In Windows 64, if you did this sequence correctly:
Anaconda prompt:
conda create -n tensorflow python=3.5
activate tensorflow
pip install --ignore-installed --upgrade tensorflow
Be sure you still are in tensorflow environment. The best way to make Spyder recognize your tensorflow environment is to do this:
conda install spyder
This will install a new instance of Spyder inside Tensorflow environment. Then you must install scipy, matplotlib, pandas, sklearn and other libraries. Also works for OpenCV.
Always prefer to install these libraries with "conda install" instead of "pip".