I will disagree with the accepted response and note that pip install [some-pypi-package] is often the best way to install PyPi packages in Conda environments.
While the packages won’t be managed by the Conda package manager, they will still be managed by the Anaconda environment. It will download the correct version of the package for the active Python install and update it correctly using the pip package manager.
When using Anaconda, you should turn to conda before pip when you can, but you don’t lose any of the replicability benefits of using Anaconda when you use pip.
Anaconda recently published a doc that supports this: https://docs.conda.io/projects/conda/en/latest/user-guide/tasks/manage-environments.html#using-pip-in-an-environment