Normally with Router>Show ? , you will not see all available show commands at user level but there is a way to see Full help of Show commands at user level. You would need to enable following command
Router> terminal full-help
Enabling full help, you will witness that there are lot more commands available at User EXEC level.
The system administrator can also configure the system to always display full help for connections made to a particular line using the full-help line configuration command