Gnome shell "show desktop" shortcut

I been thinking of anyone could guide me up, that in ubuntu 11.10 with gnome 3,
there is a option ctrl+alt+d to show the desktop by minimizing the current window.

What I was thinking was that if I press ctrl+alt+d it will lead to desktop screen and when I press again ctrl+alt+d to go back to my working window..

As of now it doesnt work in this way ..is there any way out to do that same

With Gnome Shell (17.10+)

The default keybind is Ctrl + Super + d. The setting is called Hide all normal windows

You can change it in Settings > Keyboard Shortcuts > Navigation:

With Unity (before 17.10)

The patch is already released but if you still face that problem use the following:

• Click your username on the top right of the screen and select System Settings.

• Under Hardware click Keyboard.

• Switch to the Shortcuts tab, and click Navigation in the left column. Scroll down and select Hide all normal windows which has a default value of Disabled.

If you want a non-keyboard method, there's also the "Show desktop button" option.

Simply visit this link and click on the on/off slider near the top left corner, you'll be prompted to install the widget, and from then on you'll have a small "show desktop" icon next to "Activities in your menu". (Shown here in between my Activities menu and Google Chrome Indicator)

Very handy, IMHO.

Updated 25/09/2017 with the new extension compatible with the current version of GNOME Shell, as suggested by @stefan-hamke. The out-of-date original is here.