Is it possible to access the desktop files from Android device ?
The device is connected to the desktop through USB.
Yes, its possible. But, not with ADB. ADB server runs only in Android (Device or Emulator). On PC, you get ADB client only.
You can do the same over air, too. Just connect PC & Android device in same Wi-Fi network & do the same. If you don't have Wi-Fi router, use Connectify or mHotspot (assuming its Windows PC) to make a virtual hotspot.