Control Mirror reflection's ratio

How can I use the mirror shader but to create a mirror surface like marble it will reflect but not like a mirror, or like a polished wood, car chases, all of these surfaces will reflect real object - not from a reflection map- but with distort and low reflection rate...

I hope I make it clear enough Thanks

There's a couple of distinct parts here:

1) To do realtime reflections, you still need to use a reflection map. However, you can set up a camera that renders that reflection map every frame (using a RenderTexture) if you have Unity Pro.

2) To create "less reflective" materials with the standard shaders, I believe you can either turn down the alpha channel of, or just darken, the reflection color.

3) For distortion, you may be able to get what you want by using the Bumped Reflective shader with an appropriate bumpmap. If that's not enough, you might have to dive into modifying the shader code (Cg) itself, in which case you have a lot more flexibility.