The MathWorks will SELL you a copy, that you can then download. No, you cannot download MATLAB for free, although you can get a demo copy with a limited time license.
If you have already paid for a license, then you can just go here to download the tool:
If your goal is to find a free copy of MATLAB, sorry, you are out of luck, unless you are willing to use Octave, which is free. Octave tries to remain reasonably close (to the extent possible) to MATLAB, so many m-files created for one are usable on the other.