Dear Iman, I'm afraid you can't. Garson's algorithm only gives (or at least intends to give) relative importance, not the specific partial derivative results.
Yes, I mean this is so that I am going to obtain the relative importance index for each input of ANN with percent to predict each output. How can I do it?
Just simply substitute the connection weights of your ANN into the formula of Garson's algorithm. The formula can be found in many literatures, i.e. https://www.google.com/url?sa=t&source=web&rct=j&url=http://cs.anu.edu.au/people/Tom.Gedeon/pdfs/ContribDataMinv2.pdf&ved=2ahUKEwidntG4pMDfAhUHso8KHa28DlIQFjAAegQIARAB&usg=AOvVaw1VIefle3VfxJJiG1x7LRMA
At the end of the attached paper an Illustration of the critical difference between the Connection Weight Approach (Olden and Jackson, 2002b) and Garson’s Algorithm (Garson, 1991) is given.