We present a generalization of the multiphase chemical evolution model applied to a wide set of theoretical galaxies with different masses and morphological types .
This generalized set of models has been computed using the so-called Universal Rotation Curve from Persic , Salucci & Steel ( 87 ) to calculate the radial mass distribution of 44 theoretical protogalaxies .
This distribution is a fundamental input which , besides its own effect on the galaxy evolution , defines the characteristic collapse time scale or gas infall rate onto the disk .

On the other hand , the molecular cloud and star formation efficiencies take 10 different values between 0 and 1 , as corresponding to their probability nature , for each one of the radial distributions of total mass .
This implies that for each mass radial distribution , we have 10 different evolutionary rates , which happen to be related to the morphological types of galaxies , as we will later show .
With these two hypotheses we construct a bi-parametric grid of models whose results are valid in principle for any spiral galaxy of given maximum rotation velocity or total mass , and type T from 1 to 10 .

The results include the time evolution of different regions of the disk and the halo along galactocentric distance , measured by the gas ( atomic and molecular ) and stellar masses , the star formation rate and chemical abundances of 15 elements .
The present time radial distributions of diffuse and molecular gas and star formation rate surface densities , and of oxygen abundance - defined as 12 + log ( O/H ) – are calculated and then compared with observational data .

One of the most important results of this work concerns the radial gradients of abundances .
These are completely flat for the latest morphological types , from T \sim 7 to 10 , with abundances 12 + log ( O / H ) \sim 7.5 - 8 , while they appear steep for late type galaxies ( T \sim 4 - 7 ) , in comparison when earlier types .
This is in agreement with observations and it resolves the apparent inconsistency in the trends giving larger gradients for later type galaxies while some irregulars show no gradient at all and very uniform abundances .
The explanation resides in the star formation to infall ratio provided by the multiphase models .

These models are also able to explain the existing correlations between generic characteristics of galaxies and their radial distributions , as arising from variations in the characteristic infall rate and in the cloud and star formation efficiencies with galactic morphological type and/or Arm Class .