  Photoemission spectra of the perovskites Ca$_x$Sr$_{1-x}$VO$_3$,
Ca$_x$La$_{1-x}$VO$_3$, and SrRuO$_3$ indicate that Coulomb correlations are
more pronounced at the surface than in the bulk. To investigate this effect we
use the dynamical mean field theory combined with the Quantum Monte Carlo
technique and evaluate the multi-orbital self-energy. These systems exhibit
different degrees of band filling and range from metallic to insulating. The
key input in the calculations is the layer dependent local density of states
which we obtain from a tight-binding approach for semi-infinite cubic systems.
As a result of the planar character of the perovskite $t_{2g}$ bands near the
Fermi level, the reduced coordination number of surface atoms gives rise to a
significant narrowing of the surface density of those subbands which hybridize
preferentially in planes normal to the surface. Although the total band width
coincides with the one in the bulk, the effective band narrowing at the surface
leads to stronger correlation features in the quasi-particle spectra. In
particular, the weight of the quasi-particle peak near $E_F$ is reduced and the
amplitude of the lower and upper Hubbard bands is enhanced, in agreement with
experiments.
