  A systematic study is performed of the impact of the various resummed
small-$x$ contributions to the anomalous dimensions and coefficient functions
on the evolution of unpolarized structure functions in deep-inelastic
scattering. The proton structure functions $F_2^p$ and $F_L^p$ as well as the
photon structure function $F_2^{\gamma}$ are considered together with the
corresponding parton densities. The general analytic solution of the evolution
equations in Mellin-$N$ space is derived, and different approximate solutions
are compared. Potential effects of less singular small-$x$ terms in the
anomalous dimension and coefficient functions are discussed.
