  The influence of spin and charge fluctuations on spectra of the
two-dimensional fermionic Hubbard model is considered using the strong coupling
diagram technique. Infinite sequences of diagrams containing ladder inserts,
which describe the interaction of electrons with these fluctuations, are
summed, and obtained equations are self-consistently solved for the ranges of
Hubbard repulsions $2t\leq U\leq 10t$, temperatures $0.2t\lesssim T\lesssim t$
and electron concentrations $0.7\lesssim\bar{n}\leq1$ with $t$ the intersite
hopping constant. For all considered $U$ the system exhibits a transition to
the long-range antiferromagnetic order at $T_{\rm AF}\approx 0.2t$. At the same
time no indication of charge ordering is observed. Obtained solutions agree
satisfactorily with results of other approaches and obey moments sum rules. In
the considered region of the $U$-$T$ plane, the curve separating metallic
solutions passes from $U\approx6t$ at the highest temperatures to $U=2t$ at
$T\approx T_{\rm AF}$ for half-filling. If only short-range fluctuations are
allowed for the remaining part of this region is occupied by insulating
solutions. Taking into account long-range fluctuations leads to strengthening
of maxima tails, which transform a part of insulating solutions into bad-metal
states. For low $T$, obtained results allow us to trace the gradual transition
from the regime of strong correlations with the pronounced four-band structure
and well-defined Mott gap for $U\gtrsim6t$ to the Slater regime of weak
correlations with the spectral intensity having a dip along the boundary of the
magnetic Brillouin zone due to an antiferromagnetic ordering for $U\lesssim3t$.
For $T\approx T_{\rm AF}$ and $U\gtrsim 7t$ doping leads to the occurrence of a
pseudogap near the Fermi level, which is a consequence of the splitting out of
a narrow band from a Hubbard subband.
