  We study the Coulomb pseudogap for tunneling into the two-dimensional
electron system of high-mobility (Al,Ga)As/GaAs heterojunctions subjected to a
quantizing magnetic field at filling factor $\nu \leq 1$.
  Tunnel current-voltage characteristics show that for the double maximum
observed in the tunnel resistance at $\nu \approx 1$ the pseudogap is linear in
energy with a slope that depends on filling factor, magnetic field, and
temperature. We give a qualitative account of the filling factor dependence of
the pseudogap slope and we confirm the recently reported appearance of another
relaxation time for tunneling at $\nu \approx 1$. For the tunnel resistance
peaks at $\nu=1/3$ and 2/3 a completely different behaviour of the
current-voltage curves is found and interpreted as manifestation of the
fractional gap.
