  Transport through a 1D Mott-Hubbard insulator of a finite length $L$ is
studied beyond perturbative approach. At special value of the low energy
constant of the interaction we have mapped the problem onto the exactly
solvable models and found current vs. voltage $V$ at high temperature
$T>max(m,T_L)$ and at low energy $T,V<T_L$ ($T_L=v_c/L$; $v_c:$ charge
velocity). The result shows that for the strong interaction creating a large
Mott-Hubbard gap $2m \gg T_L $ inside the wire, the transport is suppressed
near half-filling everywhere inside the gap except for an exponentially small
region of $V,T < T_L exp(-2m/T_L)$.
