  We have studied the temperature dependence of resistivity, $\rho$, for a
two-dimensional electron system in silicon at low electron densities,
$n_s\sim10^{11}$ cm$^{-2}$, near the metal/insulator transition. The
resistivity was empirically found to scale with a single parameter, $T_0$,
which approaches zero at some critical electron density, $n_c$, and increases
as a power $T_0\propto|n_s-n_c|^\beta$ with $\beta=1.6\pm0.1$ both in metallic
($n_s>n_c$) and insulating ($n_s<n_c$) regions. This dependence was found to be
sample-independent. We have also studied the diagonal resistivity at Landau
level filling factor $\nu=3/2$ where the system is known to be in a metallic
state at high magnetic field and in an insulating state at low magnetic field.
The temperature dependencies of resistivity at $B=0$ and at $\nu=3/2$ were
found to be identical. These behaviors suggest a true metal/insulator
transition in the two dimensional electron system in silicon at $B=0$, in
contrast with the well-known scaling theory.
