  In this article we perform the Wheeler-DeWitt quantization for Bianchi type
$I$ anisotropic cosmological model in the presence of a scalar field minimally
coupled to the Einstein-Hilbert gravity theory. We also consider the
cosmological (perfect) fluid to construct the matter sector of the model whose
dynamics plays the role of time. After obtaining the Wheeler-DeWitt equation
from the Hamiltonian formalism, we then define the self-adjointness relations
properly. Doing that we proceed to get a solution for the Wheeler-DeWitt
equation and construct a well behaved wave function for the universe. The
unitary evolution of the wave function in the presence of the scalar field is
finally restored by an appropriate choice of weight factor in defining the norm
of the wave packet. It is then concluded that the Big-Bang singularity can be
removed in the context of quantum cosmology.
