  Results of inclusive measurements of inelastic electron and positron
scattering from unpolarized protons and deuterons at the HERMES experiment are
presented. The structure functions $F_2^p$ and $F_2^d$ are determined using a
parameterization of existing data for the longitudinal-to-transverse
virtual-photon absorption cross-section ratio. The HERMES results provide data
in the ranges $0.006\leq x\leq 0.9$ and 0.1 GeV$^2\leq Q^2\leq$ 20 GeV$^2$,
covering the transition region between the perturbative and the
non-perturbative regimes of QCD in a so-far largely unexplored kinematic
region. They are in agreement with existing world data in the region of
overlap. The measured cross sections are used, in combination with data from
other experiments, to perform fits to the photon-nucleon cross section using
the functional form of the ALLM model. The deuteron-to-proton cross-section
ratio is also determined.
