  We have investigated the in-plane $I(V)$ characteristics and the Josephson
vortex flow resistance in high-quality La-free
Bi$_{2+x}$Sr$_{2-x}$CuO$_{6+\delta}$ (Bi2201) single crystals in parallel and
tilted magnetic fields at temperatures down to 40 mK. For parallel magnetic
fields below the resistive upper critical field $H^{*}_{c2}$, the $I(V)$
characteristic obey a power-law with a smooth change with increasing
magnetic-field of the exponent from above 5 down to 1. In contrast to the
double-layer cuprate Bi2212, the observed smooth change suggests that there is
no change in the mechanism of dissipation (no Kosterlitz-Thouless transition)
over the range of temperatures investigated. At small angles between the
applied field and the $ab$-plane, prominent current steps in the $I(V)$
characteristics and periodic oscillations of Josephson-vortex flow resistance
are observed. While the current steps are periodic in the voltage at constant
fields, the voltage position of the steps, together with the flux-flow voltage,
increases nonlinearly with magnetic field. The $ab$-flow resistance oscillates
as a function of field with a constant period over a wide range of magnetic
fields and temperatures. The current steps in the $I(V)$ characteristics and
the flow resistance oscillations can be linked to the motion of Josephson
vortices across layers.
