  Quantum dynamics and kinetics of electrically gated graphene ribbons with
lateral n-p and e-n-p junctions under magnetic field are investigated. It is
shown that the snake-like states of quasiparticles skipping along the n-p
interface do not manifest themselve in the main semiclassical part of the
ribbon conductance. Giant oscillations of the conductance of a ribbon with an
n-p-n junction are predicted and analytically calculated. Depending on the
number of junctions inside the ribbon its magnetoresistance may be controllably
changed by 50% - 90% by an extremely small change of the magnetic field or the
gate voltage.
