  The magnetic field driven superconductor/insulator transition is studied in a
large variety of $La_{2-x}Sr_xCuO_4$ thin films of various Sr dopings.
Temperature dependence of the resistivity down to 4.2 or 1.5 K under high
pulsed magnetic field (up to 57 T) is analyzed. In particular, the existence of
plateaus in the resistance versus temperature curves, in a limited range of
temperature, for given values of the magnetic field is carefully investigated.
It is shown to be associated to scaling behaviour of the resistance versus
magnetic field curves, evocative of the presence of a quantum critical point. A
three-dimensional (H,x,T) phase diagram is proposed, taking into account the
intrinsic lamellar nature of the materials by the existence of a temperature
crossover from quantum-two-dimensional to three-dimensional behavior.
