A magnetic resonance apparatus has a cylindrical body coil composed of a number of resonator segments distributed around the circumference and a control device for separate activation of the individual resonator segments. The resonator segments are electromagnetically decoupled from one another. The activation generates a radio-frequency magnetic field inside the coil for spin excitation in an examination volume. The resonator segments are activated such that the excitation field is generated only in at least one first sub-volume forming the examination volume, and at least one second sub-volume, that is not to be excited, is essentially free of the excitation field.