1. A method for providing a nuclear magnetic resonance (NMR) angiographic projection image of flowing fluids in at least a selected portion of a sample, comprising the steps of: (a) immersing the sample in a main static magnetic field; (b) nutating, in the initial portion of each of a first sequence and a second sequence of a sequential pair of imaging sequences, the spins of all nuclei of a selected species; (c) providing an evolution time interval after step (b) in each of the pair of sequences; (d) applying, in the evolution time interval of at least one of the first and second sequences of each sequence pair, a pair of flow-encoding gradient field pulses in a first magnetic field gradient impressed upon the sample, in a first direction selected to establish one axis of the NMR angiographic projection image, to cause a resulting NMR response signal from the spin of moving nucleus to differ from the NMR response signal resulting from the spin of a substantially stationary nucleus; (e) then applying a magnetic field gradient pulse in a second direction, orthogonal to the first direction, to dephase, and enhance suppression of, response signals from spins from all stationary nuclei of the selected species; (f) then acquiring, responsive to at least a second magnetic field gradient impressed upon the sample in the second direction, a set of data from the NMR response signals evoked from at least the sample portion in each of a response data acquisition portion of the first and second sequences; (g) substracting the data of one of the NMR response signal data sets acquired in the first and second sequences from the data of the other data set to substantially remove response data obtained from the substantially stationary nuclei; and (h) generating, responsive to the remaining response data, the NMR angiographic projection image as a two-dimensional projection, lying in a plane in the first and second directions, of the fluid flow in the three-dimensional sample.