[en] Possibilities of extracting information about the integral and differential properties of the excited states of complex nuclei from the experimental data on nuclear reactions are analysed. The fragmentation of few-quasiparticle states and the nuclear properties defined by it are calculated at low, intermediate, and high excitation energies within the quasiparticle-phonon model. Some examples are considered: vibrational states in deformed nuclei (Coulomb excitation, inelastic scattering of particles and nuclei on nuclei), neutron and radiative strength functions ((n,n), (nß) and (ß,n) reactions), fragmentation of deep hole states (reactions of the type (₃He,α) and (d,₃He)), and giant resonances (reactions of the type (ß,ß'), (e,e'), (p,p') and (α,α'))