The thesis is devoted to obtaining new experimental data on isomer ratios in the high-threshold photonuclear reactions with multiple particles escape. The electron linear accelerator LU-40 of KIPT NIR "Accelerator" served as a source of bremsstrahlung. Measurements were performed using a spectrometer with high purity germanium detector of Canberra company, model GC2019. For the experimental determination of the isomer ratios the method of direct ?-spectrum measurements of activation products of photonuclear reactions without prior radiochemical separation was applied. Irradiations of samples were performed in the energy range of incident bremsstrahlung up to 32-84 MeV. To calculate the characteristics of nuclear reactions and isomeric ratios the TALYS code was used. To obtain more precise parameters of GDR the EMPIRE II code was applied. 22 new values for the isomer ratios of photonuclear reactions 107Ag(g, 3n)104m, gAg, 109Ag(g, 5n)104m, gAg, 113In(g, 3n)110m, gIn, 105In(g, 5n )110m, gIn, 115In(g, 7n)108m, gIn, 90Zr(g, 2np)87m, gY, 90Zr(g, 3np)86m, gY, 91Zr(g, 3np)87m, gY, 91Zr(g, 4np )86m, gY, 54Fe(g, np)52m, gMn were obtained for the first time and incorporated into the international database EXFOR (CSISRS). A new approach was proposed to determine the isomer ratios for isomeric pairs for which due to beta-decay from isomeric and ground states the gammas irradiation from the nuclei in output channel takes place via the same nuclear level. The method was developed to determine the isomer ratios in photonuclear reactions with multiple neutrons and proton escape taking into account the contribution of precursor-nuclei in isobaric decay chain. The procedure to calculate the GDR parameters with all available output nuclear reaction channels considered for the compound-nucleus decay under the Hauser - Feshbach statistical model was suggested and tested. For 60Ni, 63Cu, 64Zn nuclei the GDR parameters were evaluated based on accounting of all output channels of photonuclear reactions
