[en] A weak-coupling approximation for the spectroscopy of medium-mass and heavy nuclei within the framework of nuclear shell theory is discussed. An exact shell-model calculation and a weak-coupling calculation have been performed, for the low-lying energy levels of sup(93-100)Mo isotopes, in a model space consisting of 2psub(1/2), 1gsub(9/2) proton orbits and 2dsub(5/2) 3ssub(1/2) neutron orbits outside a ⁸⁸Sr core. The effective two-body interaction used is that determined from a fit to the experimental data on some Zr and Nb isotopes. The results of the two calculations are in reasonable good agreement with each other and with experiment although the dimensionalities of matrices in the weak-coupling calculation are much smaller compared with those in the exact shell-model calculation. Using the wavefunctions of states obtained from the weak-coupling calculation, reduced transition strengths for various electromagnetic transitions in the Mo isotopes have also been calculated. (author)