In this work we study the electronic transport in atomic and molecular structures. By using the Green´s function method, we address the problem of the electron-electron and electron-phonon interactions and their effects on the conductance of the system. We present a detailed study of the regime where these two interactions are simultaneously important and show that they produce new effects on the properties of the system. In the Coulomb blockadge regime, the Rabi splitting due to the electron- phonon interaction produces a new effect in the conductance of nanosystem, which we called Rabi-assisted ressonant tunneling. In the Kondo regime, this splitting is responsible for a new phenomena, the non integer-charge Kondo effect.