We study the system of equations for the canonically conjugate variables p and q specified by the one-dimensional Hamiltonian H=H(p,q,Λ(1),...,Λ(N)) dependent on Nself-consistent slightly changing parameters obeying the equations: Λ(n)=εf(n)(Λ(1),...,Λ(N),p,q). A broad range of oscillatory and wave processes with weak dissipation is described by analogous systems. The general method of adiabatic invariant construction for this system is proposed. Self-consistent averaged equations for the evolution of the action integral and the parameters Λ(n) are obtained. The constructed theory is applied to a generalized model of the nonlinear resonance. The autoresonance (phase locking) regime of decay parametric instability in a dissipative medium is revealed.