We consider the fourth-order two-point boundary value problem u′′′′+Mu=λh(t)f(u), 0<t<1, u(0)=u(1)=u′(0)=u′(1)=0, where λ∈ℝ is a parameter, M∈(-π4,π4/64) is given constant, h∈C([0,1],[0,∞)) with h(t)≢0 on any subinterval of [0,1], f∈C(ℝ,ℝ) satisfies f(u)u>0 for all u≠0, and lim⁡u→-∞f(u)/u=0, lim⁡u→+∞f(u)/u=f+∞, lim⁡u→0f(u)/u=f0 for some f+∞,f0∈(0,+∞). By using disconjugate operator theory and bifurcation techniques, we establish existence and multiplicity results of nodal solutions for the above problem.