Some conditions on the existence of the firstintegral are given via the properties of equilibria and limit sets.
利用奇点和有限集的特征，给出了首次积分存在的某些条件。
2
This paper has found general integral formulas of some types of two - order nonlinear ordinary differential equations by firstintegral.
本文对几类二阶非线性常微分方程，利用首次积分求得了其通积分公式。
3
By the firstintegral method, the existence, uniqueness and nonexistence of solutions for some nonlinear ordinary differential equations with singular boundary condition are discussed.