中文摘要：

通过对几个著名小组G JR,MSTW和CTEQ的领头阶部分子分布函数进行仔细分析和比较,包括分析在不同动量标度下它们的价夸克、海夸克和胶子的分布函数以及各种部分子所占有的质子总动量,发现在小x区域,不同研究小组的胶子和海夸克的分布函数差别非常明显,说明人们对它们的认识还远未清晰.通过计算分析高扭度效应对部分子分布函数的影响,发现遮蔽效应使小x和中x区域的扭度-4的胶子和海夸克的分布函数略小于扭度-2的分布函数,反遮蔽效应使x（≥）2区域的扭度-4的胶子和海夸克分布函数大于相应的扭度-2的分布函数.最后,从数值计算角度验证了MD-DGLAP演化方程是符合动量守恒定律的。

英文摘要：

We present the parton distributions at leading order （LO） coming from GJR,MSTW and CTEQ parton sets and compare them at different momentum scales.Obvious differences exist in their gluon and sea quark distributions at small x region.Itindicates that people have not known the nucleon parton distributions very well.We analysze the influence of higher twist effects,i.e.,the shadowing effects and anti-shadowing effects,on parton distributions.Because of the shadowing effects,the twist-4 gluon and sea quark distributions are smaller than the twist-2 distributions at small and middle x region,while,the anti-shadowing effects make the twist-4 gluon and sea quark distributions larger than the twist-2 distributions at x （≥） 2 region.Finally,we present a detailed analysis of how the proton＇s momentum is shared among various parton flavors at different Q2 for different parton sets.With the numerical calculation,we show that the MD-DGLAP equations are momentum conservation.