查询词典 if and only if

Theorem 1 A series of nonnegative terms converges if and only if it's partial sums are bounded above.

定理1 正项级数收敛的充分必要条件是：它的部分和数列有上界。

Xu Jinzhong proved that a simple module over commutative ring is injective if and only if it is flat.

徐金中证明了交换环上单模是内射的当且仅当它为平坦的。

Then f has β-differentiability property if and only if each level set of f〓 has ω〓-β-exposed property.

则f具有β-可微性质的充分必要条件是f〓的每个水平集具有ω〓-β-暴露性质。

A finite distributive lattice is called a matchable distributive lattice if and only if there exists a plane weakly elementary bipartite graph such that.

一个有限分配格L称为匹配分配格当且仅当存在一个平面弱基本二部图G使得ML。

Let R be a ring with identity. Then R is a division ring if and only if every unitary module over R is a free module.

R 是有单位元的环，它是除环的充分必要条件是其上的所有幺模都是自由模。

As a consequence, we make a conclusion that the dual Toeplitz operator is normal if and only if the range of the symbol lies on a line.

在此基础上研究了对偶Toeplitz算子的正规性，得到了对偶Toeplitz算子是正规算子的充分必要条件。

We show a matrix A is similar to an orthogonal matrix over a field of characteristic 2 if and only if ( 1 ) the invariant factors of A are symmetic,(2) A has at least an elementary divisor of the form ( x + 1 ) m.

本文利用矩阵方程证明如下两个结果：设F为一个域char=2，在F上矩阵A相似于一个正交矩阵的充要条件为(1)A的不变因子是对称的。(2)A至少有一个形为(X十1)的初等因子。

It is obtained that a fuzzy mapping is convex if and only if the epigraph of this fuzzy mapping is a fuzzy set in R×E.

在此基础上，得到了一个实变量模糊数值映射是凸模糊映射的充分必要条件：这个实变量模糊数值映射的上方图是R×E中的一个凸集。

Furthermore, it is shown that every pure projective left R-module is closed under pure submodule if and only if every pure injective left R-module is closed under pure epimorphic image.

最后，作为应用，证明了每一纯投射左R-模在纯子模下封闭当且仅当每一纯内射左R-模在纯满像下封闭。

It is proved that a left R-module P is pure projective if and only if for any pure epimorphism E→M→0, where E is pure injective, Hom→Hom→0 is exact.

证明了左R-模P是纯投射的当且仅当对任意纯满射E→M→0，其中E是纯内射的，Hom→Hom→0是正合的。

However, as the name（read－only memory）implies, CD disks cannot be written onorchanged in any way.

然而，正如其名字所指出的那样，CD盘不能写，也不能用任何方式改变其内容。

Galvanizes steel pallet is mainly export which suits standard packing of European Union, the North America. galvanizes steel pallet is suitable to heavy rack. Pallet surface can design plate type, corrugated and the gap form, satisfies the different requirements.

镀锌钢托盘多用于出口，替代木托盘，免薰蒸，符合欧盟、北美各国对出口货物包装材料的法令要求；喷涂钢托盘适用于重载上货架之用，托盘表面根据需要制作成平板状、波纹状及间隔形式，满足不同的使用要求。