环

Other semirings arise naturally in such diverse areas of mathematics as combinatorics, functional analysis, topology, graph theory, Euclidean geometry, probability theory, commutative and noncommutative ring theory, optimization theory, discrete event dynamical systems, automata theory, formal language theory and the mathematical modeling of quantum physics and parallel computation systems.

在许多不同的数学领域存在着其它形式的半环，比如组合学，泛函分析，拓扑学，图论，欧式几何，概率论，交换和非交换环，优化论，离散动力系统，自动化理论，形式语言理论，量子物理的数据模型和并行计算系统。

Polynomial function ; Finite commutative ring ; Finite commutative local ring; Teichmller representatives; Witt polynomial

基础科学，数学，代数、数论、组合理论多项式函数；有限交换环；有限交换局部环； Teichmller提升； Witt多项式

Commuta-tivity is one of important properties on rings. Study of commutativity is beneficial to discussion of other properties on rings.

同时，交换代数本质上是研究交换环的，这就使得环的交换性的研究变得很重要。

The pump speeds are controlled through a closed-loop digital system, the same as is used for the cutter and compactor drives.

泵的速度通过一个闭环数字系统得以控制，和切割器及压缩器驱动上使用的闭环数字系统一样。

Based on this,449 counties,districts or cities in the Huanbohai Zone are selected for an analysis of their regional structures using principle compo...

我们对环渤海湾地区所有的449个县、市、区的就业人口结构和空间分布特征进行主成分分析和聚类分析，探讨相应都市区的结构特征以及都市区的空间组合特征等，进而确定了环渤海湾地区的内部结构。

Objective : The protective effect of bicyclol on concanavalin A induced liver nuclei DNA injury in mice was studied.

目的：通过研究双环醇对刀豆蛋白A引起小鼠肝脏细胞核和DNA损伤的保护作用而进一步探讨双环醇的作用机制。

A magnetic spring was developed,which consists of two magnetic rings with different dimension,locating concentrically with same direction of magnetization.

研制了一种磁力弹簧，它由直径大小不同的两个磁环同轴同向排列，其中一环固定，另一环可轴向滑动，组成磁力弹簧。

Target compounds have been synthesized by condensation of the aromatic nucleus and amino heterocylcle with acyl isocyanates or acylisothiocyanates in absolutely anhydrous and aprotic solvent.

为了寻找高活性的农药品种，利用生物等排原理和亚结构连接法，对脲类化合物的母体结构进行了修饰，将芳氧羧酸类及吡唑环引入酰基脲母体结构中，利用酰基异氰酸酯与杂芳环胺类化合物在无水非质子溶剂中发生亲核加成反应，合成了四个系列21种新的酰基脲类目标化合物。

This paper introduces the sufficient conditions of the similarity between someparticular block matrix on the division rings.

给出除环上某些特殊块阵的相似的充分条件，并具体给出了对于除环上n阶阵A和B，AB与BA的群逆都存在的充分必要条件，并推广了Cao等人"在两个矩阵乘积群逆的逆序法则"文章中一个结论。

1H NMR spectroscopic analysis of aromatic protons combined with theoretical analysis of molecular structures proved the existence of two rotational isomers at 300 K, as well as a rapid interconversion equilibrium at 330 K for both compounds Ⅰ and Ⅱ. However, only one conformer exists for compound Ⅲ and puerarin containing 7-phenolic hydroxyl instead of propyl in A-ring as the case of compounds Ⅰ and Ⅱ. Based on UV-Visible absorption data of neutral and basic solutions, and on the density function calculations, the 7-phenolic hydroxyl group in A-ring was found to be more acidic than the 4'-phenolic hydroxyl group in B-ring. The mechanism of derivation reaction and the structure-reactivity relationship of puerarin as an antioxidant were further discussed.

其中7-丙基葛根素Ⅱ属于新型取代衍生物；变温1H NMR和理论计算结果表明，在300 K时，葛根素和4'-丙基葛根素以单一构型存在；而7，4'-二丙基葛根素和7-丙基葛根素则存在两种核磁可分辨的旋转异构体，当温度升至330 K时，两种异构体可以相互转化；通过对比分析葛根素及其衍生物脱质子产物的紫外可见吸收光谱并结合理论计算，确定了A环上7位酚羟基比B环上4'位酚羟基先脱去质子，并由此进一步阐明了葛根素衍生化反应机理以及在抗氧化作用中可能的活性位点和结构活性关系。

Since historical times,England ,where the early inhabitants were Celts, has been conquered three times .

从有历史以来，英国，在此地早期居住的是凯尔特人，已经被征服了三次。

Bluetooth OBEX File Transfer Enables the sending and receiving of files on your phone via Bluetooth.

蓝牙OBEX文件移动允许经过蓝牙传送和接受文件。。。。