当...时

He entered the room, turned on the light and read an evening paper.

当两个或两个以上的动作用 and 或 but 连接时，按时间顺序只需用一般过去时代替过去完成时；另外在引导的从句中由于这些连词本身已经表示时间的先后，因此也可以用过去时来代替过去完成时

Results The direct flow rate reached 0.549L/min when pressure difference was 4.90kPa(500mmH_2O), and the antidromic flow rate only reached 0.028L/min when pressure difference was 4.90kPa(500mmH_2O), the direct flow rate is much more than the antidromic flow rate.

结果：当瓣膜两端顺向的压强差为4.90kPa(500mmH_2O)时，流量可达0.549L/min；当瓣膜两端逆向的压强差为4.90kPa(500mmH_2O)时，流量为0.028L/min，顺向压差的流量大于逆向压差的流量。

The result indicated that the animal occurred respiratory acidosis when IAP got 15mmHg,and occurred hypotension and ologuresis or anuresis..

结果表明，当腹腔压力达到15mmHg时机体病理生理改变即可出现酸中毒，当腹腔压力达到20mmHg时继而出现低血压、少尿、无尿等症状。

For the case of n=2 and X〓 is generic, by using Picard-Fuchs equations and the argument principle Horozov and Iliev [36] gave the least upper bound of the number of zeros of I under the condition that X〓 has one center and three saddles.

当n=2且X〓为通有的Hamilton系统时，Horozov和Iliev[36]利用幅角原理和Picard-Fuchs方程给出了当X〓有一个中心、三个鞍点时I零点上确界的个数。

As in Volume 2, where I found to my delight that the basic principles of elementary probability theory and number theory arose naturally in the study of algorithms for random number generation and arithmetic, I learned while preparing Section 7.2.1 that the basic principles of elementary combinatorics arise naturally and in a highly motivated way when we study algorithms for combinatorial generation.

如同在第二卷中那样，在那里我高兴地发现，初等概率论和数论的基本原理很自然地出现在关于随机数生成和算术的算法的研究中。而当我准备编写7.2.1小节时，我注意到，当我们研究组合生成的算法时，初等组合学的基本原理自然地并以高度带激励的方式出现。

The most such sciences can do is to help us to catch ourselves up and check ourselves, if we start to reason or to behave wrongly; and to criticize ourselves more articulately after we have made mistakes.

这些科学能够做的最多是当我们开始推理错误或者行为错误时帮助我们追上自己，检查自己，当我们犯错时，能够让我们更明白地批评自己。

As Professor Auerbach explains, most law teachers would agree that rationality is a basic value because "a body of law is more rational and civilized when every rule it contains is referred articulately and definitely to an end which it subserves, and when the grounds for desiring that end are stated or are ready to be stated in words".

正如奥尔巴克教授所言，大多数法学教师都同意理性是基本价值，因为"当法律所包含的每一规则明确、清楚地谈及它要达到的目的之时，以及当意欲达成这一目的的理由以文字表述出来或者将要表述出来之时，法律会更理性、更文明"。

The paper studies the asymptotic behavior of "interior point" on the second mean value theorem for integrals when the length of integral interval tends to be infinite,and the asymptotic estimation formulas under very weak conditions are given.

讨论当积分区间长度趋于无穷大时，积分第二中值定理的"中间点"的渐近性态，在较弱的条件下，获得积分第二中值定理的"中间点"当积分区间长度趋于无穷大时的渐近估计式。

It is proved that, when the value of critical threshold less than 1, the disease free equilibrium point is globally asymptotically stable. Further more, Bursaphelenchtis Xylophilus is used to construct the Lyapunov function, and the stability theory of Lyapunov function is used to prove that the equilibrium point is Global asymptotic stable. It explains that the Bursaphelenchus Xylophilus wiil eventually disappear.

证明了当临界阈值小于1时，无病平衡点是局部渐近稳定的，进一步利用巴尔巴欣公式构造Lyapunov函数，运用Lyapunov稳定性理论证明了该平衡点的全局渐近稳定性，说明松材线虫病会最终消失；当临界阈值大于1时，病虫害平衡点是局部渐近稳定的。

When we study at school. When we play with our friends.

当我们在学校里学习时，当我们和朋友玩耍时。

I will endeavour to find you some assistance.

我尽力帮你找人帮忙。

At first I only know bruck is the idol of American younglings, afterwards I returned back to Taiwan ,even in Beijing last year ,I saw her poster everywhere, I was so surprised at her charm.

起初我只晓得布鲁克雷德丝是美国少男少女崇拜的偶像，后来回台湾，甚至去年在北京，居然也四处看见她的海报，才惊讶她的魅力之大。