过去完成时

2 A clear glass capillary tube is fixed vertically in a beaker.

例2的问题是时态不统一，一般现在时和一般过去时交替使用，给读者的感觉好象是这个实验是在过去和现在两个时空中完成的，这是不可思议的。

We use the present perfect tense to talk about things that started in the past and continue to the present.

我们用现在完成时来谈论一些过去的某一时间开始饿。而现在正在继续的事情

Have been doing sth.---the present prefect progressive.

现在完成进行时，强调动作的持续性，表示从过去某段时间以来开始进行的某个动作，延续到说话时，有可能还要进行下去。

Present tense indicates incomplete action and preterite tense indicates complete action, while permansive tense expresses a state or condition and usually takes a particle.

过去时是象征未完成的行为，过去时是象征完成的行为，而一般现在时是代表一种状态或情景，通常是捕获一个点。

When he grew up, he worked as a sailor on a riverboat for some time and therefore he got his pen name, Mark Twain .

文章的时态主要用过去时，最后两句与现在有关，因此用了现在完成时和一般现在时。

After a further analysis, the two intralingual factors, verb salience and temporal adverbials, are found to significantly affect simple past and present perfect use and their tense marking.

通过测试动词突显度和时间状语两种语内因素对一般过去时和现在完成时的影响，发现他们能够显著影响其使用和时态标记。

Finally,the concrete is placed around the reinforced by tremie and the "slurry"is displaced as the concrete rises to fill the trench.

但个别时候，为了便于说明某一事件的发展背景，也可采用过去时或现在完成时。

Finally,the concrete is placed around the reinforced by tremie and the "slurry"is displaced as the concrete rises to fill the trench.

但个别时候，为了便于说明某一事件的发展背景，也可采用过去时或现在完成时。比如

The suffix ''- ka -'' is attached to some perfects and aorists.

后缀 ''-ka-''被附加到某些完成时和不定过去时。

A combination of the two tenses and the two aspects makes it possible for a finite verb phrase to take the following eight forms

现在时和过去时既可以单独使用，也可以和进行体或完成体结合使用，也可以同时与完成体和进行体结合使用。

In this paper, the requirement analysis, design and implementation of the system are introduced in detail.

此论文详细介绍了系统的需求分析，系统设计和具体实现。

In the context of economic globalization is increasingly deepening, China's economy can not be spared.

在经济全球化日益加深的背景下，中国经济不可能做到独善其身。