### 如何选择合适的时态

#### 时态的运用原则

##### 一般现在时

1、在阐述资料背景时,内容不受时间影响,是普遍认定存在的现象。

As one of the main nutrients, P can be found in the sediment matrix in the forms of calcium, iron or aluminum complex salts and organic species, or adsorbed onto the surface of minerals and has a predominant role in cellular energetics as ATP and as an important part of many structural and biochemically functional components for cell growth of plants including algae.

2、在描述研究目的或主要活动时，以论文为主体导向在描述研究目的或主要活动时，以论文为主体导向。

The objectives of present study are mainly to model P adsorption processes by modified Langmuir isotherm and understand the influencing patterns of such factors as pH, zeta potential, ORP, and sediment composition.

3、叙述结论或提出建议的时候，一般使用现在时，可能也会使用一些情态动词或助动词。

In conclusion, P adsorption process has complicated mechanism and would be influenced by various factors. More attempts should be made for further understanding.

4、表格或图作为主语时

Fig. 4. (A) pH dependence of zeta potential and phosphorus adsorption of sample T1 f or example. It indicates that P sorbed and zeta potential have no necessary relationship, although phosphorus sorption may be influenced by surface charge.

##### 一般过去时

1、描述实验过程、试验方法和实验结果时。

Samples were stored wet in sealed Zip-lock bags at 41℃ until used. Back to laboratory the sediment samples were air-dried at room temperature.

2、文章撰写之前某一时间的发现、研究过程或最终试验结果（作者作为主语时）。

Laboratory experiments with Fe(OOH) showed that pH increases produced liberation of P adsorbed onto the iron complexes because of competition with $OH^-$ ions(Lijklema, 1977).

Introduction部分会有部分类似于小综述用来介绍前人研究成果。

##### 现在完成时

1、内容为对某种研究趋势的概述。

NAP content and sorption characteristics have been correlated with sediment composition such as active iron, aluminum, and organic matter content, and in turn, sediment composition has been related with lake chemistry, i.e., with hardness, alkalinity, and pH.

### 如何选择合适的语态

#### 语态的运用原则

• 科技论文主要说明事实，一般用被动语态；
• 主动语态可以让文章读起来相对简单易懂；
• 具体使用哪种语态，取决于句子所要强调的重点，同时考虑表达的精炼和准确。
##### 什么时候使用被动语态
1. 阐述客观真理
2. 行动者未知或无关紧要
3. 强调被行动的人或事

P can be found in the sediment matrix in the forms of calcium.

At each sampling site three cores were used to collect the sediment and upper 5cm sediment of each core was sliced and mixed together to obtain relative homogenized materials.

##### 什么时候避免被动语态

In this study, we investigated....