如果句子的内容是不受时间影响的普遍事实, 应使用现在式；如果句子的内容是对某种研究趋势的概述, 则使用现在完成式。 如：
The authors review risk and protective factors for drug abuse, assess a number of approaches for drug abuse prevention potential with high-risk groups, and make recommendations for research and practice.
Previous research has confirmed four dimensions of temperament: ….
2.2.2 叙述研究目的或主要研究活动
如采用“论文导向”, 多使用现在式（如：This paper presents…）; 如采用“研究导向”, 则使用过去式（如：This study investigated…）.
This article summarizes research on self-initiated and professionally facilitated change of addictive behaviors using the key transtheoretical constructs of stages and processes of change.
We investigated whether captopril could reduce morbidity and mortality in patients with left ventricular dysfunction after a myocardial infarction.
2.2.3 概述实验程序、方法和主要结果 通常用现在式。
We describe a new molecular approach to analyzing the genetic diversity of complex microbial populations.
Our results indicate that p21 may be a universal inhibitor of cyclin kinases.
2.2.4 叙述结论或建议
可使用现在式、臆测动词或may, should, could等助动词。
We suggest that climate instability in the early part of the last interglacial may have delayed the melting of the Saalean ice sheets in America and Eurasia, perhaps accounting for this discrepancy.
可见, 为简洁、清楚地表达研究成果, 在论文摘要的撰写中不应刻意回避第一人称和主动语态。
3 摘要的常用表达方法
由于摘要的英文表达要求用词简明、层次清楚, 因此掌握一些特定的规范表达, 甚至建立一个适合自己需要的“句型库”(stock phrases), 对于摘要的撰写是很有帮助的。本文所选取的例句均源于SCI收录的1992 - 2002年间发表、并具较高被引频次的论文（前100位）摘要（选取例句时偏重于第一人称和主动语态）。
3.1 引言部分
3.1.1 回顾研究背景 常用词汇有：review, summarize, present, outline, describe等。 如：We review evidence for this view of addiction and discuss its implications for understanding the psychology and neurobiology of addiction.
This paper outlines some of the basic methods and strategies and discusses some related theoretical and practical issues.
3.1.2 阐明写作或研究目 常用词汇有：purpose, attempt, aim等。另外还可以用动词不定式充当目的状语来表达。如：
We attempt to recover a function of unknown smoothness from noisy sampled data.
To investigate the mechanism of Bcl-2's effect, we examined whether Bcl-2 interacted with other proteins.
3.1.3 介绍论文的重点内容或研究范围 常用的词汇有：study, present, include, focus, emphasize, emphasis, attention等。
Here we study the dependence of apoptosis on p53 expression in cells from the thymus cortex.
This article includes a brief review of the physics underlying HERWIG, followed by a description of the program itself.
3.2 方法部分
3.2.1 介绍研究或试验过程 常用词汇有：test, study, investigate, examine, experiment, discuss, consider, analyze, analysis等。
We use N-body simulations to investigate the structure of dark halos in the standard cold dark matter cosmogony.
We present an analysis of atmospheric neutrino data from a 33. 0 kton yr (535-day) exposure of the Super-Kamiokande detector.
3.2.2 说明研究或试验方法 常用词汇有：measure, estimate, calculate等。
We have developed a global model to estimate emissions of volatile organic compounds from natural sources (NVOC).
This study presents estimates of lifetime and 12-month prevalence of 14 DSM-III-R psychiatric disorders from the National Comorbidity Survey, …
3.2.3 介绍应用、用途 常用词汇有：use, apply, application等。
Our program uses a maximum likelihood approach and is based on version 3. 3 of Felsenstein's dnaml program.
As an application, we implement a compact image coding algorithm that selects important edges and compresses the image data by factors over 30.
3.3 结果部分
3.3.1 展示研究结果 常用词汇有：show, result, present等。
We show this cell death to be dependent upon expression of c-myc protein and to occur by apoptosis.
Our results suggest a widespread role for the nitric oxide-cyclic guanosine monophosphate system in the nervous system.
3.3.2 介绍结论 常用词汇有：summary, introduce, conclude等。
We introduce a procedure, SureShrink, that suppresses noise by thresholding the empirical wavelet coefficients.
By means of informal mathematical arguments, simulations and a series of worked examples, we conclude that PQL is of practical value for approximate inference on parameters and realizations of random effects in the hierarchical model.
3.4 讨论部分
3.4.1 陈述论文的论点和作者的观点 常用词汇有：suggest, report, present, explain, expect, describe等。
The results suggest that abnormalities in male sex development induced by p, p'-DDE and related environmental chemicals may be mediated at the level of the androgen receptor.
In this study, we describe a psychobiological model of the structure and development of personality that accounts for dimensions of both temperament and character.
3.4.2 阐明论证 常用词汇有：support, provide, indicate, identify, find, demonstrate, confirm, clarify等。
We showed that it is possible to identify constituents which represent only 1% of the total population.
These results demonstrate that p53 is required for radiation-induced cell death in the thymus but is not necessary for all forms of apoptosis.
3.4.3 推荐和建议 常用词汇有：suggest, suggestion, recommend, recommendation, propose, necessity, necessary, expect等。
The authors suggest that the most promising route to effective strategies for the prevention of adolescent alcohol and other drug problems is through a risk-focused approach.
We propose two algorithms to estimate the significance level for a test of HWP.
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