曼彻斯特大学语料库1. Writing about the Past-如何准确使用过去式Writing about the PastWriting about the past in English is made diffcult by the rather complex tense system. However the phrases grouped below give an indication of the uses of the main tenses in academic writng. For a comprehensive explanation of the uses of the various tenses you will need to consult a good English grammar book. A good recommendation is Practical English Usage by Michael Swan, OUP.Time phrases associated with the use of the simple past tense (specific times or periods of time in the past completed)For centuries,In the second half of the 19th century,At the end of the nineteenth century,church authorities placed restrictions on academics.During the Nazi period,Between 1933 and 1945,From 1933 to 1945,In the 1930s and 1940s,restrictions were placed on German academics.Reference to single investigations or publications in the past: simple past tense usedThe first systematic study of the X was reported by Patel et al. in 1986.Erythromycin was originally isolated from X in a soil sample from . (Wang et al., 1952). In 1975, Smith et al. published a paper in which they described . In 1990 Patel et al. demonstrated that replacement of H2O with heavy water led to .Thirty years later, Smith (1974) reported three cases of Candida Albicans which .In the 1950s Gunnar Myrdal pointed to some of the ways in which (Myrdal, 1957)In 1981, Smith and co workers demonstrated that X induced in vitro resistance to .In 1984 Jones et al. made several amino acid esters of X and evaluated them as water-soluble pro-drugs.An experimental demonstration of this effect was first carried out by .The first experimental realisation of ., by Smith et al. 12, used a .Time phrases associated with the use of the present perfect tense (for situations/actions which began in the past and continue up to the present, or for which the period of time is unspecified):Over the past few decades, the world has seen the stunning transformation of X, Y and Z.Since 1965, these four economies have doubled their share of world production and trade. Until recently, there has been little interest in X.Recently, these questions have been addressed by researchers in many fields.In recent years researchers have investigated a variety of approaches to X but .Up to now, the research has tended to focus on X rather than on Y. To date, little evidence has been found associating X with Y.So far, three factors have been identified as being potentially important: X, Y, and Z.The present perfect tense may also be used to describe recent research or scholarly activity with focus on the area of enquiry - usually more than one studyThere have been several investigations into the causes of illiteracy (Smith, 1985; Jones, 1987).The relationship between a diet high in fats and poor health has been widely investigated (Smith, 1985, Jones, 1987, Johnson, 1992).The new material has been shown to enhance cooling properties (Smith, 1985, Jones, 1987, Johnson, 1992). Invasive plants have been identified as major contributing factors for the decline of many North American species (1).A considerable amount of literature has been published on X.2. Discussions-如何展开讨论DiscussionsThe term discussion has a variety of meanings in English. In academic writing, however, it usually refers to two types of activity: a) considering both sides of an issue, or question, b) considering the results of research and the implications of these. Discussion sections in dissertations and research articles are probably the most complex in terms of their elements. The most common elements and some of the language that is typically associated with them are listed below:Background information (reference to literature or to research aim/question)A strong relationship between X and Y has been reported in the literature.Prior studies that have noted the importance of .In reviewing the literature, no data was found on the association between X and Y. As mentioned in the literature review, . Very little was found in the literature on the question of . This study set out with the aim of assessing the importance of X in .The third question in this research was .It was hypothesized that participants with a history of .The present study was designed to determine the effect of .Statements of result (usually with reference to results section)The results of this study show/indicate that .This experiment did not detect any evidence for .On the question of X, this study found that .The current study found that .The most interesting finding was that . Another important finding was that .The results of this study did not show that ./did not show any significant increase in .In the current study, comparing X with Y showed th