| Acknowledgements | 第1-5页 |
| Abstract | 第5-6页 |
| 摘要 | 第6-11页 |
| Chapter 1 Introduction | 第11-14页 |
| ·Significance and purpose | 第11页 |
| ·Theoretical basis | 第11-12页 |
| ·Research questions | 第12-13页 |
| ·Organization | 第13-14页 |
| Chapter 2 Literature Review | 第14-25页 |
| ·Lexical diversity (richness) in writings | 第14-18页 |
| ·Lexical richness and quality of writing | 第14-15页 |
| ·Lexical features of Chinese learners’writing | 第15-16页 |
| ·Lexical diversity in first and second language acquisition | 第16-18页 |
| ·Lexical diversity measures | 第18-23页 |
| ·Lexical variation measure | 第18-21页 |
| ·Lexical sophistication measure | 第21-22页 |
| ·Lexical error dimension | 第22-23页 |
| ·Holistic ratings | 第23-24页 |
| ·Summary | 第24-25页 |
| Chapter 3 Methodology | 第25-28页 |
| ·Samples | 第25-26页 |
| ·Data analysis | 第26页 |
| ·Hypotheses and research questions | 第26-28页 |
| Chapter 4 Results | 第28-54页 |
| ·Results in three dimensions of lexical diversity | 第28-46页 |
| ·Results of lexical variation | 第29-32页 |
| ·Results of lexical sophistication | 第32-38页 |
| ·Results of lexical error | 第38-45页 |
| ·Summary | 第45-46页 |
| ·Results of the writing quality | 第46-48页 |
| ·Intercorrelations | 第48-51页 |
| ·The relationship between lexical variation and lexical sophistication | 第48-49页 |
| ·The relationship between lexical variation and lexical error | 第49-50页 |
| ·The relationship between lexical sophistication and lexical error | 第50页 |
| ·Summary | 第50-51页 |
| ·Lexical diversity and writing quality | 第51-54页 |
| ·The relationship between lexical variation and writing quality | 第51-52页 |
| ·The relationship between lexical sophistication and writing quality | 第52页 |
| ·The relationship between lexical error and writing quality | 第52-53页 |
| ·Summary | 第53-54页 |
| Chapter 5 Discussion | 第54-62页 |
| ·Discussion of the results of lexical diversity in TEM writings | 第54-60页 |
| ·Discussion of the results of lexical variation | 第54-55页 |
| ·Discussion of the results of lexical sophistication | 第55-57页 |
| ·Discussion of the results of lexical error | 第57-59页 |
| ·Summary | 第59-60页 |
| ·Discussion of the relationship between lexical diversity and writing quality | 第60-61页 |
| ·Summary | 第61-62页 |
| Chapter 6 Conclusion | 第62-67页 |
| ·Major findings | 第62-63页 |
| ·Implications | 第63-65页 |
| ·Limitations and suggestions | 第65-67页 |
| ·Limitations of the present study | 第65-66页 |
| ·Suggestions for future research | 第66-67页 |
| Bibliography | 第67-70页 |
| Appendix I Some Examples of the Error Marking Scheme | 第70-71页 |
| Appendix II The Tagging Scheme for the Learner Corpus | 第71-72页 |
| Appendix Ⅲ Requirements of TEM4–03 and TEM8–05 Compositions | 第72-73页 |
| Appendix Ⅳ Marking Scheme for TEM4 and TEM8 composition | 第73-74页 |
| Appendix ⅤExample Essays | 第74-78页 |
| Appendix VI Wordlists | 第78-84页 |
