| Acknowledgements | 第6-7页 |
| Abstract | 第7-9页 |
| 摘要 | 第10-17页 |
| List of Abbreviations | 第17-18页 |
| Chapter One Introduction | 第18-22页 |
| 1.1 Research Background | 第18-19页 |
| 1.2 Significance of the Present Study | 第19-20页 |
| 1.3 Organization of the Thesis | 第20-22页 |
| Chapter Two Literature Review | 第22-36页 |
| 2.1 The Definition of Lexical Richness | 第22页 |
| 2.2 Measures of Lexical Richness | 第22-28页 |
| 2.2.1 Measures of Lexical Variation | 第23-24页 |
| 2.2.2 Measures of Lexical Density | 第24-25页 |
| 2.2.3 Measures of Lexical Frequency Profile | 第25-26页 |
| 2.2.4 Measures of Lexical Sophistication | 第26-28页 |
| 2.3 Developmental features of Lexical Richness in L2 Writing | 第28-30页 |
| 2.4 Relationship between Lexical Richness and L2 Writing Performance | 第30-36页 |
| 2.4.1 Major studies | 第30-35页 |
| 2.4.2 Summary | 第35-36页 |
| Chapter Three Theoretical Framework | 第36-40页 |
| 3.1 Introduction to the Interlanguage Theory | 第36-37页 |
| 3.2 Features of Interlanguage | 第37-38页 |
| 3.3 Summary | 第38-40页 |
| Chapter Four Methodology | 第40-47页 |
| 4.1 Research Questions | 第40页 |
| 4.2 Participants and Data Collection | 第40-41页 |
| 4.3 Data Processing | 第41-43页 |
| 4.3.1 Rating the Compositions | 第41-42页 |
| 4.3.2 Text Processing | 第42-43页 |
| 4.4 Measures for Data Analysis | 第43-47页 |
| 4.4.1 Tools for Data Analysis | 第43-44页 |
| 4.4.2 Measures for Lexical Variation and Lexical Frequency Profile | 第44-46页 |
| 4.4.3 Measures for Lexical Sophistication | 第46页 |
| 4.4.4 Measures for Lexical Density | 第46-47页 |
| Chapter Five Data Analysis and Results | 第47-64页 |
| 5.1 Features of Lexical Variation | 第47-50页 |
| 5.2 Features of Lexical Density | 第50-52页 |
| 5.3 Features of Lexical Sophistication | 第52-54页 |
| 5.4 Features of Lexical Frequency Profile | 第54-56页 |
| 5.5 Difference among Developmental Features in Lexical Richness of Studentswith Different Language Proficiency | 第56-61页 |
| 5.6 Relationship between Lexical Richness and Writing Performance | 第61-64页 |
| Chapter Six Discussion | 第64-72页 |
| 6.1 Models of Developmental Features of Lexical Richness | 第64-69页 |
| 6.1.1 Models of Developmental Features of Lexical Variation | 第64-66页 |
| 6.1.2 Models of Developmental Features of Lexical Density | 第66页 |
| 6.1.3 Models of Developmental Features of Lexical Sophistication | 第66-68页 |
| 6.1.4 Overuse of High-frequency Words | 第68-69页 |
| 6.2 Discrepancy in Lexical Richness among Learners with Different LanguageProficiency | 第69-70页 |
| 6.3 Unbalanced Effects of Lexical Richness on the Overall Writing Proficiency | 第70-72页 |
| Chapter Seven Conclusion | 第72-77页 |
| 7.1 Major Findings | 第72-74页 |
| 7.2 Pedagogical Implications | 第74-75页 |
| 7.2.1 Implication for Vocabulary Teaching | 第74-75页 |
| 7.2.2 Implication for Vocabulary Learning | 第75页 |
| 7.3 Limitations of This Research and Suggestions for Future Studies | 第75-77页 |
| Bibliography | 第77-87页 |
