| Abstract in English | 第4-5页 |
| Abstract in Chinese | 第6-10页 |
| Chapter One Introduction | 第10-15页 |
| 1.1 Background of the Study | 第10-12页 |
| 1.2 Significance of the Study | 第12-13页 |
| 1.3 Research Questions | 第13页 |
| 1.4 Hypothesis | 第13页 |
| 1.5 Overview of the Study | 第13-15页 |
| Chapter Two Literature Review | 第15-25页 |
| 2.1 Definitions of Lexical Richness | 第15-16页 |
| 2.2 Measurement Indexes for Lexical Richness | 第16-20页 |
| 2.2.1 Lexical Variation | 第16-17页 |
| 2.2.2 Lexical Sophistication | 第17-19页 |
| 2.2.3 Lexical Density | 第19-20页 |
| 2.2.4 Lexical Errors | 第20页 |
| 2.3 Studies of Lexical Richness in Second Language Writings Abroad and at Home | 第20-25页 |
| 2.3.1 Studies of Lexical Richness in Second Language Writings Abroad | 第20-22页 |
| 2.3.2 Studies of Lexical Richness in Second Language Writings at Home | 第22-25页 |
| Chapter Three Methodology | 第25-35页 |
| 3.1 Data Source | 第25页 |
| 3.2 Data Collection Procedures | 第25-26页 |
| 3.3 Measuring Methods for Lexical Richness in This Study | 第26-35页 |
| 3.3.1 Word Lists Used in This Study | 第26-31页 |
| 3.3.2 Measuring Method for Lexical Sophistication in This Study | 第31-32页 |
| 3.3.3 Measuring Method for Lexical Density in This Study | 第32页 |
| 3.3.4 Measuring Method for Lexical Variation in This Study | 第32-33页 |
| 3.3.5 Measuring Method for the Number of Errors in This Study | 第33-35页 |
| Chapter Four Data Analysis and Discussion | 第35-60页 |
| 4.1 Data Analysis | 第35-46页 |
| 4.1.1 Results of Lexical Sophistication of Different Grades | 第35-41页 |
| 4.1.2 Results of Lexical Density of Different Grades | 第41-42页 |
| 4.1.3 Results of Lexical Variation of Different Grades | 第42-43页 |
| 4.1.4 Results of Lexical Errors of Different Grades | 第43-46页 |
| 4.2 Discussion on Lexical Richness | 第46-60页 |
| 4.2.1 Discussion on the Developmental Patterns of Lexical Sophistication | 第47-54页 |
| 4.2.2 Discussion on the Developmental Pattern of Lexical Density | 第54-56页 |
| 4.2.3 Discussion on the Developmental Pattern of Lexical Variation | 第56-57页 |
| 4.2.4 Discussion on the Developmental Pattern of Lexical Errors | 第57-60页 |
| Chapter Five Conclusion | 第60-66页 |
| 5.1 Major Findings of the Study | 第60-62页 |
| 5.2 Implications of the Study | 第62-64页 |
| 5.2.1 Implications for Vocabulary Teaching and Testing | 第62-63页 |
| 5.2.2 Implications for Vocabulary Learning | 第63-64页 |
| 5.3 Limitations and Suggestions for Further Studies | 第64-66页 |
| References | 第66-71页 |
| Appendix Ⅰ Special Cases in the Word Lists | 第71-91页 |
| Appendix Ⅱ Words Not in the Word Lists | 第91-97页 |
| Acknowledgements | 第97页 |
