| Acknowledgements | 第5-6页 |
| Abstract in English | 第6-7页 |
| Abstract in Chinese | 第8-12页 |
| List of Abbreviations | 第12-13页 |
| Chapter 1 Introduction | 第13-17页 |
| 1.1 Research Orientation | 第13-14页 |
| 1.2 Significance of the present study | 第14-16页 |
| 1.3 Structure of the thesis | 第16-17页 |
| Chapter 2 Review of Related Literature | 第17-35页 |
| 2.1 Overview | 第17-18页 |
| 2.2 Studies on the development of lexical knowledge | 第18-31页 |
| 2.2.1 Empirical studies on breadth of vocabulary | 第20-28页 |
| 2.2.2 Empirical studies on depth of vocabulary | 第28-31页 |
| 2.3 Empirical studies on the correlation between breadth and depth of vocabulary and writing quality | 第31-33页 |
| 2.3.1 Correlation between lexical variation and writing quality | 第31-32页 |
| 2.3.2 Correlation between lexical density and writing quality | 第32页 |
| 2.3.3 Correlation between lexical sophistication and writing quality | 第32-33页 |
| 2.4 Comments on previous studies | 第33-35页 |
| Chapter 3 Conceptual Framework | 第35-41页 |
| 3.1 Lexical knowledge | 第35-36页 |
| 3.2 Breadth of vocabulary | 第36-38页 |
| 3.3 Depth of vocabulary | 第38-41页 |
| Chapter 4 Methodology | 第41-49页 |
| 4.1 Specific research questions | 第41页 |
| 4.2 Participants | 第41-42页 |
| 4.3 Instruments | 第42-44页 |
| 4.4 Data collection and analysis | 第44-49页 |
| 4.4.1 Data collection | 第44页 |
| 4.4.2 Data analysis | 第44-49页 |
| Chapter 5 Results and Discussion | 第49-75页 |
| 5.1 Results | 第49-63页 |
| 5.1.1 Development of participants’ breadth of vocabulary | 第49-54页 |
| 5.1.2 Development of participants’ depth of vocabulary | 第54-60页 |
| 5.1.3 Correlation of participants’ lexical knowledge with their writing ability | 第60-63页 |
| 5.2 Discussion | 第63-75页 |
| 5.2.1 Development of participants’ breadth of vocabulary | 第64-66页 |
| 5.2.2 Development of participants’ depth of vocabulary | 第66-70页 |
| 5.2.3 The effect of lexical knowledge on writing | 第70-75页 |
| Chapter 6 Conclusion | 第75-81页 |
| 6.1 Overview | 第75页 |
| 6.2 Major findings and conclusions | 第75-76页 |
| 6.3 Implications | 第76-79页 |
| 6.4 Limitations and suggestions for further research | 第79-81页 |
| References | 第81-91页 |
| Appendices | 第91-93页 |
