| 摘要 | 第1-6页 |
| ABSTRACT | 第6-11页 |
| Chapter 1 Introduction | 第11-14页 |
| ·Background of the Study | 第11-12页 |
| ·Significance of the Research | 第12-13页 |
| ·Layout of the Thesis | 第13-14页 |
| Chapter 2 Literature Review | 第14-33页 |
| ·Input Hypothesis and Language Acquisition | 第14-15页 |
| ·Output Hypothesis and Language Acquisition | 第15页 |
| ·Fossilization in SLA | 第15-16页 |
| ·Definition of Lexical Richness | 第16-17页 |
| ·Lexical Richness Measures | 第17-26页 |
| ·Measuring Lexical Variation | 第17-20页 |
| ·Measuring Lexical Sophistication | 第20-21页 |
| ·Measuring Lexical Density | 第21-25页 |
| ·Measuring Lexical Error | 第25-26页 |
| ·Previous Studies on Lexical Richness | 第26-32页 |
| ·Previous Studies Abroad | 第26-30页 |
| ·Previous Studies in China | 第30-32页 |
| ·Holistic Ratings | 第32-33页 |
| Chapter 3 Methodology | 第33-38页 |
| ·Research Questions | 第33页 |
| ·Participants | 第33-34页 |
| ·Instruments | 第34-35页 |
| ·Software Used in the Study | 第34-35页 |
| ·CET-4 and CET-6 Scores | 第35页 |
| ·Data Collection Procedures | 第35-38页 |
| Chapter 4 Results and Discussion | 第38-58页 |
| ·Results of four Dimensions of Lexical Richness | 第38-48页 |
| ·Results of Lexical Variation | 第38-39页 |
| ·Results of Lexical Sophistication | 第39-43页 |
| ·Results of Lexical Density | 第43-45页 |
| ·Results of Lexical Error | 第45-48页 |
| ·Summary | 第48页 |
| ·Evaluation of the Writing Quality | 第48-49页 |
| ·Relationship between Lexical Richness and Writing Quality | 第49-56页 |
| ·The Relationship between Lexical Variation and Writing Quality | 第49-50页 |
| ·The Relationship between Lexical Sophistication and Writing Quality | 第50-52页 |
| ·The Relationship between Lexical Density and Writing Quality | 第52-53页 |
| ·The Relationship between Lexical Error and Writing Quality | 第53-55页 |
| ·Summary | 第55-56页 |
| ·Scores of CET-4 and CET-6 Compositions | 第56-58页 |
| Chapter 5 Conclusions | 第58-63页 |
| ·Major Findings | 第58-59页 |
| ·Implications | 第59-61页 |
| ·Implications for Vocabulary Teaching | 第59-61页 |
| ·Implications for Vocabulary Learning | 第61页 |
| ·Limitations and Suggestions for Further Research | 第61-63页 |
| Reference | 第63-69页 |
| Appendix Sample Essays | 第69-71页 |
| Acknowledgements | 第71-72页 |
| Resume | 第72页 |
