| Abstract | 第1-7页 |
| 摘要 | 第7-12页 |
| List of the Tables and Figures | 第12-13页 |
| Chapter One Introduction | 第13-16页 |
| ·Research background | 第13-14页 |
| ·Research objectives | 第14页 |
| ·Research significance | 第14-15页 |
| ·Layout of the present paper | 第15-16页 |
| Chapter Two Literature Review | 第16-30页 |
| ·Definitions of hedges | 第16-17页 |
| ·Classifications of hedges | 第17-22页 |
| ·Linguistic realizations of hedges | 第22-23页 |
| ·Previous studies on hedges at home and abroad | 第23-28页 |
| ·Non-corpus-based studies on hedges at home and abroad | 第23-25页 |
| ·Corpus-based studies on hedges at home and abroad | 第25-28页 |
| ·Summary | 第28-30页 |
| Chapter Three Theoretical Framework | 第30-35页 |
| ·Cooperative Principle | 第30-32页 |
| ·Politeness Theories | 第32-35页 |
| ·Leech’s Politeness Principle | 第32-33页 |
| ·Brown and Levinson’s FTA theory | 第33-35页 |
| Chapter Four Methodology | 第35-49页 |
| ·Research questions | 第35页 |
| ·Corpora employed | 第35-37页 |
| ·Learners’ corpus: COLSEC | 第36页 |
| ·Reference corpus: BNC | 第36-37页 |
| ·Data retrieval software employed | 第37-39页 |
| ·Research framework and data retrieval principles | 第39-46页 |
| ·Hedges focused on in the current research | 第39-40页 |
| ·Data retrieval principles | 第40-46页 |
| ·Data retrieval principles for Adaptors | 第41-42页 |
| ·Data retrieval principles for Rounders | 第42-44页 |
| ·Data retrieval principles for Plausibility Shields | 第44-45页 |
| ·Data retrieval principles for Attribution Shields | 第45-46页 |
| ·Research procedure | 第46-48页 |
| ·Data collection | 第48-49页 |
| Chapter Five Results and Discussion | 第49-70页 |
| ·Overall quantitative comparison | 第49-51页 |
| ·Comparison on the distributions of different types of hedges between CCSs and NSs | 第51-58页 |
| ·Distributions of Approximators and Shields in the two sub-corpora | 第51-53页 |
| ·Distributions of the four sub-categories of hedges in the two sub-corpora | 第53-58页 |
| ·Distributions of the five Adaptors in the two sub-corpora | 第55-56页 |
| ·Distributions of the five Rounders in the two sub-corpora | 第56页 |
| ·Distributions of the five Plausibility Shields in the two sub-corpora | 第56-57页 |
| ·Distributions of the five Attribution Shields in the two sub-corpora | 第57-58页 |
| ·Comparative analysis of the pragmatic functions of hedges between CCSs and NSs | 第58-65页 |
| ·Avoiding giving wrong information | 第59-60页 |
| ·Giving the right amount of information | 第60-61页 |
| ·Filling lexical gaps | 第61-62页 |
| ·Self-protection | 第62-63页 |
| ·Achieving politeness | 第63-65页 |
| ·Possible explanations for the differences | 第65-70页 |
| ·Explanation for overuse | 第65-66页 |
| ·Explanation for underuse | 第66-67页 |
| ·Explanation for pragmatic failure | 第67-68页 |
| ·Explanation for functional deficiency | 第68-70页 |
| Chapter Six Conclusions | 第70-75页 |
| ·Major findings | 第70-71页 |
| ·Pedagogical implications | 第71-73页 |
| ·Limitations and suggestions for further studies | 第73-75页 |
| References | 第75-79页 |
| Academic Papers Published during Postgraduate Study | 第79-80页 |
| Acknowledgements | 第80-81页 |
| Appendix | 第81-95页 |
