| Abstract | 第8-9页 |
| 摘要 | 第10-14页 |
| List of Abbreviations | 第14-15页 |
| Chapter One Introduction | 第15-18页 |
| 1.1 Need of the Study | 第15页 |
| 1.2 Purpose of the Study | 第15-16页 |
| 1.3 Structure of the Study | 第16-18页 |
| Chapter Two Literature Review | 第18-28页 |
| 2.1 Previous Studies on Modality Abroad | 第18-24页 |
| 2.1.1 Studies from the Traditional Grammatical Perspective | 第18-20页 |
| 2.1.2 Studies from the Semantic Perspective | 第20-21页 |
| 2.1.3 Studies from the Systemic-functional Perspective | 第21-24页 |
| 2.2 Previous Studies on Modality in China | 第24-26页 |
| 2.3 Summary | 第26-28页 |
| Chapter Three Theoretical Framework | 第28-36页 |
| 3.1 Halliday’s Classification of Modal Verbs | 第28页 |
| 3.2 The Adaptation Theory | 第28-32页 |
| 3.2.1 The Three Key Points of Adaptation Theory | 第29-31页 |
| 3.2.2 The Four Aspects of Adaptation Theory | 第31-32页 |
| 3.3 Contextual Correlates of Adaptability | 第32-36页 |
| 3.3.1 The Physical world of Contextual Correlates of Adaptability | 第33-34页 |
| 3.3.2 The Social world of Contextual Correlates of Adaptability | 第34页 |
| 3.3.3 The Mental world of Contextual Correlates of Adaptability | 第34-36页 |
| Chapter Four Methodology | 第36-41页 |
| 4.1 Research Questions | 第36-37页 |
| 4.2 Data Collection | 第37-39页 |
| 4.3 Software | 第39页 |
| 4.4 Research Procedures | 第39-41页 |
| Chapter Five Results and Discussion | 第41-74页 |
| 5.1 Distribution of Modal Verbs and Modal Values in Introduction Sections | 第41-47页 |
| 5.1.1 Frequencies of Modal Verbs in Introduction Sections of Education andEngineering RAs | 第41-44页 |
| 5.1.2 Frequencies of Modal Values in Introduction Sections of Education andEngineering RAs | 第44-47页 |
| 5.2 The Contextual Adaptability of Modal Verbs in RA | 第47-59页 |
| 5.2.1 Choices of Modal Verbs as Adaptation to Mental World | 第48-53页 |
| 5.2.1.1 Adaptation to the Writers’ Mental World | 第48-51页 |
| 5.2.1.2 Adaptation to the Readers’ Mental Need | 第51-53页 |
| 5.2.2 Choices of Modal Verbs as Adaptation to Social World | 第53-56页 |
| 5.2.2.1 Adaptation to Politeness Principle | 第53-54页 |
| 5.2.2.2 Adaptation to Academic Norms | 第54-55页 |
| 5.2.2.3 Adaptation to Interaction Between the Writer and the Reader | 第55-56页 |
| 5.2.3 Choices of Modal Verbs as Adaptation to Physical World | 第56-59页 |
| 5.2.3.1 Adaptation to the Physical World in Form | 第57页 |
| 5.2.3.2 Adaptation to the Physical World in Content | 第57-59页 |
| 5.3 The Adaptation Features of Modal Values in Contextual Adaptability in IntroductionSections | 第59-74页 |
| 5.3.1 The Adaptation Features of Low Value Modal Verbs in ContextualAdaptability in Education and Engineering RAs | 第59-63页 |
| 5.3.2 The Adaptation Features of Median Value Modal Verbs in ContextualAdaptability in Education and Engineering RAs | 第63-66页 |
| 5.3.3 The Adaptation Features of High Value Modal Verb in Contextual Adaptabilityin Education and Engineering RAs | 第66-70页 |
| 5.3.4 Summary | 第70-74页 |
| Chapter Six Conclusion | 第74-77页 |
| 6.1 Research Findings | 第74-75页 |
| 6.2 Implication | 第75页 |
| 6.3 Limitations and Suggestions for Further Study | 第75-77页 |
| References | 第77-80页 |
| Acknowledgements | 第80-81页 |
| Appendix A: Data Sources | 第81-91页 |
| Appendix B: Published Paper | 第91页 |
