| Acknowledgements | 第4-5页 |
| Academic Achievements | 第5-6页 |
| 摘要 | 第6-7页 |
| Abstract | 第7页 |
| Chapter One Introduction | 第12-15页 |
| 1.1 Research Background | 第12-13页 |
| 1.2 Research Questions | 第13页 |
| 1.3 Significance of the study | 第13-14页 |
| 1.4 Purpose of the Study | 第14-15页 |
| 1.5 Organization of the Study | 第15页 |
| Chapter Two Literature Review | 第15-25页 |
| 2.1 Definition and Classification of causal Connectors | 第15-19页 |
| 2.1.1 Definition of causal Connectors | 第16页 |
| 2.1.2 Classifications of Causal Connectors | 第16-19页 |
| 2.1.2.1 Halliday and Hasan’s Classification | 第17-18页 |
| 2.1.2.2 Mo Junhua’s Classification | 第18页 |
| 2.1.2.3 Classification Adopted in the Present Study | 第18-19页 |
| 2.2 Theoretical Framework | 第19-22页 |
| 2.2.1 Interlanguage | 第19-21页 |
| 2.2.2 Contrastive Interlanguage Analysis (CIA) | 第21-22页 |
| 2.3 Research Status | 第22-25页 |
| 2.3.1 Previous Studies in China | 第22-23页 |
| 2.3.2 Previous Studies abroad | 第23-25页 |
| Chapter Three Methodology | 第25-36页 |
| 3.1 Corpora Used in This Study | 第25-31页 |
| 3.1.1 Introduction of SWECCL 2.0 | 第25-26页 |
| 3.1.2 Introduction of LOCNESS | 第26-27页 |
| 3.1.3 Selection of Research Objects | 第27-31页 |
| 3.2 Instrument | 第31-33页 |
| 3.2.1 Coh-Metrix3.0 | 第31-32页 |
| 3.2.2 Antconc3.2.1 | 第32-33页 |
| 3.2.3 SPSS17.0 | 第33页 |
| 3.3 Research Procedures | 第33-36页 |
| Chapter Four Results and Discussions | 第36-55页 |
| 4.1 Comparison among Chinese EFL learners | 第36-45页 |
| 4.1.1 Frequency of the Specific Causal Connectors in W1, W2,W3 | 第36-38页 |
| 4.1.2 Richness of the Specific Causal Connectors in W1，W2，W3 | 第38-41页 |
| 4.1.3 Comparison of Colloquial Tendency in W1,W2 and W3 | 第41-42页 |
| 4.1.4 Relationship between Frequency and Writing Quality | 第42-44页 |
| 4.1.5 Relationship between variety and writing Quality | 第44-45页 |
| 4.2 Comparison between Chinese and American Students’ Writings | 第45-52页 |
| 4.2.1 Comparison of Frequency between Chinese and English Native students’ Writings | 第45-47页 |
| 4.2.2 Comparison of Richness between Chinese and English Native Students' Writings | 第47-49页 |
| 4.2.3 Comparison of Colloquial Tendency between Chinese and English NativeStudents' Writings | 第49-50页 |
| 4.2.4 Overused and Underused Causal Connectors in WECCL and LOCNESS | 第50-52页 |
| 4.3 Discussion | 第52-55页 |
| 4.3.1 Register Awareness | 第52-53页 |
| 4.3.2 Avoidance Strategy | 第53-54页 |
| 4.3.3 Input Bias | 第54-55页 |
| Chapter Five Conclusion | 第55-60页 |
| 5.1 Major Findings | 第56-57页 |
| 5.2 Implications | 第57-58页 |
| 5.2.1 Distinguishing Written and Spoken Vocabulary | 第57页 |
| 5.2.2 Using Corpus | 第57-58页 |
| 5.2.3 Teaching Relative Knowledge of Causal Connectors | 第58页 |
| 5.3 Limitations | 第58-59页 |
| 5.4 Suggestions for Future Studies | 第59-60页 |
| Reference | 第60-64页 |
