致谢词示例：
Dear Professor [Name],
I am writing to express my sincere gratitude for your valuable guidance and support during the writing of my doctoral dissertation. Your guidance and expertise have been instrumental in helping me to achieve my academic goals and prepare for my doctoral defense.
Your willingness to provide无私的帮助 and invaluable feedback has made a significant difference in the quality of my research, and has also helped me to identify areas for improvement. Your insights and suggestions have been invaluable, and have helped me to approach my studies in a more comprehensive and effective way.
Furthermore, your willingness to collaborate with me has been a great source of inspiration and motivation. Your commitment to excellence and your passion for research have motivated me to work even harder, and have helped me to become a better researcher.
In conclusion, I would like to express my gratitude to you for your valuable support and guidance. Your generosity has made a significant difference in my life, and has allowed me to achieve my academic and professional goals. I hope to have the opportunity to pay it forward and support other students in the future.
Sincerely,
[Your Name]