write according to your actual situation, at least two or three. < br > Write down the specific content of the work in the paper, and get some insights and lessons from it, which is inspired by experience. Doctoral thesis is an academic thesis written by graduate students studying for doctoral degree. It requires the author, under the guidance of doctoral supervisor, to choose the potential research direction that he can grasp and control and open up new research fields. It can be seen that this requires the author to have a lot of theoretical knowledge in the professional field of this discipline, and to have in-depth understanding and thinking about the theoretical knowledge of his major. At the same time, you must have a considerable level of independent scientific research ability, and be able to put forward unique opinions and valuable scientific research results in this discipline. Therefore, compared with bachelor's dissertations and master's dissertations, doctoral dissertations have higher academic value and play an important role in promoting the development of disciplines.