板书是重要的教学手段。在课堂上,教师通过板书把需要讲授的内容清晰地反映在学生的面前。它直接沟通了教与学之间的联系,使得学生能牢固地把握住重点及难点内容,从而对所学的知识达到消化理解的目的。而笔者在教学实践中发现,有的教师的板书却不尽合理:把课堂讲授的内容不分主次地多次写满整板又多次擦去,所有的板书均不能保持较长的时间。由于主要教学内容不突出,很难 Board writing is an important teaching method. In the classroom, the teacher through the blackboard the content to be taught clearly reflected in front of the students. It directly communicates the connection between teaching and learning, enabling students to firmly grasp the key and difficult content, so as to digest and understand the learned knowledge. The author found in teaching practice, some teachers' writing on the board but not entirely reasonable: the content taught in the classroom, regardless of primary and secondary repeatedly filled the whole board and repeatedly wipe all the board can not be maintained for a long time . As the main teaching content is not prominent, it is difficult