The international publication The Physics Teacher, issued by the American Association of Physics Teacher (AAPT), was published in April 1963 and has been loved by many physicists. The authors set up an advanced search on CNKI as The Physics Teacher and published time from 2016.01.01-2021.3.13. The result was 1463 articles. Then export the searched literature results and manually delete invalid literature, and import the valid data into the BICOMB software [2] for keyword extraction, statistics and matrix generation.

Knowledge graph is an important method that has emerged in the field of library and information science in recent years. It combines the theories and methods of applied mathematics, graphics, information visualization technology, information science and other disciplines with metrological citation analysis, co-occurrence analysis and other methods. Use the visual atlas to visually display the core structure, development history, frontier fields and overall knowledge structure of the research field [3] . This research uses BICOMB, UCINET and other software as the main research tools. First, the documents are exported from CNKI and imported into BICOMB software for basic statistical analysis, manual deletion of invalid documents, statistical ranking of keywords appearing in the documents, and high-frequency words with a word frequency greater than 20 as the main keywords. Secondly, import the generated co-occurrence matrix into UCINET software to obtain a high-frequency keyword network map, and generate a clustering theme map, so that the hot themes and directions of The Physics Teacher in the past five years can be seen intuitively and clearly.

After retrieval and statistics, a total of 2262 keywords were obtained. The keyword threshold is set to 20, and 72 high-frequency words with a word frequency greater than 20 are counted, and the cumulative percentage is 56.16%. The statistical results of high-frequency words are shown in Table 1.

In the high-frequency word social network graph, the position of each node represents a different keyword, the connection between the keywords represents its internal connection, the size of the node represents centrality, and the larger the node, the more central [4] . The authors imported the high-frequency word co-occurrence matrix obtained by BICOMB software into the UCINET software, and generated the high-frequency word social network graph according to the parameters such as the centrality of the keywords, the position and the mutual relationship in the network graph, and then performed k-aggregation. The clustering map is obtained by class analysis, as shown in Figure 1. The larger the label in the figure, the stronger the keyword centrality and the higher the frequency of co-occurrence. Different label colors represent different clusters.

The high-frequency word network diagram shown in Figure 1 shows the research hotspots of different clusters. The larger the label of the same color, the more relevant research on the topic. It can be seen from Figure 1 that the research clusters of The Physics Teacher in the past five years are mainly distributed in physics teaching, physics education technology, general physics, and physics discussion. Among them, the research hotspots related to middle school physics teaching in these clusters mainly include: teaching, physics teaching aids, educational evaluation, Newtonian mechanics, physics experiments, educational

policies and management, learning modes, electromagnetics, student development, physics history, sports Science, geometric optics, etc. The marginal areas of the map, such as the Internet, textbook analysis, and other relatively low-frequency words, reflect the trend of future research to a certain extent, and may become new hotspots and cutting-edge trends in physics teaching research.

The research hotspots of The Physics Teacher in middle school physics teaching mainly include teaching [5] , physics teaching aids [6] , educational evaluation [7] , Newtonian mechanics [8] , physics experiments [9] , education policy and management [10] , Learning Mode [11] , Electromagnetism [12] , Student Development [13] , History of Physics [14] , Kinematics [15] , Geometric Optics [16] , etc.

The research found that the sample literature of middle school physics teaching research presents the characteristics of wide research fields and prominent research topics. The research hotspots and core themes are mainly distributed in physics knowledge teaching, force and motion, electricity, physics experiments, electromagnetic induction, geometric optics and physics Discipline core literacy cultivation practice and other fields [1] .

Compared with The Physics Teacher (in Chinese), The Physics Teacher pays more attention to research in the fields of student development, physics history and physics teaching aids, which reflects the difference between Chinese and international physics education to a certain extent. The 2005-2014 research shows that there is a big difference between Chinese and international physics education hot issues.

First of all, physics education in China has uneven performance in various hotspots of international physics education. Second, physics education and the development of physics cognition are not highly integrated. Third, physics education has obviously less research on student differences [17] . This is consistent with the results of this research, but it is not difficult to find that the research on physics education in China is moving closer to the research on international physics education.

After the promulgation of the 2017 version of the curriculum standard, all aspects of physics education in China have developed rapidly, with particular emphasis on the development of the core literacy of students in physics, which corresponds to the hot spots of student development in The Physics Teacher, while other fields such as student diversity, The penetration of the history of physics and the combination of information technology and education can also provide ideas and ideas for the development of physics education in China.

Students are the protagonists of learning, and teaching must conform to the cognitive development of students. More in-depth research on the cognitive development of students’ physics is a necessity and prerequisite for doing a good job in physics teaching. The diversity of students has always been a problem that people are very concerned about in teaching. The “Teaching students in accordance with their aptitude” mentioned by Confucius was first born due to the differences of students, but in physics education research in China research, we rarely meet each other. If we want to improve the national physics education level, we must conduct in-depth research on the differences of students.

Infiltrating the history of physics into physics education and teaching is also an effective supplement and important resource for physics teaching. Teachers make reasonable use of the history of physics in teaching to help students establish a correct scientific outlook, stimulate their learning interest and learning emotions, and promote students to transform from passive learning to active learning, thereby improving the effectiveness of classroom teaching and cultivating students’ scientific literacy [18] .

With the development of the times, science and technology are becoming more and more developed, and the conditions for the development of physics education in China are getting better and better. The application of information technology, especially multimedia technology, in physics education is extremely important. Modern information technology with multimedia, networking, and intelligence as its main characteristics is having a profound impact and transformational effect on traditional curriculum concepts, curriculum content, curriculum implementation and curriculum resources [19] . Keeping up with the pace of the times, making full use of modern information technology and physics teaching to combine to continuously improve classroom efficiency, improve the level of physics education in China, and enhance the core literacy of students is our ultimate goal.