This map is done by Dick Klavans with Kevin Bayack (Chemical engineer)’s help and ISI’s data. These kind of maps are used daily as a tool by him to determine which areas of science are most closely connected to one another, are most and least intellectually vital or which scientific areas produces the most patents.
The map is talking about how different nations pursue science-area of science. Here, each circular node represents scientific publications exploring a particular topics like: Astrophysics, Math, Quantum physics, Applied physics, materials, fluid mechanics, physical chemistry, Organic synthesis, Analytical chemistry, Ecology, Earth science, Biology, Biochemistry more about 23 topics. So, more amounts of particular nodes represents that the nation is more tends to that particular topic. And lines connecting nodes says about how far these area publishing on particular topic to each other (distance). For example, U.S. more tends to the topic of social science and medical science where it is lack in math, engineering and physical sciences.
This map also shows the comparison between nations like; U.S., U.K., Australia, Canada, France, Germany, Spain, China, Taiwan and Japan. The nations similar to the U.S. are U.K., Australia, Canada emphases on Social Science and Mental health. France and Germany are doing more publishing on Physics and Chemistry where Spain is more focusing on Science of Agriculture. China and Taiwan has similar profile. Both are strongly addresses toward Mathematics. Japan explores more about Medical topics.