The journals in each field of six subjects, mathematics, physics, chemistry, chemical engineering, electrical engineering, and mechanical engineering, were reorganized in the order of citation ranking based on the journal citation ranking of Journal Citation Reports. The ranking in each field was compared with that of journals in natural science in general which were included in Journal Citation Reports. It was also compared with the rankings which had already been obtained in the previous years. The diffusion ratio, that is, what percentage of the whole citation articles are covered by upper ranked twenty journals, was calculated in each subject field.
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