Core journals are the main journals of a certain discipline. Generally speaking, it refers to a professional periodical with a large amount of professional information and high quality, which can represent the development level of professional disciplines and is valued by readers of this discipline. Relevant experts have found that the actual distribution of literature information sources has the effect of core journals.

That is, a large number of scientific papers in a professional world are concentrated in a few scientific journals. This phenomenon can be seen in many fields, for example, from the study of the world literature of physics in France's Signal Bulletin, it is found that 90% abstract items are only taken from 30% of all journals, and chemical abstracts can be extracted from 9% of all journals to 75% of all abstract items.

193 1 Bradford, a famous philologist, first revealed the law of concentration and dispersion of documents, and found that 1/3 papers of a certain discipline were published in 3.2% journals in a certain period; From 65438 to 0967, UNESCO studied the distribution of secondary literature in periodicals and found that 75% of the literature appeared in 10% of the periodicals.

197 1 year, Garfield, the founder of SCI, counted the distribution of references in journals and found that 24% of the citations appeared in 1.25% of journals, and so on. All these studies show that there is a "core effect" in journals, which leads to the concept of "core journals".