The impact factor (IF) of journals is a quantitative indicator of the influence of journals. That is an average of each published papers are cited number, it is actually published in a certain number of times a year all of the source is cited journal published two years ago in the journal, with the previous two years the number of journal papers published full source Ratio.
Impact factor is not the most objective criterion for evaluating the influence of journals. Generally speaking, the higher the impact factor, the greater the influence of the journal.
For some comprehensive or major research fields, the citation rate is relatively high because of the wide range of research fields. For example, journals of biology and chemistry are generally more likely to have a higher influence.
Although the impact factor can characterize the academic quality to a certain extent, the relationship between the impact factor and academic quality is not linearly proportional . For example, it cannot be said that a journal with an impact factor of 5.0 is definitely better than a journal with an impact factor of 2.0. It does not have the function of accurately and quantitatively evaluating academic quality.
Some domestic scientific research institutions often use cumulative impact factors or individual impact factors as quantitative standards when conducting research performance evaluations. Some researchers may not be promoted to titles or award bonuses due to a 0.1 point difference in impact factors. This approach is absolutely absolute Is not desirable.
From the calculation formula, although the impact factor is only directly related to the number of citations and the number of papers, in fact, it is closely related to many factors. There are five main factors that determine the size of the impact factor:
(1) Thesis factor . Such as the publication time lag of the paper, the length of the paper, the type and the number of collaborators, etc. Publications with a shorter publication time lag are easier to obtain a higher impact factor. If the publication period of the publication is long, a considerable part of the citations are not counted due to the aging of the literature (more than 2 years), that is, they are not involved in the calculation of the impact factor, thereby reducing the impact factor.
A large amount of statistical data shows that if the published paper is a hot topic, and the length of the paper is short and published quickly, the citation rate will quickly reach a peak, which will cause the impact factor of the journal to rise rapidly, and then rapidly decline; publish complete research papers The journals have been cited for a long time, and the impact factor has been increased for a long time. There are also data showing that the average number of authors of a paper is significantly positively correlated with the total citation frequency of the paper.
(2) Journal factors. Such as journal size (number of papers published), type, etc. When calculating the impact factor, the number of published papers only counts the number of papers, newsletters, and reviews, but does not count reviews, letters, newsletters, and other frequently cited articles. Based on empirical judgment, the number of journals published is closely related to the impact factor and the total frequency of citations.
In most cases, journals with a small number of papers are likely to get high impact factors, and the impact factors of these journals will fluctuate greatly from year to year; while journals with a large number of papers and a long history of publication tend to get higher Total citation frequency.
In addition, it is also closely related to other citation indicators such as: the annual index, the half-life of journal citations, the number of regional distribution, the ratio of funded papers, and the scope and circulation of journals. The size and structure of journals will cause different impact factors of journals. Generally speaking, the larger the scale of the same type of journals, the larger the impact factors of these journals in general; the more “hot” topics or “hot” professional articles contained in the journals, the more they are always cited. The higher the frequency, the greater the impact factor of such journals.
(3) Subject factors. For example, the number of journals in different disciplines, the average number of references, the half-life of citations, etc. will all have an impact on the journal’s impact factor and total citation frequency. The impact factor and total citation frequency of journals are based on the relationship between the citations of the paper and the number of citations.
The number of citations in a subject depends on two main factors: the first is the development characteristics of each subject; the second is the proportion of the journals of the subject in the source journals of the database. Generally speaking, the more source journals of a discipline, the greater the total citation frequency and impact factor of the discipline journal. These two factors determine the imbalance of the subject impact factor and the total citation frequency distribution.
In addition, the impact factor is also affected by the professional social coverage of the subject involved in the journal. If a sci-tech journal has a very small professional social coverage and there are few similar journals, then its impact factor is not It may be very high.
Because different disciplines have different internal scientific research rules, the situations in which the scientific research results of others need to be cited are different when doing research. These differences will affect the size of the impact factor in at least two aspects. On the one hand, the difference is how much other people’s work needs to be cited, and the other is the time of cite others’ work. Since the impact factor is generally calculated only based on the literature cited in the journals in the past two years, it can be seen that the ranking results based on the distribution of citation years in the past two years are also consistent with the ranking results of the journals by using the impact factor method. It also shows that the impact factor cannot correctly reflect the influence of journals in different disciplines.
Due to historical reasons, the construction and development of different disciplines in a country are not balanced, even in different branches of the same discipline. Some disciplines are small in scale, but there are many researchers engaged in this discipline, and the capital investment in this discipline is also large, and there are more related discipline magazines, which will form a scale advantage. And often those smaller-scale disciplines do not have this scale advantage, so the impact factor and total citation frequency of such journals will not be high.
In terms of the development speed of the subject scale, different subjects are divided into “cold” and “hot”. “Hot” subjects have developed rapidly due to the needs of the times. Articles of this subject will have a high citation rate during the period of rapid development of their scale; while “unpopular” subjects are just the opposite. However, this distinction between “cold” and “hot” is often not due to the development needs of science itself, but is often caused by economic, social and other non-scientific factors.
There are also some disciplines that contain many popular topics. Although these “hot” topics have high citation rates, they do not have much scientific value. According to the above analysis, it can be considered that this kind of difference in the citation rate of papers caused only by the size of the subject and the speed of development, or the difference in the size of the impact factors of related journals and institutions, resulting in the importance of The difference in ranking is not caused by the development of the scientific wooden body, but by some other economic, historical and social non-scientific factors. Therefore, this kind of evaluation of small-scale or “cold” major disciplines is extremely What is unfair is also unreasonable.
(4) Retrieval system factors , Such as the sources of journals participating in the statistics, the statistical scope of citation entries, etc. For a specific publication, in the retrieval systems of China and foreign countries, due to the large differences in the composition of the journal groups included in it, the calculated impact factor values are quite different, and the same publication has a large difference in the retrieval systems of different languages. Significantly different impact factors and total citations.
(5) The influence of celebrity effect . Celebrity effect is often manifested as: On the one hand, people often cite celebrity articles to increase the authority of their articles, even when there are other documents that are more suitable for their articles; On the one hand, articles signed with celebrity names or articles recommended by celebrities are easily published in so-called high-end magazines, and are therefore easily included in SCI or CSCD. Sometimes the articles do not have celebrity scientific research results, but in order to be able to The names of celebrities are signed in the publications, so excessive emphasis on the citation or inclusion situation will bring artificial bias to the total citation frequency and impact factor of the article.