Number Of Source Items Research Articles

The impact of self-citation

Citation rates are used to calculate journal impact factors and for measuring the personal impact of individual scientists (Aksnes, 2003; Fowler and Aksnes, 2007), which can affect chances of academic appointments, advance in career, pay increases and grant funding (Hyland, 2003; Adler, 2009). However, the current method used to calculate citation rates has its limitations. The most widely used index published by the Institute of Scientific Information is the 2-year impact factor (Della Sala and Grafman, 2007, 2009) which calculates citation rate by summing the total citations during a given year to articles published in the previous two years and dividing this by the number of ‘source items’. What constitutes a ‘source item’ is unclear, but the number of source items can obviously affect citation rate (see Della Sala and Brooks, 2008), and can be manipulated to affect journal impact factor (see Brumback, 2009). Journal impact factors can also be highly influenced by the publication of a few highly cited papers (Buchtel and Della Sala, 2006) and it has been suggested that around 20% of all articles tend to account for 80% of all citations. In addition, it has been argued that the arbitrarily set time window of two-years disadvantages slowmoving disciplines, such as neuropsychology (Della Sala and Crawford, 2006, 2007; Della Sala and Grafman, 2009). Another factor that may affect citation rate is self-citation. Authors may choose to cite their own work in order to make their earlier work visible, to help reinforce an argument, to create an image of scientific authority (Hyland, 2003) or simply for self-aggrandizement (Hyland, 2003; Fowler and Aksnes, 2007). Self-citation can inflate the perception of an article’s or a scientist’s scientific impact, particularly when an article has many authors, increasing the possible number of self-citations (Schreiber, 2007; Della Sala and Brooks, 2008), and thus there have been calls to remove self-citations from citation rates (Schreiber, 2007). However, Fowler and Aksnes (2007)

The SCI Journal Citation Reports: A potential tool for studying journals?

In this paper, we analysed six indicators of the SCI Journal Citation Reports (JCR) over a 19-year period: number of total citations, number of citations to the two previous years, number of source items, impact factor, immediacy index and cited half-life. The JCR seems to have become more or less an authority for evaluating scientific and technical journals, essentially through its impact factor. However it is difficult to find one's way about in the impressive mass of quantitative data that JCR provides each year. We proposed the box plot method to aggregate the values of each indicator so as to obtain, at a glance, portrayals of the JCR population from 1974 to 1993. These images reflected the distribution of the journals into 4 groups designated low, central, high and extreme. The limits of the groups became a reference system with which, for example, it was rapidly possible to situate visually a given journal within the overall JCR population. Moreover, the box plot method, which gives a zoom effect, made it possible to visualize a large sub-population of the JCR usually overshadowed by the journals at the top of the rankings. These top level journals implicitly play the role of reference in evaluation processes. This often incites categorical judgements when the journals to be evaluated are not part of the top level. Our «rereading» of the JCR, which presented the JCR product differently, made it possible to qualify these judgements and bring a new light on journals.

The influence of occupational medicine on general medicine: a look at the journals.

To assess how the occupational medicine literature may affect general medical practice, representative journals were reviewed to address (1) how frequently the specialties cite each others' literature and (2) which topics are published most commonly by the respective journals. Five general medical journals were selected to contrast with six occupational medical journals. Methods included Journal Citation Reports, which enable the tabulation of impact factor, self-citation rate, and the number of source items published by the journal. MEDLINE was used to cross reference the 11 journals with designated topics in occupational medicine. The findings indicated that occupational medical journals are nearly 50 times more likely to cite the general medical literature than the converse. The journals most likely to cite the core occupational medical literature, aside from the specialty journals themselves, were the American Review of Respiratory Diseases and the American Journal of Epidemiology. In comparing the 1976 through 1980 period with the 1986 through 1990 period, occupational medical journals published 2.5 times as many source items (letters, technical reports, and papers) compared with a decade earlier. The MEDLINE search indicated that both types of journals address the same types of occupational medicine topics with the exception of gas poisoning and toxic hepatitis, which were published much more frequently in general medical journals. Pneumoconiosis was the most frequently addressed topic by occupational medical journals. Other major categories included reproductive hazards, lead poisoning, and noise-induced hearing loss. This study indicates that occupational medicine, as reflected by its journals, is a much more active scientific discipline than it was a decade earlier.

MULTIVARIATE REGRESSION MODELS FOR ESTIMATING JOURNAL USEFULNESS IN PHYSICS

Multiple regression models can be used to rank physics journals in approximately the same order as the journals are perceived useful by actual users. Four such regression models are reported here, each having a multiple R value of ·74 or greater. Perceived usefulness, the dependent variable used in constructing the models, was obtained from a survey of 167 physicists in the US and Canada. The independent, or predictor variables include easily obtainable bibliometric statistics such as number of source items published, immediacy index, ratio of citations received to citations made, total citations received, impact factor and others. Regression models that combine certain of these statistics can predict user valuation of the journals better than any single bibliometric predictor alone can do. Their advantage for serials management is in ease of estimating usefulness as judged by users, a much more difficult statistic to obtain. Where these models may not apply, it is relatively simple to construct similar models based upon surveys of other user groups. It appears likely that good models of this type can also be developed for many other disciplines.

Core journals in computer science

Attempts to identify the `core' primary journals in the newly emerging discipline of computer science. Two measures of significance have been used to draw up a core list of journals: Productivity in terms of the number of source items drawn from each journal for review in a secondary journal (Computer Reviews); and extent of use, as reflected by the frequency with which the journals are cited in a leading primary journal (IEEE Transactions on Computers) over a period of two years. This study has shown that the primary journal is the most favored medium for scholarly communication, and that computer science journal literature has consolidated into a relatively few very productive and highly cited primary journals. These core journals are indispensable in any specialized collection of computer science literature.