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( 2002 ). Li ( 2009 ), using a gravity model, found strong evidence of sub-national localisation effect at the metropolitan area and state level. Both Jaffe et al. ( 1992 ) and Li ( 2009 ) report that boarder and distance effects decrease with the age of
, from the first period to the second one, all fields presented an increase of international publication proportion. IPR and the effect of years since PhD and gender It is well known that aging affects the productivity
. 1994 ). To complement the given meta-data fields, additional data are used in our similarity calculations. These are: 1. Difference in years between publications: The age difference between publications will have an effect on the degree of
comparing the main topics dealing with the diadromous species at the international and French level and listed in the ASFA thesaurus (Aquaculture and fish farming; Growth and age; Diseases; Fisheries; Migration; Stock and abundance; Habitat; Reproduction
In a recent paper the authors have studied the role of author self-citations within the process of documented scientific communication. Two important regularities such as the relative fast ageing of self-citations with respect to foreign citations and the “square-root law” characterising the conditional expectation of self-citations for given number of foreign citation have been found studying the phenomenon of author self-citations at the macro level. The goal of the present paper is to study the effect of author self-citations on macro indicators. The analysis of citation based indicators for 15 fields in the sciences, social sciences and humanities substantiates that at this level of aggregation there is no need for any revision of national indicators and the underlying journal citation measures in the context of excluding self-citations.
effectively work in the age of technological convergence (Lee et al. 2008 ) and open innovation (Chesbrough 2003 ; Chesbrough et al. 2006 ; Laursen and Salter 2006 ; Lee et al. 2009 , 2008 ). Skills for green growth and rapid technological innovation
but it seems that the growth of fields is strongly related to the age of the field, and it would appear that societal circumstances also play an important role. Whichever circumstances influence the growth of dissertations, it would appear to
patterns of highly cited papers and their relationship to literature aging: A study of the working literature Scientometrics 7 3–6 383 – 389
of Lotka's law. The research findings can be extended to investigate author productivity by analyzing variables such as chronological and academic age, number and frequency of previous publications, access to research grants, job status, etc
Abstract
The aim of this study was to draw attention to the possible existence of "quirk", inbibliographic databases and to discuss their implications. We analysed the time-trends of"publication types" (PTs) relating to clinical medicine in the most frequently searched medicaldatabase, MEDLINE. We counted the number of entries corresponding to 10 PTs indexed inMEDLINE (1963-1998) and drew up a matrix of [10 PTs × 36 years] which we analysed bycorrespondence factor analysis (CFA). The analysis showed that, although the "internal clock" ofthe database was broadly consistent, there were periods of erratic activity. Thus, observed trendsmight not always reflect true publication trends in clinical medicine but quirks in MEDLINEindexing of PTs. There may be, for instance, different limits for retrospective tagging of entriesrelating to different PTs. The time-trend for Reviews of Reported Cases differed substantiallyfrom that of other publication types.Despite the quirks, quite rational explanations could be provided for the strongest correlationsamong PTs. The main factorial map revealed how the advent of the Randomised Controlled Trial(RCT) and the accumulation of a critical mass of literature may have increased the rate ofpublication of research syntheses (meta-analyses, practice guidelines...). The RCT is now theiogold standardls in clinical investigation and is often a key component of formal "systematicreviews" of the literature. Medical journal editors have largely contributed to this situation andthus helped to foster the birth and development of a new paradigm, "evidence based medicine"which assumes that expert opinion is biased and therefore relies heavily — virtually exclusively —on critical analysis of the peer-reviewed literature. Our exploratory factor analysis, however, leadsus to question the consistency of MEDLINEs indexing procedures and also the rationale forMEDLINE's choice of descriptors. Databases have biases of their own, some of which are notindependent of expert opinion. User-friendliness should not make us forget that outputs depend onhow the databases are constructed and structured.
