Guenther Eichhorn

The effect of use and access on citations

It has been shown (Lawrence, S. (2001). Online or invisible? Nature, 411, 521) that journal articles which have been posted without charge on the internet are more heavily cited than those which have not been. Using data from the NASA Astrophysics Data System (ads.harvard.edu) and from the ArXiv e-print archive at Cornell University (arXiv.org) we examine the causes of this effect.

The bibliometric properties of article readership information

Digital libraries such as the NASA Astrophysics Data System (Kurtz et al., 2005) permit the easy accumulation of a new type of bibliometric measure, the number of electronic accesses (“reads”) of individual articles. We explore various aspects of this new measure. We examine the obsolescence function as measured by actual reads and show that it can be well fit by the sum of four exponentials with very different time constants. We compare the obsolescence function as measured by readership with the obsolescence function as measured by citations. We find that the citation function is proportional to the sum of two of the components of the readership function. This proves that the normative theory of citation is true in the mean. We further examine in detail the similarities and differences among the citation rate, the readership rate, and the total citations for individual articles, and discuss some of the causes. Using the number of reads as a bibliometric measure for individuals, we introduce the read–cite diagram to provide a two-dimensional view of an individuals scientific productivity. We develop a simple model to account for an individuals reads and cites and use it to show that the position of a person in the read–cite diagram is a function of age, innate productivity, and work history. We show the age biases of both reads and cites and develop two new bibliometric measures which have substantially less age bias than citations: SumProd, a weighted sum of total citations and the readership rate, intended to show the total productivity of an individual; and Read10, the readership rate for articles published in the last 10 years, intended to show an individuals current productivity. We also discuss the effect of normalization (dividing by the number of authors on a paper) on these statistics. We apply SumProd and Read10 using new, nonparametric techniques to compare the quality of different astronomical research organizations.

Worldwide Use and Impact of the NASA Astrophysics Data System Digital Library

The NASA Astrophysics Data System (ADS), along with astronomys journals and data centers (a collaboration dubbed URANIA), has developed a distributed online digital library which has become the dominant means by which astronomers search, access, and read their technical literature. Digital libraries permit the easy accumulation of a new type of bibliometric measure: the number of electronic accesses (“reads”) of individual articles. By combining data from the text, citation, and reference databases with data from the ADS readership logs we have been able to create second-order bibliometric operators, a customizable class of collaborative filters that permits substantially improved accuracy in literature queries. Using the ADS usage logs along with membership statistics from the International Astronomical Union and data on the population and gross domestic product (GDP), we have developed an accurate model for worldwide basic research where the number of scientists in a country is proportional to the GDP of that country, and the amount of basic research done by a country is proportional to the number of scientists in that country times that countrys per capita GDP. We introduce the concept of utility time to measure the impact of the ADS/URANIA and the electronic astronomical library on astronomical research. We find that in 2002 it amounted to the equivalent of 736 full-time researchers, or

Effect of E-printing on Citation Rates in Astronomy and Physics

250 million, or the astronomical research done in France.

The NASA Astrophysics Data System: Data holdings

In this report we examine the change in citation behavior since the introduction of the arXiv e-print repository (Ginsparg, 2001). It has been observed that papers that initially appear as arXiv e-prints get cited more than papers that do not (Lawrence, 2001; Brody et al., 2004; Schwarz & Kennicutt, 2004; Kurtz et al., 2005a, Metcalfe, 2005). Using the citation statistics from the NASA-Smithsonian Astrophysics Data System (ADS; Kurtz et al., 1993, 2000), we confirm the findings from other studies, we examine the average citation rate to e-printed papers in the Astrophysical Journal, and we show that for a number of major astronomy and physics journals the most important papers are submitted to the arXiv e-print repository first.

The NASA Astrophysics Data System: Architecture

Since its inception in 1993, the ADS Abstract Service has become an indispensable research tool for as- tronomers and astrophysicists worldwide. In those seven years, much eort has been directed toward improving both the quantity and the quality of references in the database. From the original database of approximately 160 000 astronomy abstracts, our dataset has grown al- most tenfold to approximately 1.5 million references cov- ering astronomy, astrophysics, planetary sciences, physics, optics, and engineering. We collect and standardize data from approximately 200 journals and present the resulting information in a uniform, coherent manner. With the co- operation of journal publishers worldwide, we have been able to place scans of full journal articles on-line back to the rst volumes of many astronomical journals, and we are able to link to current version of articles, abstracts, and datasets for essentially all of the current astronomy liter- ature. The trend toward electronic publishing in the eld, the use of electronic submission of abstracts for journal articles and conference proceedings, and the increasingly prominent use of the World Wide Web to disseminate in- formation have enabled the ADS to build a database un- paralleled in other disciplines. The ADS can be accessed at: http://adswww.harvard.edu

TRENDS IN ASTRONOMICAL PUBLICATION BETWEEN 1975 AND 1996

The powerful discovery capabilities available in the ADS bibliographic services are possible thanks to the design of a flexible search and retrieval system based on a relational database model. Bibliographic records are stored as a corpus of structured documents containing fielded data and metadata, while discipline-specific knowledge is segregated in a set of files independent of the bibliographic data itself. This ancillary information is used by the database management software to compile field-specific index files used by the ADS search engine to resolve user queries into lists of relevant documents.
The creation and management of links to both internal and external resources associated with each bibliography in the database is made possible by representing them as a set of document properties and their attributes. The resolution of links available from different locations has been generalized to allow its control through a site- and user-specific preference database. To improve global access to the ADS data holdings, a number of mirror sites have been created by cloning the database contents and software on a variety of hardware and software platforms.
The procedures used to create and manage the database and its mirrors have been written as a set of scripts that can be run in either an interactive or unsupervised fashion. The modular approach we followed in software development has allowed a high degree of freedom in prototyping and customization, making our system rich of features and yet simple enough to be easily modified on a day-to-day basis.
We conclude discussing the impact that new datasets, technologies and collaborations is expected to have on the ADS and its possible role in an integrated environment of networked resources in astronomy.
The ADS can be accessed at:
http://adswww.harvard.edu

The Digital Library of the Astrophysics Data System

Trends in astronomical publication have traditionally been studied by examining the few thousand papers published in a few selected journals within a few selected years. With the development of comprehensive bibliographic databases such as ADS and SIMBAD, publication trends can now be studied using tens of thousands of papers published in a number of refereed astronomy journals. The ADS has extensive bibliographic information on almost every paper published in seven major astronomy journals over the past two decades; the SIMBAD database can be used to verify critical bibliographic information such as the number of authors and the length of the papers. Here we present results of a study of astronomical publication trends using 76,000 papers published in A&A, A&AS, AJ, ApJ, ApJS, MNRAS, and PASP between 1975 and 1996. Two trends are particularly interesting: the fraction of single-author papers has decreased by about a factor of three in the last twenty years, while astronomical papers with more than fifty authors have become increasingly common since 1990.

Access to the Astrophysics Science Information and Abstract System

The Astrophysics Data System (ADS) provides access to astronomical bibliographic information, including references, abstracts, and full journal articles, as well as links to other on-line information sources like on-line electronic journals and on-line data.

An overview of the astrophysics data system

Abstract The Astrophysics Science Information and Abstract System (ASIAS) is sponsored by NASA to make astronomical data and literature references available to the astronomical community. It provides access to abstracts, full article images in bitmapped form, and catalog and archive data through the World Wide Web. These services are accessible through the ADS Data Services page at http://adswww.harvard.edu/ads_services.html.