It can be useful for a researcher to highlight the number of citations received by his articles in order to demonstrate the impact he has made in his field. Indeed, despite some limitations, the number of citations received is one of the accepted indicators for measuring the impact of an article. A high number of citations is associated with a greater impact.

Like all indicators, those in bibliometrics have a certain amount of bias that must be taken into account. They should therefore be used in addition to each other, keeping in mind that they are based on quantitative rather than qualitative data. The CIRAD website details the calculations, the objectives and the precautions to be taken concerning these indicators.

The h-index

Introduced in 2005 by Jorge Hirsch, this index seeks to measure the productivity and impact of a scientist or group of scientists through the number of publications and citations received. Thus, a researcher will have an index of h if h of his articles have been cited at least h times.

Like any other indicators, the h-index has certain limitations:

• It varies widely between disciplines, so it should not be used to compare researchers from different disciplines;
• It varies greatly according to the age of a researcher and the duration of his career;
• It does not take into account the order of the authors, or the number of authors of an article;
• Excess citations to the h-index are ignored (an author who has published a single article with 300 citations will still have an h-index of 1).

The h-index of a researcher can be accessed on the Scopus database (this resource is available at URCA).

There are other indicators, such as the Scimago Journal Rank, the Eigenfactor or the G index.

Altmetrics

Altmetrics assess the impact on the internet of a publication or piece of information, through its dissemination and the actions and interactions it generates on social networks, blogs and microblogs, and in the press. In HAL, the metrics give the number of consultations of the record and the number of downloads of the document.

Profile tools like ImpactStory can centralize this social data (creating an account on ImpactStory requires an ORCID).

To compute bibliometric indicators, tools identify scientific publications and their citations (issued and received). Managed by commercial companies, some of them are only accessible by subscription. Despite constant evolutions, they all have limitations, such as :

• a partial coverage of scientific publications (the human and social sciences are less represented) and sometimes unknown duplicates in bibliographic references
• duplicate bibliographic references
• all quotations are taken into account, without any value level (non-exclusion of self-citations; negative quotations...)
• the lack of consideration of the quality of the articles, which only peer reviewing assesses, and of other aspects of the research activity, such as teaching, which would allow a more reliable assessment of the quality of the researcher.

The three main databases are:

• Scopus: founded in 1994 by the Elsevier company, it indexes more than 20,000 journals and 150,000 books, mainly in Health and Science but the representation of Human Sciences increases. This resource is available at URCA.
• Web of Science: Founded by Thomson Reuters, which in 1992 acquired the Institute for Scientific Information. It scans 12,000 journals and 148,000 conference proceedings, mostly in the field of Health and Science. This resource is available at URCA.
• Google Scholar: Google Scholar uses the power of the engine of the same name to browse and index scientific articles on the Web. Easy to use and free, its coverage of publications is unknown: this tool is to be used with care.