  In addition to science citation indicators of journals like impact and
immediacy, social network analysis provides a set of centrality measures like
degree, betweenness, and closeness centrality. These measures are first
analyzed for the entire set of 7,379 journals included in the Journal Citation
Reports of the Science Citation Index and the Social Sciences Citation Index
2004, and then also in relation to local citation environments which can be
considered as proxies of specialties and disciplines. Betweenness centrality is
shown to be an indicator of the interdisciplinarity of journals, but only in
local citation environments and after normalization because otherwise the
influence of degree centrality (size) overshadows the betweenness-centrality
measure. The indicator is applied to a variety of citation environments,
including policy-relevant ones like biotechnology and nanotechnology.
