  In this work we have studied the research activity for countries of Europe,
Latin America and Africa for all sciences between 1945 and November 2008. All
the data are captured from the Web of Science database during this period. The
analysis of the experimental data shows that, within a nonextensive
thermostatistical formalism, the Tsallis \emph{q}-exponential distribution
$N(c)$ satisfactorily describes Institute of Scientific Information citations.
The data which are examined in the present survey can be fitted successfully as
a first approach by applying a {\it single} curve (namely, $N(c) \propto
1/[1+(q-1) c/T]^{\frac{1}{q-1}}$ with $q\simeq 4/3$ for {\it all} the available
citations $c$, $T$ being an "effective temperature". The present analysis
ultimately suggests that the phenomenon might essentially be {\it one and the
same} along the {\it entire} range of the citation number. Finally, this
manuscript provides a new ranking index, via the "effective temperature" $T$,
for the impact level of the research activity in these countries, taking into
account the number of the publications and their citations.
