The last few years have seen the proliferation of measures that quantify the scientific output of researches. Yet, these measures focus on productivity, thus fostering the "publish or perish" paradigm. This article proposes a measure that aims at quantifying the impact of research de-emphasizing productivity, thus providing scientists an alternative, conceivably fairer, evaluation of their work. Emphasis is placed on the scientist rather than on quantities that can grow unbounded. The measure, defined initially for manuscripts, is then extended to researchers and institutions.

This paper has been published in Scientific Reports, and the final version is quite different (not at all compared with this version). I would like to withdraw it from the arXiv