It is the average number of times the nano-articles published within a year have been cited in the Journal Citation Reports.
This field displays the h-index count and is based on a list of publications ranked in descending order by the Times Cited count. The h-index is the number of item which is in the h rank of the mentioned ranking and have at least "h" citations. For example, an h-index of 20 means there are 20 items that have 20 citations or more. This metric is useful because it discounts the disproportionate weight of highly cited papers or papers that have not yet been cited.
Number of nanotechnology articles indexed in ISI (Web of Science)