Proceedings of the National Academy of Sciences of the United States of America
Proceedings of the National Academy of Sciences of the United States of America, or short PNAS Proc. Natl. Acad. Sci. USA for citations and bibliographies, is published in the U.S. scientific journal, published by the Academy of Sciences of the United States (United States National Academy of Sciences). It is published weekly since 1915 as a printed edition and has all the scientific disciplines on the subject, with an emphasis on contributions from biology and related fields such as medicine and biotechnology.
Prior to publication in PNAS are subject to a peer-reviewed scientific publications, ie an assessment by other scientists who act as independent reviewers. Members of the Academy are entitled to it, for up to four separate publications per year to organize the peer-review process itself. In addition, Academy members per year can forward up to two manuscripts by non-members of the magazine and support the selection of the appraiser and by a letter of recommendation.
The total number of previously published in PNAS article is among the highest of all scientific journals. The Impact Factor as a measure of the average number of citations per published article is in 2012 at 9,737, which PNAS by Science and Nature has the fourth-highest impact factor of all multi-disciplinary journals. Relative to the total number of citations was PNAS in the period 1994-2004 according to the Journal of Biological Chemistry, the second most frequently cited journal. Six months after the publication PNAS article in full text freely accessible.