Citations between scientific papers and related bibliometric indices, such as
the $h$-index for authors and the impact factor for journals, are being
increasingly used - often in controversial ways - as quantitative tools for
research evaluation. Yet, a fundamental research question remains still open:
to which extent do quantitative metrics capture the significance of scientific
works? We analyze the network of citations among the $449,935$ papers published
by the American Physical Society (APS) journals between 1893 and 2009, and
focus on the comparison of metrics built on the citation count with
network-based metrics. We contrast five article-level metrics with respect to
the rankings that they assign to a set of fundamental papers, called Milestone
Letters, carefully selected by the APS editors for "making long-lived
contributions to physics, either by announcing significant discoveries, or by
initiating new areas of research". A new metric, which combines PageRank
centrality with the explicit requirement that paper score is not biased by
paper age, is the best-performing metric overall in identifying the Milestone
Letters. The lack of time bias in the new metric makes it also possible to use
it to compare papers of different age on the same scale. We find that
network-based metrics identify the Milestone Letters better than metrics based
on the citation count, which suggests that the structure of the citation
network contains information that can be used to improve the ranking of
scientific publications. The methods and results presented here are relevant
for all evolving systems where network centrality metrics are applied, for
example the World Wide Web and online social networks. An interactive Web
platform where it is possible to view the ranking of the APS papers by rescaled
PageRank is available at the address http://www.sciencenow.info.

本文分析了美国物理学会期刊自 1893 年至 2009 年间发表的 449,935 篇论文的引证网络，并比较了基于引用计数的度量与网络度量之间的差异性。其中，一种结合了 PageRank 中心性、且不受时间偏差影响的新度量是总体表现最佳的度量方式，这也表明引证网络结构包含可用于提高科学出版物排名的信息。