有 serif 用的最多的是 Time New Roma，不过，那是在windows 下面
在Linux 下面是Nimbus Roman， 在后面的ubuntu 中替换成了 Liberation Serif
From Wikipedia: Nimbus Roman is a serif typeface created by URW Studio in 1982.
Nimbus Roman No 9 L is a serif typeface created by URW Studio in 1987, and eventually released under the GPL and AFPL (as Type 1 font for Ghostscript) in 1996 and LPPL in 2009. It features Normal, Bold, Italic, and Bold Italic weights, and is one of several freely licensed fonts offered by URW++.
Although the characters are not exactly the same, Nimbus Roman No 9 L has metrics almost identical to Times and Times New Roman. It is one of the Ghostscript fonts, a free alternative to 35 basic PostScript fonts (which include Times).
It is a standard typeface in many Linux distributions. It was used as default font in OpenOffice.org Writer in some Linux distributions (e.g. Ubuntu - up to version 8.10; since Ubuntu 9.04 the default font was changed to Liberation Serif).
来源：oschina
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