我怎样才能实现这种定理风格（非常常见）？

Question

考虑：

我怎样才能实现这种定义、定理等的风格？我只知道定理类环境的标准或“普通”风格（标题为粗体，正文为斜体）。

Answer 1

这里有一个解决方案，它利用包的机制amsthm来创建一种新的定理风格，称为（为什么不呢？）descrates。

\documentclass{article}
\usepackage[T1]{fontenc}
\setlength\textwidth{11cm} % just for this example

\usepackage{amsthm}
%% See p. 9 of the user guide of the 'amsthm' package 
%% for the "\newtheoremstyle" macro:
\newtheoremstyle{descrates}
   {3pt}% Space above
   {3pt}% Space below
   {}% Body font
   {}% Indent amount
   {\scshape}% Theorem head font % <-- small caps
   {.}% Punctuation after theorem head
   {.5em}% Space after theorem headi
   {}% Theorem head spec (can be left empty, meaning `normal' )

\theoremstyle{descrates} % switch to the newly create style
\newtheorem{defn}{Definition}[section]

\begin{document}
\setcounter{section}{1} % just for this example
\setcounter{defn}{32}

\begin{defn}
A topological space is said to be \textbf{Lindelöf} if 
every open cover has a \textsl{countable} subcover.
\end{defn}

\end{document}

---

附录：如果要使用ntheorem包而不是amsthm包，则需要用以下代码替换上面代码中的\usepackage{amsthm}和指令：\newtheoremstyle

\usepackage{ntheorem}
\global\theorembodyfont{\upshape}
\newtheoremstyle{descrates}%
   {\item[\hskip\labelsep\scshape ##1\ ##2.]}%
   {\item[\hskip\labelsep\scshape ##1\ ##2\ (##3).]}