有没有办法修改定理环境以便在语句之前和之后立即有一个水平线？

Question

我刚刚看到这个解决方案证明环境很好，我非常喜欢。

如何在校样末尾画一条水平线？

我想知道是否有一种优雅的方法可以在定理环境下做到这一点。

笔记 我不想使用盒子或者 mdframed 包......

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编辑：例如以下代码不起作用：

\documentclass[11pt,a4paper]{book}
    \usepackage[utf8]{inputenc}
    \usepackage[T1]{fontenc}
    \usepackage{fourier}
    \usepackage{lipsum}
    \usepackage{amsmath}

    \usepackage{thmtools} 
    \usepackage[thmmarks, thref, amsmath]{ntheorem}
    \theoremstyle{plain}
    \theoremprework{\bigskip\hrule\vspace{-1.5ex}\leavevmode\nobreak}%\leavevmode
    \theorempostwork{\vspace*{-1ex}\hrule\bigskip\leavevmode}
    \theoremheaderfont{\scshape}
    \theorembodyfont{\itshape}
    \theoremseparator{. }
    \newtheorem{thm}{Theorem}
    \begin{document}
    \tableofcontents
    \lipsum[1]
    \begin{thm}[D’Alembert-Gauss]
    The field $\mathbf C$ is algebraically closed.
    \end{thm}
    \lipsum[2]

 \addcontentsline{toc}{chapter}{List of Theorems}
 \listoftheorems[ignoreall,onlynamed={thm,lmm,prop}
\end{document} 

Answer 1

使用 \theoremprework和\theorempostwork命令非常简单ntheorem：

\documentclass[11pt,a4paper]{book}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{fourier}
\usepackage{lipsum}
\usepackage{amsmath}

\usepackage[thmmarks, thref, amsmath]{ntheorem}%
\theoremstyle{plain}
\theoremprework{\bigskip\hrule\vspace{-1.5ex}\leavevmode\nobreak}%\leavevmode
\theorempostwork{\vspace*{-1ex}\hrule\bigskip\leavevmode}
\theoremheaderfont{\scshape}
\theorembodyfont{\itshape}
\theoremseparator{. }
\newtheorem{thm}{Theorem}
\usepackage{thmtools}
\begin{document}
\tableofcontents
\bigskip

\lipsum[1]
\begin{thm}[D’Alembert-Gauss]
The field $\mathbf C$ is algebraically closed.
\end{thm}
\lipsum[2]
\bigskip
\addcontentsline{toc}{chapter}{List of Theorems}
\theoremlisttype{allname}
\listtheorems{thm}%

\end{document}