\normalfont 的替代写法

Question

当我使用时，\begin{lemma} .. \end{lemma}我应该\normalfont在后面写\begin{lemma}以得到正常字体。否则，词根中的内容将为斜体字体。

总是这样写不太舒服\normalfont。有没有更简单的方法可以让引理（和其他地方）中的所有内容都变成正常字体，而无需这样写\normalfont？

\documentclass[12pt,reqno,a4paper]{amsart}
\usepackage{extsizes}
\usepackage{blindtext}
\textheight 9.3in \textwidth 6.5in
\calclayout
\usepackage{mathtools}
\usepackage{amsmath,amsthm,amsfonts,amssymb}
\newtheorem{theorem}{Theorem}[section]
\newtheorem{construction}{Construction}[section]
\newtheorem{corollary}{Corollary}[section]
\usepackage{hyperref}
\usepackage{mathrsfs}
\usepackage[all]{xy}
\usepackage[normalem]{ulem}
\newtheorem{lemma}{Lemma}[section]
\newtheorem*{question}{Question}
\theoremstyle{definition}
\newtheorem*{solution}{Solution}
\newtheorem{definition}{Definition}[section]
\newtheorem{remark}{Remark}[section]
\newtheorem{proposition}{Proposition}[section]
\newtheorem{exercise}{Exercise} 
\newtheorem{example}{Example}[section]
\usepackage{tikz-cd}
\usepackage[utf8]{inputenc}
\usepackage[english]{babel}
% \renewcommand{\baselinestretch}{2} 
\usepackage{color}
\pagestyle{myheadings}
\begin{document}
\end{document}

Answer 1

您可以将\theoremstyle之前的设置\newtheorem{lemma}{Lemma}{section}为使用非斜体罗马字体definition的预定义样式（之后的每个 都将使用该样式，您可以使用 切换回斜体样式）：amsthm\newtheorem\theoremstyle\theoremstyle{plain}

\documentclass[12pt,reqno,a4paper]{amsart}
\usepackage{extsizes}
\usepackage{blindtext}
\textheight 9.3in \textwidth 6.5in
\calclayout
\usepackage{mathtools}
\usepackage{amsmath,amsthm,amsfonts,amssymb}
\newtheorem{theorem}{Theorem}[section]
\newtheorem{construction}{Construction}[section]
\newtheorem{corollary}{Corollary}[section]
\usepackage{hyperref}
\usepackage{mathrsfs}
\usepackage[all]{xy}
\usepackage[normalem]{ulem}
\newtheorem*{question}{Question}
\theoremstyle{definition}
\newtheorem*{solution}{Solution}
\newtheorem{definition}{Definition}[section]
\newtheorem{remark}{Remark}[section]
\newtheorem{proposition}{Proposition}[section]
\newtheorem{exercise}{Exercise} 
\newtheorem{example}{Example}[section]
\usepackage{tikz-cd}
\usepackage[utf8]{inputenc}
\usepackage[english]{babel}
% \renewcommand{\baselinestretch}{2} 
\usepackage{color}
\pagestyle{myheadings}
\theoremstyle{definition}
\newtheorem{lemma}{Lemma}[section]
\begin{document}
\begin{lemma}
  This is a lemma
\end{lemma}
\begin{theorem}
  This is a theorem
\end{theorem}
\end{document}