答案1
这主要是风格问题。我给你三种不同的策略。
\documentclass{article}
\usepackage{amsmath}
\begin{document}
First display with \verb|\frac|, in the right hand side
the fractions are smaller
\[
\frac{H_{W,WDV}}{H_{W,TDW}}=
\frac{
\frac{\Delta_{VDW}}{w_{VDW}}
}{
\frac{\Delta_{TDW}}{w_{TDW}}
}
\]
and second display with \verb|\dfrac|, in the right
hand side the fractions are larger
\[
\frac{H_{W,WDV}}{H_{W,TDW}}=
\frac{
\,\dfrac{\Delta_{VDW}}{w_{VDW}\mathstrut}\,
}{
\,\dfrac{\mathstrut \Delta_{TDW}}{w_{TDW}}\,
}
\]
Finally, a third display with the slashed form
\[
\frac{H_{W,WDV}}{H_{W,TDW}}=
\frac{
\Delta_{VDW}/w_{VDW}
}{
\Delta_{TDW}/w_{TDW}
}
\]
\end{document}
答案2
第四个显示来自 的\mfrac
(~80 % \displaystyle
) nccmath
。以 egreg 为例:
\documentclass{article}
\usepackage{nccmath}
\begin{document}
First display with \verb|\frac|, in the right hand side
the fractions are smaller: \[
\frac{H_{W,WDV}}{H_{W,TDW}}=
\frac{
\frac{\Delta_{VDW}}{w_{VDW}}
}{
\frac{\Delta_{TDW}}{w_{TDW}}
}
\]
and second display with \verb|\dfrac|, in the right
hand side the fractions are larger: \[
\frac{H_{W,WDV}}{H_{W,TDW}}=
\frac{
\,\dfrac{\Delta_{VDW}}{w_{VDW}\mathstrut}\,
}{
\,\dfrac{\mathstrut \Delta_{TDW}}{w_{TDW}}\,
}
\]
Finally, a third display with \verb|\mfrac| in the right-hand side as a compromise: \[
\frac{H_{W,WDV}}{H_{W,TDW}}=
\frac{
\,\mfrac{\Delta_{VDW}}{w_{VDW}\mathstrut}\,
}{
\,\mfrac{\mathstrut \Delta_{TDW}}{w_{TDW}}\,
}
\] \end{document}