\listfiles
\documentclass{jarticle}
\usepackage{amsmath}
\usepackage{array}
\begin{document}

\begin{equation*}
\left(\begin{array}{cccc}
a_{11} & a_{12} & \cdots & a_{1m} \\
a_{21} & a_{22} & \cdots & a_{2m} \\
\vdots & \vdots & \ddots & \vdots \\
a_{n1} & a_{n1} & \cdots & a_{nm}
\end{array}
\right)
\qquad
\left(\begin{array}{c@{}c@{}c@{}c}
a_{11} & a_{12} & \cdots & a_{1m} \\
a_{21} & a_{22} & \cdots & a_{2m} \\
\vdots & \vdots & \ddots & \vdots \\
a_{n1} & a_{n1} & \cdots & a_{nm}
\end{array}
\right)
\quad
{\renewcommand\arraystretch{0.8}
\left(\begin{array}{c@{}c@{}c@{}c}
a_{11} & a_{12} & \cdots & a_{1m} \\
a_{21} & a_{22} & \cdots & a_{2m} \\
\vdots & \vdots & \ddots & \vdots \\
a_{n1} & a_{n1} & \cdots & a_{nm}
\end{array}
\right)
}
\qquad
{\renewcommand\arraystretch{0.7}
\left(\begin{array}{c@{}c@{}c@{}c}
a_{11} & a_{12} & \cdots & a_{1m} \\
a_{21} & a_{22} & \cdots & a_{2m} \\
\vdots & \vdots & \ddots & \vdots \\
a_{n1} & a_{n1} & \cdots & a_{nm}
\end{array}
\right)
}
\end{equation*}

\end{document}
