\begin{figure}[h]
\centering
\begin{tabular}{@{}cc@{}}
\includegraphics[width=.23\textwidth]{figure9a.pdf} &
\includegraphics[width=.23\textwidth]{figure9b.pdf} \\
\end{tabular}
\caption{This is some figure side by side}
\end{figure}
https://tex.stackexchange.com/questions/84889/combining-multiple-eps-files-into-a-single-figure
\usepackage{subfigure}
%\begin{figure}[h]
%\centering
% when using pdflatex, use pdf file:
%\subfigure{
%\label{fig:subfig:a} %% label for first subfigure
% \includegraphics[width=3.0in]{figure9a.pdf}}
%\hspace{0.05in}
%\subfigure{
%\label{fig:subfig:b} %% label for second subfigure
% \includegraphics[width=1.0in]{figure9b.pdf}}
%\caption{Scatter of CCN number concentration ($S=0.2\%, cm^{-3}$) and ground precipitations ($unit: mm h^{-1}$) with four cases, connected by smoothed lines with different scale ($<30, 30-250, >250$) in 14 sites of Nanjing}
%\label{fig:subfig} %% label for entire figure
%\includegraphics[width=10cm,height=6cm]{picture.pdf}
%\caption{Scatter of CCN number concentration ($S=0.2\%, cm^{-3}$) and ground precipitations ($unit: mm h^{-1}$) with four cases, connected by smoothed lines with different scale ($<30, 30-250, >250$) in 14 sites of Nanjing}\centering
%\label{figone}
%\end{figure}
这两个插入后都不对，后面一个是图片太大了，导致了错乱
https://tex.stackexchange.com/questions/37581/latex-figures-side-by-side
\usepackage{subfig}
\begin{figure}[h]
\centering
\subfloat{\includegraphics[width=5cm]{figure11a.pdf} }%
%\qquad
\subfloat{\includegraphics[width=5cm]{figure11b.pdf}}\\
\subfloat{\includegraphics[width=5cm]{figure11c.pdf} }%
%\qquad
\subfloat{\includegraphics[width=5cm]{figure11d.pdf} }%
\caption{2 Figures side by side}%
\label{figone}%
\end{figure}
