Tikz 和 Beamer 的问题

Question

当我把这段代码放到 beamer 上时，得到了糟糕的数据

\documentclass[leqno,mathserif]{beamer} \usepackage{graphics,bm}
\usetheme{Luebeck} \setbeamercovered{transparent}
\usepackage[utf8]{inputenc} \usepackage[T1]{fontenc}
\usepackage[english,french]{babel} \usepackage{tikz}
\usetikzlibrary{positioning}
 \begin{document}
\begin{frame} \begin{figure}[h!] \centering \begin{tikzpicture}
\matrix [column sep=7mm, row sep=5mm] {   \node (se) [draw,
shape=rectangle] {Existence Forte}; &   \node (yw) [draw,
shape=circle] {Yamada-watanab}; &   \node (ul) [draw,
shape=rectangle] {Unicité en Loi}; \\   \node (d1) [draw,
shape=circle] {Définition}; & &   \node (d2) [draw, shape=circle]
{Définition}; \\   \node (we) [draw, shape=rectangle] {Existence
Faible}; &   \node (ec) [draw, shape=circle] {Engelbert-Cherny}; &  
\node (pu) [draw, shape=rectangle] {Unicité Trajectorielle}; \\ };
\draw[->, thick] (se) -- (d1); \draw[->, thick] (d1) -- (we);
\draw[->, thick] (we) -- (yw); \draw[->, thick] (yw) -- (se);
\draw[->, thick] (se) -- (ec); \draw[->, thick] (ul) -- (ec);
\draw[->, thick] (ec) -- (pu); \draw[->, thick] (pu) -- (yw);
\draw[->, thick] (pu) -- (d2); \draw[->, thick] (d2) -- (ul);
\end{tikzpicture}  \caption{les différentes notions d'existence et
d'unicité}    \end{figure}   \end{frame}
\end{document}

我的目的是这样： 感谢@samcarter，但仍然看起来像：

Answer 1

\documentclass[leqno,mathserif]{beamer} 
\usepackage{graphics,bm}
\usetheme{Luebeck} 
\setbeamercovered{transparent}
\usepackage[utf8]{inputenc} 
\usepackage[T1]{fontenc}
\usepackage[english,french]{babel} 
\usepackage{tikz}
\usetikzlibrary{positioning}
\usetikzlibrary{matrix}
\begin{document}

\begin{frame}
    \begin{figure}
      \scalebox{.8}{
        \begin{tikzpicture}
            \matrix (magic) [matrix of nodes,ampersand replacement=\&, column sep=7mm, row sep=5mm]{
                \node (se) [draw,shape=rectangle] {Existence Forte}; \&
                \node (yw) [draw,shape=circle] {Yamada-watanab}; \&
                \node (ul) [draw,shape=rectangle] {Unicité en Loi}; \\
                \node (d1) [draw,shape=circle] {Définition}; \& 
                \&   
                \node (d2) [draw, shape=circle] {Définition}; \\
                \node (we) [draw, shape=rectangle] {Existence Faible}; \&
                \node (ec) [draw, shape=circle] {Engelbert-Cherny}; \& 
                \node (pu) [draw, shape=rectangle] {Unicité Trajectorielle}; \\
            };
            \draw[->, thick] (se) -- (d1); \draw[->, thick] (d1) -- (we);
            \draw[->, thick] (we) -- (yw); \draw[->, thick] (yw) -- (se);
            \draw[->, thick] (se) -- (ec); \draw[->, thick] (ul) -- (ec);
            \draw[->, thick] (ec) -- (pu); \draw[->, thick] (pu) -- (yw);
            \draw[->, thick] (pu) -- (d2); \draw[->, thick] (d2) -- (ul);
        \end{tikzpicture}
      }
    \end{figure}
\end{frame}

\end{document}