如何使列一次显示一列

Question

我有一张由四列组成的表格。我希望前两列出现在第一张幻灯片上，而第三列和第四列应出现在第二张幻灯片上。在某种程度上，我使用以下代码实现了这一点。但是，我的水平线首先消失，然后又出现在第二张幻灯片上。查看图片

也许你知道我做错了什么？

\documentclass{beamer}
\usepackage{array}
\usepackage{boldline}
\usepackage{tikz}
\usepackage[utf8x]{inputenc}
\begin{document}

\begin{frame}[t]{Results 1: Whole Sample}
\label{wholesign}
\begin{center}
\scalebox{0.94}{

\begin{tabular} {>{\onslide<1->}lc>{\onslide<2->}cc}

\hlineB{2}
& 3SLS & 3SLS & 3SLS \\ 
& ($t$)  & ($t-1$)  & ($t-2$) \\ [1ex]
\hline 
\alert {Outcome: entrepreneurship} & & & \\
Direct effect of FDI & \textbf{−} & \textbf{−} & \textbf{−} \\ 

Wages & \textbf{−} & \textbf{−} & \textbf{−} \\

Concentration ratio & \textbf{+} & \textbf{+} & \textbf{+} \\
\hline 
& & & \\
\alert {Outcome: wages} & & & \\ 
FDI effect & \textbf{+} & \textbf{+} & \textbf{+} \\
\hline 
& & & \\
\alert {Outcome: concentration ratio} \hspace*{0.7cm} & & & \\
FDI effect & \textbf{+} & \textbf{+} & \textbf{+} \\
\hline 
& & & \\
%Total FDI effect & \textbf{−} & \textbf{−} & \textbf{−} \\
Observations & 3784 & 3782 & 3528 \\  
\hlineB{2}

\end{tabular}
    }   
\end{center}


\end{frame}

\end{document}

Answer 1

怎么样

\documentclass{beamer}
\usepackage{array}
\usepackage{boldline}
\usepackage{tikz}
\usepackage[utf8x]{inputenc}
\begin{document}

\begin{frame}[t]{Results 1: Whole Sample}
\label{wholesign}
\begin{center}
\scalebox{0.94}{

\begin{tabular}{lc>{\onslide<2->}cc<{\onslide<1->}}

\hlineB{2}
& 3SLS & 3SLS & 3SLS \\ 
& ($t$)  & ($t-1$)  & ($t-2$) \\ [1ex]
\hline 
\alert {Outcome: entrepreneurship} & & & \\
Direct effect of FDI & \textbf{AAA} & \textbf{AAA} & \textbf{AAA} \\ 

Wages & \textbf{AAA} & \textbf{AAA} & \textbf{AAA} \\

Concentration ratio & \textbf{+} & \textbf{+} & \textbf{+} \\
\hline 
& & & \\
\alert {Outcome: wages} & & & \\ 
FDI effect & \textbf{+} & \textbf{+} & \textbf{+} \\
\hline 
& & & \\
\alert {Outcome: concentration ratio} \hspace*{0.7cm} & & & \\
FDI effect & \textbf{+} & \textbf{+} & \textbf{+} \\
\hline 
& & & \\
%Total FDI effect & \textbf{AAA} & \textbf{AAA} & \textbf{AAA} \\
Observations & 3784 & 3782 & 3528 \\  
\hlineB{2}

\end{tabular}
    }   
\end{center}


\end{frame}

\end{document}