I would like to write something like the definition of a gradient operator in cartesian coordinates.
\usepackage{amsmath}
\begin{equation}
\nabla \Phi =
\begin{pmatrix}
\frac{\partial \Phi}{\partial x} \\
\frac{\partial \Phi}{\partial y} \\
\frac{\partial \Phi}{\partial z} \\
\end{pmatrix}
\end{equation}
The fractions are rendered small, as when they are rendered inline, but I don't like it in that particular instance.
I knew this would happen since it is documented there: http://en.wikibooks.org/wiki/LaTeX/Mathematics#Matrices_and_arrays
Even if I increase the spacing by adding [0.5em] after the double-backslash, it still doesn't look very good. I have a lot of space so I'd like the content of the matrix not to squeeze itself.
How can I make the content of a matrix using its normal size and not its inline size?