Try

as an example. Here, when addin' the \\ we add another \\ plus [-xmm], and you can adjust it as you wish.

The following code was used

[math]\frac{{\partial (x,y)}}

{{\partial (u,v)}} = \left| {\begin{array}{ccc}

{\dfrac{{\partial x}}

{{\partial u}}} & {\dfrac{{\partial x}}

{{\partial v}}} \\\\[-2mm]

{\dfrac{{\partial y}}

{{\partial u}}} & {\dfrac{{\partial y}}

{\partial v}}

\end{array} } \right|[/tex]