13．已知定义在$(-\infty$，$0)\bigcup (0$，$+\infty )$上的奇函数$f(x)$，对任意的$x_{1}$，$x_{2}\in (-\infty ,0)$，$x_{1}\ne x_{2}$，满足$[x_{2}f(x_{2})-x_{1}f(x_{1})](x_{2}-x_{1})>0$，且$f$（1）$=2$，则$f(x)>\frac{2}{x}$的解集为$($　　$)$