已知数列\(\{a _{n} \}\)中，\(a _{1} =1\)，\(a_{n+1}= \dfrac {(n+1)a_{n}}{n+2a_{n}}(n∈N^{*})\)．
\((1)\)求证：\(\{ \dfrac {n}{a_{n}}\}\)是等差数列；
\((2)\)若\(c _{n} =a _{n} a _{n+1}\)，且数列\(b_{n}= \dfrac {4}{3^{n}\cdot n}\)，数列\(\{b _{n} c _{n} \}\)的前\(n\)项和为\(T _{n}\)，求\(T _{n}\)的取值范围．