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已知椭圆\(C\):\( \dfrac {x^{2}}{a^{2}}+ \dfrac {y^{2}}{b^{2}}=1(a > b > 0)\),经过点\(P( \sqrt {3}, \dfrac {1}{2})\),离心率\(e= \dfrac { \sqrt {3}}{2}\).
\((1)\)求椭圆\(C\)的标准方程.
\((2)\)过点\(Q(0, \dfrac {1}{2})\)的直线与椭圆交于\(A\)、\(B\)两点,与直线\(y=2\)交于点\(M(\)直线\(AB\)不经过\(P\)点\()\),记\(PA\)、\(PB\)、\(PM\)的斜率分别为\(k_{1}\)、\(k_{2}\)、\(k_{3}\),问:是否存在常数\(λ\),使得\( \dfrac {1}{k_{1}}+ \dfrac {1}{k_{2}}= \dfrac {λ}{k_{3}}\)?若存在,求出\(λ\)的值:若不存在,请说明理由.