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大量咯血患者咯血量是
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乒乓球右手正手攻球正确的用力方向是（0.
The transformer receives on the primary winding an AC voltage and delivers on the secondary winding a different DC voltage(a lower one)
Voltage regulators are circuits designed to maintain the output of power supplies at constant amplitude despite variations of the AC source voltage or changes of the resistance of the load.
乒乓球攻球按击球位置和站位可分为正手攻球、反手攻球和侧身攻球。
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