【单选题】在等差数列{a n }中,a 4 =3,那么a 1 +a 2 +…+a 7 =( )
【单选题】盐酸普鲁卡因与NaNO 2 液反应后再与碱性β-萘酚偶合成红色沉淀,其依据为( )
【单选题】盐酸普鲁卡因与NaNO2液反应后,再与碱性β-萘酚偶合成红色沉淀,其依据为
【单选题】指一定时期内,患某病的全部患者中因该病死亡者所占的比例为
【单选题】在等差数列{a n }中,首项a 1 =0,公差d≠0,若a k =a 1 +a 2 +a 3 +…+a 7 ,则k= [ ]
【单选题】在等差数列{a n }中,a 1 +a 2 +a 3 =9,a 6 =11,则该数列的前7项的和是( )
【单选题】一定时期内,患某病的全部患者中因该病死亡者所占的比例称( )
【单选题】一定时期内,患某病的全部病人中因该病死亡者所占的比例是
【简答题】Imagine,one day,getting out of bed in Beijing and being at your office in Shanghai in only a couple of hours,and then,after a full day of work,going back home to Beijing and having dinner there. Sound...
【单选题】在等差数列{an}中,a1=21,a7=18,则公差d=( )