流行病学研究的主要问题是 A.疾病分布及影响分布的因素 B.疾病的病因 C.疾病的防

题型:单项选择题

问题:

流行病学研究的主要问题是

A.疾病分布及影响分布的因素

B.疾病的病因

C.疾病的防制措施

D.流行病研究方法

E.以上均是

考点:疾病控制(医学高级)疾病控制副主任医师(三)
题型:单项选择题

Part 1


Question 46-50


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题型:单项选择题

一般道路运输系统技术要求涉及的方面不包括()。

A.通道宽度 

B.交叉口视距不应小于10m 

C.最小转弯半径 

D.道路与建筑物、构筑物之间的最小距离

题型:单项选择题

某同学在旅游时对着大山喊话,若他能听到回声,大山离他至少 ______米.

题型:单项选择题

在“测定金属丝电阻率”实验中,若粗估金属丝的电阻Rx约为3Ω,为尽可能减小误差,要求金属丝发热功率P<0.75W,备有的部分仪器有:

A.6V电池组

B.电流表(0~0.6A,内阻0.5Ω)

C.电流表(0~3A,内阻0.01Ω)

D.电压表(0~3V,内阻1kΩ)

E.电压表(0~15V,内阻5kΩ)

F.滑动变阻器(0~100Ω,额定电流1A)

G.滑动变阻器(0~20Ω,额定电流1A)

(1)实验中用螺旋测微器测量导线直径时,可估读到______mm,用毫米刻度尺测量导线长度时,可估读到______mm;(2)上述器材中应选用的是______(用字母代替);

(3)在框内画出电路图;  

(4)在下图中,将各器材连成实验电路.

题型:单项选择题

高压起重气垫是一种适合于地震救灾的起重工具,它由如图甲所示的高压气瓶,气管、阀门与气垫连接而成,起重时,气垫放人重物与地面的间隙之间,由高压气瓶向气垫内充气,气垫在短时间内可把重物举起一定高度,如图乙所示,质地均匀的长方体石板长2m,重为6×104N,当气垫气压高达106Pa时,石板恰好被顶起,此时气垫和石板的接触面积是400cm2

(1)高压气瓶向气垫内充气时,气瓶内的气体温度_____,内能_____

(2)如果高压起重气垫在5s内可将105 N的重物举高0.1m,则其功率是多少?

(3)气垫恰好顶起石板时,气垫的中心离石板右端的支点O多远?

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