^pInstitute;
of;
Pediatrics,;
Beijing;
100020,;
China;
^pChildren's;
Hospital;
attached;
to;
Capital;
Medical;
University,;
Beijing;
100045,;
China;
^pInstitute;
of;
Respiratory;
Diseases,;
Guangzhou;
510120,;
Cruangdong,;
China;
^pHospital;
of;
Chongqing;
Medical;
University,;
Chongqing;
400014,;
China;
^pCentre;
for;
Disease;
Control;
and;
Prevention,;
Beijing;
100050,;
China;
流行病学调查; 中国城市; 患病率; 哮喘; 儿童; 多中心; 随机抽取; 呼吸道感染;