如图所示矩形挡水闸AB,已知水深h=3m,板的宽b=2.5m,求作用在矩形平板AB上的静水总压力大小以及作用点处的水深。
《煤矿安全质量标准化标准》规定,综采工作面机道梁端至煤壁的顶板冒落高度不大于()。 ["200mm","300mm","400mm"]
鼓风机的噪声属于()。 ["交通噪声","工业噪声","建筑施工噪声","生活噪声"]
Examine the structure of the EMPLOYEES table: EMPLOYEE_ID NUMBER Primary Key FIRST_NAME VARCHAR2(25) LAST_NAME VARCHAR2(25) Which three statements insert a row into the table? () ["INSERT INTO employees VALUES ( NULL, 'John', 'Smith');","INSERT INTO employees( first_name, last_name) VALUES( 'John', 'Smith');","INSERT INTO employees VALUES ( '1000', 'John', NULL);","INSERT INTO employees (first_name, last_name, employee_id) VALUES ( 1000, 'John', 'Smith');","INSERT INTO employees (employee_id) VALUES (1000);","INSERT INTO employees (employee_id, first_name, last_name) VALUES ( 1000, 'John', ' ')"]
原则上预算单位办理公务卡的对象是()。 ["在职、在编工作人员","短期、临时借调人员","离退休职工","退休或辞职职工"]
中国饮食文化中不利于心理健康的因素包括哪些方面?