【简答题】He showed us______(person) around the factory.
【单选题】下列说法正确的是[ ]
A.
刚玉、金刚砂,红宝石、蓝宝石的主要成分是氧化铝
B.
石英、硅石、水晶、珍珠、玛瑙主要成分都是SiO2
C.
工业制水泥、玻璃都要用到石灰石;制水泥、陶瓷都要用到粘土
D.
氮化硅陶瓷,光导纤维,钠硅玻璃都属于新型硅酸盐材料
【单选题】When Apple showed the world Siri, I believe they showed us the next major【C1】______user 【C2】______ The idea of talking to computers is nothing new. It has, of course, been【C3】______in scifi novels, mo...
【简答题】短周期元素组成的单质A、B、C和甲、乙、丙、丁四种化合物,它们之间有图示的转化关系,已知C为密度最小的气体,甲俗称刚玉,是红宝石的主要成分。 ⑴写出丙的名称: , B的分子式 。 ⑵组成单质A的元素在周期表中的位置是 。 (3)写出下列变化的方程式: ①A与NaOH溶液反应的化学方程式 。 ②乙溶液与过量CO 2 反应的离子方程式 。 ⑷反应①的反应类型属于 。
【简答题】A widely-used gas that is currently produced from fossil fuels can instead be made by an artificial leaf that uses only sunlight, carbon dioxide and water, and which could ually be used to develo...
【单选题】为昏迷病人插管,当胃管插至15cm(会厌部)时,要将病人头部托起,其目的是
【简答题】阅读理解 (共 5 小题,每小题 2 分,共 10 分) In a world with limited land, water and other natural resources ( 资源 ), the harm from the traditional business model is on the rise. Actually, the past decades has seen mo...
【简答题】They showed us the place. They once lived and worked in that place.
【单选题】关于青贮饲料调制以下说法正确的是( )。
A.
用玉米秸青贮时,一般在玉米果穗成熟,玉米叶全部枯黄时收割青贮效果较好
B.
青贮饲料切碎、装填时间越短、密封越严实,青贮效果越好
C.
豆科牧草(如苜蓿)蛋白质含量高,比禾本科牧场更易青贮
D.
青贮饲料调制时,若添加乳酸菌,可提高青贮效果