碳钢的再结晶退火温度一般为（）℃。 A.300 B.1000 C.750～850 D 发布时间：2019-02-19 10:08 │ 来源：www.tikuol.com 题型：单项选择题 问题： 碳钢的再结晶退火温度一般为（）℃。A.300B.1000C.750～850D.680～720
题型：单项选择题 足量铜与一定量的浓硝酸反应，得到硝酸铜溶液和NO2、N2O4、NO的混合气体，这些气体与1.68 LO2(标准状况)混合后通入水中，所有气体完全被水吸收生成硝酸．若向所得硝酸铜溶液中加入5 mol/L NaOH溶液至Cu2＋恰好完全沉淀，则消耗NaOH溶液的体积是[ ]A．60 mL B．45 mL C．30 mL D．15 mL 查看答案
题型：单项选择题 男孩，11岁，畏寒发热12天，伴头痛，纳差，轻度咳嗽，偶有恶心。近2天便秘。体检：体温39.5℃，热性面容，神萎，心率100次/分，双肺呼吸音稍粗，腹略胀，肝肋下2.5cm，脾肋下1.5cm.血压16/9kPa。该病儿需做的首要检查是（）A.血常规B.血培养及肥达反应C.肝功能D.OT试验E.胸部X线片 查看答案
题型：单项选择题 Since life began eons ago, thousands of creatures have come and gone. Some, such as the dinosaurs, became extinct due to naturally changing ecologic conditions. More recent threats to life forms are humans and their activities. Man has drained marshes, burned prairies, dammed and diverted rivers. Some of the more recent casualties of man’s expansion have been the dodo, great auk, passenger pigeon, Irish elk, and Steller’s sea cow. Sadly, we can no longer attribute the increasing decline in our wild animals and plant species to "natural" processes. Many species are dying out because of exploitation, habitat alteration or destruction, pollution, or the introduction of new species of plants and animals to an area. As mandated by Congress, protecting endangered species, and restoring them to the point where their existence is no longer jeopardized, is the primary objective of the U.S. Fish and Wilidlife Service’s Endangered Species Program.Which of the following is NOT a cause of increasing decline of wild animal population A．ExploitationB．PollutionC．Habitat alterationD．Congressional law 查看答案