单选题有两排座位，前排6个座位，后排7个座位．若安排2人就座，规定前排中间2个座位不能坐，且此2人始终不能相邻而坐，则不同的坐法种数为______．

单选题(1-2x) n =a 7 x 7 +a 6 x 6 +…+a 1 x+a 0 ，则a 1 +a 3 +a 5 +a 7 的值为______．

单选题有两批电子元件，其合格率分别为0．9和0．8．现从每批元件中随机各抽取一件，则取出的两件产品中恰有一件合格品的概率为( )．

单选题甲、乙两人独立地对同一目标射击一次，其命中率分别为0．6和0．5，现已知目标被命中，是甲射中的概率为 ( )

单选题Disability among the elderly has declined markedly in the United States in the past two decades. In 1984, 25 percent of the elderly population reported difficulty with activities associated with independent living. By 1999, the share had fallen to 20 percent, a decline of one-fifth. Although these basic facts are well known, their interpretation is not clear. Is the reduction in disability a result of improved medical care, individual behavioral changes, environmental modifications that allow the elderly to better function by themselves, or other demographic changes? Will the trend continue, or is it time limited? What does the reduction in disability mean for years of healthy life and labor force participation? The researchers David Cutler, Mary Beth Landrum, and Kate Stewart focus on disability caused by cardiovascular disease to investigate the role of improved medical care on reductions in disability. By looking at just one condition, they can analyze health shocks and their outcomes in some detail. Cardiovascular disease is a natural condition to analyze, because it is the most common cause of death in the United States and most other developed countries. Also, more is spent on cardiovascular disease than on any other condition, clearly a case where medical care could really matter. The researchers measure disability as the presence of impairments in. Activities of Daily Living (ADLs) and Instrumental Activities of Daily Living (IADLs). Their data source, the National Long-Term Care Survey(NLTCS) , includes information on six ADL measures: eating, getting in or out of bed, walking around inside, dressing, bathing, and getting to or using the toilet. There are also questions about eight IADL measures: doing light housework or laundry, preparing meals, shopping for groceries, getting around outside, managing money, taking medications, and making telephone calls. The NLTCS is a nationally representative longitudinal survey of the health and disability profile of the population aged 65 and over. Cutler and his co-researchers find that reduced disability associated with cardiovascular disease accounts for a significant part of the total reduction in disability--between 14 and 22 percent. The evidence suggests that improvements in medical care, including both increased use of relevant procedures and pharmaceuticals, led to a significant part of this decline in disability. Regions with higher use experienced substantial reductions in mortality and disability. While precise data on the implications of reduced disability are lacking, the possible impact of disability reductions is staggering. The researchers estimate that preventing disability after an acute cardiovascular event can add as much as 3.7 years of quality-adjusted life expectancy, or perhaps $ 316,000 of value. The cost of this outcome is significantly smaller. The initial treatment costs range from $ 8,610 to $ 16,332, depending on the procedure used. Further, recent cost analyses reported that annual Medicare spending was lower for the non-disabled than the disabled, which suggests that higher treatment costs may be offset by lower future spending among a more healthy population. By virtually any measure, therefore, the researchers conclude that medical technology after acute cardiovascular episodes is worth the cost.

单选题曲线y=x2与直线x=0，x=1，y=t(0＜t＜1)所围的图形的面积为( )．

单选题函数z=x 2 -xy+y 2 +9x-6y+20有______

单选题设函数，则f(x)的间断点______

单选题设函数f(x)在(-∞，+∞)内有定义，且f(x)的反函数为g(x)．记则

单选题在一次运动会上有4项比赛的冠军在甲、乙、丙3人中产生，那么不同的夺冠情况共有______种．A．B．43C．34D．E．

单选题设f(x)有一阶导数且f(0)=1，则

单选题有已知a，b，c是三个正整数，且a＞b＞c，若a，b，c的算术平均值为，几何平均值是4，且b，c之积恰为a，则a，b，c的值依次为()．

单选题质地均匀的骰子六面分别刻有1-6的点数，掷两次骰子，得到向上一面的两个点数，则下列事件中，发生可能性最大的是。

单选题如右图所示，正方形ABCD的面积是25，矩形DCEF中CF=8，则DF的长为()。

单选题This book is written expressly for students in an attempt to present the material that is most useful and interesting to them. Previous courses in chemistry are not necessary for the understanding of the material, although those students who have had high school chemistry will find that a review of the inorganic section will better enable them to master the organic and biochemistry sections that follow. The author has felt that in the past there was an improper selection of material from inorganic, organic, and biochemistry in the majority of the textbooks of chemistry for nurse. The tendency has been to develop the inorganic chemistry to such an extent that organic and biochemistry is covered too briefly. The recent advances in biochemistry and their widespread application to the practice of medicine and nursing have considerably altered the situation. Not only is biochemistry more closely allied to the practical chemistry of medicine and nursing but also it is of more interest to the student. In the author's experience the response to biochemistry has always been more favorable than to the other sections. Within the brief period allotted to chemistry, therefore, the sections on inorganic, organic, and biochemistry should be so arranged that a good share of the time is spent in the study of biochemistry. This book presents mainly those fundamentals of inorganic and organic chemistry that are necessary for the understanding of the section on biochemistry. The fundamental points suggested in the Curriculum Guide are included in the book, with some additions in the biochemistry section. The author feels that a study of urine, vitamins, nutrition, and hormones is so obviously a part of biochemistry that at least the fundamentals should be included in this course. The book has been planned in such a way that it may be adapted to various courses in chemistry. The material suggested by the Curriculum Guide is covered in the first nineteen chapters and may be used in accelerated courses or where minimum time is allotted to chemistry. When the time allotted to the course is sixty to ninety hours, the entire contents of the book may be used to advantage. While the book has been written especially to fit the needs of Schools of Nursing, it could readily be applied in instances where students are required to take but one course in chemistry. The apathetic attitude of nonprofessional students toward a course in inorganic chemistry may well be overcome by the proper presentation of material selected from inorganic, organic, and biochemistry.

单选题设其中f(x)为连续函数，则等于()

单选题设f(0)=0，则f(x)在点x=0可导的充要条件为[]

单选题马克思指出：“在同一时间内，劳动就一种属性来说必然创造价值，就另一种属性来说必然保存或转移价值。”这句话表明______。 A．工人在同一时间内劳动两次，一次由自己的劳动把新价值加到劳动对象上，另一次把消耗掉的生产资料的价值转移到产品上 B．新价值的创造和生产资料原有价值的保存或转移，是同一劳动引起的两种不同结果 C．生产资料价值的保存或转移到产品中去是在劳动过程中发生的 D．土地、设备、原材料等生产要素是生产过程中必不可少的物质要素，它们和劳动结合，共同生产出使用价值

单选题设f(x)在(-∞，+∞。)存在二阶导数，且f(x)=-f(-x)，当x＜0时有f'(x)＜0，f"(x)＞0，则当x＞0时有______。 A．f'(x)＜0，f"(x)＞0 B．f'(x)＞0，f"(x)＜0 C．f'(x)＞0，f"(x)＞0 D．f'(x)＜0，f"(x)＜0

单选题设f(x)=ax 3 -6ax 2 +b在区间[-1，2]上的最大值是3，最小值是-29，且a＞0，则