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A．营养不足B．红细胞生成相对不足C．消耗增加D．骨髓造血容量减少E．血浆容量增高，血液被稀释下列红细胞增多是上述哪一种病因 真性红细胞增多症（）
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On July 12, 1993, a young professor of American history named Frederick Jackson Turner stood up to speak. The scene was the American History Congress at the Chicago World’s Fair. (62) His paper was titled "The significance of the Frontier in American History." Turner had a new idea. (63) And many historians who heard him recognized that he had come upon a simple theory that seemed right.To Turner, the frontier was one of the most powerful forces shaping the American character. He pointed out that the frontier was a place for new beginnings, a place where men and women could build new lives. Thus, the frontier represented hope and opportunity to Americans. Turner also pointed out that these new lives on the frontier were shaped by tile hardships of surviving in the wilderness. Thus, life on the frontier produced determination in Americans and made them believe in the value of work. (64)According to Turner’s theory, the frontier was a place where everyone had to struggle equally hard. (65) Thus, frontier life helped shape the American ideal of equality, independence, and democracy. According to Turner’s theory, the frontier was a place where everyone had to struggle equally hard.
药物作用开始快慢取决于（）
A．脂水分配系数与毒效应B．分离度与毒效应C．挥发度和蒸气压与毒效应D．分散度与毒效应E．纯度与毒效应 化合物经皮肤吸收，脂溶性越高其毒性越大（）
A sick or injured person can obtain medical care in several different places. These include provider practices such as medical offices and clinics, hospitals and nursing homes.There are about 200,000 medical offices, clinics, and other provider practices in the United States. Earlier in the 20th century most physicians were single people working in their own offices or in partnership with another doctor. Patients visited the office, received an examination or other service, and paid a fee. This traditional fee-for-service medicine has been declining. Many physicians now practice in groups where they share the same offices and equipment with other doctors. Group practices may combine primary care physicians, several kinds of specialists, laboratories, and equipment for diagnosing disease. Physicians who practice in a group reduce their own expenses and provide patients with a wider range of services.Many doctors are joining with hospitals, insurance companies, and industrial employers to provide managed care for groups of patients. These plans manage to avoid unnecessary services and reduce costs. Rather than taking a fee from each patient, managed care physicians may receive an annual salary from a fixed sum for each patient.Patients who are too sick for care in a doctor’s office go to a hospital. Hospitals offer Patients 24-hour care from a staff of health professionals. They provide services not available elsewhere, such as major surgery, child birth, and intensive care for the critically ill. Hospital care is the most expensive form of health care. Efforts to control health care costs have emphasized reducing the number of patients admitted to hospitals and their length of stay. During the 1980s and 1990s, these efforts led to the closing of more than 600 hospitals.Patients who need long-term medical care because of advanced age or chronic illness may stay in a nursing home. The United States has about 23,000 nursing homes with about 1.3 million patients. "Physicians who practice in a group reduce their own expenses and provide patients with a wider range of services." in this sentence "expenses" can be explained as（）
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