单选题关于机体抗凝机制的叙述，下列哪项不正确?

单选题A.抑制B.兴奋C.两者均是D.两者均否

单选题大叶性肺炎的合并证不包括

单选题A．胰腺导管分泌B．胃分泌H+C．两者都是D．两者均否

单选题下列哪项生理活动是由α受体介导的

单选题对于声波骨传导的叙述，恰当的是

单选题血管紧张素Ⅱ不具备下列哪项生理功能?

单选题下列选项中，符合前B细胞淋巴母细胞白血病／淋巴瘤的叙述是

单选题延缓伤口愈合的因素是

单选题有关月经周期中激素变化的叙述，错误的是

单选题A.胃液的酸度较高而酶含量低B.胃液的酸度及酶含量均低C.胃液的量最大、酸度及酶含量较高D.胃液的酶含量最高，酸度也高

单选题作为神经递质，下列哪一种物质仅存在于中枢神经系统

单选题下列病变除了哪项外均是肺源性心脏病的病变

单选题男，36岁，酗酒时间约8年余。近半年来经常出现恶心、呕吐、食欲不振。肝穿刺显示肝细胞广泛脂肪变性，肝细胞灶状坏死。肝细胞内可见大小不等的红染的半透明小体。这些透明小体为

单选题区分心肌快、慢反应自律细胞的主要根据是

单选题患者，女，60岁，咳嗽，咳痰10多年。体格检查：可平卧，桶状胸，两肺少量湿啰音，剑突下可见收缩期搏动，三尖瓣区可听见收缩期杂音，肝脾不大，下肢无水肿。其诊断可能为

单选题EGF的生理功能是

单选题心动周期中，在下列哪个时期左心室容积最大( )(1994年)

单选题如下哪种肿瘤常分泌激素

单选题The United States experienced some of the most extreme weather events in its history this spring, including deadly outbreaks of tornadoes, near-record flooding, drought and wildfires. Damages from these disasters have already passed $ 32 billion, and the hurricane season, which is just beginning, is projected to be above average, according to the National Oceanic and Atmospheric Administration. Government scientists said Wednesday that the frequency of extreme weather has increased over the past two decades, in part as a result of global warming caused by the accumulation of carbon dioxide in the atmosphere. But they were careful not to blame humans for this year's rash of deadly events, saying that in some ways weather patterns were returning to those seen at the beginning of the last century. "Looking at long-term patterns since 1980, indeed, extreme climatological and meteorological events have increased," said Thomas R. Karl, director of NOAA's National Climatic Data Center. "But in the early part of the 20th century, there was also a tendency for more extreme events followed by a quiet couple of decades. " Presenting a new NOAA report on 2011 extreme weather, Dr. Karl said that extremes of precipitation have increased as the planet warms and more water evaporates from the oceans. He also said models suggest that as carbon dioxide builds up in the atmosphere and heats the planet, droughts will increase in frequency and intensity. "But it is difficult and unlikely to discern a human fingerprint, if there is one, on the drought record of the United States," he said. Some other climate scientists were more categorical about the human contribution to extreme climate events. Kevin Trenberth, distinguished senior scientist at the National Center for Atmospheric Research, said that when the greenhouse effect caused by burning fossil fuels is added to the natural variability of climate, weather disasters can be expected to occur more frequently. "Global warming is contributing to an increased incidence of extreme weather because the environment in which all storms form has changed from human activities," Dr. Trenberth said in a telephone interview Wednesday. "Records are not just broken, they are smashed. It is as clear a warning as we are going to get about prospects for the future. " April was a particularly devastating month for tornadoes and rainfall, with 875 tornadoes reported during the month and heavy rain and snowmelt contributing to Mississippi River flooding later in the spring that surpassed the historic floods of 1927 and 1937. So far this year, there have been nearly 1,400 preliminary tornado reports nationwide; those reports will most likely be whittled down to about 900 confirmed tornadoes, the second-highest annual total recorded in modern times. The record is 1,011 confirmed tornadoes in 2008. The year also is on track to be one of the deadliest, with 536 fatalities so far from tornadoes, placing 2011 in sixth place in United States history and the deadliest since 1936.