首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   101001篇
  免费   9688篇
  国内免费   53篇
  110742篇
  2022年   728篇
  2021年   1386篇
  2020年   941篇
  2019年   1133篇
  2018年   1456篇
  2017年   1315篇
  2016年   2236篇
  2015年   3702篇
  2014年   4165篇
  2013年   5324篇
  2012年   6729篇
  2011年   6630篇
  2010年   4410篇
  2009年   3964篇
  2008年   5628篇
  2007年   5811篇
  2006年   5565篇
  2005年   5120篇
  2004年   5115篇
  2003年   4811篇
  2002年   4571篇
  2001年   1287篇
  2000年   1035篇
  1999年   1327篇
  1998年   1297篇
  1997年   974篇
  1996年   913篇
  1995年   905篇
  1994年   839篇
  1993年   890篇
  1992年   948篇
  1991年   805篇
  1990年   794篇
  1989年   801篇
  1988年   799篇
  1987年   767篇
  1986年   702篇
  1985年   792篇
  1984年   911篇
  1983年   814篇
  1982年   925篇
  1981年   944篇
  1980年   880篇
  1979年   623篇
  1978年   633篇
  1977年   625篇
  1976年   566篇
  1975年   537篇
  1974年   563篇
  1973年   512篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
The clinical and laboratory findings in seven children with Kawasaki disease are reviewed. Four of the patients had the more complicated course that has characterized the cases diagnosed in North America. This suggests that the benign forms are often mistaken for other febrile illnesses. The patients were two girls and five boys ranging in age from 4 months to 7 years; six were Caucasian and one was a North American Indian. Fever, redness of the oral mucosa, an erythematous or scarlatiniform rash and cervical adenopathy were seen in all; six patients had the characteristic fingertip desquamation and nonexudative conjunctivitis. Cardiac involvement occurred in four patients, two of whom had coronary artery aneurysm or thrombosis. Arthritis or arthralgia was seen in six patients, and aseptic meningitis occurred in four. Of the three patients with jaundice two underwent laparotomy and excision of a hydropic gallbladder; one of them died from Klebsiella pneumoniae sepsis and disseminated intravascular coagulopathy.  相似文献   
72.
73.
In a previous study, our laboratory showed that young dogs born at sea level (SL) and raised from 2.5 mo of age to beyond somatic maturity at a high altitude (HA) of 3,100 m show enhanced resting lung function (Johnson RL Jr, Cassidy SS, Grover RF, Schutte JE, and Epstein RH. J Appl Physiol 59: 1773-1782, 1985). To examine whether HA-induced adaptation improves pulmonary gas exchange during exercise and whether adaptation is reversible when animals return to SL before somatic maturity, we raised 2.5-mo-old foxhounds at HA (3,800 m) for 5 mo (to age 7.5 mo) before returning them to SL. Lung function was measured under anesthesia 1 mo and 2 yr after return to SL and during exercise approximately 1 yr after return. In animals exposed to HA relative to simultaneous litter-matched SL controls, resting circulating blood and erythrocyte volumes, lung volumes, septal volume estimated by a rebreathing technique, and lung tissue volume estimated by high-resolution computed tomography scan were persistently higher. Lung diffusing capacity, membrane diffusing capacity, and pulmonary capillary blood volume estimated at a given cardiac output were significantly higher in animals exposed to HA, whereas maximal oxygen uptake and hematocrit were similar between groups. We conclude that relatively short exposure to HA during somatic maturation improves long-term lung function into adulthood.  相似文献   
74.
75.
The camel tick,Hyalomma dromedarii, exhibited positive scototaxis in an arena, e.g. it oriented towards a black or grey target in front of a white background. The degree of the scototactic response varied with the size and the elevation of the target, with its luminance contrast, with its shape and with the speed by which the target was moved: (1) the response to stationary and moving targets increased with increasing target size; (2) presentation of the targets at an elevation of 11o–15o induced the highest response; (3) the response decreased with decreasing luminance contrast of the target; (4) targets with the shape of a disk, a triangle standing on a vertex, a vertical bar or a silhouette of a dromedary caused high responses; a low response was observed when the target was a horizontal bar and there was no response to a striped pattern; (5) the smaller the size of a disk, the faster it had to be moved to elicit an optimum response.The smallest disk which elicited a significant response appeared under a visual angle of 4.8o for a thick at the starting point. The smallest dromedary-shaped silhouette which elicited a significant response corresponded to the silhouette of a real dromedary at a distance of 18 m.  相似文献   
76.
77.
Biological screening for hereditary thrombophilia must be performed with constant concern for quality of the results and the interpretation. Different guidelines are available common to most laboratory tests, common to hemostasis tests, thrombophilia screening or specific for each test. These different steps are discussed in this paper with a special focus on the diagnosis of antithrombin, protein C and protein S deficiencies.  相似文献   
78.
79.
80.
First appearing in 2000, and with 20,000 copies sold as it entered its sixth printing in 2004, Richard Trudgen's Why Warriors Lie down and Die is a minor publishing phenomenon. Although scholarly forums have generally ignored the book, Christian media outlets, the popular press and neo‐conservative political activists have enthusiastically received and promoted it. An examination of the merits of Why Warriors Lie down and Die suggests that its popularity is only partly explained by original observations or insights on the part of the author. The most important explanation, and implication, of the book's remarkable take‐up lies in the opportune way in which it corresponds with now ascendant neo‐conservative political perspectives on indigenous policy.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号