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   518021篇
  免费   33763篇
  国内免费   624篇
耳鼻咽喉   6911篇
儿科学   17013篇
妇产科学   13701篇
基础医学   85536篇
口腔科学   14502篇
临床医学   44894篇
内科学   94259篇
皮肤病学   12333篇
神经病学   36591篇
特种医学   18580篇
外国民族医学   63篇
外科学   77646篇
综合类   8561篇
一般理论   119篇
预防医学   39432篇
眼科学   12175篇
药学   40836篇
中国医学   1017篇
肿瘤学   28239篇
  2018年   5002篇
  2015年   4574篇
  2014年   6163篇
  2013年   9682篇
  2012年   13076篇
  2011年   14480篇
  2010年   8417篇
  2009年   7878篇
  2008年   13883篇
  2007年   14920篇
  2006年   15126篇
  2005年   14576篇
  2004年   14226篇
  2003年   13535篇
  2002年   13416篇
  2001年   24205篇
  2000年   25214篇
  1999年   20702篇
  1998年   5486篇
  1997年   4749篇
  1996年   5076篇
  1995年   4669篇
  1994年   4359篇
  1993年   4170篇
  1992年   15817篇
  1991年   16413篇
  1990年   16509篇
  1989年   15868篇
  1988年   14632篇
  1987年   14496篇
  1986年   13660篇
  1985年   13037篇
  1984年   9672篇
  1983年   8283篇
  1982年   4580篇
  1981年   4247篇
  1979年   9455篇
  1978年   6884篇
  1977年   5791篇
  1976年   5634篇
  1975年   6420篇
  1974年   7669篇
  1973年   7157篇
  1972年   6986篇
  1971年   6696篇
  1970年   6198篇
  1969年   5903篇
  1968年   5574篇
  1967年   5022篇
  1966年   4462篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
Regional effects of craniotomy on cerebral circulation and metabolism, such as regional cerebral blood flow (rCBF), regional cerebral oxygen consumption (rCMRO2), regional oxygen extraction fraction (rOEF), and regional cerebral blood volume (rCBV) were examined by a PET (positron emission tomography) study concerning surgery that was performed on unruptured aneurysm patients. Eight patients with intracranial un-ruptured aneurysms were studied pre- and post-operatively by the 15O labelled-gas steady-state method, using HEADTOME-III. All patients underwent aneurysmal surgery performed by the transsylvian approach. There was a significant increase in the mean OEF values taken from the whole-brains of 8 patients, but there was not a significant change in CBF, CMRO2 or CBV. The increase in OEF was caused by decrease of O2 content, which was caused by post-operative decrease in the Hb value. So, this OEF increase was not the direct effect of craniotomy. In 2 patients, the rCBF and rCMRO2, in the fronto-temporal region (where craniotomy was performed) increased post-operatively. This regional effect suggests transient reactive hyperemia following compressive ischemia during the operative procedure, and metabolic demands for recovery of brain function. In 2 other patients, who had relatively low rCBFs during the pre-operative study, rCBF and rCMRO2 in the bi-frontal region had decreased more at the post-operative study. This change appears to have been caused by removal of cerebrospinal fluid and depression of the frontal lobe. From this study, it becomes evident that the regional effect of craniotomy on cerebral circulation and metabolism is not so great, when adequate microsurgical techniques are used.  相似文献   
52.
Management of splenic injuries in children has evolved over the past two decades. Splenectomies or splenorrhaphies are now performed infrequently, with the majority of hemodynamically stable children with splenic injuries managed nonoperatively. This article reviews the imaging features of acute splenic injuries in children as well as the appearance of healing splenic injuries. Follow-up evaluation and outcomes in children with splenic injuries also are addressed.  相似文献   
53.
54.
55.
The response of single detergent treated bovine retinal pigment epithelial cells in culture to ATP was measured with an image analyser. The most pronounced contraction was produced by 1.0 mM ATP with most change taking place in the first 10 min. At 1 h the area had decreased by about 33%, perimeter 22% and maximum length 25%. By way of comparison rabbit skin fibroblasts had a decreased area of approximately 40%, perimeter 25% and maximum length 22%. Bovine aortic smooth muscle cells on the other hand decreased in area by 55%, perimeter 40% and maximum length 36%. It is hoped that this assay may be used to evaluate drugs which could counteract contractile events in proliferative vitreoretinopathy.  相似文献   
56.
Maya families from Guatemala migrated to the United States in record numbers from the late 1970s to the early 1990s. Births to Maya immigrant women have created a sizable number of Maya American children. The height and sitting height of 5 to 12 years children (n = 431) were measured in 1999 and 2000. Leg length was estimated and the sitting height ratio was calculated. These data were compared with a sample of Maya children living in Guatemala measured in 1998 (n = 1,347). Maya American children are currently 11.54 cm taller and 6.83 cm longer‐legged, on average, than Maya children living in Guatemala. Consequently, the Maya Americans have a significantly lower average sitting height ratio (i.e., relatively longer legs in proportion to length of the head and trunk) than do the Maya in Guatemala. These results add support to the hypothesis that both the height and body proportions of human populations are sensitive indicators of the quality of the environment for growth. Am. J. Hum. Biol. 14:753–761, 2002. © 2002 Wiley‐Liss, Inc.  相似文献   
57.
58.
59.
60.
Formulae for the calculation of the count of microorganisms isolated from natural bacterial biocenoses of a child's body have been derived. The authors suggest a variant of simplified drip method for the computation of microorganism colonies in solid media. The described method helps cut down the nutrient media consumption at least 3-fold and is time-saving.  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