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   1450350篇
  免费   100603篇
  国内免费   3992篇
耳鼻咽喉   21469篇
儿科学   42028篇
妇产科学   40370篇
基础医学   204990篇
口腔科学   42668篇
临床医学   123621篇
内科学   282935篇
皮肤病学   33509篇
神经病学   115879篇
特种医学   59808篇
外国民族医学   435篇
外科学   222448篇
综合类   31572篇
现状与发展   9篇
一般理论   470篇
预防医学   98912篇
眼科学   34433篇
药学   110671篇
  4篇
中国医学   4295篇
肿瘤学   84419篇
  2018年   15232篇
  2017年   12303篇
  2016年   14288篇
  2015年   17033篇
  2014年   22758篇
  2013年   32351篇
  2012年   43623篇
  2011年   45267篇
  2010年   26645篇
  2009年   25303篇
  2008年   40719篇
  2007年   43496篇
  2006年   43283篇
  2005年   41700篇
  2004年   39979篇
  2003年   38239篇
  2002年   37212篇
  2001年   64942篇
  2000年   66461篇
  1999年   56400篇
  1998年   15362篇
  1997年   14012篇
  1996年   13336篇
  1995年   12569篇
  1994年   11761篇
  1992年   43204篇
  1991年   41691篇
  1990年   40902篇
  1989年   39881篇
  1988年   37224篇
  1987年   36686篇
  1986年   35117篇
  1985年   33335篇
  1984年   25004篇
  1983年   21189篇
  1982年   12772篇
  1981年   11697篇
  1979年   24080篇
  1978年   17178篇
  1977年   14910篇
  1976年   13480篇
  1975年   15345篇
  1974年   18172篇
  1973年   17638篇
  1972年   16887篇
  1971年   15785篇
  1970年   14966篇
  1969年   14390篇
  1968年   13503篇
  1967年   12047篇
排序方式: 共有10000条查询结果,搜索用时 29 毫秒
21.
Low molecular weight heparins are widely used in the prophylaxis and treatment of thrombotic disorders. The effect of low molecular weight heparins on coagulation was examined ultrastructurally in an animal model. A test and a control group was formed, each consisting of five rabbits. Nadroparine (225 Institute of Chaoy Unit/kg twice daily) was applied to the test group for 10 days. The control group received 1 ml saline solution subcutaneously. Blood and vascular tissue samples collected at the end of the 10th day were evaluated under a JEM 100 B electron microscope. Platelet degranulation and agglutination was observed in the control group. Fibrin materials were detected in the cytoplasms and surroundings of degranulated platelets. Erythrocyte accumulation was remarkable on the vascular endothelium with intact coagulation periods. In the test group, outer membranes of platelets, hyalomere, and granular structures in the granulomeres were detected to be nearly intact. There were rare erythrocytes in the large vascular lumens. The aggregation phase had occurred but no agglutination was detected. Nadroparine seems to preserve consistency of lipoprotein membranes of platelets and granular structures containing enzymes, which contribute to the coagulation mechanisms.  相似文献   
22.
Summary: A female patient with isovaleric acidaemia had a successful outcome from pregnancy.  相似文献   
23.
24.
25.
26.
To determine if impaired energy metabolism might contribute to some aspects of Alzheimer disease (AD), including the vulnerability of the CA1 region of the hippocampal formation and the altered cytoskeleton evident in neurofibrillary tangles, we examined the effects of metabolic poisons on neuronal damage and cytoskeletal disruption in the hippocampal formation. Intrahippocampal injection of 3-nitropropionic acid (3-NP) and malonic acid resulted in neuronal death, particularly in CA1. Cytoskeletal disruption included loss of dendritic MAP2, but sparing of axonal τ. MK-801 (a noncompetitive NMDA receptor antagonist) did not atenuate the lesions produced by intrahippocampal injection of malonate. MK-801, however, was effective against intrastriatal malonate. Acute systemic 3-NP resulted in neuronal damage and cytoskeletal disruption in the CA1 region of the hippocampal formation, including an extensive loss of MAP2 immuno-reactivity, but sparing of τ. The neuronal loss in CA1 was delayed as compared to striatum. Chronic intraventricular infusion of 3-NP produced a different pattern of neuronal damage. Loss of τ-1 immuno-reactivity was observed in CA3 and CA1 s. oriens, whereas MAP2 immunostaining was preserved. These results demonstrate that chronic and acute administration of metabolic inhibitors produce distinct patterns of neuronal damage and cytoskeletal disruption. The results further suggest a differential involvement of the NMDA receptor in malonate-induced neuronal damage in striatum as compared to the hippocampus. The pattern of neuronal damage and cytoskeletal disruption observed following acute metabolic impairment resembled some aspects of neurofibrillary pathology in AD, but did not result in τ hyperphosphorylation.  相似文献   
27.
AIM: Cardiovascular risk factors can be present in children and young adults. We previously found abnormal microvascular function in children who had glucose intolerance and insulin resistance. The aim of the present study was to investigate whether they also have abnormalities in left ventricular mass (LVM) and arterial stiffness. METHODS: We measured heart dimensions and LVM using echocardiography, and arterial stiffness using pulse wave analysis in 23 children with good glucose handling (postfeeding glucose: 3.9 to 5 mmol/L) and 21 with poor glucose handling (7.7 to 11.4 mmol/L). RESULTS: The time to pulse reflection was slightly shorter in the poorer glucose handlers (mean+/-SD: 143+/-10 vs 153+/-20 ms, P=0.04), suggestive of increased arterial stiffness. Also in this group, there were significant relationships between intraventricular septal thickness, blood pressure and body mass index, but not in the normal glucose handlers. CONCLUSIONS: We have found that normal children who are in the lowest quintile of glucose tolerance in comparison with their peers are exhibiting the first signs of arterial stiffening. In addition, we have seen the beginnings of a relationship between blood pressure, body mass index and left ventricular enlargement in this group. While these changes may not yet be clinically significant, their emergence might be further evidence of early predisposition to cardiovascular disease.  相似文献   
28.
Setting goals to maintain hope.   总被引:3,自引:0,他引:3  
  相似文献   
29.
30.
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