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   1508473篇
  免费   95970篇
  国内免费   2928篇
耳鼻咽喉   20890篇
儿科学   46856篇
妇产科学   41685篇
基础医学   203737篇
口腔科学   41452篇
临床医学   125163篇
内科学   292640篇
皮肤病学   30908篇
神经病学   122760篇
特种医学   62213篇
外国民族医学   437篇
外科学   236362篇
综合类   33488篇
现状与发展   6篇
一般理论   443篇
预防医学   109714篇
眼科学   34099篇
药学   109444篇
  4篇
中国医学   3615篇
肿瘤学   91455篇
  2018年   32632篇
  2017年   26085篇
  2016年   29095篇
  2015年   12835篇
  2014年   17608篇
  2013年   26188篇
  2012年   39890篇
  2011年   54941篇
  2010年   38620篇
  2009年   31269篇
  2008年   52217篇
  2007年   57340篇
  2006年   38066篇
  2005年   38323篇
  2004年   38557篇
  2003年   38417篇
  2002年   36187篇
  2001年   64124篇
  2000年   65961篇
  1999年   55772篇
  1998年   14923篇
  1997年   13727篇
  1996年   13097篇
  1995年   12378篇
  1994年   11608篇
  1992年   42982篇
  1991年   41529篇
  1990年   40851篇
  1989年   39795篇
  1988年   37180篇
  1987年   36631篇
  1986年   35063篇
  1985年   33278篇
  1984年   24955篇
  1983年   21159篇
  1982年   12753篇
  1981年   11653篇
  1979年   24031篇
  1978年   17154篇
  1977年   14919篇
  1976年   13480篇
  1975年   15347篇
  1974年   18176篇
  1973年   17632篇
  1972年   16883篇
  1971年   15770篇
  1970年   14991篇
  1969年   14432篇
  1968年   13535篇
  1967年   12070篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
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   
32.
Summary: A female patient with isovaleric acidaemia had a successful outcome from pregnancy.  相似文献   
33.
34.
35.
36.
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   
37.
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   
38.
Setting goals to maintain hope.   总被引:3,自引:0,他引:3  
  相似文献   
39.
40.
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