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   1762724篇
  免费   120539篇
  国内免费   3450篇
耳鼻咽喉   25631篇
儿科学   54484篇
妇产科学   49801篇
基础医学   259295篇
口腔科学   52017篇
临床医学   150584篇
内科学   337187篇
皮肤病学   40039篇
神经病学   135426篇
特种医学   68560篇
外国民族医学   492篇
外科学   271797篇
综合类   38002篇
现状与发展   6篇
一般理论   540篇
预防医学   125882篇
眼科学   41824篇
药学   134016篇
  4篇
中国医学   3806篇
肿瘤学   97320篇
  2018年   15840篇
  2015年   15524篇
  2014年   21650篇
  2013年   33137篇
  2012年   43719篇
  2011年   46948篇
  2010年   27755篇
  2009年   26658篇
  2008年   45012篇
  2007年   49010篇
  2006年   49757篇
  2005年   48133篇
  2004年   46858篇
  2003年   45318篇
  2002年   44712篇
  2001年   81775篇
  2000年   84393篇
  1999年   71021篇
  1998年   19066篇
  1997年   17259篇
  1996年   16948篇
  1995年   15947篇
  1994年   14934篇
  1992年   55147篇
  1991年   54496篇
  1990年   54009篇
  1989年   52559篇
  1988年   48929篇
  1987年   48207篇
  1986年   46037篇
  1985年   43846篇
  1984年   32845篇
  1983年   27959篇
  1982年   16512篇
  1981年   15097篇
  1980年   14102篇
  1979年   31802篇
  1978年   22888篇
  1977年   19718篇
  1976年   18212篇
  1975年   20882篇
  1974年   24739篇
  1973年   23756篇
  1972年   22935篇
  1971年   21600篇
  1970年   20316篇
  1969年   19527篇
  1968年   18318篇
  1967年   16483篇
  1966年   15157篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
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   
42.
Summary: A female patient with isovaleric acidaemia had a successful outcome from pregnancy.  相似文献   
43.
44.
45.
46.
47.
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   
48.
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   
49.
Setting goals to maintain hope.   总被引:3,自引:0,他引:3  
  相似文献   
50.
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