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   1357839篇
  免费   95788篇
  国内免费   2981篇
耳鼻咽喉   19915篇
儿科学   40810篇
妇产科学   39026篇
基础医学   190019篇
口腔科学   40264篇
临床医学   114743篇
内科学   266745篇
皮肤病学   30432篇
神经病学   108500篇
特种医学   54593篇
外国民族医学   435篇
外科学   211618篇
综合类   31393篇
现状与发展   6篇
一般理论   460篇
预防医学   94119篇
眼科学   32053篇
药学   101398篇
  5篇
中国医学   3027篇
肿瘤学   77047篇
  2018年   12124篇
  2015年   12284篇
  2014年   17195篇
  2013年   26097篇
  2012年   34198篇
  2011年   36110篇
  2010年   21446篇
  2009年   20904篇
  2008年   34755篇
  2007年   37983篇
  2006年   38634篇
  2005年   37375篇
  2004年   36330篇
  2003年   35264篇
  2002年   34761篇
  2001年   63962篇
  2000年   65641篇
  1999年   55751篇
  1998年   14914篇
  1997年   13718篇
  1996年   13135篇
  1995年   12412篇
  1994年   11665篇
  1992年   43017篇
  1991年   41511篇
  1990年   40810篇
  1989年   39814篇
  1988年   37230篇
  1987年   36630篇
  1986年   35139篇
  1985年   33320篇
  1984年   25049篇
  1983年   21281篇
  1982年   12843篇
  1981年   11741篇
  1980年   10956篇
  1979年   24066篇
  1978年   17203篇
  1977年   14971篇
  1976年   13501篇
  1975年   15363篇
  1974年   18187篇
  1973年   17660篇
  1972年   16876篇
  1971年   15790篇
  1970年   14972篇
  1969年   14387篇
  1968年   13503篇
  1967年   12059篇
  1966年   11309篇
排序方式: 共有10000条查询结果,搜索用时 20 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.

Background  

A public hospital in New Mexico required collection of 50% of estimated costs prior to elective surgeries for self-pay patients. This study assesses the impact of this policy on access to elective surgical procedures.  相似文献   
39.
Setting goals to maintain hope.   总被引:3,自引:0,他引:3  
  相似文献   
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