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   2883444篇
  免费   217539篇
  国内免费   5444篇
耳鼻咽喉   38833篇
儿科学   95056篇
妇产科学   79960篇
基础医学   409159篇
口腔科学   85620篇
临床医学   258685篇
内科学   557218篇
皮肤病学   63662篇
神经病学   228455篇
特种医学   111934篇
外国民族医学   698篇
外科学   436934篇
综合类   70041篇
现状与发展   6篇
一般理论   1010篇
预防医学   220026篇
眼科学   68229篇
药学   214676篇
  9篇
中国医学   6363篇
肿瘤学   159853篇
  2018年   30238篇
  2017年   23294篇
  2016年   25698篇
  2015年   29434篇
  2014年   40860篇
  2013年   61003篇
  2012年   83658篇
  2011年   88196篇
  2010年   52260篇
  2009年   49148篇
  2008年   82993篇
  2007年   87954篇
  2006年   88854篇
  2005年   85611篇
  2004年   83546篇
  2003年   79779篇
  2002年   77417篇
  2001年   140784篇
  2000年   144836篇
  1999年   121239篇
  1998年   32799篇
  1997年   29207篇
  1996年   29152篇
  1995年   28150篇
  1994年   26200篇
  1993年   24377篇
  1992年   96071篇
  1991年   93325篇
  1990年   90483篇
  1989年   87281篇
  1988年   80415篇
  1987年   78833篇
  1986年   74911篇
  1985年   71891篇
  1984年   53278篇
  1983年   45753篇
  1982年   26354篇
  1981年   23581篇
  1979年   49375篇
  1978年   34047篇
  1977年   28941篇
  1976年   27160篇
  1975年   28757篇
  1974年   35078篇
  1973年   33714篇
  1972年   31140篇
  1971年   29219篇
  1970年   27014篇
  1969年   25303篇
  1968年   23303篇
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
951.
952.
953.
Reproductive problems, including congenital malformations, reduced hatching success, and decreased survival of hatchlings, have been observed in colonial-nesting water birds at the San Francisco Bay National Wildlife Refuge (SFBNWR). Twenty-four black-crowned night heron (Nycticorax nycticorax) eggs were collected from SFBNWR in 1983. Twelve of these were collected from separate nests when late-stage embryos were pipping, and an additional egg was randomly collected from each nest for organochlorine analysis. Overt anomalies and skeletal defects were not apparent. Embryonic weights (with partially absorbed yolk sacs removed) were 15% lower (p less than 0.05) in SFBNWR embryos compared to control embryos from the Patuxent Wildlife Research Center (PWRC). Crown-rump length and femur length were shorter for SFBNWR embryos. The geometric mean polychlorinated biphenyl (PCB) concentration in SFBNWR eggs was 4.1 ppm wet weight, with a range of 0.8-52.0 ppm. A negative correlation (r = -0.61; p less than 0.05) existed between embryonic weight and log-transformed PCB residues in whole eggs collected from the same nest at SFBNWR, suggesting a possible impact of PCBs on embryonic growth. A correlation with embryonic weight did not occur for DDE [1,1-dichloro-2,2-bis(p-chlorophenyl) ethylene] residues. Liver microsomal aryl hydrocarbon hydroxylase activity was neither significantly elevated nor correlated with PCB, DDE, or PCB plus DDE log-transformed residues. It is unknown whether the apparent association between PCBs and lower weight is persistent through hatching.  相似文献   
954.
In view of the strong evidence supporting the hypothesis that high Expressed Emotion of a key relative contributes to relapse in psychiatric patients, methods used in Expressed Emotion research were applied in an investigation of psychiatric disorder in stroke patients receiving hospital based rehabilitation and support. Patient mood in 37 stroke patients was related to the critical attitude of a key relative. Patient depression may also have been associated with severity of dysphasia, but no link was found between patient mood and the other measures of cognitive or physical deficit used in this study. Psychiatric distress in the key relative had a rather different causal basis. Relatives' psychiatric disorders were associated with physical burden, cognitive deficit, and severity of dysphasia. This study suggests that, when the patient is dependent for self-care, rehabilitation-assisted recovery may alleviate relative distress more than patient distress.  相似文献   
955.
956.
957.
The resolution of three 2-substituted derivatives of idazoxan is described. The enantiomers show large separations in activity in a variety of in vitro and in vivo tests, and the active isomers are all potent and selective antagonists at the alpha 2-adrenoreceptor. The significance of these results in relation to those published on the enantiomers of idazoxan and to those on optically active alpha 2-adrenoreceptor agonists is discussed.  相似文献   
958.
Disposition of paracetamol oral elixir was determined in two male patients after administration via feeding jejunostomy and compared with four male controls who received the same dose by mouth. Area under the plasma concentration-time curve, elimination half-life, and time to maximum concentration were similar in both groups after 650 mg paracetamol elixir. The absolute amounts and ratio of paracetamol glucuronide to sulphate, the major urinary metabolites after therapeutic paracetamol doses, were similar after jejunal administration as compared to oral administration. Paracetamol is absorbed and biotransformed in a similar manner after either jejunal or oral administration. Therefore, it may be administered effectively via jejunostomy tube in patients who require this route of administration.  相似文献   
959.
Summary An infant girl is described who had cor triatriatum and partial anomalous pulmonary venous connection of the left pulmonary veins to the coronary sinus, the first report of this combination of lesions. The infant also had a Dandy-Walker malformation and multiple facial and intrathoracic hemangiomas. The cardiac diagnosis was made by two-dimensional echocardiography. Cardiac catheterization and angiography confirmed the findings and also demonstrated a persistent left superior vena cava draining to the coronary sinus. The infant underwent successful surgical repair. Partial anomalous pulmonary venous connection and left superior vena cava not infrequently are associated with cor triatriatum. Although two-dimensional echocardiography is sensitive for the detection of cor triatriatum, preoperative cardiac catheterization is necessary to identify unequivocally systemic and pulmonary venous connections.  相似文献   
960.
The effect of proteases inhibitors, epsilon-amino-caproic acid and gordox, on reproduction of rotavirus SA-11 in MA-104 cells was studied by enzyme immunoassay. These inhibitors were shown to exert an inhibiting effect on rotavirus reproduction.  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