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   1021篇
  免费   37篇
  国内免费   65篇
耳鼻咽喉   2篇
儿科学   54篇
妇产科学   10篇
基础医学   98篇
口腔科学   36篇
临床医学   160篇
内科学   223篇
皮肤病学   23篇
神经病学   16篇
特种医学   244篇
外科学   60篇
综合类   31篇
预防医学   37篇
眼科学   14篇
药学   81篇
肿瘤学   34篇
  2021年   8篇
  2020年   2篇
  2019年   3篇
  2018年   4篇
  2017年   5篇
  2016年   7篇
  2015年   14篇
  2014年   17篇
  2013年   26篇
  2012年   29篇
  2011年   21篇
  2010年   28篇
  2009年   44篇
  2008年   21篇
  2007年   70篇
  2006年   34篇
  2005年   23篇
  2004年   14篇
  2003年   12篇
  2002年   14篇
  2001年   19篇
  2000年   14篇
  1999年   19篇
  1998年   60篇
  1997年   71篇
  1996年   70篇
  1995年   60篇
  1994年   42篇
  1993年   51篇
  1992年   14篇
  1991年   19篇
  1990年   15篇
  1989年   45篇
  1988年   27篇
  1987年   39篇
  1986年   12篇
  1985年   26篇
  1984年   15篇
  1983年   23篇
  1982年   19篇
  1981年   17篇
  1980年   20篇
  1979年   1篇
  1978年   5篇
  1977年   9篇
  1976年   4篇
  1975年   6篇
  1966年   2篇
  1948年   1篇
  1947年   1篇
排序方式: 共有1123条查询结果,搜索用时 15 毫秒
71.
Gallium-67 lung uptake: conjugate-view technique   总被引:1,自引:0,他引:1  
A conjugate-view technique is derived for calculation of absolute gallium-67 (Ga-67) uptake from scintillation-camera images. The technique combines counts of posterior and anterior images of the lung with an attenuation correction obtained from cobalt-57 (Co-57) transmission imaging. The formulation is such that the effects of Compton scatter build-up are accounted for. Studies utilizing a canine model indicated that, normally, more activity is located in the chest wall than in the lungs. The quantitative technique must therefore accurately account for a variety of Ga-67 distributions, including that in the chest wall. Calculations were performed using a three-component model comparing results obtained with the conjugate-view approach to the actual uptake. These calculations suggest that an assumption of uniform activity distribution allows an accuracy of approximately +/- 10% over a broad range of body-part thicknesses and uptake by the lungs. It was concluded that the conjugate-view technique is necessarily approximate but can provide clinically useful results.  相似文献   
72.

Background

Haemorrhage after Cardio Pulmonary Bypass (CPB) Surgery is a well recognised complication that leads to significant morbidity and mortality. The incidence varies between 5-25% depending upon the clinical situation. Several factors are implicated as causative but none have been precisely proved.

Methods

Our study was an attempt to evaluate the haemostatic defect with particular reference to platelet function abnormalities during cardio pulmonary bypass surgery, in order to reduce the morbidity and mortality associated with post CPB haemorrhage. Flow cytometric evaluation of different platelet glycoproteins like GPIb/IX, GPIIb/IIIa and GMP-140 was done.

Results

The marker expression showed deregulation during surgery which returned to base after bypass was terminated. In contrast, the cases with bleeding showed significant variation. P-Selectin (GMP 140) expression decreased progressively till 3rd post-operative day showing lack of activation of platelets in cases of severe bleeding.

Conclusion

Longer duration of CPB initiates plasmin generation through heparin, which raises the PAI-1-tPA complex and thereby down regulating the functions of platelets. This suggests a link between duration of CPB, bleeding, platelet dysfunction and fibrinolysis. Hence serial estimations of the levels of GMP-140 and tPA can predict severe bleeding.Key Words: CardioPulmonary Bypass, Platelet dysfunction, flowcytometry, platelet glycoproteins, haemorrhage  相似文献   
73.
74.
75.
A collaborative research study was conducted in order to improve our understanding of the source-to-receptor pathway for ambient fine particulate matter (aerodynamic diameter < or = 2.5 mu m; PM2.5) and subsequently to investigate the identity and sources of toxic components in PM2.5 responsible for adverse health effects in allergic humans. This research used a Harvard fine particle concentrator to expose Brown Norway rats, with and without ovalbumin-induced allergic airway disease, to concentrated air particles (CAPs) generated from ambient air in an urban Detroit community where the pediatric asthma rate was three times higher than the national average. Rats were exposed to CAPs during the exposure periods in July (mean = 676 microg/m3) and September (313 microg/m3) of 2000. Twenty-four hours after exposures lung lobes were either lavaged with saline to determine cellularity and protein in bronchoalveolar lavage fluid (BALF), or removed for analysis by inductively coupled plasma-mass spectrometry (ICP-MS) to detect ambient PM2.5-derived trace element retention. PM2.5 trace elements of anthropogenic origin, lanthanum (La), vanadium (V), manganese (Mn), and sulfur (S), were recovered from the lung tissues of CAPs-exposed rats. Recovery of those pulmonary anthropogenic particles was further increased in rats with allergic airways. In addition, eosinophils and protein in BALF were increased only in allergic animals exposed to CAPs. These results demonstrate preferential retention in allergic airways of air particulates derived from identified local combustion sources after a short-term exposure. Our findings suggest that the enhancement of allergic airway responses by exposure to PM2.5 is mediated in part by increased pulmonary deposition and localization of potentially toxic elements in urban air.  相似文献   
76.
葛根素对高血压患者血浆内皮素和一氧化氮的影响   总被引:29,自引:0,他引:29  
目的:检测正常人与高血压病(EH)患者血浆内皮素、一气体氮的变化及葛根素对其的干预效应。方法:EH对照组口服苯磺酸氨氯地平5mg/d,或合和盐酸苯那普利10mg/d,每日一次,15d为一疗程。EH伍用治疗组同时合用5%GNS250ml+葛根素注射液400mg静滴,两组治疗前后检测血浆ET、NO水平变化。结果:EH各组血浆ET较正常人组均显著增高(P〈0.01),血浆NO水平及NO/ET比值除轻度E  相似文献   
77.
A multicenter clinical study was conducted using iohexol, a second-generation nonionic contrast medium, for excretory urography performed in 130 children. Doses of iohexol (300 mg iodine/ml) ranged between 150 and 660 mgI/kg (0.5 and 2.2 ml/kg). Iohexol was tolerated well, and no significant adverse reactions occurred. Sixty-five iohexol urograms were evaluated to determine the minimum dose for adequate visualization of the kidneys and collecting systems. A dose greater than 300 mgI/kg (1.0 ml/kg) always resulted in a urogram of diagnostic quality, while visualization was insufficient for diagnosis in 10% of studies done with doses of 150-300 mgI/kg (0.5-1.0 ml/kg). Another 65 iohexol urograms were compared in a blinded manner with a similar number of studies performed using iothalamate meglumine at comparable iodine concentration and dose. Visualization of calyces and pelvoinfundibular structures achieved with iohexol was rated better with statistical significance, but there was no difference in visualization of the renal parenchyma or ureters. Use of iohexol in excretory urography may be advantageous in children who are at greatest risk for an adverse reaction to contrast media or in those most likely to benefit from use of a low osmolality contrast agent.  相似文献   
78.
Scales for the measurement of attitudes toward blood donation   总被引:1,自引:0,他引:1  
Attitudes toward blood donation are frequently assumed to vary along a single dimension from unfavorable to favorable. In contrast, theories of attitude structure specify three distinct attitude components: affect, cognition, and behavior. This article describes the development of three new scales for the measurement of affective, cognitive, and behavioral components of attitudes toward blood donation. The scales were developed using the method of equal-appearing intervals and were administered to both donors of blood and nondonors. Correlations among the scales were relatively small and supported the three-component distinction. Affect was more strongly correlated with the number of prior donations than was cognition, which suggested an important role for emotional factors in blood donation. Scores on all three scales showed the attitudes of blood donors to be more favorable than those of nondonors.  相似文献   
79.
80.
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