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   44150篇
  免费   4026篇
  国内免费   138篇
耳鼻咽喉   519篇
儿科学   1333篇
妇产科学   909篇
基础医学   6117篇
口腔科学   909篇
临床医学   5075篇
内科学   9358篇
皮肤病学   509篇
神经病学   3382篇
特种医学   1475篇
外科学   6896篇
综合类   755篇
现状与发展   1篇
一般理论   43篇
预防医学   3875篇
眼科学   787篇
药学   3170篇
中国医学   131篇
肿瘤学   3070篇
  2023年   316篇
  2022年   561篇
  2021年   1264篇
  2020年   655篇
  2019年   1026篇
  2018年   1222篇
  2017年   869篇
  2016年   906篇
  2015年   1004篇
  2014年   1446篇
  2013年   1875篇
  2012年   2912篇
  2011年   2985篇
  2010年   1581篇
  2009年   1345篇
  2008年   2371篇
  2007年   2432篇
  2006年   2265篇
  2005年   2214篇
  2004年   2062篇
  2003年   1954篇
  2002年   1854篇
  2001年   819篇
  2000年   734篇
  1999年   803篇
  1998年   462篇
  1997年   424篇
  1996年   366篇
  1995年   346篇
  1994年   336篇
  1993年   267篇
  1992年   568篇
  1991年   508篇
  1990年   495篇
  1989年   443篇
  1988年   446篇
  1987年   443篇
  1986年   431篇
  1985年   421篇
  1984年   364篇
  1983年   325篇
  1982年   264篇
  1981年   258篇
  1980年   225篇
  1979年   301篇
  1978年   265篇
  1977年   223篇
  1975年   195篇
  1974年   226篇
  1973年   246篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
There is a cluster of high-incidence areas of oesophageal cancer in south-eastern South America, including Southern Brazil, Uruguay and parts of Argentina. The present case-control study investigated the hypothesis that this may be due to the drinking of maté, a traditional beverage drunk at a very high temperature, and also studied the role of other known risk factors such as alcohol and tobacco. Cases (171) and age- and sex-matched controls (342) were recruited from hospitals in the State of Rio Grande do Sul in Southern Brazil. The crude odds ratio for daily maté drinkers was 1.92 relative to those drinking less frequently than daily (p = 0.006). Other risk factors included the drinking of cachaça (a sugar cane spirit), smoking, rural residence, low fruit consumption and high intake of meats. After adjustment for these variables through conditional logistic regression, the odds ratio associated with daily maté drinking was reduced to 1.47 (90% CI = 0.87 - 2.50). Although the study failed to provide evidence of a strong association between maté and oesophageal cancer, the cluster of high rates could be explained by relative risks of the magnitude observed. This is due to the fact that approximately 70% of adult males and 50% of females are daily drinkers. In addition, this study revealed that alcohol, tobacco smoking and rural residence are the main risk factors for oesophageal cancer in this population and the fruit consumption confers some degree of protection.  相似文献   
72.
New inferior vena caval filters for percutaneous placement were made by attaching filter wires similar to those in the bird's nest inferior vena caval filter onto expandable metallic stents. These stents formed a base on which to anchor the filter to the wall of the inferior vena cava. The stent filter can be introduced through a 12- to 13-French catheter sheath system. The system was successfully tested in 13 dogs.  相似文献   
73.
Five cases of fetal ventriculomegaly are described in detail. Following ultrasonography, either computerized tomography or magnetic resonance imaging was used in an attempt to clarify the structural pathology of the ventriculomegaly. In two patients, a precise diagnosis was achieved while a probable diagnosis was established in a third patient. The diverse etiology of fetal ventriculomegaly in these five cases demonstrates that ancillary medical imaging may be necessary to achieve diagnostic precision prior to therapeutic intervention.  相似文献   
74.
While there is a burgeoning body of research linking smoking during pregnancy to problem behaviour in offspring, a major criticism of this work has been the crude measurement of exposure in these studies (e.g. retrospective, self-reported only) that could lead to biased estimates. To address this issue, we used a pregnancy cohort with repeated prospective measures of exposure as well as biological assays to generate estimates of exposure patterns using a range of modelling techniques. In this paper we report on the analytical approaches we have developed, including patterns of exposure over time and best-estimate approaches that combine self-report and cotinine measures, and compare their predictive value in relation to different dimensions of fetal growth as a first step towards examining the utility of greater precision of exposure measurement.
Surprisingly, in this sample the more complex assessments of exposure, including biological measures, generally did not perform better than simple indicators of exposure based on repeated self-report measures, with one exception: a combined self-report cotinine 'best estimate' of third trimester exposure was uniquely associated with lower brain : body ratio. Further study is needed using more sophisticated cotinine assays and testing prediction of a range of outcomes to ascertain whether these findings represent true differences or are specific to the sample, methods and outcomes used. Such research will inform the development of guidelines for adequate exposure characterisation in developmental studies.  相似文献   
75.
76.
The aim of this study was to evaluate the effectiveness of incremental and maximum bite advancement during treatment of Class II Division 1 malocclusion with the Twin-block appliance in the permanent dentition. It was performed at 3 district general hospitals in the United Kingdom with 4 operators. Two hundred three patients, 10-14 years old, were randomized. Control patients had the initial bite taken edge-to-edge for appliance construction with a standard Twin-block. Experimental patients had 2 mm initial bite advancement and subsequent 2 mm advancements at 6 weekly intervals with a Twin-block appliance incorporating advancement screws. Data were collected at the start and the finish of Twin-block treatment. The use of incremental advancement of the Twin-block did not confer any advantages in terms of process and outcome of the treatment. However, patient compliance was influenced by operator and patient age. The duration of treatment was influenced by operator and initial overjet. Incremental bite advancement produced no advantages over maximum advancement.  相似文献   
77.
78.
79.
In patients with cancer, constipation is a common complication. However, unlike in the general population, the impact of the symptoms of constipation on the quality of life in cancer patients is often greater. More importantly, in patients who are in the more advanced stages of the disease, constipation may also be suggestive of disease progression. Constipation as a symptom in this population is of significant importance as it may lead to life-threatening complications, i.e. bowel perforation due to fecal impaction. Therefore, in this regard, this problem deserves particular attention, as early recognition and management of complications may prevent further physical deterioration. This review aims to provide an overview of the management of constipation in patients with cancer. A symptom-based criteria definition for chronic constipation and prevalence of the problem in cancer patients provides a brief introduction. For the initial assessment and evaluation of constipation in cancer patients, an algorithm is described. The different possible etiologies of constipation in cancer patients are also discussed. Regarding therapeutic management, guidelines and recommendations for the use of different types of laxatives, stool softeners, suppositories and rectal enemas, prokinetic agents, antidepressant medications, and miscellaneous agents are succinctly discussed. Management of fecal impaction and opioid-induced bowel dysfunction are also described. Lastly, a brief overview of the management of acute colonic pseudo-obstruction and surgical or endoscopic options for large bowel obstruction are described.  相似文献   
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