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   11508篇
  免费   868篇
  国内免费   24篇
耳鼻咽喉   83篇
儿科学   377篇
妇产科学   441篇
基础医学   1354篇
口腔科学   301篇
临床医学   1222篇
内科学   2797篇
皮肤病学   296篇
神经病学   833篇
特种医学   445篇
外国民族医学   3篇
外科学   1633篇
综合类   178篇
一般理论   7篇
预防医学   916篇
眼科学   402篇
药学   590篇
中国医学   7篇
肿瘤学   515篇
  2021年   127篇
  2019年   126篇
  2018年   174篇
  2017年   145篇
  2016年   123篇
  2015年   152篇
  2014年   219篇
  2013年   330篇
  2012年   458篇
  2011年   485篇
  2010年   308篇
  2009年   260篇
  2008年   446篇
  2007年   425篇
  2006年   464篇
  2005年   481篇
  2004年   444篇
  2003年   414篇
  2002年   416篇
  2001年   424篇
  2000年   378篇
  1999年   316篇
  1998年   106篇
  1997年   101篇
  1996年   100篇
  1995年   90篇
  1994年   94篇
  1993年   98篇
  1992年   337篇
  1991年   317篇
  1990年   284篇
  1989年   295篇
  1988年   264篇
  1987年   289篇
  1986年   245篇
  1985年   219篇
  1984年   172篇
  1983年   157篇
  1982年   98篇
  1981年   103篇
  1980年   106篇
  1979年   171篇
  1978年   139篇
  1977年   121篇
  1976年   97篇
  1975年   97篇
  1974年   116篇
  1973年   115篇
  1972年   97篇
  1970年   95篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
目的:明确集中的电话干预能否降低慢性心衰门诊患者死亡或因心衰加重而住院的发生率。设计:多中心、随机对照试验。地点:阿根廷的51个中心(包括公立、私立的医院及流动设施)。参与者:1518例患有稳定的慢性心衰且已接受最佳药物治疗方案治疗的门诊患者,由心脏科主治医师分层后随机分为电话干预组和常规治疗组。干预:在常规治疗的基础上,由一个中心通过护士频繁的电话随访对患者进行教育、辅导和监督。主要观察指标:全因死亡或由于心衰加重而住院。结果:99.5%的患者完成了全部随访。常规治疗组758例患者中由于心衰加重而住院或死亡的比例(235…  相似文献   
3.
4.
(1) The estrous cycle in the rat may be used to study recurrent changes in motor behaviors and motivation which are strongly related to cyclic hormonal and CNS changes. (2) The peak in motivated behaviors occurs during a sharply defined period on the night between proestrus and estrus and is evident in facilitated wheel-running, lordosis, and intracranial self-stimulation. (3) Behaviors without a clearly motivated character do not show an estrous cyclicity. (4) The estrous cyclic variation in intracranial self-stimulation was observed at a specific locus — the pars campacta of the substantia nigra. (5) A neurochemical link between sexually motivated behavior, wheel running and intracranial self-stimulation is suggested. This link is in part dopaminergic but is probably also activated by many other systems.  相似文献   
5.
Intrusive thoughts and images, often of a violent, horrific, or blasphemous nature are the hallmark of Obsessive Compulsive Disorder (OCD). OCD patients frequently also often have reductions in normal serotonergic (5-HT) function. This paper proposes a model of 5-HT function involving the routine filtering and suppression of violent or libidinal impulses. This model accounts for OCD as an instance of failed inhibition. The model also appears to resemble Freud's model of ego-id interactions at least in part, suggesting that it may be possible to psychobiologically substantiate a Freudian metaphor.  相似文献   
6.
7.
The structural consequences of bone density changes associated with lytic metastatic lesions were investigated using an experimental model of regular, lytic metastatic lesions in bone. Circular holes were drilled in the mid-diaphyseal cortex of paired adult canine femora. The region around the defect was demineralized in one bone of each pair with 0.8 N HCl. Specimens were tested to failure in four-point bending. Defect size was determined from conventional planar radiographs as the maximum apparent defect diameter divided by the periosteal diameter. Demineralization resulted in irregular defect geometries, which increased the maximum defect dimension 33% to 57% with respect to the original drill hole diameter. Demineralization resulted in additional strength reductions beyond those expected from the original drill hole alone. Despite the irregular demineralization patterns observed, strength reductions were in close agreement with those predicted from data for regular, nondemineralized holes (r2 = 0.93). The results demonstrate that irregular diaphyseal defect borders may not require more complex fracture risk predictors than can be determined from analytic and experimental studies of regular defect geometries. Our results also demonstrate that errors of over 100% can occur when measuring diaphyseal defect size from radiographs that are not optimally aligned with respect to the defect.  相似文献   
8.
9.
To evaluate use of a digital photostimulable phosphor imaging system in the neonatal nursery, 150 newborns were divided into three groups of 50. In the first two groups, screen-film and computed radiographs of the chest were obtained at the same radiation exposure; in the third group, computed radiographs were obtained with a 50% dose reduction (half-exposure computed radiographs). All images were blindly evaluated by three readers who scored the quality of visualization of the mediastinum, lung, bone, soft tissues, and endotracheal and nasogastric tubes, and also image density. No statistical differences in visualization of tubes existed among the three groups. Visualization of the mediastinum, lung, bones, and soft tissues was statistically significantly better on computed radiographs than on half-exposure computed radiographs; visualization of the lungs, bones, and soft tissues was statistically significantly better on screen-film radiographs than half-exposure computed radiographs. Image density was statistically better on computed and half-exposure computed radiographs than on screen-film radiographs.  相似文献   
10.
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