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   3398篇
  免费   191篇
  国内免费   10篇
耳鼻咽喉   73篇
儿科学   59篇
妇产科学   66篇
基础医学   533篇
口腔科学   62篇
临床医学   198篇
内科学   633篇
皮肤病学   430篇
神经病学   283篇
特种医学   54篇
外科学   371篇
综合类   11篇
预防医学   307篇
眼科学   84篇
药学   197篇
中国医学   3篇
肿瘤学   235篇
  2023年   14篇
  2022年   20篇
  2021年   42篇
  2020年   32篇
  2019年   69篇
  2018年   83篇
  2017年   67篇
  2016年   81篇
  2015年   68篇
  2014年   96篇
  2013年   137篇
  2012年   233篇
  2011年   231篇
  2010年   154篇
  2009年   118篇
  2008年   233篇
  2007年   241篇
  2006年   216篇
  2005年   194篇
  2004年   192篇
  2003年   179篇
  2002年   210篇
  2001年   68篇
  2000年   77篇
  1999年   67篇
  1998年   38篇
  1997年   14篇
  1996年   34篇
  1995年   17篇
  1994年   17篇
  1993年   23篇
  1992年   30篇
  1991年   32篇
  1990年   28篇
  1989年   24篇
  1988年   22篇
  1987年   13篇
  1986年   18篇
  1985年   16篇
  1984年   8篇
  1980年   5篇
  1979年   8篇
  1975年   5篇
  1972年   4篇
  1968年   4篇
  1962年   6篇
  1960年   4篇
  1930年   4篇
  1925年   4篇
  1922年   4篇
排序方式: 共有3599条查询结果,搜索用时 15 毫秒
71.
72.
73.

Background

In vitro studies have shown the feasibility of coronary lesion grading with computed tomography angiography (CTA), intravascular ultrasound (IVUS) and optical coherence tomography (OCT) as compared to histology, whereas OCT had the highest discriminatory capacity.

Objective

We investigated the ability of CTA and IVUS to differentiate between early and advanced coronary lesions in vivo, OCT serving as standard of reference.

Methods

Multimodality imaging was prospectively performed in 30 NSTEMI patients. Plaque characteristics were assessed in 1083 cross-sections of 30 culprit lesions, co-registered among modalities. Absence of plaque, fibrous and fibrocalcific plaque on OCT were defined as early plaque, whereas lipid rich-plaque on OCT was defined as advanced plaque. Odds ratios adjusted for clustering were calculated to assess associations between plaque types on CTA and IVUS with early or advanced plaque.

Results

Normal findings on CTA as well as on IVUS were associated with early plaque. Non-calcified, calcified plaques and the napkin ring sign on CTA were associated with advanced plaque. On IVUS, fatty and calcified plaques were associated with advanced plaque.

Conclusions

In vivo coronary plaque characteristics on CTA and IVUS are associated with plaque characteristics on OCT. Of note, normal findings on CTA and IVUS relate to early lesions on OCT. Nevertheless, multiple plaque features on CTA and IVUS are related to advanced plaques on OCT, which may make it difficult to use qualitative plaque assessment in clinical practice.  相似文献   
74.
75.
76.
77.
78.
Synaptic integration in rat frontal cortex shaped by network activity   总被引:6,自引:0,他引:6  
Neocortical neurons in vivo are embedded in networks with intensive ongoing activity. How this network activity affects the neurons' integrative properties and what function this may imply at the network level remain largely unknown. Most of our knowledge regarding synaptic communication and integration is based on recordings in vitro, where network activity is strongly diminished or even absent. Here, we present results from two complementary series of experiments based on intracellular in vivo recordings in anesthetized rat frontal cortex. Specifically, we measured 1) the relationship between the excursions of a neuron's membrane potential and the spiking activity in the surrounding network and 2) how the summation of several inputs to a single neuron changes with the different levels of its membrane potential excursions and the associated states of network activity. The combination of these measurements enables us to assess how the level of network activity influences synaptic integration. We present direct evidence that integration of synaptic inputs in frontal cortex is linear, independent of the level of network activity. However, during periods of high network activity, the neurons' response to synaptic input is markedly reduced in both amplitude and duration. This results in a drastic shortening of its window for temporal integration, requiring more precise coordination of presynaptic spike discharges to reliably drive the neuron to spike under conditions of high network activity. We conclude that ongoing activity, as present in the active brain, emphasizes the need for neuronal cooperation at the network level, and cannot be ignored in the exploration of cortical function.  相似文献   
79.
A large outbreak with an aminoglycoside-resistant Enterobacter cloacae (AREC) clone occurred at the University Medical Center Utrecht beginning in 2001 and continued up through the time that this study was completed. This clone (genotype I) contains a conjugative R plasmid carrying the qnrA1, bla(CTX-M-9), and aadB genes, encoding resistance to quinolones, extended-spectrum beta-lactamases, and aminoglycosides, respectively. The aim of this study was to determine whether this clone was more transmissible than other AREC strains. Therefore, the dissemination of this genotype and of other E. cloacae strains was studied. In addition, infection control measures taken were evaluated. Pulsed-field gel electrophoresis analysis divided the 191 AREC strains into 42 different genotypes, of which 5 (12%) involved at least three patients. Aside from this outbreak (133 patients), only two other small outbreaks occurred, showing that the infection control measures were successful for all strains but one. Among 324 aminoglycoside-susceptible E. cloacae strains, 34/166 (20%) genotypes were identified from at least three patients, but only 4 involved small outbreaks. The outbreak strain was also detected in 11 of 15 other Dutch hospitals and caused outbreaks in at least 4. Evaluation of infection control measures showed that the outbreak strain disseminated throughout the hospital despite adequate implementation of internationally accepted guidelines on the control of multidrug-resistant Enterobacteriaceae (MRE). In conclusion, some MRE strains are better able to spread than others, and these strains may not be controlled by the current infection control guidelines. Strategies to identify such strains in an early phase and adapted guidelines for such "superbugs" are needed to prevent these clones from becoming endemic.  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