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   6938篇
  免费   405篇
  国内免费   99篇
耳鼻咽喉   90篇
儿科学   104篇
妇产科学   131篇
基础医学   719篇
口腔科学   267篇
临床医学   573篇
内科学   2183篇
皮肤病学   85篇
神经病学   596篇
特种医学   247篇
外科学   1169篇
综合类   14篇
一般理论   1篇
预防医学   276篇
眼科学   68篇
药学   328篇
中国医学   6篇
肿瘤学   585篇
  2024年   14篇
  2023年   136篇
  2022年   260篇
  2021年   473篇
  2020年   274篇
  2019年   310篇
  2018年   345篇
  2017年   242篇
  2016年   285篇
  2015年   297篇
  2014年   386篇
  2013年   428篇
  2012年   608篇
  2011年   529篇
  2010年   296篇
  2009年   290篇
  2008年   395篇
  2007年   360篇
  2006年   326篇
  2005年   264篇
  2004年   207篇
  2003年   175篇
  2002年   131篇
  2001年   41篇
  2000年   33篇
  1999年   30篇
  1998年   28篇
  1997年   14篇
  1996年   17篇
  1995年   16篇
  1994年   13篇
  1992年   12篇
  1991年   13篇
  1990年   13篇
  1989年   19篇
  1988年   17篇
  1987年   14篇
  1986年   11篇
  1985年   11篇
  1979年   8篇
  1978年   9篇
  1977年   8篇
  1976年   5篇
  1974年   13篇
  1973年   6篇
  1972年   7篇
  1971年   8篇
  1970年   9篇
  1969年   7篇
  1966年   5篇
排序方式: 共有7442条查询结果,搜索用时 15 毫秒
111.
112.
Bovine coronavirus (BoCV) is an important pathogen of cattle, causing severe enteric disease and playing a role in the bovine respiratory disease complex. Similar to other coronaviruses, a remarkable variability characterizes both its genome and biology. Despite their potential relevance, different aspects of the evolution of BoCV remain elusive. The present study reconstructs the history and evolution of BoCV using a phylodynamic approach based on complete genome and spike protein sequences. The results demonstrate high mutation and recombination rates affecting different parts of the viral genome. In the spike gene, this variability undergoes significant selective pressures—particularly episodic pressure—located mainly on the protein surface, suggesting an immune-induced selective pressure. The occurrence of compensatory mutations was also identified. On the contrary, no strong evidence in favor of host and/or tissue tropism affecting viral evolution has been proven. The well-known plasticity is thus ascribable to the innate broad viral tropism rather than mid- or long-term adaptation. The evaluation of the geographic spreading pattern clearly evidenced two clusters: a European cluster and an American–Asian cluster. While a relatively dense and quick migration network was identified in the former, the latter was dominated by the primary role of the United States (US) as a viral exportation source. Since the viral spreading pattern strongly mirrored the cattle trade, the need for more intense monitoring and preventive measures cannot be underestimated as well as the need to enforce the vaccination of young animals before international trade, to reduce not only the clinical impact but also the transferal and mixing of BoCV strains.  相似文献   
113.
The aim of this study was to assess the prefrontal cortex (PFC) oxygenation response to a 5-min incremental tilt board balance task (ITBBT) in a semi-immersive virtual reality (VR) environment driven by a depth-sensing camera. It was hypothesized that the PFC would be bilaterally activated in response to the increase of the ITBBT difficulty, given the PFC involvement in the allocation of the attentional resources to maintain postural control. Twenty-two healthy male subjects were asked to use medial–lateral postural sways to maintain their equilibrium on a virtual tilt board (VTB) balancing over a pivot. When the subject was unable to maintain the VTB angle within ±35° the VTB became red (error). An eight-channel fNIRS system was employed for measuring changes in PFC oxygenated-deoxygenated hemoglobin (O2Hb-HHb, respectively). Results revealed that the number of the performed board sways and errors augmented with the increasing of the ITBBT difficulty. A PFC activation was observed with a tendency to plateau for both O2Hb-HHb changes within the last 2 min of the task. A significant main effect of the level of difficulty was found in O2Hb and HHb (p < 0.001). The study has demonstrated that the oxygenation increased over the PFC while the subject was performing an ITBBT in a semi-immersive VR environment. This increase was modulated by the task difficulty, suggesting that the PFC is bilaterally involved in attention-demanding tasks. This task could be considered useful for diagnostic testing and functional neurorehabilitation given its adaptability in elderly and in patients with movement disorders.  相似文献   
114.
115.
116.
Several studies have shown a significant adenoma miss rate up to 35% during screening colonoscopy, especially in patients with diminutive adenomas. The use of artificial intelligence(AI) in colonoscopy has been gaining popularity by helping endoscopists in polyp detection, with the aim to increase their adenoma detection rate(ADR) and polyp detection rate(PDR) in order to reduce the incidence of interval cancers. The efficacy of deep convolutional neural network(DCNN)-based AI system for polyp detection has been trained and tested in ex vivo settings such as colonoscopy still images or videos. Recent trials have evaluated the real-time efficacy of DCNN-based systems showing promising results in term of improved ADR and PDR. In this review we reported data from the preliminary ex vivo experiences and summarized the results of the initial randomized controlled trials.  相似文献   
117.
118.
119.
120.
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