首页 | 官方网站   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   2017篇
  免费   124篇
  国内免费   10篇
医药卫生   2151篇
  2023年   18篇
  2022年   36篇
  2021年   49篇
  2020年   23篇
  2019年   33篇
  2018年   43篇
  2017年   30篇
  2016年   45篇
  2015年   38篇
  2014年   45篇
  2013年   71篇
  2012年   107篇
  2011年   116篇
  2010年   63篇
  2009年   71篇
  2008年   93篇
  2007年   114篇
  2006年   118篇
  2005年   109篇
  2004年   94篇
  2003年   99篇
  2002年   78篇
  2001年   65篇
  2000年   69篇
  1999年   59篇
  1998年   19篇
  1997年   14篇
  1996年   14篇
  1995年   15篇
  1994年   13篇
  1993年   7篇
  1992年   37篇
  1991年   37篇
  1990年   33篇
  1989年   36篇
  1988年   34篇
  1987年   26篇
  1986年   18篇
  1985年   25篇
  1984年   20篇
  1983年   12篇
  1982年   8篇
  1980年   12篇
  1979年   15篇
  1978年   8篇
  1973年   10篇
  1971年   5篇
  1968年   6篇
  1967年   5篇
  1965年   5篇
排序方式: 共有2151条查询结果,搜索用时 15 毫秒
71.
For many animal taxa, the extent to which phylogeny can account for the form of species' social systems has seldom been investigated formally. A quantitative phylogenetic analysis of social systems in the order Primates reveals that social organization may be strongly conserved in some lineages, even in the face of considerable ecological variability. This result has important implications for efforts to understand the evolution of animal societies and for attempts to reconstruct the social organization of early humans.  相似文献   
72.
Epidemiologic studies suggest that human herpesvirus 8 (HHV-8) may be sexually transmitted. To study the potential for HHV-8 transmission through cervicovaginal (CV) secretions, the presence of HHV-8 DNA was investigated by nested polymerase chain reaction in the cellular fraction of CV secretions from 36 human immunodeficiency virus type 1 (HIV-1)-seropositive and 29 HIV-1-seronegative women. The same patients were tested for antibodies to two defined HHV-8 antigens (latency-associated nuclear antigen and open-reading frame 65-encoded structural protein) and for HHV-8 DNA in their peripheral blood mononuclear cells (PBMC). The findings were compared with the rate of HHV-8 detection in semen samples of 20 HIV-1-infected men. HHV-8 DNA was detected in the CV samples from only 1 HHV-8-seropositive AIDS patient, in 3 PBMC samples (1/29 HIV-1-seronegative patients, 1/3 AIDS patients with Kaposi's sarcoma, and 1/19 AIDS patients), and in 1 of 20 semen samples. HHV-8 infection was more common in HIV-1-infected than uninfected women. Thus HHV-8 DNA is only rarely detectable in CV secretions and semen of HHV-8-infected individuals.  相似文献   
73.
74.
75.
76.
77.
Adult patients with Niemann-Pick disease type C (NPC) usually develop cognitive impairment progressing to dementia, whose pathophysiology remains still unclear. Noteworthy parallels exist in cognitive impairment and cellular pathology of NPC and Alzheimer’s disease (AD). In particular, alterations of cholinergic system, which represent one of the pathological hallmarks and contribute to cognitive deterioration in AD, have recently been demonstrated in a human brain autopsy and in an experimental model of NPC. This finding raised the issue that central cholinergic circuits dysfunction may contribute to pathophysiology of cognitive impairment in NPC as well, and prompted us to evaluate the cholinergic functional involvement in NPC patients by applying a neurophysiologic technique, named short-latency afferent inhibition (SAI). We describe clinical, biochemical, molecular and neuropsychological features, and SAI findings in three patients affected by NPC. Diagnosis of NPC was assessed by molecular analysis of the NPC1 gene in all patients. In two of them, biochemical analysis of intracellular accumulation of unesterified cholesterol was also performed. The main clinical features were cerebellar ataxia, vertical supranuclear gaze palsy and a variable degree of cognitive impairment ranging from only memory impairment to severe dementia. Electrophysiological evaluation revealed a reduced SAI in all three patients. Our SAI findings provide evidence of cholinergic dysfunction in patients with the adult form of NPC, supporting that cholinergic alterations may play a role in cognitive impairment in NPC, and strengthening the similarities between NPC and AD.  相似文献   
78.
The pandemic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has garnered the attention of scientists worldwide in the search for an effective treatment while also focusing on vaccine development. Several drugs have been used for the management of coronavirus disease 2019 (COVID-19), which has affected many hospitals and health centers worldwide. Statistically significant results are lacking on the effectiveness of the experimented drugs in reducing COVID-19 morbidity or mortality, as there are very few published randomized clinical trials. Despite this, the literature offers some material for study and reflection. This opinion review attempts to address three burning questions on COVID-19 treatment options. (1) What kind of studies are currently published or ongoing in the treatment of patients with COVID-19? (2) What drugs are currently described in the literature as options of treatment for patients affected by the infection? And (3) Are there specific clinical manifestations related to COVID-19 that can be treated with a customized and targeted therapy? By answering these questions, we wish to create a summary of current COVID-19 treatments and the anti-COVID-19 treatments proposed in the recent clinical trials developed in the last 3 mo, and to describe examples of clinical manifestations of the SARS-CoV-2 infection with a cause-related treatment.  相似文献   
79.
Retinal stem cell culture has become a powerful research tool, but it requires reliable methods to obtain high‐quality images of living and fixed cells. This study describes a procedure for using phase contrast microscopy to obtain three‐dimensional (3‐D) images for the study of living cells by photographing a living cell in a culture dish from bottom to top, as well as a procedure to increase the quality of scanning electron micrographs and laser confocal images. The procedure may also be used to photograph clusters of neural stem cells, and retinal explants with vigorous axonal growth. In the case of scanning electron microscopy and laser confocal images, a Gaussian procedure is applied to the original images. The methodology allows for the creation of anaglyphs and video reconstructions, and provides high‐quality images for characterizing living cells or tissues, fixed cells or tissues, or organs observed with scanning electron and laser confocal microscopy. Its greatest advantage is that it is easy to obtain good results without expensive equipment. The procedure is fast, precise, simple, and offers a strategic tool for obtaining 3‐D reconstructions of cells and axons suitable for easily determining the orientation and polarity of a specimen. It also enables video reconstructions to be created, even of specimens parallel to the plastic base of a tissue culture dish, It is also helpful for studying the distribution and organization of living cells in a culture, as it provides the same powerful information as optical tomography, which most confocal microscopes cannot do on sterile living cells. Anat Rec, 297:770–780, 2014. © 2014 Wiley Periodicals, Inc.  相似文献   
80.
A 9-year-old boy was found to have ruptured sinus of Valsalva aneurysm (RSVA) and aortic coarctation. Following relief of aortic coarctation by balloon angioplasty, transcatheter coil occlusion of the RSVA was performed successfully under transesophageal echocardiographic and fluoroscopic monitoring; bioptome-assisted delivery of 0.052" Gianturco coil was undertaken via a 7 Fr sheath stabilized by an 0.035" guidewire passing through the RSVA and the sheath. This report details the technique of occlusion.  相似文献   
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-23

京公网安备 11010802026262号