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   6122篇
  免费   627篇
  国内免费   9篇
  2023年   24篇
  2021年   83篇
  2020年   79篇
  2019年   70篇
  2018年   94篇
  2017年   78篇
  2016年   114篇
  2015年   209篇
  2014年   241篇
  2013年   290篇
  2012年   364篇
  2011年   407篇
  2010年   263篇
  2009年   211篇
  2008年   320篇
  2007年   357篇
  2006年   342篇
  2005年   344篇
  2004年   293篇
  2003年   270篇
  2002年   297篇
  2001年   79篇
  2000年   81篇
  1999年   92篇
  1998年   84篇
  1997年   57篇
  1996年   44篇
  1995年   59篇
  1994年   49篇
  1993年   45篇
  1992年   52篇
  1991年   59篇
  1990年   58篇
  1989年   52篇
  1988年   46篇
  1987年   36篇
  1986年   34篇
  1985年   46篇
  1984年   34篇
  1983年   43篇
  1982年   46篇
  1981年   52篇
  1980年   51篇
  1979年   40篇
  1978年   32篇
  1976年   41篇
  1975年   37篇
  1974年   25篇
  1973年   27篇
  1969年   24篇
排序方式: 共有6758条查询结果,搜索用时 46 毫秒
1.
During an HIV-1 prevention clinical trial in East Africa, we observed 16 cases of primary HIV-1 infection in women coincident with pregnancy or breastfeeding. Nine of eleven pregnant women initiated rapid combination antiretroviral therapy (ART), despite having CD4 counts exceeding national criteria for ART initiation; breastfeeding women initiated ART or replacement feeding. Rapid ART initiation during primary HIV-1 infection during pregnancy and breastfeeding is feasible in this setting.  相似文献   
2.
Exposure to fine particles can cause various diseases, and an easily accessible method to monitor the particles can help raise public awareness and reduce harmful exposures. Here we report a method to estimate PM air pollution based on analysis of a large number of outdoor images available for Beijing, Shanghai (China) and Phoenix (US). Six image features were extracted from the images, which were used, together with other relevant data, such as the position of the sun, date, time, geographic information and weather conditions, to predict PM2.5 index. The results demonstrate that the image analysis method provides good prediction of PM2.5 indexes, and different features have different significance levels in the prediction.  相似文献   
3.
4.
5.
6.
7.
Electrical stimulation of the nervous system for therapeutic purposes, such as deep brain stimulation in the treatment of Parkinson’s disease, has been used for decades. Recently, increased attention has focused on using microstimulation to restore functions as diverse as somatosensation and memory. However, how microstimulation changes the neural substrate is still not fully understood. Microstimulation may cause cortical changes that could either compete with or complement natural neural processes, and could result in neuroplastic changes rendering the region dysfunctional or even epileptic. As part of our efforts to produce neuroprosthetic devices and to further study the effects of microstimulation on the cortex, we stimulated and recorded from microelectrode arrays in the hand area of the primary somatosensory cortex (area 1) in two awake macaque monkeys. We applied a simple neuroprosthetic microstimulation protocol to a pair of electrodes in the area 1 array, using either random pulses or pulses time-locked to the recorded spiking activity of a reference neuron. This setup was replicated using a computer model of the thalamocortical system, which consisted of 1980 spiking neurons distributed among six cortical layers and two thalamic nuclei. Experimentally, we found that spike-triggered microstimulation induced cortical plasticity, as shown by increased unit-pair mutual information, while random microstimulation did not. In addition, there was an increased response to touch following spike-triggered microstimulation, along with decreased neural variability. The computer model successfully reproduced both qualitative and quantitative aspects of the experimental findings. The physiological findings of this study suggest that even simple microstimulation protocols can be used to increase somatosensory information flow.  相似文献   
8.
9.
10.
The Rab, ARF, and Arl members of the Ras superfamily of small GTPases work together to control specific intracellular trafficking pathways. Here we focus on their roles in protein transport to and within the Golgi apparatus.  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