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   12937篇
  免费   1204篇
  国内免费   14篇
  2023年   63篇
  2022年   97篇
  2021年   193篇
  2020年   157篇
  2019年   188篇
  2018年   204篇
  2017年   167篇
  2016年   276篇
  2015年   506篇
  2014年   565篇
  2013年   646篇
  2012年   844篇
  2011年   856篇
  2010年   564篇
  2009年   505篇
  2008年   723篇
  2007年   740篇
  2006年   701篇
  2005年   664篇
  2004年   615篇
  2003年   594篇
  2002年   543篇
  2001年   162篇
  2000年   144篇
  1999年   191篇
  1998年   187篇
  1997年   127篇
  1996年   122篇
  1995年   139篇
  1994年   106篇
  1993年   99篇
  1992年   111篇
  1991年   119篇
  1990年   120篇
  1989年   98篇
  1988年   90篇
  1987年   75篇
  1986年   86篇
  1985年   84篇
  1984年   82篇
  1983年   76篇
  1982年   92篇
  1981年   94篇
  1980年   83篇
  1979年   68篇
  1978年   58篇
  1977年   51篇
  1976年   66篇
  1975年   61篇
  1974年   63篇
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
1.
2.
3.
4.
5.
6.
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   
7.
During the process optimisation of glucoamylase production by Aspergillus awamori, cell morphology was controlled at such a state that spore aggregation was completely prevented. Samples from five fermentations on complex media using either glucose or starch as carbon source were characterised with a Bohlin CS rheometer. The experimental data were conveniently described in terms of the power law model.  相似文献   
8.
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   
9.
Saturation and competitive binding analyses demonstrated the presence of a high affinity (KD = 0.92 nM), specific antiestrogen binding site (AEBS) in rat liver microsomes and at least 75% of total liver AEBS was recovered in this fraction. When microsomes were further separated into smooth and rough fractions, AEBS was concentrated in the latter. Subsequent dissociation of ribosomes from the rough membranes revealed that AEBS was associated with the membrane and not the ribosomal fraction. Antiestrogen binding activity could not be extracted from membranes with 1 M KCl or 0.5 M acetic acid but could be solubilized with sodium cholate. These data indicate that AEBS is an integral membrane component of the rough microsomal fraction of rat liver.  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