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   1469篇
  免费   53篇
电工技术   11篇
化学工业   210篇
金属工艺   8篇
机械仪表   19篇
建筑科学   54篇
矿业工程   3篇
能源动力   46篇
轻工业   177篇
水利工程   8篇
石油天然气   19篇
无线电   200篇
一般工业技术   174篇
冶金工业   447篇
原子能技术   20篇
自动化技术   126篇
  2022年   6篇
  2021年   32篇
  2020年   23篇
  2019年   20篇
  2018年   25篇
  2017年   31篇
  2016年   29篇
  2015年   15篇
  2014年   25篇
  2013年   42篇
  2012年   59篇
  2011年   63篇
  2010年   66篇
  2009年   43篇
  2008年   47篇
  2007年   52篇
  2006年   44篇
  2005年   47篇
  2004年   36篇
  2003年   26篇
  2002年   30篇
  2001年   20篇
  2000年   26篇
  1999年   33篇
  1998年   109篇
  1997年   82篇
  1996年   54篇
  1995年   46篇
  1994年   34篇
  1993年   40篇
  1992年   20篇
  1991年   18篇
  1990年   16篇
  1989年   16篇
  1988年   8篇
  1987年   14篇
  1986年   8篇
  1985年   20篇
  1984年   6篇
  1983年   14篇
  1981年   17篇
  1980年   13篇
  1979年   12篇
  1978年   15篇
  1977年   20篇
  1976年   24篇
  1975年   8篇
  1973年   7篇
  1971年   7篇
  1970年   5篇
排序方式: 共有1522条查询结果,搜索用时 15 毫秒
1.
Abnormal levels of glutathione, a cellular antioxidant, can lead to a variety of diseases. We have constructed a near-infrared ratiometric fluorescent probe to detect glutathione concentrations in biological samples. The probe consists of a coumarin donor, which is connected through a disulfide-tethered linker to a rhodamine acceptor. Under the excitation of the coumarin donor at 405 nm, the probe shows weak visible fluorescence of the coumarin donor at 470 nm and strong near-infrared fluorescence of the rhodamine acceptor at 652 nm due to efficient Forster resonance energy transfer (FRET) from the donor to the acceptor. Glutathione breaks the disulfide bond through reduction, which results in a dramatic increase in coumarin fluorescence and a corresponding decrease in rhodamine fluorescence. The probe possesses excellent cell permeability, biocompatibility, and good ratiometric fluorescence responses to glutathione and cysteine with a self-calibration capability. The probe was utilized to ratiometrically visualize glutathione concentration alterations in HeLa cells and Drosophila melanogaster larvae.  相似文献   
2.
ABSTRACT

Design and implementation of an effective dissemination programme for decentralised renewable energy system necessitate an accurate estimate of its utilisation potential. Hence, in this study, an attempt has been made to develop frameworks to estimate the utilisation potential of decentralised renewable energy systems in the state of Uttarakhand in India. Estimations imply large resource, technical and economic potentials of the domestic solar water heater, solar home system, solar lantern, family size biogas plant and improved biomass cookstove in Uttarakhand. With higher impact on the purchasing power of households, prevailing soft loan scheme has been found to be more appropriate than a capital subsidy for promoting the usage of decentralised renewable energy systems.  相似文献   
3.
4.
Lasers containing a nanopatterned active layer demonstrating excellent threshold characteristics are presented. The nanopatterned active layer is fabricated using high-resolution electron beam lithography and selective-area metal organic chemical vapour deposition crystal growth. Results demonstrating an order of magnitude improvement over previous results are reported.  相似文献   
5.
In this work, we have created a new type of structure, the nanopore active layer, for achieving quantization of carrier states in a semiconductor. The nanopore structure consists of a periodic two-dimensional array of localized energy barriers perturbing an otherwise conventional quantum well. This perturbation leads to the formation of intraband forbidden energy gaps which are observed experimentally.  相似文献   
6.
7.
8.
The visual sector of the reticular thalamic nucleus has come under some intense scrutiny over recent years, principally because of the key role that the nucleus plays in the processing of visual information. Despite this scrutiny, we know very little of how the connections between the reticular nucleus and the different areas of visual cortex and the different visual dorsal thalamic nuclei are organized. This study examines the patterns of reticular connections with the visual cortex and the dorsal thalamus in the rat, a species where the visual pathways have been well documented. Biotinylated dextran, an anterograde and retrograde tracer, was injected into different visual cortical areas [17; rostral 18a: presumed area AL: (anterolateral); caudal 18a: presumed area LM (lateromedial); rostral 18b: presumed area AM (anteromedial); caudal 18b: presumed area PM (posteromedial)] and into different visual dorsal thalamic nuclei (posterior thalamic, lateral geniculate nuclei), and the patterns of anterograde and retrograde labelling in the reticular nucleus were examined. From the cortical injections, we find that the visual sector of the reticular nucleus is divided into subsectors that each receive an input from a distinct visual cortical area, with little or no overlap. Further, the resulting pattern of cortical terminations in the reticular nucleus reflects largely the patterns of termination in the dorsal thalamus. That is, each cortical area projects to a largely distinct subsector of the reticular nucleus, as it does to a largely distinct dorsal thalamic nucleus. As with each of the visual cortical areas, each of the visual dorsal thalamic (lateral geniculate, lateral posterior, posterior thalamic) nuclei relate to a separate territory of the reticular nucleus, with little or no overlap. Each of these dorsal thalamic territories within the reticular nucleus receives inputs from one or more of the visual cortical areas. For instance, the region to the reticular nucleus that is labelled after an injection into the lateral geniculate nucleus encompasses the reticular regions which receive afferents from cortical areas 17, rostral 18b and caudal 18b. These results suggest that individual cortical areas may influence the activity of different dorsal thalamic nuclei through their reticular connections.  相似文献   
9.
Describes methods and techniques of play therapy for use with multicultural and diverse populations. Barriers to counseling multicultural children and Eurocentric play therapy techniques with multicultural populations are highlighted. Specific guidelines and examples for play therapy with multicultural children are provided. Recommendations and implications for mental health professionals are also discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
10.
A 73-year-old HTLV-1 infected male developed overt ATL following 3-years observation, and the clonality of HTLV-1 infected cells changed before overt ATL onset. 10 micrograms of DNA, extracted from mononuclear cells was digested with PstI, and the clonal proliferation of HTLV-1 infected cells was examined by Southern blotting with LTR probe. 4 bands were observed 3 years prior to ATL onset, and 2 different bands were detected 2 years and 6 months later. This suggests that in some ATL cases, the clonality of monoclonally proliferated HTLV-1 infected cells may be changeable before overt ATL onset.  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