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   2116篇
  免费   100篇
  国内免费   17篇
电工技术   40篇
化学工业   426篇
金属工艺   43篇
机械仪表   74篇
建筑科学   46篇
矿业工程   2篇
能源动力   134篇
轻工业   168篇
水利工程   16篇
石油天然气   12篇
无线电   248篇
一般工业技术   535篇
冶金工业   150篇
原子能技术   15篇
自动化技术   324篇
  2023年   36篇
  2022年   91篇
  2021年   88篇
  2020年   90篇
  2019年   65篇
  2018年   118篇
  2017年   91篇
  2016年   61篇
  2015年   53篇
  2014年   99篇
  2013年   171篇
  2012年   99篇
  2011年   137篇
  2010年   102篇
  2009年   109篇
  2008年   84篇
  2007年   79篇
  2006年   63篇
  2005年   65篇
  2004年   57篇
  2003年   21篇
  2002年   34篇
  2001年   33篇
  2000年   20篇
  1999年   15篇
  1998年   38篇
  1997年   33篇
  1996年   16篇
  1995年   20篇
  1994年   26篇
  1993年   20篇
  1992年   17篇
  1991年   17篇
  1990年   7篇
  1989年   7篇
  1988年   7篇
  1987年   16篇
  1986年   6篇
  1985年   13篇
  1984年   8篇
  1983年   8篇
  1982年   10篇
  1981年   13篇
  1980年   12篇
  1979年   8篇
  1978年   7篇
  1977年   11篇
  1976年   12篇
  1975年   4篇
  1972年   4篇
排序方式: 共有2233条查询结果,搜索用时 31 毫秒
1.
Wireless Personal Communications - Recently, the theory of effective rate has attracted much attention, since it can take the delay aspect into account when performing channel capacity analysis. In...  相似文献   
2.
3.
Neural Processing Letters - Part of Speech (POS) tagging is a sequential labelling task and one of the core applications of Natural Language Processing. It has been a challenging problem for the...  相似文献   
4.
ABSTRACT

Solvent extraction studies were performed to understand the extraction behavior of Np4+ and NpO2 2+ from acidic feeds with CMPO (octyl (phenyl)-N,N-diisobutyl carbamoyl methyl phosphine oxide) dissolved in 1-butyl-3-methylimidazolium bis(trifluoromethane sulfonyl)imide, a water immiscible ionic liquid. Slope analyses on the distribution data revealed the extraction of ML2 type species, where M = Np4+ or NpO2 2+, and L = CMPO. Studies were also carried out with Pu4+ and UO2 2+ under identical conditions. The nature of the extracted species was found to vary with the nature of the ionic species.  相似文献   
5.
In the recent sub-20 nm technology node, the process variability issues have become a major problem for scaling of MOS devices. We present a design for a strained Si/SiGe FinFET on an insulator using a 3D TCAD simulator. The impact of metal gate work function variability (WFV) on electrical parameters is studied. Such impact of WFV for different mole fractions (x) of the SiGe layer in a strained SOI-FinFET with varying grain size is presented. The results show that as the mole fraction is increased, the variability in threshold voltage (σVT) and off current (σIoff) is decreased; while, the variability of on-current (σIon) is increased. A notable observation is the distribution of electrical parameters approaches a normal distribution for smaller grain sizes.  相似文献   
6.
Analytical model for the transconductance, cut off frequency, transit time and fringing capacitance of LDD MOSFETs is presented with a simple approach. The analysis is carried out considering the LDD device as a conventional MOSFET with a series resistance [Z.-H. Liu et al., Threshold voltage model for submicrometer MOSFETs. IEEE Trans Electron Devices 1993; ED-40: 86–94] and a simple closed form expressions for cut off frequency and transit time is obtained. The total gate capacitance, i.e. the geometric and fringing capacitance, is calculated for both LDD and non-LDD devices and lower fringing capacitance is reported in LDD devices. Lower cut-off frequencies and higher transit time are reported in LDD devices for the same channel length.  相似文献   
7.
We have analyzed both conformational and functional changes caused by two large cis-acting deletions (delta 159 and delta 549) located within the read-through domain, a 850 nucleotide hairpin, in coliphage Q beta genomic RNA. Studies in vivo show that co-translational regulation of the viral coat and replicase genes has been uncoupled in viral genomes carrying deletion delta 159. Translational regulation is restored in deletion delta 549, a naturally evolved pseudorevertant. Structural analysis by computer modeling shows that structural features within the read-through domain of delta 159 RNA are less well determined than they are in the read-through domain of wild-type RNA, whereas predicted structure in the read-through domain of evolved pseudorevertant delta 549 is unusually well determined. Structural analysis by electron microscopy of the genomic RNAs shows that several long range helices at the base of the read-through domain, that suppress translational initiation of the viral replicase gene in the wild-type genome, have been destabilized in delta 159 RNA. In addition, the structure of local hairpins within the read-through region is more variable in delta 159 RNA than in wild-type RNA. Stable RNA secondary structure is restored in the read-through domain of delta 549 RNA. Our analyses suggest that structure throughout the read-through domain affects the regulation of viral replicase expression by altering the likelihood that long-range interactions at the base of the domain will form. We discuss possible kinetic and equilibrium models that can explain this effect, and argue that observed changes in structural plasticity within the read-through domain of the mutant genomes are key in understanding the process. During the course of these studies, we became aware of the importance of the information contained in the energy dot plot produced by the RNA secondary structure prediction program mfold. As a result, we have improved the graphical representation of this information through the use of color annotation in the predicted optimal folding. The method is presented here for the first time.  相似文献   
8.
17-4 PH stainless steel is used as internal drive shaft material in liquid engine pumps. One of the drive shafts failed during operation. The shaft pieces were in contact for short duration after failure, which has resulted in abrasion of fractured surfaces. Samples from the location of failure were taken, and investigation of the failure was carried out using optical and scanning electron microscopy. The microstructural analysis of the material and fractographic analysis of the fractured surface show that the failure was caused by excessive torsion.  相似文献   
9.
Electrochemical impedance measurements have been used to characterize zinc selenide films prepared by electrochemical co-deposition at a platinum rotating disk electrode. Estimations of capacitance and polarization resistance of variously prepared electrodeposits have been carried out to determine charge carrier density and corrosion rates.  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