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   1932篇
  免费   84篇
  国内免费   14篇
电工技术   30篇
化学工业   441篇
金属工艺   45篇
机械仪表   61篇
建筑科学   48篇
矿业工程   1篇
能源动力   147篇
轻工业   138篇
水利工程   16篇
石油天然气   13篇
无线电   210篇
一般工业技术   498篇
冶金工业   93篇
原子能技术   36篇
自动化技术   253篇
  2024年   4篇
  2023年   28篇
  2022年   92篇
  2021年   89篇
  2020年   87篇
  2019年   66篇
  2018年   102篇
  2017年   81篇
  2016年   68篇
  2015年   49篇
  2014年   100篇
  2013年   171篇
  2012年   105篇
  2011年   141篇
  2010年   92篇
  2009年   108篇
  2008年   98篇
  2007年   84篇
  2006年   61篇
  2005年   61篇
  2004年   50篇
  2003年   23篇
  2002年   40篇
  2001年   30篇
  2000年   18篇
  1999年   10篇
  1998年   21篇
  1997年   15篇
  1996年   9篇
  1995年   12篇
  1994年   20篇
  1993年   10篇
  1992年   14篇
  1991年   4篇
  1990年   7篇
  1989年   2篇
  1988年   8篇
  1987年   6篇
  1986年   1篇
  1985年   8篇
  1984年   8篇
  1983年   7篇
  1982年   2篇
  1981年   7篇
  1980年   2篇
  1979年   5篇
  1978年   1篇
  1977年   1篇
  1973年   1篇
  1972年   1篇
排序方式: 共有2030条查询结果,搜索用时 281 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.
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   
5.
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   
6.
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   
7.
We describe twin girls with bilateral cerebrovascular disease. In one child, a diagnosis of moyamoya disease was made after presentation in infancy with an acute hemiparesis; her asymptomatic sibling was found to have significant bilateral cerebrovascular disease after neuropsychological evaluation and assessment with transcranial Doppler ultrasound. Both subjects showed a discrepancy between verbal and performance IQ and deficits on a test of frontal-lobe function suggesting that these domains should be targeted in cognitive assessment. Family members of subjects with moyamoya are at risk of cerebrovascular disease. Clinical symptoms do not reliably predict disease and those at risk should be offered screening with non-invasive vascular imaging.  相似文献   
8.
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   
9.
10.
1,3,5‐Triglyceratetriazine [first tier (G1)] and tri(1,3,5‐triglycerate) triazine [second tier (G2)] dendrimers were prepared with 1,3,5‐trichlorotriazine and sodium glycerate in a 1 : 3 mass ratio in an ethanolic medium.G1 and G2 were amorphous, white, solid substances. Their structures were elucidated with IR, 1H‐NMR, and 13C‐NMR, and their thermal stability was studied with thermogravimetric analysis. The activation energy was calculated with the Freeman–Carroll model. Densities, viscosities, and surface tensions for 0.01–0.08 mol/kg aqueous solutions increased at 0.01 mol/kg for sodium glycerate, 1,3,5‐trichlorotriazine, 1,3,5‐triazine triglycerate chloride, G1, and G2. These values were measured at 298.15 K. The apparent molal volume, reduced viscosity, and inherent viscosity were calculated from the densities and viscosities, respectively. The data were regressed for the limiting densities, limiting apparent molal volumes, intrinsic viscosities, limiting inherent viscosities, and limiting surface tensions for solute–solvent interactions. The positive limiting apparent molal volume values were noted in the order of G2 > 1,3,5‐triazine triglycerate chloride > G1 > 1,3,5‐trichlorotriazine > sodium glycerate, with weaker hydrophilic intermolecular interactions of G2. The higher intrinsic viscosity and limiting inherent viscosity values for G2 implied stronger G2–H2O hydrophilic interactions, and the higher limiting apparent molal volume of G2 indicated slightly higher dynamic conformational changes in comparison with G1, with stronger structural activities. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  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