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   734763篇
  免费   9360篇
  国内免费   2365篇
电工技术   13598篇
综合类   623篇
化学工业   110752篇
金属工艺   27386篇
机械仪表   22703篇
建筑科学   17999篇
矿业工程   2890篇
能源动力   20221篇
轻工业   63363篇
水利工程   6772篇
石油天然气   9390篇
武器工业   30篇
无线电   91232篇
一般工业技术   142274篇
冶金工业   138242篇
原子能技术   13472篇
自动化技术   65541篇
  2021年   5978篇
  2020年   4415篇
  2019年   5689篇
  2018年   9365篇
  2017年   9438篇
  2016年   10157篇
  2015年   7052篇
  2014年   11484篇
  2013年   35524篇
  2012年   19148篇
  2011年   26601篇
  2010年   20785篇
  2009年   23655篇
  2008年   24632篇
  2007年   24647篇
  2006年   22147篇
  2005年   20084篇
  2004年   19381篇
  2003年   19035篇
  2002年   18276篇
  2001年   18152篇
  2000年   16998篇
  1999年   17931篇
  1998年   43254篇
  1997年   30848篇
  1996年   23994篇
  1995年   18321篇
  1994年   16314篇
  1993年   16027篇
  1992年   11784篇
  1991年   11174篇
  1990年   10867篇
  1989年   10326篇
  1988年   9927篇
  1987年   8550篇
  1986年   8420篇
  1985年   9900篇
  1984年   9210篇
  1983年   8133篇
  1982年   7538篇
  1981年   7587篇
  1980年   7086篇
  1979年   6883篇
  1978年   6618篇
  1977年   7795篇
  1976年   10353篇
  1975年   5613篇
  1974年   5340篇
  1973年   5296篇
  1972年   4363篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
For the first time, we successfully fabricated and demonstrated high performance metal-insulator-metal (MIM) capacitors with HfO/sub 2/-Al/sub 2/O/sub 3/ laminate dielectric using atomic layer deposition (ALD) technique. Our data indicates that the laminate MIM capacitor can provide high capacitance density of 12.8 fF//spl mu/m/sup 2/ from 10 kHz up to 20 GHz, very low leakage current of 3.2 /spl times/ 10/sup -8/ A/cm/sup 2/ at 3.3 V, small linear voltage coefficient of capacitance of 240 ppm/V together with quadratic one of 1830 ppm/V/sup 2/, temperature coefficient of capacitance of 182 ppm//spl deg/C, and high breakdown field of /spl sim/6 MV/cm as well as promising reliability. As a result, the HfO/sub 2/-Al/sub 2/O/sub 3/ laminate is a very promising candidate for next generation MIM capacitor for radio frequency and mixed signal integrated circuit applications.  相似文献   
72.
73.
The hydrogen annealing process has been used to improve surface roughness of the Si-fin in CMOS FinFETs for the first time. Hydrogen annealing was performed after Si-fin etch and before gate oxidation. As a result, increased saturation current with a lowered threshold voltage and a decreased low-frequency noise level over the entire range of drain current have been attained. The low-frequency noise characteristics indicate that the oxide trap density is reduced by a factor of 3 due to annealing. These results suggest that hydrogen annealing is very effective for improving device performance and for attaining a high-quality surface of the etched Si-fin.  相似文献   
74.
Effect of anisotropy of tin on thermomechanical behavior of solder joints   总被引:2,自引:0,他引:2  
Properties of body centered tetragonal tin are highly anisotropic. As a consequence large stresses can develop at the tin grain boundaries due to coefficient of thermal expansion mismatch during temperature excursions. A modeling approach to evaluate the 3D stress states that develop at grain boundaries during thermomechanical fatigue in tin-based solder is presented. Development of significant amounts of stresses in the plane of the grain boundary can cause grain-boundary sliding and surface-relief effects, while those normal to the grain boundary can cause grain-boundary decohesion and cracking.  相似文献   
75.
Current features are considered in the calculation of carrying capacities for constructions in engineering plant (EP). Methods and algorithms are described for EP calculations with comprehensive incorporation of the effects from technological and working defects on the behavior of structures under standard and emergency conditions. __________ Translated from Khimicheskoe i Neftegazovoe Mashinostroenie, No. 8, pp. 38–40, August, 2006.  相似文献   
76.
Starting from a microscopic Hamiltonian defined on a semi-infinite cubic lattice, and employing a mean-field approximation, the surface parameters relevant for wetting in confined ternary mixtures are derived. These are found in terms of the microscopic coupling constants, and yield a physical interpretation of their origins. In comparison with the standard expression for the surface free-energy density, several new terms arising from the derivation are identified. The influence of the surface parameters on a predicted unbinding transition in a mixture of oil, water, and amphiphile demonstrate that existing results are robust to the addition of the extra surface terms.  相似文献   
77.
78.
79.
The primary objective of this project is to identify gaps, whether real or perceived, that hinder effective groundwater management in New Zealand. These gaps show as gaps in information, gaps in implementation, gaps in technological and management tools, and gaps in understanding of fundamental processes. The secondary objective is to propose a management strategy to close the identified gaps. Several methods are used to meet these objectives: surveys distributed to selected staff in each regional council; the review of various written reports; the analysis of land-use databases; and private consultation within each regional council. Results show that groundwater management in New Zealand is generally reactionary with the main gaps being in strategic planning and national guidelines. Most gaps appear to be predominantly information and implementation issues. In some cases there are gaps in the understanding of fundamental processes within an aquifer system, including the long-term effects of land-use on groundwater quality. An adaptive management approach is suggested as a means of closing these gaps.  相似文献   
80.
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