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   1083837篇
  免费   31238篇
  国内免费   13414篇
电工技术   29461篇
技术理论   31篇
综合类   19767篇
化学工业   168718篇
金属工艺   47116篇
机械仪表   43428篇
建筑科学   42550篇
矿业工程   12853篇
能源动力   28811篇
轻工业   82524篇
水利工程   12568篇
石油天然气   29706篇
武器工业   2264篇
无线电   129005篇
一般工业技术   186590篇
冶金工业   154299篇
原子能技术   16392篇
自动化技术   122406篇
  2023年   6026篇
  2022年   11561篇
  2021年   17258篇
  2020年   12785篇
  2019年   12776篇
  2018年   29166篇
  2017年   29451篇
  2016年   26249篇
  2015年   18511篇
  2014年   25133篇
  2013年   51422篇
  2012年   38934篇
  2011年   53203篇
  2010年   43906篇
  2009年   43515篇
  2008年   45235篇
  2007年   45734篇
  2006年   37757篇
  2005年   34828篇
  2004年   28934篇
  2003年   27570篇
  2002年   25732篇
  2001年   24436篇
  2000年   23965篇
  1999年   26208篇
  1998年   49752篇
  1997年   36405篇
  1996年   29178篇
  1995年   22648篇
  1994年   19902篇
  1993年   18553篇
  1992年   13853篇
  1991年   12727篇
  1990年   11982篇
  1989年   11202篇
  1988年   10642篇
  1987年   9058篇
  1986年   8795篇
  1985年   10152篇
  1984年   9378篇
  1983年   8248篇
  1982年   7665篇
  1981年   7670篇
  1980年   7152篇
  1979年   6907篇
  1978年   6620篇
  1977年   7795篇
  1976年   10353篇
  1975年   5613篇
  1974年   5340篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
The magneto-optical Kerr effect for red (628 nm) and green (532 nm) light is used to study magnetization processes in 2D magnonic crystals obtained by etching pits with the diameter D ≈ 32 μm to a depth of t ≤ 2 μm in a 16.1-μm-thick film of yttrium iron garnet (YIG). Hysteresis loops obtained in the case of the inplane crystal magnetization at 628 nm are characterized by lower saturation fields H s and higher remanent magnetizations than those obtained at 532 nm, a result that is attributed to different absorption coefficients of the YIG film at these wavelengths. This difference between the magnetization curves reflects the fact that the magnonic-crystal surface probed with the green light makes a greater contribution to the magneto-optical Kerr effect. Therefore, the green light is more sensitive to the demagnetizing fields, which govern magnetization processes in the magnonic crystals.  相似文献   
42.
简要介绍了通用串行总线USB的特点,对USB接口芯片USBN9602的内部结构、引脚、寄存器组作了详细的论述,并介绍了其应用。  相似文献   
43.
A hybrid power compensator (HPC) consisting of a static VAr compensator and a dynamic compensator needs to be optimally controlled during the compensation of nonlinear loads. The HPC must be controlled to meet minimum requirements in terms of power factor and harmonic distortion, while at the same time minimizing its total cost. An artificial neural network (ANN) is used to control the HPC amidst a very dynamic power system environment. The performance of a reference ANN is evaluated while controlling an HPC connected to a typical nonlinear industrial load. The training and performance of the ANN is then optimized in terms of training set size, training set packing and ANN topology and the performance compared to the reference ANN. This paper highlights the importance of optimising the mentioned ANN parameters to achieve optimum ANN training and modeling accuracy. The results obtained reveals that the application of an ANN in controlling an HPC is feasible given that the ANN parameters are chosen appropriately.  相似文献   
44.
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   
45.
46.
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   
47.
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   
48.
49.
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   
50.
Membrane separation technology represents an alternative way to achieve biomass retention in anaerobic bioreactors for wastewater treatment. Due to high biomass concentrations of anaerobic reactors, cake formation is likely to represent a major cause of flux decline. In the presented research, experiments are performed on the effect of biomass concentration and level of gas sparging on the hydraulic capacity of a submerged anaerobic membrane bioreactor. Both parameters significantly affected the hydraulic capacity, with biomass exerting the most pronounced effect. After 50 days of continuous operation the critical flux remained virtually unchanged, despite an increase in membrane resistance, suggesting that biomass characteristics and hydraulic conditions determine the bio-layer formation rather than the membrane's fouling level. The concept of bio-layer management is introduced to describe the programmed combination of actions performed in order to control the formation of biomass layer over membranes.  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