全文获取类型
收费全文 | 1077923篇 |
免费 | 33431篇 |
国内免费 | 14931篇 |
专业分类
电工技术 | 31772篇 |
技术理论 | 58篇 |
综合类 | 20616篇 |
化学工业 | 167069篇 |
金属工艺 | 45487篇 |
机械仪表 | 42816篇 |
建筑科学 | 45871篇 |
矿业工程 | 13928篇 |
能源动力 | 29911篇 |
轻工业 | 86645篇 |
水利工程 | 11998篇 |
石油天然气 | 31509篇 |
武器工业 | 2680篇 |
无线电 | 129781篇 |
一般工业技术 | 179893篇 |
冶金工业 | 161783篇 |
原子能技术 | 16475篇 |
自动化技术 | 107993篇 |
出版年
2023年 | 6722篇 |
2022年 | 12323篇 |
2021年 | 18169篇 |
2020年 | 13869篇 |
2019年 | 13049篇 |
2018年 | 17478篇 |
2017年 | 18874篇 |
2016年 | 18243篇 |
2015年 | 18768篇 |
2014年 | 26796篇 |
2013年 | 53695篇 |
2012年 | 38371篇 |
2011年 | 48052篇 |
2010年 | 39534篇 |
2009年 | 41505篇 |
2008年 | 42271篇 |
2007年 | 41827篇 |
2006年 | 40035篇 |
2005年 | 36101篇 |
2004年 | 29652篇 |
2003年 | 28286篇 |
2002年 | 26333篇 |
2001年 | 26088篇 |
2000年 | 25408篇 |
1999年 | 28196篇 |
1998年 | 53281篇 |
1997年 | 38995篇 |
1996年 | 31537篇 |
1995年 | 24396篇 |
1994年 | 21547篇 |
1993年 | 19694篇 |
1992年 | 14752篇 |
1991年 | 13716篇 |
1990年 | 12732篇 |
1989年 | 12101篇 |
1988年 | 11518篇 |
1987年 | 9639篇 |
1986年 | 9365篇 |
1985年 | 10634篇 |
1984年 | 9852篇 |
1983年 | 8973篇 |
1982年 | 8267篇 |
1981年 | 8262篇 |
1980年 | 7751篇 |
1979年 | 7530篇 |
1978年 | 7109篇 |
1977年 | 8534篇 |
1976年 | 11589篇 |
1975年 | 6012篇 |
1974年 | 5787篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
van Schoor G. van Wyk J.D. Shaw I.S. 《Industrial Electronics, IEEE Transactions on》2003,50(3):546-553
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
42.
A VQ-based blind image restoration algorithm 总被引:5,自引:0,他引:5
Learning-based algorithms for image restoration and blind image restoration are proposed. Such algorithms deviate from the traditional approaches in this area, by utilizing priors that are learned from similar images. Original images and their degraded versions by the known degradation operator (restoration problem) are utilized for designing the VQ codebooks. The codevectors are designed using the blurred images. For each such vector, the high frequency information obtained from the original images is also available. During restoration, the high frequency information of a given degraded image is estimated from its low frequency information based on the codebooks. For the blind restoration problem, a number of codebooks are designed corresponding to various versions of the blurring function. Given a noisy and blurred image, one of the codebooks is chosen based on a similarity measure, therefore providing the identification of the blur. To make the restoration process computationally efficient, the principal component analysis (PCA) and VQ-nearest neighbor approaches are utilized. Simulation results are presented to demonstrate the effectiveness of the proposed algorithms. 相似文献
43.
Shi-Jin Ding Hang Hu Lim H.F. Kim S.J. Yu X.F. Chunxiang Zhu Li M.F. Byung Jin Cho Chan D.S.H. Rustagi S.C. Yu M.B. Chin A. Dim-Lee Kwong 《Electron Device Letters, IEEE》2003,24(12):730-732
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
44.
45.
Jeong-Soo Lee Yang-Kyu Choi Daewon Ha Balasubramanian S. Tsu-Jae King Bokor J. 《Electron Device Letters, IEEE》2003,24(3):186-188
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
46.
第三节 常见氧化物膜目前研究最多的氧化物膜可谓二氧化硅和二氧化钛膜 ,这两种薄膜也是接受呈色离子、制备彩色镀膜常用的基体膜 ,所以 ,有必要将它们单独列出 ,加以讨论。1 二氧化钛膜在所有高折射率材料中 ,由钛的化合物制备的氧化物膜具有特殊的实际意义。因此 ,对二氧化 相似文献
47.
48.
L. B. Knayz'kov 《Journal of Infrared, Millimeter and Terahertz Waves》2003,24(11):1931-1938
Variants are considered of palarizational frequency-selective multipath interference devices for millimetric- and submillimetric- wave receivers. Main expressions are presented that describe their characteristics. Advantages are pointed out of the devices as compared with Fabry-Perot interferometers when solving problems of received frequency-band shaping, heterodyne noise rejection, and signal- and heterodyne-radiation transfer to mixer. 相似文献
49.
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
50.
对在实际组网中选择合理的ASON架构和保护方式作了相应分析,并为搭建可向ASON平滑演进的传统网络时需注意的问题提供了参考意见, 相似文献