全文获取类型
收费全文 | 6033篇 |
免费 | 347篇 |
国内免费 | 32篇 |
专业分类
电工技术 | 88篇 |
综合类 | 9篇 |
化学工业 | 1298篇 |
金属工艺 | 132篇 |
机械仪表 | 148篇 |
建筑科学 | 224篇 |
矿业工程 | 9篇 |
能源动力 | 214篇 |
轻工业 | 406篇 |
水利工程 | 39篇 |
石油天然气 | 29篇 |
无线电 | 1123篇 |
一般工业技术 | 1123篇 |
冶金工业 | 473篇 |
原子能技术 | 35篇 |
自动化技术 | 1062篇 |
出版年
2024年 | 12篇 |
2023年 | 118篇 |
2022年 | 213篇 |
2021年 | 348篇 |
2020年 | 249篇 |
2019年 | 220篇 |
2018年 | 272篇 |
2017年 | 224篇 |
2016年 | 335篇 |
2015年 | 211篇 |
2014年 | 270篇 |
2013年 | 411篇 |
2012年 | 306篇 |
2011年 | 363篇 |
2010年 | 272篇 |
2009年 | 261篇 |
2008年 | 261篇 |
2007年 | 220篇 |
2006年 | 166篇 |
2005年 | 145篇 |
2004年 | 119篇 |
2003年 | 109篇 |
2002年 | 83篇 |
2001年 | 88篇 |
2000年 | 63篇 |
1999年 | 64篇 |
1998年 | 215篇 |
1997年 | 103篇 |
1996年 | 88篇 |
1995年 | 78篇 |
1994年 | 51篇 |
1993年 | 73篇 |
1992年 | 39篇 |
1991年 | 37篇 |
1990年 | 28篇 |
1989年 | 37篇 |
1988年 | 22篇 |
1987年 | 22篇 |
1986年 | 25篇 |
1985年 | 22篇 |
1984年 | 27篇 |
1983年 | 16篇 |
1982年 | 14篇 |
1981年 | 17篇 |
1980年 | 14篇 |
1979年 | 13篇 |
1978年 | 13篇 |
1977年 | 13篇 |
1976年 | 10篇 |
1973年 | 8篇 |
排序方式: 共有6412条查询结果,搜索用时 31 毫秒
81.
Abhishek K. Srivastava Vladimir G. Chigrinov Hoi Sing Kwok 《Journal of the Society for Information Display》2015,23(6):253-272
The ferroelectric liquid crystals, because of their fast electro‐optical response, are one of the most important classes of liquid crystals. Here, in this review, we have summarized the different electro‐optical modes for ferroelectric liquid crystals. Clark–Lagerwall effect (surface stabilized ferroelectric liquid crystal), deformed helix ferroelectric (DHF) effect, electrically suppressed helix (ESH) mode, DHF orientational Kerr effect, and ESH diffraction modes have been discussed. All of the crucial features, that is, optics, electro‐optics, dynamics, and their dependence on material parameters, operational regime, and applications, have been reviewed. 相似文献
82.
83.
84.
85.
In this paper, we introduce an internet voting protocol which satisfies desired security requirements of electronic voting. In the newly proposed protocol, we allow the adversaries to get more power than in any previous works. They can be coercers or vote buyers outside, and corrupted parties inside our system. These adversaries also have ability to collude with each other to ruin the whole system. Our main contribution is to design an internet voting protocol which is unsusceptible to most of sophisticated attacks. We employ the blind signature technique and the dynamic ballots instead of complex cryptographic techniques to preserve privacy in electronic voting. Moreover, we also aim at the practical system by improving the blind signature scheme and removing physical assumptions which have often been used in the previous works. 相似文献
86.
Nguyen TQ Buckley JM Ames C Deviren V 《Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine》2011,225(2):194-198
Intraoperative contouring of posterior rods in lumbar arthrodesis constructs introduces stress concentrations that can substantially reduce fatigue life. The sensitivity of titanium (Ti) and stainless steel (SS) to intraoperative contouring has been established in the literature; however, notch sensitivity has yet to be quantified for cobalt chrome (CoCr), which is now being advocated for use in posterior arthrodesis constructs. The goal of this study is to evaluate the sensitivity of CoCr rods to intraoperative contouring for posterior lumbar screwrod arthrodesis constructs. In this paper lumbar bilateral vertebrectomy models are constructed based on ASTM F1717-01 with curved rods (26-30 degrees total curvature) and poly-axial pedicle screws. Three types of constructs are assembled: first, 5.5 mm SS rods with SS screws (6.5 x 35 mm), second, 6.0 mm Ti rods with Ti screws (7.5 x 35 mm), and third, 6.0 mm CoCr rods with Ti screws (7.5 x 35 mm). All specimens are tested at 4 Hz in dynamic axial compression-bending with a load ratio of ten and maximum load levels of 250, 400, and 700 N until run-out at 2 000 000 cycles. Results are presented that show that the fatigue life of CoCr constructs tend to be greater than Ti constructs at all levels. At the 400 N maximum loading, CoCr lasts an average of 350 000 cycles longer than the Ti constructs. The CoCr constructs are able to sustain the 250 N load until run-out at 2 000 000 cycles but they fail at high load levels (maximum 700 N). The CoCr constructs fail at the neck of the Ti screw at high loads whereas Ti screws fail at the notch induced by contouring. Since CoCr is compatible with magnetic resonance imaging and has high static strength characteristics, the results of this study suggest that it may be an appropriate substitute for Ti. 相似文献
87.
Jeanbourquin D Sage D Nguyen L Schaeli B Kayal S Barry DA Rossi L 《Water science and technology》2011,64(5):1108-1114
Discharges of combined sewer overflows (CSOs) and stormwater are recognized as an important source of environmental contamination. However, the harsh sewer environment and particular hydraulic conditions during rain events reduce the reliability of traditional flow measurement probes. An in situ system for sewer water flow monitoring based on video images was evaluated. Algorithms to determine water velocities were developed based on image-processing techniques. The image-based water velocity algorithm identifies surface features and measures their positions with respect to real world coordinates. A web-based user interface and a three-tier system architecture enable remote configuration of the cameras and the image-processing algorithms in order to calculate automatically flow velocity on-line. Results of investigations conducted in a CSO are presented. The system was found to measure reliably water velocities, thereby providing the means to understand particular hydraulic behaviors. 相似文献
88.
89.
In this paper, a new algorithm, named VICUR, is presented for curve reconstruction problem. From a set of unorganized points, the proposed algorithm can construct curves that look natural to human vision. The VICUR algorithm is based on two connectivity criteria: proximity and good continuation from the prominent Gestalt principles of perception. Experimental results are presented to show the effectiveness of VICUR. 相似文献
90.
Xiaoyu Wang Wen Wang Yong Huang Nhan Nguyen Kalmanje Krishnakumar 《Journal of Intelligent Manufacturing》2008,19(4):383-396
Hard turning with cubic boron nitride (CBN) tools has been proven to be more effective and efficient than traditional grinding
operations in machining hardened steels. However, rapid tool wear is still one of the major hurdles affecting the wide implementation
of hard turning in industry. Better prediction of the CBN tool wear progression helps to optimize cutting conditions and/or
tool geometry to reduce tool wear, which further helps to make hard turning a viable technology. The objective of this study
is to design a novel but simple neural network-based generalized optimal estimator for CBN tool wear prediction in hard turning.
The proposed estimator is based on a fully forward connected neural network with cutting conditions and machining time as
the inputs and tool flank wear as the output. Extended Kalman filter algorithm is utilized as the network training algorithm
to speed up the learning convergence. Network neuron connection is optimized using a destructive optimization algorithm. Besides
performance comparisons with the CBN tool wear measurements in hard turning, the proposed tool wear estimator is also evaluated
against a multilayer perceptron neural network modeling approach and/or an analytical modeling approach, and it has been proven
to be faster, more accurate, and more robust. Although this neural network-based estimator is designed for CBN tool wear modeling
in this study, it is expected to be applicable to other tool wear modeling applications. 相似文献