全文获取类型
收费全文 | 1545篇 |
免费 | 11篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 10篇 |
综合类 | 2篇 |
化学工业 | 154篇 |
金属工艺 | 25篇 |
机械仪表 | 31篇 |
建筑科学 | 40篇 |
矿业工程 | 9篇 |
能源动力 | 24篇 |
轻工业 | 110篇 |
水利工程 | 4篇 |
石油天然气 | 8篇 |
无线电 | 220篇 |
一般工业技术 | 171篇 |
冶金工业 | 592篇 |
原子能技术 | 7篇 |
自动化技术 | 150篇 |
出版年
2021年 | 8篇 |
2020年 | 6篇 |
2019年 | 10篇 |
2018年 | 20篇 |
2017年 | 16篇 |
2016年 | 9篇 |
2015年 | 9篇 |
2014年 | 22篇 |
2013年 | 45篇 |
2012年 | 43篇 |
2011年 | 44篇 |
2010年 | 36篇 |
2009年 | 42篇 |
2008年 | 40篇 |
2007年 | 35篇 |
2006年 | 44篇 |
2005年 | 38篇 |
2004年 | 32篇 |
2003年 | 28篇 |
2002年 | 33篇 |
2001年 | 30篇 |
2000年 | 50篇 |
1999年 | 50篇 |
1998年 | 149篇 |
1997年 | 105篇 |
1996年 | 67篇 |
1995年 | 62篇 |
1994年 | 41篇 |
1993年 | 47篇 |
1992年 | 33篇 |
1991年 | 19篇 |
1990年 | 30篇 |
1989年 | 18篇 |
1988年 | 14篇 |
1987年 | 22篇 |
1986年 | 19篇 |
1985年 | 28篇 |
1984年 | 20篇 |
1983年 | 12篇 |
1982年 | 13篇 |
1981年 | 12篇 |
1980年 | 12篇 |
1979年 | 9篇 |
1978年 | 10篇 |
1977年 | 16篇 |
1976年 | 31篇 |
1975年 | 6篇 |
1974年 | 16篇 |
1973年 | 6篇 |
1971年 | 6篇 |
排序方式: 共有1557条查询结果,搜索用时 15 毫秒
111.
Fabrication of air-channel structures for microfluidic,microelectromechanical, and microelectronic applications 总被引:1,自引:0,他引:1
Bhusari D. Reed H.A. Wedlake M. Padovani A.M. Allen S.A.B. Kohl P.A. 《Journal of microelectromechanical systems》2001,10(3):400-408
A method is presented for fabricating micro-air-channel structures encapsulated by a dielectric material using a sacrificial polymer based on polynorbornene (PNB) chemistry. A spin-coated film of PNB was patterned to define the exact geometry of the air-channels using conventional lithographic and etching techniques. The sacrificial polymer was encapsulated with a permanent dielectric material. The composite was then raised to elevated temperatures to produce gaseous products which permeate through the encapsulating material (SiO2 , SiNx or other polymer) leaving behind minimal solid residue. Air-channels integrated with metal interconnections can be formed via a Damascene, or in-lay process. After patterning the sacrificial polymer, copper was electroplated, followed by encapsulation with the dielectric. Various issues pertaining to the processing steps have been investigated and are discussed, such as type of encapsulants, feasible air-channel sizes, and processing conditions. Such air-channel structures are believed to have potential applications in microelectronics, displays, printers, multilevel wiring boards, microscale chemical reactors on a chip, and microelectromechanical devices 相似文献
112.
Experiments examined the effect of relationships between a response and an outcome on human judgments of causal effectiveness. In Experiment 1, the time between outcomes obtained on a variable ratio (VR) schedule became the intervals for a yoked variable interval (VI) schedule. Response rates were higher on the VR than on the VI schedule. In Experiment 2, the number of responses required per outcome on a VR schedule were matched to that on a master VI 20-s schedule. Both ratings of causal effectiveness and response rates were higher in the VR schedule. In Experiment 3, tandem VI fixed-ratio (FR) schedules produced higher rates and judgments than equivalent conjunctive VI FR schedule. In Experiment 4, a VI schedule with a reinforcement requirement for a short interresponse time (IRT) produced higher rates and judgments than a simple VI schedule. These results corroborate the view that schedules are a determinant of both response rates and causal judgments. Few current theories of causal judgment predict this pattern of results. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
113.
A parametric waste-specific study was conducted to assess the effects of membrane rotational speed and feed oil concentration on the pressure independent “limiting” flux in a high-shear rotary ultrafiltration (HSRUF) system. The limiting flux data were adequately described by the thin-film model. The transition from pressure dependent to pressure independent behavior occurred at lower oil concentrations as membrane rotational speed was decreased and pressure was increased due to an increase in the thickness of the solute boundary layer at the membrane surface. A gel layer oil concentration, OCgel, of 39% was reported, and OCgel was determined to be constant with respect to average transmembrane pressure and membrane rotational speed. The solute mass transfer coefficient increased with membrane rotation and was greater than reported for conventional ultrafiltration systems. The greater mass transfer characteristics determined for the HSRUF system were attributed to the efficient delivery of “cleaning energy” to the membrane surface due to the effective decoupling of feed pressurization from recirculation∕hydraulic turbulence. 相似文献
114.
All of the conventional CFAR detection algorithms that use space-time processing involve a time-consuming matrix-inversion operation. Based on today's technology, this computational complexity sometimes makes the full-rank solution difficult to realize. In this correspondence, a CFAR detection algorithm, which does not need a matrix inversion, is developed by an adaptation and extension of Hotelling's principal-component method studied recently by Kirsteins and Tufts (1994). Finally, the performance of the new CFAR test statistic is analyzed, and the effect of the rank reduction on performance is evaluated for an example scenario 相似文献
115.
116.
Reed Catherine L.; Lederman Susan J.; Klatzky Roberta L. 《Canadian Metallurgical Quarterly》1990,44(4):522
Three experiments involving a total of 75 college students investigated the role of size information in haptic classification of custom-made planar objects when size covaries with hardness, texture, or planar contour. Exp 1 showed facilitation of classification by redundant (RD) size and shape cues, indicating the coprocessing of size and shape. Exps 2 and 3 used a withdrawal paradigm: Classification trials began with 2 RD properties, and 1 was then held constant (withdrawn). Exp 2 showed that when size and shape were RD, withdrawal of either impaired responses, whereas when size was RD with texture or hardness, only size withdrawal had an effect. Exp 3 demonstrated that this size weighting was not restricted to a single procedure for exploration. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
117.
Algebraic decoding of the (32, 16, 8) quadratic residue code 总被引:1,自引:0,他引:1
Reed I.S. Yin X. Truong T.-K. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1990,36(4):876-880
An algebraic decoding algorithm for the 1/2-rate (32, 16, 8) quadratic residue (QR) code is found. The key idea of this algorithm is to find the error locator polynomial by a systematic use of the Newton identities associated with the code syndromes. The techniques developed extend the algebraic decoding algorithm found recently for the (32, 16, 8) QR code. It is expected that the algebraic approach developed here and by M. Elia (1987) applies also to longer QR codes and other BCH-type codes that are not fully decoded by the standard BCH decoding algorithm 相似文献
118.
JM Jürgensmeier S Krajewski RC Armstrong GM Wilson T Oltersdorf LC Fritz JC Reed S Ottilie 《Canadian Metallurgical Quarterly》1997,8(2):325-339
The dental profession faces educational, scientific, and ethical challenges in orofacial pain and headache. Past educational deficiencies are being addressed with guidance and recommendations from the AADS, the ADA, and the AAOP. With education and further research, many dental ethical questions in TMD will be resolved. The educational process must continue with a solid foundation in scientific basis provided in university settings. The appropriate use of TMD diagnostic machines, treatment modalities, and management of perpetuating factors such as sleep will evolve with the new knowledge of scientific discovery. These are some of the many challenges of orofacial pain and headache disorders that warrant special consideration. 相似文献
119.
We present an architecture for network-authenticated disks that implements distributed file systems without file servers or encryption. Our system provides network clients with direct network access to remote storage 相似文献
120.
We report the fabrication of low-loss stripe optical wave-guides in LiNbO 3by He+ implantation. At a wavelength of 633 nm the waveguides were found to have a propagation loss as low as l-OdBcm?1, dependent on the make-up of the vertical waveguide walls. These waveguides were also found to exhibit no photorefractive effects. 相似文献