全文获取类型
收费全文 | 248篇 |
免费 | 9篇 |
专业分类
电工技术 | 1篇 |
化学工业 | 48篇 |
金属工艺 | 6篇 |
机械仪表 | 1篇 |
建筑科学 | 8篇 |
矿业工程 | 5篇 |
能源动力 | 14篇 |
轻工业 | 16篇 |
水利工程 | 1篇 |
无线电 | 48篇 |
一般工业技术 | 55篇 |
冶金工业 | 18篇 |
原子能技术 | 1篇 |
自动化技术 | 35篇 |
出版年
2023年 | 2篇 |
2022年 | 1篇 |
2021年 | 4篇 |
2020年 | 2篇 |
2019年 | 2篇 |
2018年 | 12篇 |
2017年 | 2篇 |
2016年 | 3篇 |
2015年 | 8篇 |
2014年 | 4篇 |
2013年 | 17篇 |
2012年 | 17篇 |
2011年 | 17篇 |
2010年 | 5篇 |
2009年 | 9篇 |
2008年 | 11篇 |
2007年 | 8篇 |
2006年 | 9篇 |
2005年 | 16篇 |
2004年 | 12篇 |
2003年 | 7篇 |
2002年 | 6篇 |
2001年 | 5篇 |
2000年 | 4篇 |
1999年 | 5篇 |
1998年 | 8篇 |
1997年 | 7篇 |
1996年 | 7篇 |
1995年 | 5篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 7篇 |
1991年 | 1篇 |
1990年 | 4篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 5篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1976年 | 4篇 |
排序方式: 共有257条查询结果,搜索用时 15 毫秒
1.
2.
The aim of this work is to propose an original solution to the acoustic impedance mismatch between a PZT transducer and a water load. The characteristic acoustic impedance of the PZT is around 33 MRayl. Theoretically, a quarter-wave layer with characteristic acoustic impedance equal to 7 MRayl is necessary to match the transducer to water. In practice, it is difficult to find a material with this particular impedance. Two or more quarter-wave layers may also be used. The following proposed solution consists in using two matching layers where one of them is the glue. Moreover, their thicknesses are not equal to a quarter of their individual wavelength. Once the glue is taken as the first matching layer, the specific material of the second layer can easily be found. In this work, the second layer, which is also the front layer, is made of glass. The thickness of each matching layer is then calculated as a function of the characteristic acoustic impedance of the two layers. The influence of the thickness of these layers is discussed. The proposed matching configuration is analyzed and theoretical results have been carefully and successfully compared with measurements. 相似文献
3.
4.
Koen Grijspeerdt Herwig Bogaert Willy Verstraete 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1996,67(4):404-412
A model clarifier was designed using conventional methods for the surface calculation and an alternative pathway for the determination of the height and constructed accordingly. In addition, a new approach was used to evaluate the necessary scraper speed in comparison to full-scale clarifiers. Scaling effects were taken into account. The model clarifier was first tested by tracer experiments. Conductivity measurements were used for the clarification zone, whereas the thickening zone was tested using pyrene as an organic tracer compound. Finally, the behaviour of the model clarifier was compared with a full-scale settler. The results indicated that operation of the model clarifier was representative of full-scale behaviour, except for severe overloads. Hence, the small-scale clarifier qualified as a model for small-scale studies and could be installed on large-scale plants to monitor more transparently plant performance and sludge behaviour 相似文献
5.
Marie-Louise Wind Beatrice Braun-Cula Fabian Schax Christian Herwig Prof. Christian Limberg 《Israel journal of chemistry》2020,60(10-11):1057-1060
The isolation and identification of intermediates formed in the course of the activation of dioxygen at transition metal centers reveals important mechanistic insights concerning such processes. We previously reported the reaction of the dinuclear CrII complex [L2Cr2(MeCN)2][Li(MeCN)]2 (L=PhSi(OSiPh2O−)3) ( 5 ) with dioxygen, which resulted in the formation of the CrIV oxo complex [L2Cr2O2][Li(THF)2]2 ( 6 ), as the final room temperature stable product. Here we now report the isolation and characterization of an intermediate en route to 6 , namely the dinuclear CrIII superoxo complex [L2Cr2(O2)2][Li(MeCN)]2 ( 7 ). 7 is the first example of a structurally characterized dinuclear CrIII superoxo complex with two independent side-on bound superoxo ligands. Reactivity studies outline the capability of this superoxo complex to activate weak O−H bonds. 相似文献
6.
7.
8.
9.
W. Rogiest K. Laevens D. Fiems H. Bruneel 《AEUE-International Journal of Electronics and Communications》2010,64(10):953-959
Circumventing the speed bottleneck of electronic switching, novel switching approaches like optical burst switching (OBS) and optical packet switching (OPS) handle the switching of bursts (or packets) in backbone nodes optically, and include a set of fiber delay lines (FDLs) for optical buffering. While previous work acknowledges the performance difference between optical FDL buffers and electronic RAM buffers, the important role of synchronization herein has received little attention to date. 相似文献
10.
Arnar ��lafsson Bj?rn T��r J��nsson Laurent Amsaleg Herwig Lejsek 《Multimedia Systems》2011,17(2):83-100
In recent years, some approximate high-dimensional indexing techniques have shown promising results by trading off quality
guarantees for improved query performance. While the query performance and quality of these methods has been well studied,
however, the performance of index maintenance has not yet been reported in any detail. Here, we focus on the dynamic behavior
of the balanced NV-tree, which is a disk-based approximate index for very large collections. We report on an initial study
of the effects of several implementation choices for the balanced NV-tree, and show that with appropriate implementation,
significant performance improvements are possible. Overall, the proposed techniques not only reduce maintenance cost, but
can also improve search performance significantly with minimal loss of search quality. 相似文献