全文获取类型
收费全文 | 852篇 |
免费 | 38篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 11篇 |
综合类 | 3篇 |
化学工业 | 165篇 |
金属工艺 | 16篇 |
机械仪表 | 24篇 |
建筑科学 | 29篇 |
能源动力 | 21篇 |
轻工业 | 58篇 |
水利工程 | 4篇 |
石油天然气 | 4篇 |
无线电 | 60篇 |
一般工业技术 | 180篇 |
冶金工业 | 142篇 |
原子能技术 | 27篇 |
自动化技术 | 147篇 |
出版年
2023年 | 5篇 |
2022年 | 15篇 |
2021年 | 20篇 |
2020年 | 14篇 |
2019年 | 15篇 |
2018年 | 15篇 |
2017年 | 8篇 |
2016年 | 20篇 |
2015年 | 21篇 |
2014年 | 23篇 |
2013年 | 51篇 |
2012年 | 32篇 |
2011年 | 71篇 |
2010年 | 50篇 |
2009年 | 46篇 |
2008年 | 45篇 |
2007年 | 31篇 |
2006年 | 27篇 |
2005年 | 29篇 |
2004年 | 23篇 |
2003年 | 19篇 |
2002年 | 17篇 |
2001年 | 7篇 |
2000年 | 17篇 |
1999年 | 20篇 |
1998年 | 50篇 |
1997年 | 28篇 |
1996年 | 21篇 |
1995年 | 14篇 |
1994年 | 15篇 |
1993年 | 7篇 |
1992年 | 5篇 |
1991年 | 8篇 |
1990年 | 12篇 |
1989年 | 4篇 |
1988年 | 7篇 |
1987年 | 8篇 |
1986年 | 5篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1982年 | 12篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1977年 | 3篇 |
1976年 | 6篇 |
1975年 | 5篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1971年 | 3篇 |
1928年 | 2篇 |
排序方式: 共有891条查询结果,搜索用时 0 毫秒
51.
Ceramic Diesel Particulate Filters 总被引:2,自引:0,他引:2
Joerg Adler 《International Journal of Applied Ceramic Technology》2005,2(6):429-439
Twenty-five years of diesel particulate filter (DPF) developments have shown that ceramic materials are well-suited candidates to fulfill the harsh requirements of exhaust after treatment. The introduction of DPF in passenger cars in Europe in 2000 was a real breakthrough from both a scientific and a commercial point of view. Different systems and filter materials can be used as DPF; however, at the moment silicon carbide wall flow filters seem to be at advantage. There is a continual demand for cost-effective and reliable materials and systems forced by increasing legal emission standards. 相似文献
52.
53.
Karlheinz Grotz Joerg U. Mayer Georg K. Suessmeier 《Signal Processing: Image Communication》1989,1(2):103-115
A new combination of coding methods for a 64 kbit/s transmission system for typical videophone situations is investigated. The codec structure is based on a standard hybrid discrete cosine transform (DCT) codec with temporal prediction. The picture is divided blockwise into changed and unchanged areas. One motion vector with subpel accuracy is computed and transmitted for each block of the changed area. For the forward analysis, the prediction error is calculated in the whole picture. Only the blocks with the highest prediction errors are updated by a DCT with a perception adaptive quantization. The number of DCT update blocks depends on the remaining bits after the transmission of the overhead information. The codec is controlled by a forward analysis of the prediction error and is not based on a buffer control. The spatial resolution of the source signal is reduced in two steps to prevent a codec overload caused by too much activity between two frames. 相似文献
54.
W. Tillmann M. Abdulgader L. Hagen J. Nellesen 《Journal of Thermal Spray Technology》2014,23(1-2):40-50
The powder injection parameters, the location of the injection port, as well as the metal matrix composites are important features, which determine the deposition efficiency and embedding behavior of hard materials in the surrounding matrix of the twin wire arc-spraying process. This study investigates the applicability of external powder injection and aims to determine whether the powder injection parameters, the location, and the material combination (composition of the matrix as well as hard material) need to be specifically tailored. Therefore, the position of the injection port in relation to the arc zone was altered along the spraying axis and perpendicular to the arc. The axial position of the injection port determines the thermal activation of the injected powder. An injection behind the arc, close to the nozzle outlet, seems to enhance the thermal activation. The optimal injection positions of different hard materials in combination with zinc-, nickel- and iron-based matrices were found to be closer to the arc zone utilizing a high-speed camera system. The powder size, the mass of the particle, the carrier gas flow, and the electric insulation of the hard material affect the perpendicular position of the radial injection port. These findings show that the local powder injection, the wetting behavior of particles in the realm of the molten pool as well as the atomization behavior of the molten pool all affect the embedding behavior of the hard material in the surrounded metallic matrix. Hardness measurement by means of nanoindentation and EDX analysis along transition zones were utilized to estimate the bonding strength. The observation of a diffusion zone indicates a strong metallurgical bonding for boron carbides embedded in steel matrix. 相似文献
55.
Michel F Deines E Hering-Bertram M Garth C Hagen H 《IEEE transactions on visualization and computer graphics》2007,13(6):1680-1687
Acoustic quality in room acoustics is measured by well defined quantities, like definition, which can be derived from simulated impulse response filters or measured values. These take into account the intensity and phase shift of multiple reflections due to a wave front emanating from a sound source. Definition (D50) and clarity (C50) for example correspond to the fraction of the energy received in total to the energy received in the first 50 ms at a certain listener position. Unfortunately, the impulse response measured at a single point does not provide any information about the direction of reflections, and about the reflection surfaces which contribute to this measure. For the visualization of room acoustics, however, this information is very useful since it allows to discover regions with high contribution and provides insight into the influence of all reflecting surfaces to the quality measure. We use the phonon tracing method to calculate the contribution of the reflection surfaces to the impulse response for different listener positions. This data is used to compute importance values for the geometry taking a certain acoustic metric into account. To get a visual insight into the directional aspect, we map the importance to the reflecting surfaces of the geometry. This visualization indicates which parts of the surfaces need to be changed to enhance the chosen acoustic quality measure.We apply our method to the acoustic improvement of a lecture hall by means of enhancing the overall speech comprehensibility (clarity) and evaluate the results using glyphs to visualize the clarity (C50) values at listener positions throughout the room. 相似文献
56.
S Kaasa K Bjordal N Aaronson T Moum E Wist S Hagen A Kvikstad 《Canadian Metallurgical Quarterly》1995,(13-14):2260-2263
The EORTC Core Quality of Life questionnaire (EORTC QLQ-C30) is designed to measure cancer patients' physical, psychological and social functions. The questionnaire is composed of multi-item scales and single items. 247 patients completed the EORTC QLQ-C30 before palliative radiotherapy and 181 after palliative radiotherapy. The questionnaire was well accepted with a high completion rate in the present patient population consisting of advanced cancer patients with short life expectancy. In addition, the questionnaire was found to be useful to detect the effect of palliative radiotherapy over time. The scale reliability was excellent for all scales except the role functioning scale. Excellent criterion validity was found for the emotional functioning scale where it was correlated with GHQ-20. Performance of the questionnaire was improved after the second evaluation as compared with the first. The present study shows that the EORTC QLQ-C30 is found to be practical and valid in measuring quality of life in patients with advanced disease. 相似文献
57.
Hummel M Garth C Hamann B Hagen H Joy KI 《IEEE transactions on visualization and computer graphics》2010,16(6):1319-1328
Integral surfaces are ideal tools to illustrate vector fields and fluid flow structures. However, these surfaces can be visually complex and exhibit difficult geometric properties, owing to strong stretching, shearing and folding of the flow from which they are derived. Many techniques for non-photorealistic rendering have been presented previously. It is, however, unclear how these techniques can be applied to integral surfaces. In this paper, we examine how transparency and texturing techniques can be used with integral surfaces to convey both shape and directional information. We present a rendering pipeline that combines these techniques aimed at faithfully and accurately representing integral surfaces while improving visualization insight. The presented pipeline is implemented directly on the GPU, providing real-time interaction for all rendering modes, and does not require expensive preprocessing of integral surfaces after computation. 相似文献
58.
Ekkart Kindler Wolfgang Reisig Hagen Völzer Rolf Walter 《Formal Aspects of Computing》1997,9(4):409-424
A technique to model and to verify distributed algorithms is suggested. This technique (based on Petri nets) reduces the modelling and analysis effort to a reasonable level. The paper outlines the technique using the example of a typical network algorithm, theecho algorithm.Supported by the DFG-projects Verteilte Algorithmen and Konsensalgorithmen 相似文献
59.
Influence of Molybdenum Silicide Additions on High-Temperature Oxidation Resistance of Silicon Nitride Materials 总被引:2,自引:0,他引:2
Hagen Klemm Katja Tangermann Christian Schubert Waldemar Hermel 《Journal of the American Ceramic Society》1996,79(9):2429-2435
The influence of additions of molybdenum disilicide (MoSi2 ) on the microstructure and the mechanical properties of a silicon nitride (Si3 N4 ) material, with neodymium oxide (Nd2 O3 ) and aluminum nitride (AIN) as sintering aids, was studied. The composites, containing 5, 10, and 17.6 wt% MoSi2 , were fabricated by hot pressing. All materials exhibited a similar phase composition, detected by X-ray diffractometry. Up to MoSi2 additions of 10 wt%, mechanical properties such as strength, fracture toughness, or creep at 1400°C were not affected significantly, in comparison to that of monolithic Si3 N4 . The oxidation resistance of the composites, in terms of weight gain, degraded. After 1000 h of oxidation at 1400° and 1450°C in air, a greater weight gain (by a factor of approximately three) was obtained, in comparison to that of the material without MoSi2 . Nevertheless, after 1000 h of oxidation, the degradation in strength of the composites was considerably less severe than that of the material without MoSi2 . An additional layer was formed, caused by processes at the surface of the Si3 N4 material, preventing the formation of pores, cracks, or glassy-phase-rich areas, which are common features of oxidation damage in Si3 N4 materials. This surface layer, containing Mo5 Si3 and silicon oxynitride (Si2 ON2 ), was the result of reactions between MoSi2 , Si3 N4 , and the oxygen penetrating by diffusion into the material during the hightemperature treatment. 相似文献
60.