全文获取类型
收费全文 | 4869篇 |
免费 | 301篇 |
国内免费 | 25篇 |
专业分类
电工技术 | 56篇 |
综合类 | 10篇 |
化学工业 | 1281篇 |
金属工艺 | 130篇 |
机械仪表 | 136篇 |
建筑科学 | 134篇 |
矿业工程 | 6篇 |
能源动力 | 360篇 |
轻工业 | 573篇 |
水利工程 | 48篇 |
石油天然气 | 77篇 |
武器工业 | 1篇 |
无线电 | 488篇 |
一般工业技术 | 964篇 |
冶金工业 | 222篇 |
原子能技术 | 36篇 |
自动化技术 | 673篇 |
出版年
2024年 | 18篇 |
2023年 | 121篇 |
2022年 | 199篇 |
2021年 | 327篇 |
2020年 | 220篇 |
2019年 | 232篇 |
2018年 | 268篇 |
2017年 | 256篇 |
2016年 | 262篇 |
2015年 | 181篇 |
2014年 | 270篇 |
2013年 | 456篇 |
2012年 | 306篇 |
2011年 | 379篇 |
2010年 | 223篇 |
2009年 | 199篇 |
2008年 | 154篇 |
2007年 | 150篇 |
2006年 | 115篇 |
2005年 | 76篇 |
2004年 | 68篇 |
2003年 | 71篇 |
2002年 | 53篇 |
2001年 | 37篇 |
2000年 | 46篇 |
1999年 | 31篇 |
1998年 | 49篇 |
1997年 | 36篇 |
1996年 | 32篇 |
1995年 | 32篇 |
1994年 | 29篇 |
1993年 | 28篇 |
1992年 | 15篇 |
1991年 | 27篇 |
1990年 | 17篇 |
1989年 | 15篇 |
1988年 | 19篇 |
1987年 | 14篇 |
1986年 | 17篇 |
1985年 | 17篇 |
1984年 | 15篇 |
1983年 | 19篇 |
1982年 | 13篇 |
1981年 | 15篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 12篇 |
1976年 | 8篇 |
1974年 | 7篇 |
1973年 | 5篇 |
排序方式: 共有5195条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
Omar Snchez Estrella Asp María C Martí Marlene Roeckel 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(11):1261-1267
Most of the kinetic studies on nitrification have been performed in diluted salts medium. In this work, the ammonia oxidation rate (AOR) was determined by respirometry at different ammonia (0.01 and 33.5 mg N‐NH3 L?1), nitrite (0–450 mg N‐NO2? L?1) and nitrate (0 and 275 mg N‐NO3? L?1) concentrations in a saline medium at 30 °C and pH 7.5. Sodium azide was used to uncouple the ammonia and nitrite oxidation, so as to measure independently the AOR. It was determined that ammonia causes substrate inhibition and that nitrite and nitrate exhibit product inhibition upon the AOR. The effects of ammonia, nitrite and nitrate were represented by the Andrews equation (maximal ammonia oxidation rate, rAOMAX, = 43.2 [mg N‐NH3 (g VSSAO h)?1]; half saturation constant, KSAO, = 0.11 mg N‐NH3 L?1; inhibition constant KIAO, = 7.65 mg N‐NH3 L?1), by the non‐competitive inhibition model (inhibition constant, KINI, = 176 mg N‐NO2? L?1) and by the partially competitive inhibition model (inhibition constant, KINA, = 3.3 mg N‐NO3? L?1; α factor = 0.24), respectively. The rAOMAX value is smaller, and the KSAO value larger, than the values reported in diluted salts medium; the KIAO value is comparable to those reported. Process simulations with the kinetic model in batch nitrifying reactors showed that the inhibitory effects of nitrite and nitrate are significant for initial ammonia concentrations larger than 100 mg N‐NH4+ L?1. Copyright © 2005 Society of Chemical Industry 相似文献
5.
Chun Yang Yin Sharifah Aishah Syed Abdul KadirYing Pei Lim Sharifah Nawirah Syed-AriffinZurinawati Zamzuri 《Fuel Processing Technology》2008
Ash derived from combustion of Malaysian oil palm biomass (empty fruit bunches consisting of fibers) was physically and chemically characterized in order to provide a comprehensive understanding of its specific properties in terms of toxicity, compositions and reusability. Principal analyses conducted include particle size distribution, scanning electron microscopy, elemental dispersive X-ray, elemental analysis, toxicity characteristic leaching procedure (TCLP) as well as thermogravimetric, X-ray diffractometry and Fourier-transform infrared analyses. TCLP result indicated that the oil palm ash (OPA) should not be classified as toxic wastes in terms of heavy metal leachability since leachable copper, cadmium, lead and nickel concentrations were detected below the stipulated leachability limits. It was determined that the OPA contained high amount of potassium as well as presence of silica which implied its suitability to be reused as crude fertilizer or cement replacement material. 相似文献
6.
We propose a new framework in wavelet video coding to improve the compression rate by exploiting the spatiotemporal regularity of the data. A sequence of images creates a spatiotemporal volume. This volume is said to be regular along the directions in which the pixels vary the least, hence the entropy is the lowest. The wavelet decomposition of regularized data results in a fewer number of significant coefficients, thus yielding a higher compression rate. The directions of regularity of an image sequence depend on both its motion content and spatial structure. We propose the representation of these directions by a 3-D vector field, which we refer to as the spatiotemporal regularity flow (SPREF). SPREF uses splines to approximate the directions of regularity. The compactness of the spline representation results in a low storage overhead for SPREF, which is a desired property in compression applications. Once SPREF directions are known, they can be converted into actual paths along which the data is regular. Directional decomposition of the data along these paths can be further improved by using a special class of wavelet basis called the 3-D orthonormal bandelet basis. SPREF -based video compression not only removes the temporal redundancy, but it also compensates for the spatial redundancy. Our experiments on several standard video sequences demonstrate that the proposed method results in higher compression rates as compared to the standard wavelet based compression. 相似文献
7.
Abdul Aleaf 《电子产品世界》2008,15(12)
消费者对于移动多媒体的需求是毫无疑问的,满足这些需求的技术已经开发成功,对于设计人员而言,剩下的问题就是如何利用这些技术,并将成功的产品带入市场。本文将讨论如何减省移动多媒体设备内关键元件的功耗,此外也会对现今移动多媒体设备设计人员所面对的工程挑战作出概括的分析,并就目前及新涌现的硅技术,提出可克服这些工程挑战的解决方案。 相似文献
8.
Patricio Toro Raúl Quijada Omar Murillo Mehrdad Yazdani‐Pedram 《Polymer International》2005,54(4):730-734
The mechanical, morphological behavior and water absorption characteristics of polypropylene (PP) and silica, or PP and rice‐husk, composites have been studied. The silica used in this study as filler was a commercial type produced from soluble glass or rice husks. The compatibilizing effect of PP grafted with monomethyl itaconate (PP‐g‐MMI) and/or with vinyltriethoxysilane (PP‐g‐VTES) as polar monomers on the mechanical properties and water absorption was also investigated. In general, a high loading of the studied fillers in the polymer matrix increases the stiffness and the water absorption capacity. This effect is more noticeable in the tensile modulus of the PP/silica composite with PP‐g‐VTES as compatibilizer. However, the increase of the rice‐husk charge as a natural filler in the PP matrix decreases the stiffness, and in the presence of PP‐g‐MMI as compatibilizer in PP/rice‐husk, the tensile modulus and water absorption of the composite were improved. The better adhesion and phase continuity in the PP/silica and PP/rice‐husk composites with different compatibilizers was confirmed by the morphological study. Copyright © 2004 Society of Chemical Industry 相似文献
9.
KS Ghenghesh AS Altomi A Elgrari MR Alosta Omar AM Sharif Eddin SS Abied 《Canadian Metallurgical Quarterly》1995,72(1-2):13-15
Twenty seven Aeromonas strains (5A. hydrophila, 8A. sobria and 14A. caviae) isolated from children with diarrhoea and 34 Aeromonas strains (9A. hydrophila, 7A. sobria an 18A. caviae) isolated from children without diarrhoea were tested from haemolysin production. The results obtained showed that haemolysin production using human, horse or sheep erythrocytes was significantly associated with A.hydrophila and A sobria but not with A.caviae, regardless of whether these strains were isolated from children with or without diarrhoea. Human or horse rather than sheep erythrocytes are recommended for use in the haemolysin assay. 相似文献
10.
Uma Maheswar Rao S. S. M. S. Abdul Majeed C. Venkataseshaiah R. Sarathi 《Bulletin of Materials Science》2002,25(6):473-475
In the present work, tracking phenomena has been studied with silicone rubber material under the a.c. and d.c. voltages following
IEC-587 standards. The surface condition of the tracked zone was analysed using wide angle X-ray diffraction (WAXD) and thermogravimetric
differential thermal analysis (TG-DTA) studies. The tracking time was different for a.c. and d.c. voltages. 相似文献