全文获取类型
收费全文 | 4476篇 |
免费 | 307篇 |
国内免费 | 100篇 |
专业分类
电工技术 | 80篇 |
综合类 | 97篇 |
化学工业 | 1062篇 |
金属工艺 | 186篇 |
机械仪表 | 124篇 |
建筑科学 | 264篇 |
矿业工程 | 52篇 |
能源动力 | 159篇 |
轻工业 | 491篇 |
水利工程 | 38篇 |
石油天然气 | 74篇 |
武器工业 | 14篇 |
无线电 | 441篇 |
一般工业技术 | 717篇 |
冶金工业 | 236篇 |
原子能技术 | 42篇 |
自动化技术 | 806篇 |
出版年
2023年 | 47篇 |
2022年 | 74篇 |
2021年 | 201篇 |
2020年 | 111篇 |
2019年 | 117篇 |
2018年 | 146篇 |
2017年 | 150篇 |
2016年 | 172篇 |
2015年 | 143篇 |
2014年 | 206篇 |
2013年 | 320篇 |
2012年 | 299篇 |
2011年 | 299篇 |
2010年 | 233篇 |
2009年 | 224篇 |
2008年 | 236篇 |
2007年 | 232篇 |
2006年 | 192篇 |
2005年 | 142篇 |
2004年 | 133篇 |
2003年 | 169篇 |
2002年 | 185篇 |
2001年 | 139篇 |
2000年 | 78篇 |
1999年 | 69篇 |
1998年 | 59篇 |
1997年 | 52篇 |
1996年 | 53篇 |
1995年 | 46篇 |
1994年 | 31篇 |
1993年 | 41篇 |
1992年 | 19篇 |
1991年 | 17篇 |
1990年 | 16篇 |
1989年 | 19篇 |
1988年 | 16篇 |
1987年 | 24篇 |
1986年 | 14篇 |
1985年 | 9篇 |
1984年 | 12篇 |
1983年 | 14篇 |
1982年 | 12篇 |
1981年 | 11篇 |
1980年 | 10篇 |
1979年 | 15篇 |
1978年 | 9篇 |
1977年 | 8篇 |
1976年 | 8篇 |
1974年 | 11篇 |
1973年 | 9篇 |
排序方式: 共有4883条查询结果,搜索用时 312 毫秒
51.
Anibal Mario Nervi Raul Omar Peluffo Rodolfo R. Brenner Alicia Isabel Leikin 《Lipids》1980,15(4):263-268
The effect of ethanol on the fatty acid desaturation by rat liver has been studied using liquid diets of different composition.
Acute ethanol administration increased triacylglycerols of total liver lipids, but did not modify significantly the lipidic
composition of microsomes. The Δ6 and Δ5 desaturases were inhibited by ethanol whereas the Δ9 desaturase and fatty acid synthetase
were apparently modified only by diet composition. NADH-cytochrome (cyt.) c reductase was partially inhibited, whereas NADH-cyt.
b5 reductase remained practically unaltered and NADPH-cyt. c reductase activity was enhanced. Decreased electrons supplied by
the microsomal cyt. b5 electron transport chain would not be the reason for the inhibition of Δ6 and Δ5 desaturases by ethanol. 相似文献
52.
Fiber Coating Concepts for Brittle-Matrix Composites 总被引:4,自引:0,他引:4
Janet B. Davis Jan P. A. Löfvander Anthony G. Evans Ewald Bischoff Mario L. Emiliani 《Journal of the American Ceramic Society》1993,76(5):1249-1257
The current interest in tough, high-temperature materials has motivated fiber coating development for brittle-matrix composites with brittle reinforcements. Such coatings are needed for controlled interface debonding and frictional sliding. The system investigated in this study was sapphire fiber-reinforced alumina. This system is thermochemically stable for severe use conditions, exhibits little thermal expansion mismatch, and utilizes the excellent strength and creep resistance of sapphire reinforcements. Porous oxide and refractory metal coatings which satisfy requirements for toughness improvement in these composites were identified by employing a variety of newly developed mechanical testing techniques for determining the interfacial fracture energies and sliding resistances. 相似文献
53.
Jean-Marc Tulliani Laura MontanaroAlfredo Negro Mario Collepardi 《Cement and Concrete Research》2002,32(6):843-849
A case history of a severe degradation of concrete foundation plinths and piers of an about-35-year-old building located in Northern Italy is described. Significant amounts of gypsum, near ettringite and/or thaumasite were detected by X-ray diffraction analyses performed on ground concrete samples. Large gypsum crystals were mainly located at the interface between the cement paste and aggregates, as observed by scanning electron microscopy coupled to energy-dispersive spectroscopy microanalysis. The degradation effects increased with decreasing the distance of concrete structures from an absorbing well located in the courtyard of the building. The well was recognized as the sulfate source due to the microorganism metabolism of sulfur compounds present in the sewage. Consequences of this attack were a very poor bond strength between cement paste and aggregates and a severe cracking of the concrete cover of the steel reinforcement. 相似文献
54.
Massimo Guglielmi Giovanna Brusatin Giacomo Facchin Mario Gleria Roger De Jaeger Marco Musiani 《Journal of Inorganic and Organometallic Polymers》1996,6(3):221-236
In this paper the sol-gel preparation of hybrid materials made of metal oxide and polytorganophosphazenel components is described. The main problem focused on during this research was to avoid phase separation in order to get homogeneous materials. This problem was pursued looking at the formation of genuine chemical bonds between the exploited polyphosphazenes and the inorganic composite networks. Investigations on the thermal, mechanical, and electroconductive properties of the synthesized, phosphazene-containing composite materials showed that these matrices presented improved mechanical and thermal features with respect to those of the original phosphazene macromolecule, while the ionic conductivities of the prepared molecular hybrids doped with lithium or silver trillate are of the same order of magnitude as those measured for the neat, original phosphazene substrate.Presented at the Ist Italian Workshop on Cyclo- and Polytphosphazenel Materials. February 15–16, 1996. at the CNR Research Area in Padova, Italy. 相似文献
55.
In tiled Chip Multiprocessors (CMPs) last-level cache (LLC) banks are usually shared but distributed among the tiles. A static mapping of cache blocks to the LLC banks leads to poor efficiency since a block may be mapped away from the tiles actually accessing it. Dynamic policies either rely on the static mapping of blocks to a set of banks (D-NUCA) or rely on the OS to dynamically load pages to statically mapped addresses (first-touch). 相似文献
56.
Emilio Soto Candela Mario Ortega Pérez Clemente Marín Romero David C. Pérez López Gustavo Salvador Herranz Manuel Contero Mariano Alcañiz Raya 《Multimedia Tools and Applications》2014,70(3):1837-1868
In this paper, a computer vision based interactive multi-touch tabletop system called HumanTop is introduced. HumanTop implements a stereo camera vision subsystem which allows not only an accurate fingertip tracking algorithm but also a precise touch-over-the-working surface detection method. Based on a pair of visible spectra cameras, a novel synchronization circuit makes the camera caption and the image projection independent from each other, providing the minimum basis for the development of computer vision analysis based on visible spectrum cameras without any interference coming from the projector. The assembly of both cameras and the synchronization circuit is not only capable of performing an ad-hoc version of a depth camera, but it also introduces the recognition and tracking of textured planar objects, even when contents are projected over them. On the other hand HumanTop supports the tracking of sheets of paper and ID-code markers. This set of features makes the HumanTop a comprehensive, intuitive and versatile augmented tabletop that provides multitouch interaction with projective augmented reality on any flat surface. As an example to exploit all the capabilities of HumanTop, an educational application has been developed using an augmented book as a launcher to different didactic contents. A pilot study in which 28 fifth graders participated is presented. Results about efficiency, usability/satisfaction and motivation are provided. These results suggest that HumanTop is an interesting platform for the development of educational contents. 相似文献
57.
58.
针对合同网协议协商机制缺乏问题求解质量与效率分析的情况,设定假设条件,构建马尔可夫链模型,得出了利用目前已有的合同类型无法保证全局收敛的结论.在此基础上,提出了变邻域合同系的概念,通过分析控制方式对收敛性的影响,得出了集中式控制可以保证全局收敛以及分布式控制以概率保证全局收敛的结论,并设计了概率的计算方法.采用Doebin理论,对应用变邻域合同系的收敛速率进行分析,得出了集中式控制收敛速率与分布式控制收敛速率的上下界估计. 相似文献
59.
Fragmentation of support/catalyst particles during propylene polymerization in the gas phase is analyzed via a mathematical model including energy and mass transfer with chemical reaction processes. The rupture phenomenon is considered specifically by the model, and evaluated as it proceeds in time, Two different regions are recognized in the polymerizing particle at fragmentation time: an inner core resembling the original solid support/catalyst structure, and an external set of layers where most of the polymerization occurs. Model predictions concerning the effects of fragmentation on polymerization are discussed. The influence of different degrees of fragmentation on thermal runaways and monomer availability at active sites located inside the support/catalyst/polymer complex is shown. Monomer concentration profiles inside the growing particles are explained in terms of the combined fragmentation-polymerization interaction. Results show a strong influence of catalyst structure on critical phenomena during early polymerization stages, and suggest the possibility of controlling critical parameters via the definition of fragment structure at catalyst preparation time. 相似文献
60.
This paper introduces a novel solution for the multi‐input multi‐output (MIMO) quantitative feedback theory control design problem with tracking error specifications. Looking for a minimum controller overdesign, the technique finds new controller quantitative feedback theory bounds based on necessary and sufficient conditions for the existence of suitable associated prefilter matrix elements. It improves previous approaches to the subject and includes (i) the possibility of a free selection of the nominal plant, (ii) a less conservative application of the Schwartz inequality to decisively reduce the potential controller overdesign, (iii) a methodology to design independently the elements of the prefilter matrix, and (iv) a scope of application to both sequential and nonsequential MIMO controller design methods. The benefits of the new control design technique are illustrated by means of two examples. The first one, a standard 2 × 2 MIMO problem, is provided for comparison purposes with previous approaches. The second example, included as a major control challenge, deals with a well‐known demanding distillation column benchmark problem. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献