全文获取类型
收费全文 | 745篇 |
免费 | 25篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 12篇 |
综合类 | 2篇 |
化学工业 | 122篇 |
金属工艺 | 15篇 |
机械仪表 | 24篇 |
建筑科学 | 15篇 |
矿业工程 | 1篇 |
能源动力 | 71篇 |
轻工业 | 47篇 |
水利工程 | 6篇 |
石油天然气 | 8篇 |
无线电 | 104篇 |
一般工业技术 | 126篇 |
冶金工业 | 63篇 |
原子能技术 | 6篇 |
自动化技术 | 152篇 |
出版年
2023年 | 7篇 |
2022年 | 16篇 |
2021年 | 39篇 |
2020年 | 27篇 |
2019年 | 39篇 |
2018年 | 32篇 |
2017年 | 42篇 |
2016年 | 34篇 |
2015年 | 20篇 |
2014年 | 43篇 |
2013年 | 64篇 |
2012年 | 36篇 |
2011年 | 45篇 |
2010年 | 39篇 |
2009年 | 25篇 |
2008年 | 17篇 |
2007年 | 20篇 |
2006年 | 20篇 |
2005年 | 16篇 |
2004年 | 11篇 |
2003年 | 12篇 |
2002年 | 6篇 |
2001年 | 2篇 |
2000年 | 6篇 |
1999年 | 8篇 |
1998年 | 21篇 |
1997年 | 12篇 |
1996年 | 13篇 |
1995年 | 18篇 |
1994年 | 10篇 |
1993年 | 10篇 |
1992年 | 8篇 |
1991年 | 7篇 |
1990年 | 6篇 |
1989年 | 8篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1974年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有774条查询结果,搜索用时 0 毫秒
771.
Ali Akbar Emdadi Syamak Hossein Nedjad Habib Badri Ghavifekr 《Metallurgical and Materials Transactions A》2014,45(2):906-910
This study investigates the magnetostrictive functionality of crystallographic textures developed by directional solidification of a vacuum-melted galfenol cast button. A polycrystalline Fe82.4Ga17.6 alloy was melted using vacuum arc melting and solidified in a water-cooled copper mold. Optical metallography confirmed the development of large columnar grains in the solidification microstructure. Phase constitution and magnetic domain structures of sample were studied by X-ray diffraction (XRD) and magnetic force microscopy (MFM). The results showed that the cast button has a disordered body-centered cubic (bcc) (A2) single-phase structure that consisted of a combination of well-aligned stripe-like and maze-like magnetic domains. To investigate the magnetostriction behavior, a couple of pins were cut along columnar grains as well as in the transverse direction. Magnetostriction was measured in the presence of an externally applied magnetic field. It was found that pins cut along the columnar grains comprised very high magnetostriction, whereas transverse pins had lower magnetostriction against the applied field. 相似文献
772.
ne way to speed up the execution of sequential programs is to divide them into concurrent segments and execute such segments in a parallel manner over a distributed computing environment. We argue that the execution speedup primarily depends on the concurrency degree between the identified segments as well as communication overhead between the segments. To guar-antee the best speedup, we have to obtain the maximum possible concurrency degree between the identified segments, taking communication overhead into consideration. Existing code distributor and multi-threading approaches do not fulfill such re-quirements;hence, they cannot provide expected distributability gains in advance. To overcome such limitations, we propose a novel approach for verifying the distributability of sequential object-oriented programs. The proposed approach enables users to see the maximum speedup gains before the actual distributability implementations, as it computes an objective function which is used to measure different distribution values from the same program, taking into consideration both remote and sequential calls. Experimental results showed that the proposed approach successfully determines the distributability of different real-life software applications compared with their real-life sequential and distributed implementations. 相似文献
773.
O. M. O. Habib E. B. Moawad D. S. Badawy F. A. Mansour 《Advanced Synthesis \u0026amp; Catalysis》1990,332(5):791-796
4-(Phenylhydrazono-4′-benzenesulphonato)-3-methyl-2-pyrazolin-5-one ( 2 ) was prepared by treating 4-(4′-hydroxyphenylhydrazono)-3-methyl-2-pyrazolin-5-one ( 1 ) with benzenesulphonyl chloride. Heating 2 with acetic anhydride, chloroacetyl chloride and benzenesulphonyl chloride afforded the N-acetyl ( 3 ), N-chloroacetyl ( 4 ) and O-benzenesulphonyl ( 5 ) derivatives, respectively. 2 reacted with benzenesulphonyl chloride under cooling conditions to give the N-benzenesulphonyl derivative ( 6 ). 2 undergoes Mannich reaction to give the N-Mannich base ( 7 ). Reaction of 2 with formaldehyde in methanol afforded the N-hydroxymethyl derivative ( 8 ) which undergoes condensation with ethyl acetoacetate, ethyl cyanoacetate and malononitrile to give compounds 9 , 10 and 11 respectively. The antimicrobial activity of these products against gram-positive (+ve), gram-negative (−ve) bacteria and fungi was screened. They showed potential bactericidal activity and some of them exhibited high fungicidal activity. 相似文献
774.
Very fine alumina nanoparticles were loaded in novolac type phenolic resin (PF) using solution mixing method. The concentration of nanoalumina in PF was varied between 2.5 to 20 wt%. All the compounds were compression molded and then subjected to scanning electron microscopy (SEM), tensile, flexural, and dynamic mechanical analysis (DMA) tests. SEM analysis showed that the nanoalumina were dispersed uniformly at low concentrations, however, at high concentrations, dispersion was suppressed leading to agglomerates in the composites. Mechanical testing revealed that the nanoalumina had a great influence on the strength and stiffness of PF resin particularly at concentrations below 5 wt%. However, at concentration above 5 wt%, the stress concentrations were developed because of the formation of big aggregates that results in strength reduction. Theoretical analyses based on Pukanszky and micromechanical models of tensile modulus revealed that strong interfacial interaction and thick interphase region around the alumina nanoparticles is formed. DMA results suggested that the nanoalumina increased the crosslinking density of the PF resin, possibly around the interface region. It was also postulated that an apparent percolation state is established above 5 wt% loading of nanoalumina in which interphase region comes to contact before direct contact of particle leading to continuous interphase region. POLYM. COMPOS., 35:1285–1293, 2014. © 2013 Society of Plastics Engineers 相似文献