全文获取类型
收费全文 | 8581篇 |
免费 | 873篇 |
国内免费 | 546篇 |
专业分类
电工技术 | 650篇 |
综合类 | 547篇 |
化学工业 | 1438篇 |
金属工艺 | 459篇 |
机械仪表 | 513篇 |
建筑科学 | 629篇 |
矿业工程 | 235篇 |
能源动力 | 262篇 |
轻工业 | 636篇 |
水利工程 | 229篇 |
石油天然气 | 298篇 |
武器工业 | 97篇 |
无线电 | 1076篇 |
一般工业技术 | 1235篇 |
冶金工业 | 441篇 |
原子能技术 | 111篇 |
自动化技术 | 1144篇 |
出版年
2024年 | 43篇 |
2023年 | 154篇 |
2022年 | 299篇 |
2021年 | 406篇 |
2020年 | 338篇 |
2019年 | 283篇 |
2018年 | 286篇 |
2017年 | 322篇 |
2016年 | 340篇 |
2015年 | 394篇 |
2014年 | 517篇 |
2013年 | 661篇 |
2012年 | 663篇 |
2011年 | 646篇 |
2010年 | 540篇 |
2009年 | 519篇 |
2008年 | 492篇 |
2007年 | 452篇 |
2006年 | 385篇 |
2005年 | 332篇 |
2004年 | 222篇 |
2003年 | 209篇 |
2002年 | 251篇 |
2001年 | 214篇 |
2000年 | 129篇 |
1999年 | 141篇 |
1998年 | 145篇 |
1997年 | 91篇 |
1996年 | 82篇 |
1995年 | 60篇 |
1994年 | 48篇 |
1993年 | 43篇 |
1992年 | 62篇 |
1991年 | 37篇 |
1990年 | 22篇 |
1989年 | 28篇 |
1988年 | 9篇 |
1987年 | 12篇 |
1986年 | 14篇 |
1985年 | 12篇 |
1984年 | 14篇 |
1983年 | 10篇 |
1982年 | 12篇 |
1981年 | 10篇 |
1980年 | 6篇 |
1979年 | 10篇 |
1978年 | 4篇 |
1976年 | 9篇 |
1975年 | 5篇 |
1969年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
911.
Effect of thermo-mechanical treatment process on microstructure and mechanical properties of 2A97 Al-Li alloy 总被引:1,自引:0,他引:1
2A97 Al-Li alloy was processed by thermo-mechanical treatment at different pre-stretch deformations of 0, 3% and 6%. The microstructure observation results reveal that some δ′ and T1 precipitates are found in α(Al) matrix of 2A97 alloy processed by the heat treatment with no pre-stretch deformation. When the pre-stretch deformation is 3% and 6%, respectively, amounts of tiny T1 and a few of S′ precipitates precipitates are observed in the microstructures of 2A97 alloy. The tensile test results show that the tensile properties of 2A97 alloys are improved via thermo-mechanical treatment. When the pre-stretch deformation is from 0, 3% to 6%, the ultimate tensile strength values of the 2A97 alloys increase gradually from 447.7, 516.5 to 534.3 MPa, and the elongations decrease from 17.6%, 12.8% to 10.2%, respectively. Moreover, with increasing pre-stretch deformation amount from 0 to 6%, the in-plane anisotropy value of 2A97 alloys becomes more obvious. 相似文献
912.
This paper discusses fouling in reverse osmosis in terms of the critical flux of foulants and the fouling mechanisms based on hydraulic resistance and loss of driving force due to cake-enhanced osmotic pressure (CEOP). In many cases CEOP is the dominant effect and this is exacerbated by the use of constant flux processing. The implications of increasing critical flux are described and the potential benefit of using AC field gradients to do this is illustrated for a model foulant. 相似文献
913.
复杂环境下钢砼支撑爆破拆除 总被引:1,自引:1,他引:0
介绍了在周围环境苛刻的条件下,采用爆破方法拆除钢筋混凝土支撑的成功实例。给出了爆破方案的设计、参数的选取、爆破网路的连接、安全防护措施。为今后在环境复杂的条件下进行控制爆破拆除支撑积累了经验。 相似文献
914.
Yasodha Sivasothy Wong Keng Chong Abdul Hamid Ibrahim M. Eldeen Shaida Fariza Sulaiman Khalijah Awang 《Food chemistry》2011
The essential oils obtained by hydrodistilation of the leaves and rhizomes of Zingiber officinale var. rubrum Theilade were analysed by capillary GC and GC–MS. Forty-six constituents were identified in the leaf oil, while 54 were identified in the oil from the rhizomes. The leaf oil was clearly dominated by β-caryophyllene (31.7%), while the oil from the rhizomes was predominantly monoterpenoid, with camphene (14.5%), geranial (14.3%), and geranyl acetate (13.7%) the three most abundant constituents. The evaluation of antibacterial activities using the micro-dilution technique revealed that both the leaf and rhizome oils were moderately active against the Gram-positive bacteria Bacilluslicheniformis, Bacillus spizizenii and Staphylococcus aureus, and the Gram-negative bacteria Escherichia coli, Klebsiella pneumoniae and Pseudomonas stutzeri. 相似文献
915.
916.
表面等离子谐振引起表面场的增强 ,因而能增加样品的吸收敏感特性 .从理论上分析了这种敏感特性机制 ,为了取得最佳吸收强度 ,计算出金属薄膜为最佳厚度 相似文献
917.
Chong Hee Kim 《Information Processing Letters》2010,110(20):882-886
Fast exponentiation algorithms are central in the implementation of public key cryptography. They should be secure as well as efficient. Nowadays physical attacks such as side channel analysis or fault attacks become big threats in the implementation of cryptographic algorithms. In this article, we propose two new fault attacks using Jacobi symbol. Furthermore we show that Joye's regular right-to-left algorithms are vulnerable to them. 相似文献
918.
Byoung Ho Lee Sun Mi Kim Mohamed El Mehtedi Enrico Evangelista Chong Soo Lee 《Metals and Materials International》2010,16(2):197-203
The influence of stress state on the high temperature workability of rolled AZ31 Mg alloy was investigated on the basis of
a processing map. To construct the processing map, high temperature compression tests were carried out on samples oriented
parallel to the rolling direction at various temperatures (25 °C∼450 °C) and strain rates (10−3 s−1∼5s−1), and then the results were compared with those of a torsion test. The overall efficiency profiles of both the compression
and torsion processing maps were similar to each other, but the index of dissipation efficiency in the torsion was somewhat
lower than that in the compression. The microstructure of the compressed specimens revealed much finer grained structure than
that of the torsion specimens. Such microstructural differences were attributed to the different tendencies of twin formation
and texture evolution depending on the stress state. 相似文献
919.
Practical silicon photonic interconnects become possible nowadays after the realization of the practical silicon light sources,where the hybrid integrations of Ⅲ-Ⅴ semiconductors and silicon by bonding... 相似文献
920.
Wei Shi Lei Wang Mavluda Umar Tunsagul Awut Hongyu Mi Chong Tan Ismayil Nurulla 《Polymer International》2009,58(7):800-806
BACKGROUND: Various poly(arylene ethynylene)s (PAEs) have been prepared and applied as molecular wires, in sensors, in nonlinear optics and as electroluminescent materials. But, to our knowledge, there has been no attention paid to the investigation of conjugated PAEs containing both triarylamine and quinoxaline groups. The influence imparted by the introduction of triarylamine and quinoxaline on the photophysical and electrochemical properties of PAEs is of interest. RESULTS: Two kinds of novel PAE derivatives, with electron‐donating triphenylamine groups in the backbone and electron‐accepting pendent quinoxaline moieties and bearing side chains of different lengths, were successfully synthesized with the Sonogashira coupling reaction. These polymers are soluble in common organic solvents and exhibit good film‐forming ability and thermal stability. UV‐visible investigations indicate that the ground states of these materials are unaffected by the polarity of their medium. An efficient intramolecular charge transfer effect is observed from an investigation of their photoluminescence properties in different solvents. Cyclic voltammetry study reveals that these polymers possess relatively high highest occupied molecular orbital levels due to the incorporation of triphenylamine segments into the polymer backbones. CONCLUSION: Primary characterization of these novel PAE derivatives shows that they might serve as potential active materials in optoelectronic devices. Copyright © 2009 Society of Chemical Industry 相似文献