全文获取类型
收费全文 | 38440篇 |
免费 | 5439篇 |
国内免费 | 2083篇 |
专业分类
电工技术 | 860篇 |
技术理论 | 1篇 |
综合类 | 2840篇 |
化学工业 | 12159篇 |
金属工艺 | 7985篇 |
机械仪表 | 3125篇 |
建筑科学 | 2979篇 |
矿业工程 | 1277篇 |
能源动力 | 696篇 |
轻工业 | 1573篇 |
水利工程 | 530篇 |
石油天然气 | 818篇 |
武器工业 | 663篇 |
无线电 | 983篇 |
一般工业技术 | 6176篇 |
冶金工业 | 2514篇 |
原子能技术 | 140篇 |
自动化技术 | 643篇 |
出版年
2024年 | 270篇 |
2023年 | 976篇 |
2022年 | 1399篇 |
2021年 | 2014篇 |
2020年 | 1793篇 |
2019年 | 1416篇 |
2018年 | 1465篇 |
2017年 | 1744篇 |
2016年 | 1792篇 |
2015年 | 1811篇 |
2014年 | 2254篇 |
2013年 | 2431篇 |
2012年 | 2859篇 |
2011年 | 2738篇 |
2010年 | 2023篇 |
2009年 | 2135篇 |
2008年 | 1746篇 |
2007年 | 2343篇 |
2006年 | 2290篇 |
2005年 | 1714篇 |
2004年 | 1540篇 |
2003年 | 1229篇 |
2002年 | 1020篇 |
2001年 | 923篇 |
2000年 | 780篇 |
1999年 | 587篇 |
1998年 | 518篇 |
1997年 | 420篇 |
1996年 | 346篇 |
1995年 | 259篇 |
1994年 | 232篇 |
1993年 | 162篇 |
1992年 | 156篇 |
1991年 | 107篇 |
1990年 | 115篇 |
1989年 | 149篇 |
1988年 | 27篇 |
1987年 | 37篇 |
1986年 | 17篇 |
1985年 | 26篇 |
1984年 | 22篇 |
1983年 | 20篇 |
1982年 | 20篇 |
1980年 | 8篇 |
1979年 | 6篇 |
1978年 | 3篇 |
1966年 | 3篇 |
1965年 | 2篇 |
1959年 | 3篇 |
1957年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
Effect of Strain Rate on Discontinuous Flow and Mechanical Characteristics of High-Nitrogenous Steel
Experimental study on the effect of strain rate on discontinuous flow and mechanical characteristics of the high-nitrogenous steel Kh23AG19F has been performed. Within the range of strain rates from 4.62 · 10-5 to 1.85 · 10 -4 s-1, discontinuous flow, reflected by serration on the tensile diagram, is chiefly determined by intergranular deformation mechanisms. Under strain rates over 1.85 · 10-2 s-1, combined deformation modes prevail, which cause a change in the character of discontinuous flow and transform a serrated tensile diagram into a wavy graph, with the yield stress of steel increased significantly. 相似文献
32.
33.
T-ZnO晶须增强环氧树脂复合材料的力学行为 总被引:10,自引:0,他引:10
研究了以四脚状氧化锌(T-ZnO)晶须为增强剂,环氧树脂复合材料的力学行为。结果表明,由具有三维空间结构的T-ZnO晶须为增强剂所制备的环氧树脂复合材料具有各向同性的力学性能,T-ZnO晶须填加质量分数为6%时,就可使材料的力学性能改善;拉伸强度提高到169%,拉伸功几乎提高了100%,冲击强度提高到300%,抗弯的断裂功提高到158%,而压缩强度略有下降。 相似文献
34.
The mechanical properties of a medium molecular weight polyethylene (MMW‐PE) and an ultrahigh molecular weight PE (UHMW‐PE) binary mixture with different weight fractions crystallized from the melt at 0.1 and 450 MPa were studied. The tensile modulus, yield stress, and strain were obtained as a function of the weight fractions in the PE mixtures at 25 and 85°C. The tensile modulus in the sample crystallized at 0.1 MPa decreased from 1.5 GPa of pure MMW‐PE to about 0.4 GPa of pure UHMW‐PE with the UHMW‐PE content but it did not decrease with the UHMW‐PE in the sample crystallized at 450 MPa in testing at 25°C. A decreasing rate of the storage modulus E′ of UHMW‐PE in a dynamic measurement for the sample crystallized at 0.1 MPa with the temperature is larger than that of the sample crystallized at 450 MPa. These experimental facts are interpreted in relation to the molecular motion and crystallinity of the sample. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1962–1968, 2003 相似文献
35.
36.
机械合金化Fe-Ni粉末的相结构 总被引:1,自引:0,他引:1
使用XRD和Moessbauer等方法,研究了在Ar气氛下机械合金化Fe—Ni粉末相结构的变化.结果表明,在机械合金化Fe64-Ni36粉末过程中,fcc相的数量随着球磨时间的增加先增加然后减少,与加乙醇球磨Fe64-Ni36的情形相同.当Ni的含量(原子分数)大于50%时,有fcc相、顺磁相和FeNi3形成,当Ni的含量低于50%时,bcc相的数量随着Ni含量减少而增加.Moessbauer谱的结果表明,因球磨时间或Fe、Ni比例的不同,Fe—Ni球磨粉末固溶体具有不同结构的原子配比。 相似文献
37.
38.
39.
The feature scale planarization of the copper chemical mechanical planarization (CMP) process has been characterized for two
copper processes using Hitachi 430-TU/Hitachi T605 and Cabot 5001/Arch Cu10K consumables. The first process is an example
of an abrasive-free polish with a high-selectivity barrier slurry, while the second is an example of a conventional abrasive
slurry with a low-selectivity barrier slurry. Copper fill planarization has been characterized for structures with conformal
deposition as well as with bumps resulting from bottom-up fill. Dishing and erosion were characterized for several structures
after clearing. The abrasive-free polish resulted in low sensitivity to overpolish and low saturation levels for dishing and
erosion. Consequently, this demonstrated superior performance when compared to the International Technology Roadmap for Semiconductors
(ITRS) 2000 roadmap targets for planarization. While the conventional slurry could achieve the 0.13-μm technology node requirements,
the abrasive-free polish met the planarization requirements beyond the 0.10-μm technology node. 相似文献
40.
V S R Murthy 《Bulletin of Materials Science》1993,16(2):87-108
Research and development efforts on high-temperature, oxidation-resistant fibres have increased over the past decade due to
the demand for light-weight, stiff and strong composite materials in aerospace applications. Varieties of ‘high-performance’,
continuous, non-oxide fibres with low-density, high tensile strength and tensile modulus have been developed either from organic
precursors or via chemical vapour deposition for fabrication of ceramic matrix composites. Fibres derived from polymer precursors
(e.g. Nicalon, Tyranno, HPZ) are small in diameter (compared to CVD monofilaments) and are ideally suited for ceramic composites.
Processing, microstructural stability and mechanical properties of these newly developed SiC and Si3N4 base fibres are briefly reviewed in this paper. 相似文献