全文获取类型
收费全文 | 34217篇 |
免费 | 1314篇 |
国内免费 | 1128篇 |
专业分类
电工技术 | 1039篇 |
技术理论 | 1篇 |
综合类 | 776篇 |
化学工业 | 4397篇 |
金属工艺 | 3017篇 |
机械仪表 | 1671篇 |
建筑科学 | 1225篇 |
矿业工程 | 303篇 |
能源动力 | 1172篇 |
轻工业 | 1696篇 |
水利工程 | 344篇 |
石油天然气 | 1166篇 |
武器工业 | 88篇 |
无线电 | 3837篇 |
一般工业技术 | 7951篇 |
冶金工业 | 4520篇 |
原子能技术 | 421篇 |
自动化技术 | 3035篇 |
出版年
2024年 | 45篇 |
2023年 | 204篇 |
2022年 | 357篇 |
2021年 | 543篇 |
2020年 | 415篇 |
2019年 | 510篇 |
2018年 | 715篇 |
2017年 | 713篇 |
2016年 | 758篇 |
2015年 | 743篇 |
2014年 | 1041篇 |
2013年 | 2172篇 |
2012年 | 1506篇 |
2011年 | 2117篇 |
2010年 | 1728篇 |
2009年 | 1899篇 |
2008年 | 1937篇 |
2007年 | 1930篇 |
2006年 | 1707篇 |
2005年 | 1579篇 |
2004年 | 1199篇 |
2003年 | 1075篇 |
2002年 | 1087篇 |
2001年 | 1023篇 |
2000年 | 995篇 |
1999年 | 1072篇 |
1998年 | 1739篇 |
1997年 | 1285篇 |
1996年 | 1095篇 |
1995年 | 729篇 |
1994年 | 573篇 |
1993年 | 482篇 |
1992年 | 317篇 |
1991年 | 300篇 |
1990年 | 203篇 |
1989年 | 214篇 |
1988年 | 145篇 |
1987年 | 102篇 |
1986年 | 73篇 |
1985年 | 64篇 |
1984年 | 44篇 |
1983年 | 35篇 |
1982年 | 31篇 |
1981年 | 31篇 |
1980年 | 19篇 |
1979年 | 10篇 |
1978年 | 9篇 |
1976年 | 20篇 |
1975年 | 11篇 |
1973年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
X. S. Ning K. Suganuma T. Okamoto A. Koreeda Y. Miyamoto 《Journal of Materials Science》1989,24(8):2879-2883
Two kinds of additive-free silicon nitride ceramics were brazed with aluminium; one was with as-ground faying surfaces and
the other was with faying surfaces heat-treated at 1073K for 1.8 ksec in air. The heat-treatment of the silicon nitride ceramics
formed a silicon oxynitride layer on the faying surfaces and increased the brazing strength of the joints. A silica-alumina
non-crystalline layer and a β′-sialon layer were formed successively from the aluminium side at the interface of the joints.
The heat-treatment which made the former layer thicker is a necessary process in making reliable, strong brazed joints. 相似文献
82.
The change in polystyrene (PS) layer thickness, which has been simultaneously determined during post-yield deformation, shows
that crazing is the basic mechanism of toughening in all laminated films, and that shear deformation supplements the contribution
of crazing especially for samples with high polyethylene (PE) volume fractions. Crazes formed in PS layers in the laminated
films are slender and regular compared with the short and lenticular crazes formed in bulk PS film. When PE volume fraction
increased, craze advance speed decreased because of the reduction of the stress concentration effect at craze tips. The life-time
of the first mature craze to be formed at a given strain rate increased with PE volume fraction because the PE supporting
the mature crazes could effectively inhibit craze rupture and blunt out the propagating crack by absorbing the stored elastic
energy in the PS layer that would have been dissipated as fracture surface energy. 相似文献
83.
Most algorithms on receiver autonomous integrity monitoring (RAIM) are under the assumption of a single-satellite fault, because there is an extremely small probability that significant simultaneous multiple-satellite faults may occur. However, after the implementation of the Galileo system in a few years, there will be more satellites in view for the user to utilise together with GPS satellites, and a combination of them will bring better performance for RAIM. On the other hand, with the help of wide area augmentation system and the use of dual-frequency operation, pseudo-range errors will be reduced greatly. Thus, tighter alert limits are required for RAIM, and formerly `small' errors should not be neglected. All of those factors make it necessary to consider simultaneous multiple-satellite faults. A detailed theoretical analysis of RAIM under the condition of two-satellite faults for both vertical and horizontal directions is presented. The characteristic/max slopes for every pair of satellites are then deduced in order to calculate the tighter vertical/horizontal protection level for RAIM 相似文献
84.
On structural and high temperature electrochemical properties of ZrO2 thin film coating on Zr metal produced by carbonate melt 总被引:1,自引:0,他引:1
Melt of NaCO3 can favor oxidation of Zr to form ZrO2 thin film on Zr surface, which is used to make Zr/ZrO2 oxidation/reduction electrode of pH sensor for testing elevated temperature aqueous solutions. Using SEM, EPMA, XPS, EXAFS
and HRTEM, we found that ZrO2 film is tightness and solid with 20 μm thickness composed by nanometer-sized monoclinic crystals. Zr/ZrO2 interface is characterized of zoning structure according to topography and chemical composition in five zones: oxygen-rich
ZrO2, ZrO2, oxygen-rich Zr metal, oxygen-bearing Zr and Zr from outmost to center. Melt oxidation process of Zr involved oxidation time,
air and temperature. The air is important effect on structural and electrochemical properties of ZrO2 thin film for making elevate temperature electrochemical sensor. If oxygen air largely presented in carbonate melting process,
ZrO2 thin film is not tightness and not for oxidation/reduction electrode. 相似文献
85.
Daniel X. Gouveia Odair P. Ferreira Antonio G. Souza Filho M. G. da Silva J. A. C. de Paiva Oswaldo L. Alves Josué Mendes Filho 《Journal of Materials Science》2007,42(2):534-538
The thermal decomposition properties of Mg–Fe hydrotalcites were studied through in situ 57Fe Mössbauer spectroscopy and in situ X-ray diffraction. Abrupt changes in the quadrupolar splitting measured in the Mössbauer spectra revealed a phase transition from the starting lamellar structure to a new crystalline arrangement. By analyzing the Mössbauer parameters we show that the material is highly disordered in the 300–400 °C temperature range. This hypothesis is confirmed by the X-ray results whose diffractograms indicated the collapse of the lamellar structure and the formation of a solid solution. 相似文献
86.
87.
88.
89.
90.
Polyurethane elastomer composites were developed using milled fiberglass and their mechanical properties were studied. In particular, the organically chemical treatment of the milled fiberglass was investigated in detail. It was demonstrated that both strength and toughness of the resulting elastomer composites were improved considerably with the addition content of fiberglass. Furthermore, it was indicated that the optimal properties can be achieved by the proper addition of milled fiberglass that was chemically treated using coupling agent. 相似文献