全文获取类型
收费全文 | 6002篇 |
免费 | 638篇 |
国内免费 | 291篇 |
专业分类
电工技术 | 220篇 |
综合类 | 303篇 |
化学工业 | 2134篇 |
金属工艺 | 1125篇 |
机械仪表 | 136篇 |
建筑科学 | 38篇 |
矿业工程 | 345篇 |
能源动力 | 174篇 |
轻工业 | 68篇 |
水利工程 | 4篇 |
石油天然气 | 331篇 |
武器工业 | 26篇 |
无线电 | 278篇 |
一般工业技术 | 806篇 |
冶金工业 | 864篇 |
原子能技术 | 52篇 |
自动化技术 | 27篇 |
出版年
2024年 | 31篇 |
2023年 | 89篇 |
2022年 | 136篇 |
2021年 | 160篇 |
2020年 | 190篇 |
2019年 | 153篇 |
2018年 | 181篇 |
2017年 | 223篇 |
2016年 | 210篇 |
2015年 | 218篇 |
2014年 | 253篇 |
2013年 | 369篇 |
2012年 | 381篇 |
2011年 | 417篇 |
2010年 | 301篇 |
2009年 | 309篇 |
2008年 | 266篇 |
2007年 | 384篇 |
2006年 | 368篇 |
2005年 | 319篇 |
2004年 | 269篇 |
2003年 | 229篇 |
2002年 | 226篇 |
2001年 | 207篇 |
2000年 | 167篇 |
1999年 | 171篇 |
1998年 | 125篇 |
1997年 | 100篇 |
1996年 | 77篇 |
1995年 | 74篇 |
1994年 | 59篇 |
1993年 | 52篇 |
1992年 | 45篇 |
1991年 | 39篇 |
1990年 | 29篇 |
1989年 | 24篇 |
1988年 | 9篇 |
1987年 | 6篇 |
1986年 | 10篇 |
1985年 | 10篇 |
1984年 | 9篇 |
1983年 | 8篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1975年 | 4篇 |
1951年 | 1篇 |
排序方式: 共有6931条查询结果,搜索用时 0 毫秒
11.
A new discharge system for resistive self-heating has been constructed for the measurement of accurate thermophysical properties. A constant-current pulse is used to heat metals over a time interval of 50 to 100 s, reaching temperatures up to the boiling point. New techniques have been developed to obtain sound speeds in the pulse-heated sample, emissivities, and vapor pressure. A new pyrometer allows the extension of the measured temperature range down to the melting point of copper. 相似文献
12.
REN Jianshi ZHAO Huilin ZHANG Gongshu Institute of Metal Research Academia Sinica.Shenyang China ZHANG Gongshu Senior Engineer Institute of Metal Research Academia Sinica Shenyang China 《金属学报(英文版)》1990,3(7):65-69
Glow discharge cathodic sputtering of alloys containing second phase precipitates or injectedoxide particles has been observed with energy dispersive X-ray spectrometer and scanningelectron microprobe.It was shown that the formation of cones during the sputtering in thesealloys is due to masking of the matrix by glow sputtering second phase precipitates or oxideparticles.At steady state,the density of cottes were found to be a function of the densities pre-cipitates or oxide particles in bulk alloy.In addition to the changes of local sputtering rate,theelectrostatic effect may play a role on the formation fo cones. 相似文献
13.
14.
D. Chang R. Schafrik 《金属学报(英文版)》2005,18(5):561-574
1. Introduction Freedom to travel anywhere in the world, both quickly and inexpensively, defines our modern era. Despite year-to-year variation, the long term demand for travel by airplane continues to grow. Three ma- jor systems comprise the modern airplane: the aircraft structure that encompasses the fuselage, wings, and landing gear; the avionics that enable flight through crowded skies in nearly all weather conditions; and the propulsion system that powers the aircraft. Improvements in mat… 相似文献
15.
It is demonstrated that the nickel can be deposited directly on the surface of carbon nanotubes without pre-sensitization by Sn^2+ and Pd^2+ in a watt bath containing suspended nanotubes by electroplating. The nickel is deposited as spherical nanoparticle on the nanotubes. By increasing reaction time, the carbon nanotube is fully coated with nickel. A probable model, which represents the formation process of carbon nanotube-nickel composites by electroplating, is presented. The results show that this method is efficient and simple for preparing carbon nanotube-metal composite. 相似文献
16.
The combined erosion-oxidation of nickel, cobalt, and the oxides of these metals have been studied at 780°C in air to examine two regimes of interactionnamely, a regime of erosion-enhanced oxidation during which an oxide scale of constant thickness covers metal specimens, and a regime of oxidation-affected erosion that is characterized by a composite surface layer of metal, oxide, and erodent. In the case of cobalt, these two regimes have been documented and the transition from one regime to another described. For the range of conditions examined, only the oxidation-affected erosion regime was observed for nickel due to its lower oxidation rate compared to cobalt. 相似文献
17.
Phosphorus was added to Fe-50 wt.% Ni in the form of a coated composite powder via an electroless plating process. Addition
of phosphorus to Fe-50 wt.% Ni facilitated increases in density and grain size, both of which were beneficial to magnetic
performance. Because of the homogeneous distribution of phosphorus in the powder, the optimal phosphorus addition was much
lower than for those using Fe3P as the phosphorus precursor. The optimal phosphorus addition was close to its maximum solubility in Fe-50 wt.% Ni (about
0.5 wt.%), above which precipitation of excessive phosphorus in the form of iron nickel phosphide, (Fe,Ni)3P, effectively degraded the magnetic properties of Fe-50 wt.% Ni. Without the addition of phosphorus, good magnetic properties
could be achieved only when the sintering temperature was high enough (>1200 °C) to result in a high sintered density and
large grains in the sintered structure. 相似文献
18.
根据已知镍基合金成分和γ′相成分,运用分层宽容多目标优化法,分别计算了γ相成分及γ′相含量.优化测算过程的实现是通过建立使杠杆定律等式两端数值差最小和两相共格错配度最小的目标函数,并通过设置γ′相含量和基体相成分取值范围的约束条件而实现的.验证了该方法的可行性和准确性. 相似文献
19.
NICKEL ELECTROPLATING has been practicallyused for decades.There is an unknown part in theplating,although this is easy to plate.Applications ofthe plating are described from the practical viewpoint.Purpose of Nickel Electroplating(1)Decorative,and corrosion resistanceNickel electroplating is deposited on iron,cupper,zinc and aluminum substrate etc.,and chromiumplating is usually deposited on nickel plating.Hexavalent chromium plating has an important effecton the corrosion resisitan… 相似文献
20.
The catalytic partial oxidation of CH4 to syngas was carried out over an Ni–Mg/Al mixed-oxide catalyst prepared from layered double hydroxide-type precursors. The catalysts were characterized by XRD, TPR, UV-DRS, XRF, BET and CHNS analysis. The effects of the catalyst composition and the calcination temperature on the catalytic performance and the extent of catalyst deactivation were investigated. Ni–Mg/Al oxide catalysts converted CH4 into syngas efficiently with high selectivity. The catalyst performance was strongly related to the Ni particle size and the calcination temperature. The catalysts that were calcined at higher temperature exhibited a better catalytic performance. In conclusion, the NiAl2O4 spinel phase had a positive effect on the stability of the catalyst. 相似文献