全文获取类型
收费全文 | 838篇 |
免费 | 29篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 37篇 |
综合类 | 3篇 |
化学工业 | 230篇 |
金属工艺 | 15篇 |
机械仪表 | 16篇 |
建筑科学 | 12篇 |
能源动力 | 39篇 |
轻工业 | 64篇 |
水利工程 | 5篇 |
无线电 | 76篇 |
一般工业技术 | 170篇 |
冶金工业 | 56篇 |
原子能技术 | 42篇 |
自动化技术 | 109篇 |
出版年
2023年 | 4篇 |
2022年 | 6篇 |
2021年 | 7篇 |
2019年 | 13篇 |
2018年 | 14篇 |
2017年 | 4篇 |
2016年 | 14篇 |
2015年 | 9篇 |
2014年 | 14篇 |
2013年 | 31篇 |
2012年 | 37篇 |
2011年 | 47篇 |
2010年 | 30篇 |
2009年 | 28篇 |
2008年 | 36篇 |
2007年 | 31篇 |
2006年 | 28篇 |
2005年 | 29篇 |
2004年 | 38篇 |
2003年 | 29篇 |
2002年 | 28篇 |
2001年 | 17篇 |
2000年 | 20篇 |
1999年 | 20篇 |
1998年 | 27篇 |
1997年 | 28篇 |
1996年 | 15篇 |
1995年 | 16篇 |
1994年 | 10篇 |
1993年 | 22篇 |
1992年 | 10篇 |
1991年 | 12篇 |
1990年 | 12篇 |
1989年 | 17篇 |
1988年 | 15篇 |
1987年 | 10篇 |
1986年 | 8篇 |
1985年 | 7篇 |
1984年 | 11篇 |
1983年 | 11篇 |
1982年 | 8篇 |
1981年 | 12篇 |
1980年 | 15篇 |
1979年 | 15篇 |
1978年 | 8篇 |
1977年 | 7篇 |
1976年 | 10篇 |
1975年 | 6篇 |
1973年 | 5篇 |
1968年 | 5篇 |
排序方式: 共有874条查询结果,搜索用时 15 毫秒
61.
Corrosion characteristics of reduced activation ferritic steel, JLF-1 (8.92Cr–2W) in molten salts Flibe and Flinak 总被引:1,自引:0,他引:1
Masatoshi Kondo Takuya Nagasaka Qi Xu Takeo Muroga Akio Sagara Nobuaki Noda Daisuke Ninomiya Masaru Nagura Akihiro Suzuki Takayuki Terai Naoki Fujii 《Fusion Engineering and Design》2009,84(7-11):1081-1085
Static corrosion tests were performed in molten salts, LiF–BeF2 (Flibe) and LiF–NaF–KF (Flinak), at 500 °C and 600 °C for 1000 h. The purpose is to investigate the corrosion characteristics of reduced activation ferritic steels, JLF-1 (8.92Cr–2W) in the fluids. The concentration of hydrogen fluoride (HF) in the fluids was measured by slurry pH titration method before and after the exposure. The HF concentration determined the fluoridation potential. The corrosion was mainly caused by dissolution of Fe and Cr into the fluids due to fluoridation and/or electrochemical corrosion. Carbon on the surface might be dissolved into the fluids due to the corrosion, and this resulted to the decrease of carbide on the surface. The corrosion depth of the JLF-1 specimen, which was obtained from the weight losses, was 0.637 μm in Flibe at 600 °C and 6.73 μm in Flinak at 600 °C. 相似文献
62.
Masaru Nagura Akihiro Suzuki Takeo Muroga Takayuki Terai 《Fusion Engineering and Design》2009,84(7-11):1384-1387
Er2O3 is candidate material for insulating coating to prevent the magnetohydrodynamic (MHD) pressure drop in the self-cooled liquid Li blanket system. Although Er2O3 is stable material, detailed chemical behavior in liquid Li is not clear. Corrosion behavior of bulk Er2O3 in Li is investigated in static and flowing condition in the present study. After these tests, good compatibility of Er2O3 was confirmed and slight formation of LiErO2 was detected by XRD analysis. This chemical behavior did not change in a static and flowing tests, however some of the corrosion product of LiErO2 was removed easily by the Li flow. Intensity of LiErO2 peaks in XRD spectrum suggests that the temperature gradient may affect the reaction rate in the natural convection loop. Since corrosion rate of Er2O3 is very small, slight change in state will be important information to evaluate lifetime of coating. 相似文献
63.
64.
65.
A third-generation biosensor for superoxide anion (O2-) was developed by immobilizing superoxide dismutase (SOD) on a self-assembled monolayer of cysteine on gold electrode; i.e., a SOD/cysteine-modified gold electrode (SOD/Cys/Au) was fabricated. A rapid and direct electron transfer of SOD was realized at the gold electrode by using the cysteine molecule as an electron-transfer promoter. The promoted direct electron transfer of SOD and biomolecular recognition by the exploitation of specific and significant enzyme-substrate reactivity of SOD toward O2- combined with the low operating potential enabled a sensitive measurement of O2-. At SOD/Cys/Au, O2- could be specifically oxidized and reduced to O2 and hydrogen peroxide, respectively, through the inherent catalytic reaction of SOD. This allowed us to measure O2- by polarizing the electrode both anodically and cathodically. We could successfully measure O2- by suitably polarizing the electrode, typically at 300 and -200 mV versus Ag/AgCl without the virtual interference from physiological levels of H2O2, ascorbic acid, uric acid, and metabolites of neurotransmitters. The response mechanism of SOD/Cys/Au to O2- and its sensor characteristics are also presented and discussed. 相似文献
66.
三甲基甲硅烷基异恶唑的负离子与P-取代苄腈(2a)-(2e),反应制得的N-甲硅在-1-氮杂烯丙基负离子(3a)-(3e),央无水四氢呋喃存在下与过量查耳酮反应,生成相应的吡啶衍生物(5a)-(5e),回收率达40-70%。 相似文献
67.
68.
69.
Linear elastic fracture mechanics, which has been applied to fragile substances and successfully used for studying the brittle fracture of metallic materials, was utilized to gain an understanding of the fracture phenomena of sea ice.The present paper reports the first results of investigations into the fracture-toughness value of sea ice, which was analyzed experimentally as a function of strain rate on the basis of the stress-intensity-factor concept.The fracture toughness, KIC, of sea ice, which was measured by an in-situ three-point bending test on notched specimens, shows almost constant value if the strain rate is less then 10?3 s?1 and decreases with increasing strain rate if the strain rate exceeds 10?3 s?1. KIC data show considerably less scatter than existing data such as the compressive, tensile and flexural strengths.It was confirmed in the present study that the linear elastic-fracture-mechanics concept is effective for analyzing the fracture phenomena of sea ice. Moreover, the KIC value was shown to be closely related to sea-ice structures (e.g. the size of crack-like flaws such as brine cells).It is also suggested that the fracture-toughness test might prove to be a standard testing method to obtain the sea-ice strength, since once K1C and crack-like flaw sizes are determined, the less-scattered critical-fracture stress can be calculated. 相似文献
70.
Kamino T Yaguchi T Kuroda Y Ohnishi T Ishitani T Miyahara Y Horita Z 《Journal of electron microscopy》2004,53(5):459-463
Transmission electron microscopy (TEM) samples of an Mg-Al alloy has been prepared using a Ga-focused ion beam (FIB) milling at two different operating voltages of 10 kV and 40 kV to investigate the influence of the FIB energy on the sample quality. The fine structures of the samples have been studied using a high resolution TEM, and the concentration of the implanted Ga was analysed using an energy dispersive X-ray (EDX) analysis. The result of the TEM observation revealed that point defects were introduced to the sample finally milled at 40 kV but not at 10 kV. However, crystal lattice images and electron diffraction patterns were clearly observed on both the samples. The typical influence of the FIB energy was indicated in the elemental analysis. The relative Ga concentration in the thin sample finally milled at 10 kV was 1.0-2.0 at% that is less than half of 4.0-6.0 at% of the Ga concentration in the sample finally milled at 40 kV. A comparison between the experimental results of the Ga concentration measurement with simulation was also discussed. 相似文献