全文获取类型
收费全文 | 1542篇 |
免费 | 26篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 114篇 |
综合类 | 4篇 |
化学工业 | 393篇 |
金属工艺 | 34篇 |
机械仪表 | 52篇 |
建筑科学 | 42篇 |
能源动力 | 55篇 |
轻工业 | 117篇 |
水利工程 | 3篇 |
无线电 | 89篇 |
一般工业技术 | 223篇 |
冶金工业 | 278篇 |
原子能技术 | 69篇 |
自动化技术 | 98篇 |
出版年
2022年 | 9篇 |
2021年 | 29篇 |
2020年 | 6篇 |
2019年 | 7篇 |
2018年 | 9篇 |
2017年 | 18篇 |
2016年 | 19篇 |
2015年 | 12篇 |
2014年 | 26篇 |
2013年 | 74篇 |
2012年 | 40篇 |
2011年 | 51篇 |
2010年 | 60篇 |
2009年 | 69篇 |
2008年 | 71篇 |
2007年 | 58篇 |
2006年 | 49篇 |
2005年 | 53篇 |
2004年 | 40篇 |
2003年 | 37篇 |
2002年 | 53篇 |
2001年 | 18篇 |
2000年 | 29篇 |
1999年 | 44篇 |
1998年 | 97篇 |
1997年 | 74篇 |
1996年 | 55篇 |
1995年 | 38篇 |
1994年 | 50篇 |
1993年 | 44篇 |
1992年 | 25篇 |
1991年 | 23篇 |
1990年 | 14篇 |
1989年 | 18篇 |
1988年 | 15篇 |
1987年 | 27篇 |
1986年 | 27篇 |
1985年 | 22篇 |
1984年 | 19篇 |
1983年 | 16篇 |
1982年 | 16篇 |
1981年 | 15篇 |
1980年 | 11篇 |
1979年 | 12篇 |
1978年 | 11篇 |
1977年 | 11篇 |
1976年 | 19篇 |
1975年 | 8篇 |
1973年 | 7篇 |
1972年 | 4篇 |
排序方式: 共有1571条查询结果,搜索用时 15 毫秒
51.
Tomohiro Kubo 《International journal of control》2013,86(5):404-410
A class of linear quadratic regulators of the system with time-delay in the states is constructed by a memoryless feedback, and its robustness is evaluated. First, a static non-linear perturbation is inserted in the input channel, and a robust stability condition is derived. As its special case, it is shown that the regulator has infinite gain margin and at least 50% gain reduction tolerance. Next, a dynamic linear perturbation is inserted in the same point, and an alternative stability condition is derived. It assures that the regulator has at least 60o phase margin. These results coincide with those of the finite dimensional LQ regulator. 相似文献
52.
Phase transformation and interface segregation behavior in Si3N4 ceramics sintered with La2O3–Lu2O3 mixed additive
下载免费PDF全文
![点击此处可从《Journal of the American Ceramic Society》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Ryosuke Urakami Yukio Sato Masayoshi Ogushi Takeshi Nishiyama Aoi Goto Kazuhiro Yamada Ryo Teranishi Kenji Kaneko Mikito Kitayama 《Journal of the American Ceramic Society》2017,100(3):1231-1240
Microstructure and mechanical property of silicon nitride (Si3N4) ceramic are strongly dependent on the selection of sintering additives. When rare‐earth (RE) oxide is used as the sintering additive, segregation of RE ions at interface between Si3N4 grain and intergranular glassy film (IGF) is believed to play a critical role. Although the ionic radius of RE ion is known to be an empirical parameter to modify the mechanical property, the correlation between the segregated ions and their ionic radii is still under controversy. In order to address this issue, (i) rate of α‐β phase transformation and (ii) segregation behavior at the interface were studied for Si3N4 ceramics sintered using mixture of La2O3 and Lu2O3 as additives in this study. Specimens of Lu content 30% and higher exhibited lower activation energies for the α‐β phase transformation as compared with those of Lu content 20% and lower. In terms of the segregation behavior, La was preferably segregated at one site and Lu at the other site along β‐Si3N4/IGF interface in the specimens of Lu content 30% and higher. It is understood from these results that Lu segregation site should be more closely related with grain growth. 相似文献
53.
Atsushi Iizuka Satoshi Takeda Kazukiyo Kumagai Yukio Yanagisawa 《Chemical Engineering Communications》2017,204(3):321-326
The effect of the addition of microbubbles on the formation of silver nanoparticles produced in an ultrasonic radiation-mediated process was investigated. The addition of microbubbles with an area-based median diameter of 26.0?µm and a bubble volume density of 0.18?cm3/L significantly increased the silver nanoparticle formation rate during the sonochemical process. The size distribution of the silver nanoparticles was largely unaffected by the addition of the microbubbles. The influence of changes in the microbubble volume density on the formation of the silver nanoparticles was also investigated; it was confirmed that the rate of formation of the silver nanoparticles increased moderately with increasing volume density. The gradient in absorption spectra was approximately 30 times larger for the case when microbubbles (median diameter: 28.3?µm) were added at 0.74?cm3/L, compared with the case without microbubbles. The results suggested that the microbubbles provided reaction sites similar to cavitation bubbles in the ultrasonic reaction. 相似文献
54.
Hirofumi Chiba Yukio Suzuki Yoshiaki Yasuda Mitsuyasu Kumagai Takaaki Koyama Shuji Tanaka 《Electrical Engineering in Japan》2021,214(1):62-68
This paper reports a deep‐ultraviolet LED (deep‐UV‐LED) package based on silicon MEMS process technology (Si‐PKG). The package consists of a cavity formed by silicon crystalline anisotropic etching, through‐silicon vias (TSVs) filled with electroplated Cu, bonding metals made of electroplated Ni/AuSn and a quartz lid for hermetic sealing. A deep‐UV LED die is directly mounted in the Si‐PKG by AuSn eutectic bonding without a submount. It has advantages in terms of size, heat dissipation, light utilization efficiency, productivity and cost over conventional AlN ceramic packages. We confirmed a light output of 30 mW and effective reflection on Si (111) cavity slopes in the Si‐PKG. Based on simulation, further improvement of the optical output is expected by optimizing DUV‐LED die mount condition. 相似文献
55.
Toru Moriyama Jun-ichi Mashiko Toshinori Matsui Koichiro Enomoto Tetsuya Matsui Kojiro Iizuka Masashi Toda Yukio Pegio Gunji 《Artificial Life and Robotics》2016,21(3):247-252
The soldier crab appears in great numbers and feeds while wandering during daytime low tide. When they see an approaching object, they screw themselves into the sand. The mechanism of formation of mass wandering has not been clarified. In this study, to investigate if the soldier crabs use visual images of neighbors as a stimulus for wandering, dummy crabs were presented to crabs. In the experiments, one, two, four, or eight dummies were placed in a circle on a sand arena. Each crab was placed in the center of the arena and observed whether it burrowed into the sand or wandered. The proportions of wandering individuals in each experimental treatment were compared with the expected value. Significantly more crabs were wanderers when only two and four dummies were present. This result suggests that soldier crabs chose burrowing or wandering depending on visual image of the distribution of the neighbors. 相似文献
56.
Thawhid Khan Shunsuke Koide Yukio Tamura Hiroshi Yamamoto Ardian Morina Anne Neville 《Tribology Letters》2018,66(1):43
Oxy-nitriding is a widely used industrial process aiming to improve the tribological properties and performance of components. Previous studies have shown the effectiveness of the treatment with friction and wear performance, but very few have focussed on optimising this behaviour. The lubrication properties of several EP and AW additives were examined to investigate their effectiveness in improving the tribological properties of the layers formed after treatment. Previous studies showed the presence of an oxide layer on the sample could improve the effectiveness of the sulphurised olefin (SO) and tricresyl phosphate (TCP) additives. The friction and wear behaviour of oxy-nitrided samples were analysed using a tribometer and surface profiler. Scanning electron microscope, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy were employed to identify the morphologies and chemical compositions of the treated surface before and after testing. No real effect on friction was observed when using the SO or TCP additives, mostly due to lack of interaction with the less reactive iron nitride layer and their roles as anti-wear additives. However, when the zinc dialkyldithiophosphate-containing lubricant was used, a higher friction coefficient was observed. Greater improvements in anti-wear properties with the presence of additives in comparison with only using base oil were reported, with the TCP additive producing the lowest wear rates. The study effectively demonstrated that the additive package type used could impact the tribological and tribochemical properties of oxy-nitrided surfaces. 相似文献
57.
58.
59.
Hydration of cyanopyridine on CeO2(110) surfaces was studied using periodic DFT+U calculations. One of two adsorption modes of 2-cyanopyridine occurs with two-point interaction which causes substrate specificity. A catalytic cycle for the hydration of 2-cyanopyridine was proposed. Cooperativity of Lewis and Brønsted acid sites was found to stabilize the intermediates for the hydration. 相似文献
60.