全文获取类型
收费全文 | 1591篇 |
免费 | 38篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 69篇 |
综合类 | 1篇 |
化学工业 | 338篇 |
金属工艺 | 53篇 |
机械仪表 | 30篇 |
建筑科学 | 28篇 |
能源动力 | 62篇 |
轻工业 | 101篇 |
水利工程 | 3篇 |
石油天然气 | 2篇 |
无线电 | 129篇 |
一般工业技术 | 307篇 |
冶金工业 | 370篇 |
原子能技术 | 43篇 |
自动化技术 | 99篇 |
出版年
2023年 | 6篇 |
2022年 | 13篇 |
2021年 | 22篇 |
2020年 | 12篇 |
2019年 | 17篇 |
2018年 | 19篇 |
2017年 | 14篇 |
2016年 | 31篇 |
2015年 | 16篇 |
2014年 | 52篇 |
2013年 | 66篇 |
2012年 | 46篇 |
2011年 | 58篇 |
2010年 | 59篇 |
2009年 | 59篇 |
2008年 | 67篇 |
2007年 | 73篇 |
2006年 | 44篇 |
2005年 | 61篇 |
2004年 | 52篇 |
2003年 | 46篇 |
2002年 | 36篇 |
2001年 | 40篇 |
2000年 | 24篇 |
1999年 | 42篇 |
1998年 | 141篇 |
1997年 | 82篇 |
1996年 | 71篇 |
1995年 | 43篇 |
1994年 | 52篇 |
1993年 | 43篇 |
1992年 | 12篇 |
1991年 | 22篇 |
1990年 | 21篇 |
1989年 | 30篇 |
1988年 | 19篇 |
1987年 | 17篇 |
1986年 | 13篇 |
1985年 | 11篇 |
1984年 | 9篇 |
1983年 | 11篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1977年 | 11篇 |
1976年 | 14篇 |
1975年 | 5篇 |
1973年 | 3篇 |
排序方式: 共有1635条查询结果,搜索用时 15 毫秒
121.
Preloading clayey deposit by vacuum pressure with cap-drain: Analyses versus performance 总被引:4,自引:0,他引:4
A method of improving soft clayey deposit by combining cap-drain (CPVD) with vacuum pressure is described. The method uses a surface or subsurface soil layer as a sealing layer with no need to place an air-tightening sheet on the ground surface. It is explained that the method has advantages for the following situations: (a) a higher air/water permeability layer at ground surface and (b) combining vacuum pressure with embankment load. A case history of consolidating a reclaimed clayey deposit by combining CPVD with vacuum pressure is analyzed and discussed. The site was in an under-consolidated state before starting the project. It is shown that the method is effective, and the method proposed by Chai et al. [Ground deformation induced by vacuum consolidation. Journal of Geotechnical and Geoenvironmental Engineering, ASCE 131(12), 1552–1561] for calculating the vacuum-pressure-induced ground deformation is useful for the design of the vacuum consolidation project. The back-calculation shows that for this under-consolidated deposit, vacuum pressure caused plane strain type isotropic deformation near the ground surface. 相似文献
122.
Kuwatsuka H. Mikawa T. Miura S. Yasuoka N. Tanahashi T. Wada O. 《Photonics Technology Letters, IEEE》1990,2(1):54-55
An AlxGa1-xSb avalanche photodiode (APD) with an Al composition of 0.05 has been fabricated and tested. The measured gain-bandwidth (GB) product of the highly doped diode is 90 GHz. Such a large GB product has never been previously achieved by any APD materials sensitive in the long-wavelength region. This suggests the advantage of the AlxGa1-xSb material system for very high-speed operation 相似文献
123.
Now that environmental awareness is enhanced on a global basis, great hopes are placed on the expanded use of hydrogen stations and fuel-cell vehicles (FCVs) that economize hydrogen energy. Hydrogen stations must be safe and secure because they store large quantities of hydrogen under higher pressure than the hydrogen actually consumed by FCVs. Thus, multiple safety measures are taken to ensure that hydrogen does not leak from the stations. Furthermore, in the unlikely event of leakage, the damage needs to be kept on an allowable level. For this reason, it is necessary to understand the behavior of hydrogen gas leaking from the stations. 相似文献
124.
125.
126.
127.
Fotini-Niovi Pavlidou Marina Ruggieri Mario Gerla Ryu Miura 《Wireless Personal Communications》2004,28(2):161-162
Wireless Personal Communications - 相似文献
128.
Kazuo Kato Osamu Miura 《IEEJ Transactions on Electrical and Electronic Engineering》2014,9(3):288-293
The spatial frequency contained in visual objects is known to affect human psychophysiology. In our previous study, we showed that event‐related potentials are affected by spatial frequency during a simple calculation task. In that study, however, we did not investigate the contribution of oscillatory neural activities. The purpose of the present study is to characterize the changes in oscillatory neural activity associated with cognitive processes, and to investigate how these signals are affected by the spatial frequency of a visual stimulus during simple calculation tasks. We investigate these issues by analyzing our previously collected electroencephalography (EEG) dataset using the same visual stimulus, tasks, subjects, and EEG recordings. In that study, four types of vertically striped visual stimuli were used. The visual stimuli contained embedded numbers (from 0 to 9) that possessed the following frequency (f) characteristics: white noise, 1/f, 1/f2, and 1/f3. The subjects were instructed to perform two tasks: ‘add numbers’ (addition task) and ‘do not add numbers’ (reference task). EEG data were recorded, and event‐related synchronization (ERS) and desynchronization (ERD) for each visual stimulus were analyzed on the basis of the intertrial variances of wavelet coefficients for theta, alpha, low‐beta, and gamma band activity. Eight healthy men (21–23 years) were recruited to participate in the study. Our results suggest the presence of a frequency discrimination function in the theta band activity in the fronto‐central area at the latency of 198 ms during the addition task. The alpha‐band ERD during completion of the reference task also showed a spatial frequency dependency. This phenomenon was observed in the left temporal‐parietal area at a latency of 376 ms, and is thought to be related to the perceptual filter. We conclude that the observed changes in oscillatory neural activity associated with cognitive processes are affected by spatial frequency. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. 相似文献
129.
Ken Takahashi Yasushi Minagawa Shigeki Yamada Tsunehiro Unno 《Solar Energy Materials & Solar Cells》2001,66(1-4)
Improvement of efficiency of Al0.36Ga0.64As solar cells is advanced in two aspects of minority-carrier lifetime: reduction of majority-carrier concentration in the emitter and base layers, and reduction of deep levels in the back-surface-field (BSF) layer. A pp−n−n structure is proposed to optimize the use of the effect of reduced majority-carrier concentration, and its effectiveness verified in a preparatory experiment on Al0.3Ga0.7As solar cells. A very poor photoluminescence (PL) decay time (below 0.3 ns) of a BSF layer heavily doped with Si becomes 14-fold longer when Se is applied to the dopant instead of Si, resulting in an improvement of the external quantum efficiency near the absorption edge. These two aspects of this study lead to the realization of 16.6% efficiency under 1-sun, AM 1.5 global conditions with an Al0.36Ga0.64As solar cell. 相似文献
130.
The spatial distribution of microorganisms and their in situ activities in anaerobic granules were investigated by fluorescence in situ hybridization (FISH), beta imaging and microsensors. FISH results revealed a layered structure of microorganisms in the granule, where Chloroflexi was present in the outermost layer, Smithella spp. and Syntrophobacter spp. were found in a depth of ca. 100 μm, and Archaea was restricted to the inner layer (below ca. 300 μm from the surface). Substrate uptake patterns elucidated by beta imaging demonstrated that glucose uptake was highest at 50 μm depth, whereas propionate uptake had a peak at 200 μm depth. In addition, microsensor measurements revealed that acid was produced mainly at 100 μm depth and H(2) production was detected at a depth from 100 to 200 μm. H(2) consumption and corresponding CH(4) production were found below 200 μm from the surface. Direct comparison of these results implied sequential degradation of complex organic compounds in anaerobic granules; Chloroflexi contributed to fermentation of organic compounds and acid production in the outermost layer, volatile fatty acids were oxidized and H(2) was produced mainly by Smithella spp. and Syntrophobacter spp. at a depth from 100 to 200 μm, and Archaea produced CH(4) below ca. 300 μm from the surface. 相似文献