全文获取类型
收费全文 | 614篇 |
免费 | 32篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 4篇 |
化学工业 | 112篇 |
金属工艺 | 17篇 |
机械仪表 | 15篇 |
建筑科学 | 58篇 |
矿业工程 | 2篇 |
能源动力 | 15篇 |
轻工业 | 78篇 |
水利工程 | 3篇 |
石油天然气 | 3篇 |
无线电 | 55篇 |
一般工业技术 | 91篇 |
冶金工业 | 60篇 |
原子能技术 | 4篇 |
自动化技术 | 133篇 |
出版年
2023年 | 2篇 |
2022年 | 3篇 |
2021年 | 9篇 |
2020年 | 12篇 |
2019年 | 10篇 |
2018年 | 20篇 |
2017年 | 14篇 |
2016年 | 16篇 |
2015年 | 17篇 |
2014年 | 20篇 |
2013年 | 53篇 |
2012年 | 41篇 |
2011年 | 50篇 |
2010年 | 46篇 |
2009年 | 34篇 |
2008年 | 33篇 |
2007年 | 41篇 |
2006年 | 30篇 |
2005年 | 25篇 |
2004年 | 26篇 |
2003年 | 20篇 |
2002年 | 16篇 |
2001年 | 12篇 |
2000年 | 9篇 |
1999年 | 11篇 |
1998年 | 11篇 |
1997年 | 8篇 |
1996年 | 7篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 7篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1985年 | 5篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1974年 | 3篇 |
1968年 | 3篇 |
1966年 | 1篇 |
1965年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有650条查询结果,搜索用时 958 毫秒
51.
Birgit J.M. Hausmann Mughees Khan Yinan Zhang Tom M. Babinec Katie Martinick Murray McCutcheon Phil R. Hemmer Marko Lončar 《Diamond and Related Materials》2010,19(5-6):621-629
We present a design and a top-down fabrication method for realizing diamond nanowires in both bulk single crystal and polycrystalline diamond. Numerical modeling was used to study coupling between a Nitrogen Vacancy (NV) color center and optical modes of a nanowire, and to find an optimal range of nanowire diameters that allows for large collection efficiency of emitted photons. Inductively coupled plasma (ICP) reactive ion etching (RIE) with oxygen is used to fabricate the nanowires. Drop-casted nanoparticles (including Au, SiO2 and Al2O3) as well as electron beam lithography defined spin-on glass and evaporated Au have been used as an etch mask. We found Al2O3 nanoparticles to be the most etch resistant. At the same time FOx e-beam resist (spin-on glass) proved to be a suitable etch mask for fabrication of ordered arrays of diamond nanowires. We were able to obtain nanowires with near-vertical sidewalls in both polycrystalline and single crystal diamond. The heights and diameters of the polycrystalline nanowires presented in this paper are ≈ 1 μm and 120–340 nm, respectively, having a 200 nm/min etch rate. In the case of single crystal diamond (types Ib and IIa) nanowires the height and diameter for different diamonds and masks shown in this paper were 1–2.4 μm and 120–490 nm with etch rates between 190 and 240 nm/min. 相似文献
52.
Experiments examined the effect of relationships between a response and an outcome on human judgments of causal effectiveness. In Experiment 1, the time between outcomes obtained on a variable ratio (VR) schedule became the intervals for a yoked variable interval (VI) schedule. Response rates were higher on the VR than on the VI schedule. In Experiment 2, the number of responses required per outcome on a VR schedule were matched to that on a master VI 20-s schedule. Both ratings of causal effectiveness and response rates were higher in the VR schedule. In Experiment 3, tandem VI fixed-ratio (FR) schedules produced higher rates and judgments than equivalent conjunctive VI FR schedule. In Experiment 4, a VI schedule with a reinforcement requirement for a short interresponse time (IRT) produced higher rates and judgments than a simple VI schedule. These results corroborate the view that schedules are a determinant of both response rates and causal judgments. Few current theories of causal judgment predict this pattern of results. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
53.
Hot-wire chemical vapor deposition (HWCVD) has been employed as an economically scalable method for the deposition of crystalline molybdenum oxide nanoparticles at high density. Under optimal synthesis conditions, only crystalline nanostructures with a smallest dimension of ~ 3-50 nm are observed with extensive transmission electron microscopy analyses. The incorporation of crystalline molybdenum oxide nanoparticles into battery electrodes has led to profound advancements in state-of-the-art negative electrodes (anodes) in lithium-ion batteries. The nanoparticle materials exhibit a high rate capability as anticipated for the reduced solid-state Li-ion diffusion length. 相似文献
54.
55.
Chakra Wijesundera Claudio Ceccato Peter Fagan Zhiping Shen Wayne Burton Phil Salisbury 《Journal of the American Oil Chemists' Society》2008,85(8):693-699
Canola-quality Indian mustard (Brassica juncea) is being developed as a complimentary oilseed crop to canola (Brassica napus) for cultivation in hot and low-rainfall areas, where canola does not perform well. In Australia, several B. juncea breeding lines have been developed for commercial cultivation and for eventual processing as canola oil. However, there still
are significant species-based differences in the fatty acid composition with B. juncea containing lower levels of linoleic acid and higher levels of oleic and linolenic acids compared with B. napus. This has raised concern about possible oxidative stability differences between the oils. Oils (unrefined) extracted from
different breeding lines of each species were subjected to accelerated autoxidation, and development of oxidative rancidity
was assessed by four separate techniques: depletion of polyunsaturated fatty acids, depletion of tocopherol, development of
primary oxidation products, and development of secondary oxidation products (propanal and hexanal). All the tests showed that
the newly developed B. juncea oils are more stable to autoxidation than conventional canola (B. napus) oil, despite containing marginally higher linolenic levels. Oxidative stability does not appear to be a barrier to using
oils from these emerging lines of B. juncea for partial or full replacement of conventional canola oil. 相似文献
56.
57.
White Jennifer L.; Moffitt Terrie E.; Silva Phil A. 《Canadian Metallurgical Quarterly》1989,57(6):719
The purpose of the study was to test the replicability of a protective effect of high IQ against criminality. Support has been found in prior studies for the hypotheses that Ss at high risk would have an elevated risk of serious criminal involvement, that seriously criminal Ss would have a lower mean IQ score than noncriminal Ss, and that Ss at high risk who had not become involved in serious criminal behavior would have the highest IQs. This report tests these hypotheses in a prospective design. Subjects were 1,037 members of a longitudinal investigation of a New Zealand birth cohort. IQs were examined for male and female Ss who were divided into 4 groups formed on the basis of risk status at age 5 years and delinquency outcome at ages 13 and 15. Analyses were conducted with and without mild delinquents excluded from the nondelinquent groups. We found that male and female delinquents showed significantly lower IQ scores than nondelinquents. By varying S selection procedures, we also found that a very high IQ may help boys, even those at risk, to stay free of delinquency altogether. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
58.
Recent improvements in SPH modeling of hypervelocity impact 总被引:4,自引:0,他引:4
Larry D. Libersky Phil W. Randles Ted C. Carney David L. Dickinson 《International Journal of Impact Engineering》1997,20(6-10):525-532
Four improvements to Smoothed Particle Hydrodynamics which enhance its ability to simulate hypervelocity impact are discussed and applied to the impact fracture of a steel cube on an aluminum plate at 2.2 km/s. 相似文献
59.
60.
Gorrie Catherine A.; Waite Phil M. E.; Rogers Lesley J. 《Canadian Metallurgical Quarterly》2008,122(6):1343
[Correction Notice: An erratum for this article was reported in Vol 123(2) of Behavioral Neuroscience (see record 2009-04037-027). In this article, there were errors in figure 4 on p.1347 (missing labels along the x-axis) and in figure 5 on p. 1348 (distortion in the reproduction of the panels). The corrected figures are included.] Cortical asymmetries are well established in humans for language and motor regions and correlate with handedness. Here the authors investigate structural differences in the hemispheres of left- and right-handed common marmosets using surface photography and histology. The hand preferences of 11 marmosets were assessed over their adult life span using a simple reaching task. A significant correlation was found between the length of the right lateral sulcus/brain weight and the % right-hand preference (r = .86, p = .001). Cortical thickness on the superior bank of the right lateral sulcus posteriorly was also positively correlated with % right-hand preference (r = .69, p = .025). Comparison of this site with previously published functional maps of the marmoset cortex show this area corresponds to SII, a region involved in tactile processing and somatosensory discriminations. It is suggested that the correlation between SII thickness and right-hand preference would be consistent with the fact that right-handed marmosets are more proactive than left-handers in exploring novel objects by touch. Enlargement of a cortical area involved tactile discriminations could be a precursor to the evolution of right-handedness as a population bias. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献