全文获取类型
收费全文 | 867篇 |
免费 | 35篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 5篇 |
综合类 | 2篇 |
化学工业 | 131篇 |
金属工艺 | 33篇 |
机械仪表 | 34篇 |
建筑科学 | 33篇 |
矿业工程 | 3篇 |
能源动力 | 22篇 |
轻工业 | 73篇 |
水利工程 | 7篇 |
石油天然气 | 7篇 |
无线电 | 62篇 |
一般工业技术 | 135篇 |
冶金工业 | 267篇 |
原子能技术 | 26篇 |
自动化技术 | 67篇 |
出版年
2022年 | 9篇 |
2021年 | 7篇 |
2020年 | 9篇 |
2019年 | 10篇 |
2018年 | 17篇 |
2017年 | 19篇 |
2016年 | 12篇 |
2015年 | 15篇 |
2014年 | 21篇 |
2013年 | 59篇 |
2012年 | 26篇 |
2011年 | 31篇 |
2010年 | 21篇 |
2009年 | 27篇 |
2008年 | 35篇 |
2007年 | 27篇 |
2006年 | 32篇 |
2005年 | 21篇 |
2004年 | 23篇 |
2003年 | 20篇 |
2002年 | 20篇 |
2001年 | 16篇 |
2000年 | 17篇 |
1999年 | 16篇 |
1998年 | 35篇 |
1997年 | 21篇 |
1996年 | 17篇 |
1995年 | 15篇 |
1992年 | 7篇 |
1990年 | 7篇 |
1989年 | 14篇 |
1988年 | 10篇 |
1987年 | 13篇 |
1986年 | 11篇 |
1985年 | 12篇 |
1984年 | 15篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1980年 | 12篇 |
1979年 | 12篇 |
1977年 | 12篇 |
1976年 | 11篇 |
1975年 | 9篇 |
1974年 | 14篇 |
1973年 | 10篇 |
1972年 | 10篇 |
1971年 | 8篇 |
1964年 | 8篇 |
1956年 | 6篇 |
1955年 | 7篇 |
排序方式: 共有907条查询结果,搜索用时 62 毫秒
1.
Patrick R. Taylor Ph.D. Milton Manrique Ph.D. 《JOM Journal of the Minerals, Metals and Materials Society》1996,48(6):43-45
Due to several inherent advantages, plasma processing technology may become a very useful tool in the production of new materials. An increasing research effort based on experimental as well as theoretical investigations has been invested in this area for the synthesis of advanced materials. In describing the thermal-plasma processing technique, this article employs examples from research at the Plasma Processing Laboratory at the University of Idaho. 相似文献
2.
Under carefully chosen conditions, solidification theory may be applied to solid-state transformations, and this has been
done here for composition-invariant diffusion transformations. The predictions of the modeling are compared with isovelocity
experiments in two iron systems, Fe-7.29 wt pct Cr and Fe-3.1 wt pct Ni. The ferrite to austenite phase transformation is
used to demonstrate that stabilization of a planar transformation front at absolute stability is the natural lower velocity
limit for a composition-invariant (massive) transformation. The results of the model, which includes nonequilibrium effects,
clearly show that steady-state plane-front growth leading to composition invariance can be obtained at various temperatures
depending on the growth velocity. In the lower velocity range, at the limit of absolute stability (of the order of 10 μm/s in the systems studied), the transformation interface moves under conditions of local equilibrium, and the temperature
corresponds to the lower solvus temperature. At higher velocity (of the order of the interface diffusion rate, which in these
systems is of the order of cm/s), the transformation is predicted to proceed at temperatures close to T
0. At even higher rates, atom attachment kinetic undercooling will decrease the transformation temperature with respect to
T
0. In some cases, this temperature might even drop below the lower solvus.
This article is based on a presentation made at the symposium entitled “The Mechanisms of the Massive Transformation,” a part
of the Fall 2000 TMS Meeting held October 16–19, 2000, in St. Louis, Missouri, under the auspices of the ASM Phase Transformations
Committee. 相似文献
3.
A Confocal Scanning Laser Microscope equipped with a gold image furnace was used to directly observe the precipitation of MnS during solidification of high sulphur steels under isothermal conditions in the temperature region 1440 to 1480°C on the free surface of the steel melt. For the case of Al‐killed steels, below 1480°C MnS particles were found to precipitate with Fe forming simultaneously around them. This MnS containing structure continued to grow rapidly (264 μm/s) as a surface film. The film gradually changed, as the level of S in the melt decreased, into a eutectic structure (with lamella spacing of 2 μm) as predicted by thermodynamics. In Si‐ killed steels there was significantly lower tendency to form MnS both in terms of time until precipitation occurred and growth rate. 相似文献
4.
Martin E. Valdez H. Shibata Alan W. Cramb 《Metallurgical and Materials Transactions B》2006,37(6):959-965
The objective of this study is to determine the conditions under which the inclusions present in liquid steel can act as heterogeneous
nucleants for solidification. In order to study the factors that define the undercooling of a given metal/oxide couple, the
undercooling of a pure iron sessile droplet in contact with Al2O3, ZrO2, and MgO substrates was measured under controlled oxygen partial pressures by observing droplet recalescence. The results
showed that the undercooling of iron, in contact with a particular substrate, did not have a unique value, but was significantly
affected by the oxygen content on the gas phase. For oxygen partial pressures between 10−21 and 10−19, the undercooling of iron on ZrO2 substrates was stable and around 290 °C. In the same range of oxygen partial pressure, the undercooling of iron on MgO substrates
remained below 100 °C due to the low stability of this oxide. At lower oxygen contents, substrate decomposition might be the
cause for the observed drop in the undercooling of iron on ZrO2 substrates to below 100 °C. The undercooling also decreased for increasing oxygen content as verified when the gas was changed
from gettered Ar/Ar-H2 to CO/CO2 mixtures. The variation in undercooling was related to the wetting of the substrate by the liquid metal, where the deep undercooling
observed in the ZrO2 experiments occurred when the highest contact angle between the liquid metal and the substrate was achieved. 相似文献
5.
6.
7.
KristieValdez OlivierMeilhon 《电子设计应用》2004,(4):69-72
本文用一种创新的方法提出了四种功率因数校正(PFC)电路设计。两种临界导通模式(CRM)升压.一种连续导通模式(CCM)升压和一种CCM单段回扫,并且推荐了基于功率要求、效率、失真程度、电路板空间和成本限制的解决方案。 相似文献
8.
9.
S Dawson D Bennett SD Carter M Bennett J Meanger PC Turner MJ Carter I Milton RM Gaskell 《Canadian Metallurgical Quarterly》1994,56(2):133-143
Twelve specific pathogen-free cats were infected either by intra-articular inoculation or by contact exposure to one of two strains of feline calicivirus (FCV), either F65, a field strain originating from an outbreak of lameness in a group of cats, or a vaccine strain. Following either route of exposure, both strains induced signs typical of FCV infection including oral and nasal ulceration, conjunctivitis and ocular discharge. These signs were of equal severity for both virus strains, but overall, following either route of infection, F65 induced more severe disease than the vaccine strain, with marked pyrexia, lethargy and lameness. Vaccine virus only induced a relatively mild lameness following intra-articular inoculation. Gross pathological and histopathological lesions were seen in some of the joints, but again changes were more severe in the F65-exposed cats. Virus was isolated from both normal and affected joints from both groups of F65-exposed cats, and from a joint from each cat inoculated intra-articularly with vaccine virus. Mild transient lameness was also seen in one of two control cats inoculated intra-articularly, but no pathological changes were seen or virus isolated from joints. A cDNA probe used in RNA dot blot hybridisation experiments was found to be specific and more sensitive than virus isolation in detecting FCV in selected tissues. This may be useful in future studies on the pathogenesis of FCV disease and in studies on viral persistence in FCV carriers. 相似文献
10.
I Woolley H Valdez C Walker A Landay D Zdunek G Hess MM Lederman 《Canadian Metallurgical Quarterly》1998,19(4):408-412
OBJECTIVE: To determine whether postmenopausal oestrogen replacement therapy affects carotid artery pulsatility index. DESIGN: A prospective double-blind placebo controlled trial. SETTING: University associated teaching hospital. PARTICIPANTS: Twenty-eight postmenopausal women who were more than 12 months postmenopausal and who had not taken exogenous oestrogen. INTERVENTIONS: Independent randomisation to receive oral oestradiol (2 mg daily) or placebo for 20 to 24 weeks. MAIN OUTCOME MEASURES: Internal carotid artery Doppler pulsatility index, measured within one centimetre of the carotid bifurcation. RESULTS: Replicate data were available from 27 women. The mean pulsatility index decreased by -0.11 in 15 women receiving oestradiol, compared with a mean rise of 0.05 in the 12 women who received placebo (P = 0.006, 95% CI for treatment difference 0.06-0.31). CONCLUSIONS: Oestrogen replacement decreases postmenopausal carotid artery pulsatility index, probably reflecting decreased peripheral vascular resistance. This is a further mechanism whereby hormone replacement therapy may impart cardiovascular protection. 相似文献