全文获取类型
收费全文 | 2246篇 |
免费 | 3篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 17篇 |
化学工业 | 101篇 |
金属工艺 | 13篇 |
机械仪表 | 18篇 |
建筑科学 | 16篇 |
能源动力 | 13篇 |
轻工业 | 56篇 |
水利工程 | 2篇 |
石油天然气 | 1篇 |
无线电 | 106篇 |
一般工业技术 | 154篇 |
冶金工业 | 1651篇 |
原子能技术 | 5篇 |
自动化技术 | 98篇 |
出版年
2023年 | 7篇 |
2022年 | 9篇 |
2020年 | 7篇 |
2019年 | 8篇 |
2018年 | 13篇 |
2017年 | 11篇 |
2016年 | 15篇 |
2014年 | 14篇 |
2013年 | 26篇 |
2012年 | 14篇 |
2011年 | 34篇 |
2010年 | 21篇 |
2009年 | 23篇 |
2008年 | 22篇 |
2007年 | 23篇 |
2006年 | 30篇 |
2005年 | 24篇 |
2004年 | 22篇 |
2003年 | 22篇 |
2002年 | 26篇 |
2001年 | 30篇 |
2000年 | 13篇 |
1999年 | 55篇 |
1998年 | 468篇 |
1997年 | 275篇 |
1996年 | 181篇 |
1995年 | 108篇 |
1994年 | 102篇 |
1993年 | 90篇 |
1992年 | 24篇 |
1991年 | 27篇 |
1990年 | 31篇 |
1989年 | 35篇 |
1988年 | 34篇 |
1987年 | 55篇 |
1986年 | 34篇 |
1985年 | 20篇 |
1984年 | 5篇 |
1983年 | 10篇 |
1982年 | 26篇 |
1981年 | 13篇 |
1980年 | 24篇 |
1978年 | 10篇 |
1977年 | 46篇 |
1976年 | 96篇 |
1975年 | 9篇 |
1973年 | 7篇 |
1971年 | 6篇 |
1965年 | 4篇 |
1960年 | 4篇 |
排序方式: 共有2251条查询结果,搜索用时 0 毫秒
1.
The authors report the case of a woman admitted to hospital for minor trauma of the left hip and who presented major ST segment elevation on the second day suggesting an acute anterior wall myocardial infarction at the same time as a cerebrovascular accident. Complementary investigations and follow-up excluded the diagnosis of myocardial infarction with normalisation of the ECG on the 5th day. ECG changes during cerebrovascular accidents may be very variable ranging from extrasystoles to ST elevation mimicking myocardial infarction. They carry a poor prognosis with an increased risk of sudden death necessitating continuous ECG monitoring until the ECG reverts to normal. The cardiac involvement is not ischaemic but due to disease of the insular cortex of the brain which induces myocytolysis (centered around the intra-cardiac nerve endings) due to the sudden liberation of catecholamines. These lesions may be treated by propranolol or phentolamine. 相似文献
2.
3.
4.
Belonging to the Annonaceae family, marolo (Annona coriaceae) is a native species of the Brazilian "cerrado" región (Minas Gerais, Goiás and Distrito Federal) and can be found in South American tropical zones. Its fruits are highly consumed by local people and commercialized in markets or street stalls. There is, however, a tendency for the extinction of marolo due to deforestation and the large scale plantation of monocultures instead of native plants. The literature still offers no data on the chemical composition of the proximate composition and vitamin C, A and tannin contents were carried out on the yellow marolo pulp as well as the determination of the physico-chemical characteristics of the seed oil. Five batches of fruit from the Alfenas region--south of Minas Gerais State--were analysed in this work and their average composition were: humidity 77%, total sugar 15%, reducing sugar 11%, crude protein 1%, lipids 3%, fiber 5% and fixed mineral residue 1%. The contents of vitamin C and A were 8.2 mg/100g and 117.5 RE/100g, respectively, and the tannin content was 245 mg/100g. The results showed high fiber and lipid contents of marolo pulp in comparison with many other tropical fruit pulps. The vitamin C contents were equivalent to those found in avocado, pineapple and watermelon, while the vitamin A contents were equivalent to papaya, peach, guava and several other tropical fruits. Marolo seed contains 45% of oil on a dry basis. Its composition and physico-chemical characteristics showed the possibility of producing a good quality oil, with great potential for the fine oil market. However the presence of alkaloids in the oil needs to be further studied. Their elimination could be done by refining or extraction in a continuous press. The results exalt the high quality of marolo pulp, showing that the preservation of native species should be stimulated. 相似文献
5.
The flow of a model non-polar liquid through small carbon nanotubes is studied using non-equilibrium molecular dynamics simulation.
We explain how a membrane of small-diameter nanotubes can transport this liquid faster than a membrane consisting of larger-diameter
nanotubes. This effect is shown to be back-pressure dependent, and the reasons for this are explored. The flow through the
very smallest nanotubes is shown to depend strongly on the depth of the potential inside, suggesting atomic separation can
be based on carbon interaction strength as well as physical size. Finally, we demonstrate how increasing the back-pressure
can counter-intuitively result in lower exit velocities from a nanotube. Such studies are crucial for optimisation of nanotube
membranes. 相似文献
6.
A beam of charged vortex rings is used to study the vorticity present downstream from an array of 2-m-diameter orifices through which a steady flow of superfluid 4He is driven at known velocity and pressure head p. From the measured attentuation of the beam at low p, we infer a density of vortex line less than predicted by the Feynman critical velocity model. Possible explanations are considered. We find evidence that an interconnected tangle of vortices is formed above a certain value of p, which is in reasonable agreement with theory, at least for one orifice plate. Charge transfer and transient attenuation measurements indicate that this tangle decays in part into small vortex rings. These results are compared with an earlier experiment of Gamota.Research supported in part by the National Science Foundation under grant DMR 72-02971. 相似文献
7.
8.
van der Schalk Job; Fischer Agneta; Doosje Bertjan; Wigboldus Dani?l; Hawk Skyler; Rotteveel Mark; Hess Ursula 《Canadian Metallurgical Quarterly》2011,11(2):286
In the present research, we test the assumption that emotional mimicry and contagion are moderated by group membership. We report two studies using facial electromyography (EMG; Study 1), Facial Action Coding System (FACS; Study 2), and self-reported emotions (Study 2) as dependent measures. As predicted, both studies show that ingroup anger and fear displays were mimicked to a greater extent than outgroup displays of these emotions. The self-report data in Study 2 further showed specific divergent reactions to outgroup anger and fear displays. Outgroup anger evoked fear, and outgroup fear evoked aversion. Interestingly, mimicry increased liking for ingroup models but not for outgroup models. The findings are discussed in terms of the social functions of emotions in group contexts. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
9.
G. Xiong R. Shao S. J. Peppernick A. G. Joly K. M. Beck W. P. Hess M. Cai J. Duchene J. Y. Wang W. D. Wei 《JOM Journal of the Minerals, Metals and Materials Society》2010,62(12):90-93
Photoelectron emission microscopy (PEEM) is a versatile technique that can image a variety of materials including metals, semiconductors and even insulators. Under favorable conditions the most advanced aberration corrected instruments have a spatial resolution approaching 2 nm. Although PEEM cannot compete with transmission or scanning electron microscopies for ultimate resolution, the technique is much gentler and has the unique advantage of imaging structure as well as electronic and magnetic states on the nanoscale. Since the image contrast is derived from spatial variations in electron photoemission intensity, PEEM is ideal for interrogating both static and dynamic electronic properties of complex nanostructured materials. Here, we review the key principles and contrast mechanisms of PEEM and briefly summarize materials applications of PEEM. 相似文献
10.
M.S. Burroughs K. Hess N. Holonyak W.D. Laidig G.E. Stillman 《Solid-state electronics》1982,25(2):161-167
The influence of alloy clustering in ternary AxB1?xC III–V compounds on the impact ionization rate is discussed. A simple alloy clustering model is introduced and impact ionization rates are calculated assuming that the electron wavevector is much larger than the reciprocal cluster size. We show that the impact ionization rates of electrons and holes exhibit the same asymmetry as the band edge discontinuity of the AB-AC heterojunction. Numerical values are obtained for AlxGa1?xAs as a function of alloy composition x. 相似文献