全文获取类型
收费全文 | 78250篇 |
免费 | 2826篇 |
国内免费 | 226篇 |
专业分类
电工技术 | 749篇 |
综合类 | 668篇 |
化学工业 | 12335篇 |
金属工艺 | 1240篇 |
机械仪表 | 1491篇 |
建筑科学 | 1911篇 |
矿业工程 | 460篇 |
能源动力 | 1461篇 |
轻工业 | 8313篇 |
水利工程 | 922篇 |
石油天然气 | 209篇 |
武器工业 | 6篇 |
无线电 | 3268篇 |
一般工业技术 | 8401篇 |
冶金工业 | 29344篇 |
原子能技术 | 404篇 |
自动化技术 | 10120篇 |
出版年
2024年 | 123篇 |
2023年 | 455篇 |
2022年 | 836篇 |
2021年 | 1094篇 |
2020年 | 717篇 |
2019年 | 896篇 |
2018年 | 1585篇 |
2017年 | 1758篇 |
2016年 | 2204篇 |
2015年 | 1729篇 |
2014年 | 1688篇 |
2013年 | 2851篇 |
2012年 | 3985篇 |
2011年 | 4547篇 |
2010年 | 2366篇 |
2009年 | 2433篇 |
2008年 | 2119篇 |
2007年 | 1978篇 |
2006年 | 1605篇 |
2005年 | 4163篇 |
2004年 | 3369篇 |
2003年 | 2759篇 |
2002年 | 1531篇 |
2001年 | 1224篇 |
2000年 | 764篇 |
1999年 | 1181篇 |
1998年 | 8757篇 |
1997年 | 5449篇 |
1996年 | 3674篇 |
1995年 | 2087篇 |
1994年 | 1607篇 |
1993年 | 1696篇 |
1992年 | 421篇 |
1991年 | 482篇 |
1990年 | 454篇 |
1989年 | 458篇 |
1988年 | 443篇 |
1987年 | 357篇 |
1986年 | 320篇 |
1985年 | 327篇 |
1984年 | 165篇 |
1983年 | 162篇 |
1982年 | 235篇 |
1981年 | 284篇 |
1980年 | 302篇 |
1979年 | 117篇 |
1978年 | 152篇 |
1977年 | 803篇 |
1976年 | 1771篇 |
1975年 | 141篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
A comprehensive study of hazelnut oil composition with comparisons to other vegetable oils,particularly olive oil. 总被引:4,自引:0,他引:4
Benitez-Sánchez Pedro Luis León-Camacho Manuel Aparicio Ramón 《European Food Research and Technology》2003,218(1):13-19
Crude and refined hazelnut oils from different countries were characterised by major and minor compounds. Fatty acids, triacylglycerides, waxes, sterols, methyl-sterols, terpenic and aliphatic alcohols, tocopherols, tocotrienols and hydrocarbons were identified and quantified by gas chromatography and high-performance liquid chromatography. The levels of these chemical compounds in hazelnut oils together with the equivalent carbon numbers and triacylglyceride carbon numbers, were compared with the results of analyses of samples of other vegetable oils. The statistical procedure of cluster analysis was used to characterise hazelnut oils versus other edible oils. 相似文献
82.
Sébastien Ambellouis Fran?ois Cabestaing Jack-Gérard Postaire 《IEEE transactions on image processing》2006,15(6):1601-1609
Energy-based methods for motion estimation in image sequences process the input data either in the spatiotemporal or in the frequency domain. In both cases, the algorithms already described in the literature often require a huge number of elementary operations. In this paper, we describe a class of velocity selective filters which yield an accurate detection of the edges moving in the sequence. We first present a filtering scheme based on a convolution operation computed on a finite size neighborhood and describe its properties in the spatiotemporal and frequency domains. Then, we show that filters with similar properties can be implemented recursively, i.e., as convolutions computed on infinite-size neighborhoods. As an example, we finally show the filters' responses in the case of two superimposed translational motions. 相似文献
83.
84.
Presents an obituary and information about the life and accomplishments of Josef Maria Bro?ek. Born August 14, 1913, in the ancient town of Melnik, in central Bohemia, today the Czech Republic, Josef spent his childhood in Poland (Warsaw, 1913- 1915) and in Siberia (1915-1920). His education in Czechoslovakia culminated with a thesis on "Memory, Its Measurement and Structure" and a PhD awarded in June 1937. In the history of psychology, his lifetime project bore the title "Historiography of Psychology Around the World," and it covered about 20 geographical areas. Extensive attention was devoted to institutional and organizational developments as journals, academic settings, archives, museums, research groups, conferences, and institutes. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
85.
86.
An Imhoff tank was reconstructed into a 250 m3 UASB reactor in order to treat a malting plant wastewater. The UASB was inoculated with sludge from an anaerobic lagoon used for slaughterhouse wastewater treatment. After two months of operation the reactor achieved full load with an HRT of 17 h, a COD removal higher than 80% and a biogas production of 300 m3/day (77% average methane content), with an organic loading rate of 3.6 kgCOD/m3.d (0.24 kgCOD/kgVSS.d). A yield coefficient of 0.09 gVSS/gCODrem was found from a mass balance. The fat present in the inoculated sludge (48 mg/gSSV) did not affect the start up performance. Sludge from the inoculum with high content of fat (270 mg/gSSV), was separated by flotation in the first week of operation. The COD removal efficiency was scarcely influenced by the reactor operation temperature (17-25 degrees C). 相似文献
87.
J. Gutirrez J. M. Barandiarn Z. Kaczkowski 《Materials Science and Engineering: A》2004,370(1-2):392-395
The change of magnetoelastic properties after thermal treatments has been investigated for two groups of metallic glasses. (Fe79Co21)75+xSi15−1.4xB10+0.4x (x (at.%)=0, 2, 4, 6, 8, 10) has been studied both in the as-prepared state and after thermal annealing in an applied magnetic field, to achieve a particular domain structure, at temperatures well below the crystallization temperatures. Changes in the ΔE effect, magnetomechanical coupling (k) and internal friction coefficient (Q−1) are reported, reaching values of about 60% of the saturation value ES. Fe64Ni10Nb3Cu1Si13B9 alloys annealed in vacuum for 1 h in the temperature range 350–550 °C showed maximum values of the ΔE effect and k of 61% and 0.85, respectively, accompanied by a minimum value of Q of around 2 for the sample annealed at 460 °C. These variations are related to the progress of nanocrystalization. The properties achieved are among the best reported for magnetomechanical applications. 相似文献
88.
89.
Three different vanadium-modified Pd/Al2O3 catalysts were prepared and tested as catalysts for the deep oxidation of methane. Vanadium was added to the palladium catalyst by incipient wetness of palladium catalyst in order to modify its properties and improve its thermal stability and thioresistance. The behaviour of vanadium-modified catalysts depends on the concentration of this compound, being 0.5 wt.% the optimum amount. However, when strong catalyst poisons are present in the gas (SO2), these modified catalysts do not show a better performance than unmodified catalyst. Bimetallic catalysts were tested with and without further reduction, being observed that reduced bimetallic catalysts perform worse than the non-reduced ones. 相似文献
90.