全文获取类型
收费全文 | 2737篇 |
免费 | 140篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 29篇 |
综合类 | 1篇 |
化学工业 | 675篇 |
金属工艺 | 49篇 |
机械仪表 | 62篇 |
建筑科学 | 97篇 |
矿业工程 | 4篇 |
能源动力 | 113篇 |
轻工业 | 186篇 |
水利工程 | 10篇 |
石油天然气 | 4篇 |
无线电 | 317篇 |
一般工业技术 | 524篇 |
冶金工业 | 174篇 |
原子能技术 | 11篇 |
自动化技术 | 622篇 |
出版年
2024年 | 2篇 |
2023年 | 30篇 |
2022年 | 44篇 |
2021年 | 69篇 |
2020年 | 64篇 |
2019年 | 53篇 |
2018年 | 75篇 |
2017年 | 71篇 |
2016年 | 92篇 |
2015年 | 66篇 |
2014年 | 108篇 |
2013年 | 189篇 |
2012年 | 195篇 |
2011年 | 243篇 |
2010年 | 185篇 |
2009年 | 162篇 |
2008年 | 157篇 |
2007年 | 162篇 |
2006年 | 121篇 |
2005年 | 99篇 |
2004年 | 82篇 |
2003年 | 63篇 |
2002年 | 59篇 |
2001年 | 54篇 |
2000年 | 40篇 |
1999年 | 48篇 |
1998年 | 70篇 |
1997年 | 52篇 |
1996年 | 27篇 |
1995年 | 23篇 |
1994年 | 20篇 |
1993年 | 20篇 |
1992年 | 24篇 |
1991年 | 14篇 |
1990年 | 14篇 |
1989年 | 9篇 |
1988年 | 6篇 |
1987年 | 10篇 |
1986年 | 7篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 6篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1956年 | 1篇 |
排序方式: 共有2878条查询结果,搜索用时 0 毫秒
81.
A comparative study of three ventilation systems supplying air to a typical Canadian indoor ice rink illustrates the power, energy and operating cost savings which can be achieved by using the relatively warm air from the air cooled condensers of the refrigeration system. The direct use of this warm air for ventilation results in a reduction of energy consumption during the winter amounting to 24.2% of the yearly consumption of the heating system. On the other hand, the use of a heat exchanger to heat the ventilation air results in energy consumption reductions throughout the year. Depending on the size of the heat exchanger these gains can be as high as 60.8% of the heating energy consumption by the existing system. Based on actual prices of electricity and the heat exchanger it is established that the cost savings over the life of the equipment are at least three times higher than the cost of the heat exchanger. 相似文献
82.
83.
Olivier Bouquin Martine Lejeune Jean-Pierre Boilot 《Journal of the American Ceramic Society》1991,74(5):1152-1156
The reaction sequences during calcination of oxide mixtures were studied for the PbMg1/3 Nb2/3 O3 ─PbTiO3 (PMN-PT) system. The effect of reactivity and composition of the starting mixtures was investigated. In the present study, a B-site-deficient, cubic pyrochlore phase in the PbO-Nb2 O5 system was formed at 500°C. The perovskite phase of PMN was formed at 7007deg;C through the diffusion of MgO into the pyrochlore phase. The lattice parameter of the pyrochlore phase decreased as this transformation to perovskite progressed. 相似文献
84.
S. Vranckx K.A. Heufer C. Lee H. Olivier L. Schill W.A. Kopp K. Leonhard C.A. Taatjes R.X. Fernandes 《Combustion and Flame》2011,158(8):1444-1455
Despite considerable interest in butanol as a potential biofuel candidate, its ignition behaviour at elevated pressures still remains largely unexplored. The present study investigates the oxidation of n-butanol in air at pressures near 80 bar. Ignition delays were determined experimentally in the temperature range of 795–1200 K between 61 and 92 bar. The time of ignition was determined by recording pressure and CH-emission time histories throughout the course of the experiments. The results display the first evidence of the influence of negative temperature coefficient (NTC) behaviour which was not observed in earlier ignition studies. The high-pressure measurements show that NTC behaviour is enhanced as pressures are increased. The experimental results were modelled using an improved chemical kinetic mechanism which includes a simplified sub-mechanism for butyl-peroxy formation and isomerisation reactions currently incompletely accounted for in n-butanol kinetic models. The detailed mechanism validated with the high-pressure ignition results for realistic engine in-cylinder conditions can have significant impact on future advanced low-temperature combustion engines. 相似文献
85.
Benoit Charlas Olivier Gillia Pierre Doremus Didier Imbault 《International Journal of Hydrogen Energy》2012
The storage of hydrogen in hydride materials is currently much researched as a mean of energy storage. This reversible storage is achieved by successive hydriding and dehydriding reactions. During these reactions, the material undergoes structural transformations which result in swelling of the hydride powder grains due to the absorption of hydrogen. This phenomenon can generate major mechanical stresses on the cell containing the hydride. The present experimental study examines the cyclic swelling of a granular bed consisting of hydride Ti–Cr–V + Zr–Ni. Two superimposed phenomena are identified: a cyclic rearrangement causing a reduction and then an increase in porosity coupled with gradual densification of the stack. 相似文献
86.
Minh Trung DangGuillaume Wantz Habiba BejboujiMathieu Urien Olivier J. DautelLaurence Vignau Lionel Hirsch 《Solar Energy Materials & Solar Cells》2011,95(12):3408-3418
Polymeric photovoltaic (PV) solar cells have been fabricated using six solvents: chloroform (CHCl3), toluene (T), chlorobenzene (CB), orthodichlorobenzene (ODCB), 1,2,3,4-tetrahydronaphthalene (THN) and 1,2,4-trichlorobenzene (TCB). The active layers were composed of poly(3-hexyl)thiophene (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM). Special care has been taken to keep all experimental parameters constant (thickness of the active layers, donor/acceptor weight ratio, area of active surface and electrodes) in order to avoid artefacts and truly study the effect of solvents. Studies using atomic force microscopy (AFM) and optical absorption (UV-vis) showed the relationship between the photovoltaic performance and the evaporation rate of solvents. The use of solvents with high boiling point results in a higher degree of organization in the structure of P3HT. A direct comparison with devices processed with thermal treatment has also been performed. As often reported thermal annealing increases photo-conversion efficiency of devices created from common solvents, due to better separation of phase between the two materials of the blend. In the case of solvents with high boiling point such as THN and TCB, neither phase separation nor modification of P3HT crystallization induced by thermal annealing has been observed. However thermal treatment appears to enhance performance, ensuing the evaporation of remaining solvent in the active layers. An overview of the effect of solvent on the electrical properties of films containing pure P3HT and P3HT:PCBM blend reported in the literature has been completed for the discussion. 相似文献
87.
88.
89.
Hassan Al Sabea Lucie Norel Olivier Galangau Thierry Roisnel Olivier Maury Franois Riob Stphane Rigaut 《Advanced functional materials》2020,30(30)
This work describes a class of complex combining three dithienylethene units and a lanthanide ion used as an optical system displaying a double encryption method: i) a colorful code, drawn and erased under UV and visible irradiations respectively, due to coloration and discoloration of the photochromic entities, and ii) a concomitant gradual disappearance and progressive restoration of the associated lanthanide ion luminescence triggered with the same stimuli. The innovation of the system stems from the emission color tunability, i.e., with either a lanthanide ion emitting only in the visible range (Eu3+) or with another lanthanide ion emitting only in the near infrared (NIR) range (Yb3+), therefore observable, or not, to the naked eye. This system is the very first one to achieve efficient repeatable modulation of pure NIR luminescence on photochemical command. Furthermore, it is proven to be highly efficient when embedded in a PDMS polymer opening real opportunities for practical applications as anti‐counterfeiting. 相似文献
90.
Iron-catalyzed oxidation of arsenic(III) by oxygen and by hydrogen peroxide: pH-dependent formation of oxidants in the Fenton reaction 总被引:1,自引:0,他引:1
The oxidation kinetics of As(III) with natural and technical oxidants is still notwell understood, despite its importance in understanding the behavior of arsenic in the environment and in arsenic removal procedures. We have studied the oxidation of 6.6 microM As(II) by dissolved oxygen and hydrogen peroxide in the presence of Fe(II,III) at pH 3.5-7.5, on a time scale of hours. As(III) was not measurably oxidized by O2, 20-100 microM H2O2, dissolved Fe(III), or iron(III) (hydr)-oxides as single oxidants, respectively. In contrast, As(III) was partially or completely oxidized in parallel to the oxidation of 20-90 microM Fe(II) by oxygen and by 20 microM H2O2 in aerated solutions. Addition of 2-propanol as an *OH-radical scavenger quenched the As(III) oxidation at low pH but had little effect at neutral pH. High bicarbonate concentrations (100 mM) lead to increased oxidation of As-(III). On the basis of these results, a reaction scheme is proposed in which H2O2 and Fe(II) form *OH radicals at low pH but a different oxidant, possibly an Fe(IV) species, at higher pH. With bicarbonate present, carbonate radicals might also be produced. The oxidant formed at neutral pH oxidizes As(III) and Fe(II) but does not react competitively with 2-propanol. Kinetic modeling of all data simultaneously explains the results quantitatively and provides estimates for reaction rate constants. The observation that As(III) is oxidized in parallel to the oxidation of Fe(II) by O2 and by H2O2 and that the As(III) oxidation is not inhibited by *OH-radical scavengers at neutral pH is significant for the understanding of arsenic redox reactions in the environment and in arsenic removal processes as well as for the understanding of Fenton reactions in general. 相似文献