全文获取类型
收费全文 | 1011篇 |
免费 | 24篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 14篇 |
化学工业 | 235篇 |
金属工艺 | 27篇 |
机械仪表 | 12篇 |
建筑科学 | 11篇 |
矿业工程 | 2篇 |
能源动力 | 78篇 |
轻工业 | 58篇 |
水利工程 | 4篇 |
石油天然气 | 4篇 |
无线电 | 94篇 |
一般工业技术 | 251篇 |
冶金工业 | 136篇 |
原子能技术 | 15篇 |
自动化技术 | 96篇 |
出版年
2024年 | 4篇 |
2023年 | 7篇 |
2022年 | 6篇 |
2021年 | 30篇 |
2020年 | 24篇 |
2019年 | 41篇 |
2018年 | 40篇 |
2017年 | 32篇 |
2016年 | 29篇 |
2015年 | 15篇 |
2014年 | 29篇 |
2013年 | 113篇 |
2012年 | 32篇 |
2011年 | 53篇 |
2010年 | 38篇 |
2009年 | 47篇 |
2008年 | 32篇 |
2007年 | 48篇 |
2006年 | 38篇 |
2005年 | 26篇 |
2004年 | 22篇 |
2003年 | 24篇 |
2002年 | 19篇 |
2001年 | 16篇 |
2000年 | 13篇 |
1999年 | 21篇 |
1998年 | 38篇 |
1997年 | 30篇 |
1996年 | 17篇 |
1995年 | 16篇 |
1994年 | 17篇 |
1993年 | 16篇 |
1992年 | 13篇 |
1991年 | 12篇 |
1990年 | 8篇 |
1989年 | 3篇 |
1988年 | 8篇 |
1987年 | 6篇 |
1986年 | 2篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1983年 | 5篇 |
1982年 | 1篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 10篇 |
1978年 | 13篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 4篇 |
排序方式: 共有1037条查询结果,搜索用时 0 毫秒
41.
In this contribution, we report the analysis and interpretation of the mechanical property measurements for a new class of SiAlON ceramic. The hardness and indentation fracture toughness were measured on the hot pressed Ba-doped S-SiAlON ceramic using Vickers indentation at varying loads (up to 300 N). An important observation was that all the investigated S-SiAlON exhibited the characteristic rising R-curve behavior with a maximum toughness of up to 10–12 MPa m1/2 for ceramics, hot pressed both at 1700 and 1750 °C. Crack deflection by large elongated S-phase grains and crack bridging by β-Si3N4 needles has been found to be the major toughening mechanisms for the observed high toughness. Theoretical estimates, using a toughening model based on crack bridging and deflection by platelet shaped ‘S’-phase grains and β-Si3N4 needles, reveal the interfacial friction of around 200 MPa. Careful analysis of the indentation data reveals the average (apparent) hardness modestly increases with indent load in all S-SiAlON samples, with more significant effect for S-SiAlON, hot pressed at 1600 °C. This effect has been analyzed in the light of the established model of ‘indentation-induced cracking’ phenomenon. Our experimental results suggest that a modest combination of average hardness of 15 GPa and indentation toughness of around 12 MPa m1/2 could be achieved in Ba-S-SiAlON ceramic and further improvement requires microstructural tailoring. 相似文献
42.
Chemically deposited zinc oxide thin film gas sensor 总被引:4,自引:0,他引:4
Zinc oxide (ZnO) thin films were prepared by a low cost chemical deposition technique using sodium zincate bath. Structural characterizations by X-ray diffraction technique (XRD) and scanning electron microscopy (SEM) indicate the formation of ZnO films, containing 0.05–0.50 m size crystallites, with preferred c-axis orientation. The electrical conductance of the ZnO films became stable and reproducible in the 300–450 K temperature range after repeated thermal cyclings in air. Palladium sensitised ZnO films were exposed to toxic and combustible gases e.g., hydrogen (H2), liquid petroleum gas (LPG), methane (CH4) and hydrogen sulphide (H2S) at a minimum operating temperature of 150 °C; which was well below the normal operating temperature range of 200–400 °C, typically reported in literature for ceramic gas sensors. The response of the ZnO thin film sensors at 150 °C, was found to be significant, even for parts per million level concentrations of CH4 (50 ppm) and H2S (15 ppm). 相似文献
43.
S. Ghosh A. Guha K. M. Krishna A. K. Mukhopadhyay H. S. Maiti 《Materials and Manufacturing Processes》2006,21(7):662-668
During the last decade, worldwide attention of researchers has focused on nano-ceramic composites with superior mechanical behavior and improved reliability for structural applications. Here we report the development of a multi-layer composite (MLC) of tape cast nano zirconia with high failure energy. The MLC samples were fabricated by thermocompression of green tapes prepared from 3 mole % yttria stabilized zirconia (3-YSZ) powder with a primary crystallite size of 27 nm. Depending on the number of layers, the MLC samples exhibited failure energy (238.97 KJm-3) more than two times higher than that of the single tape (≈107 KJm-3) with a reasonably high bi-axial flexural strength (≈630 MPa), high hardness (≈ 13 GPa at 49 N), and indentation fracture toughness nearly four times as high as that of the single tape. In addition, these MLC materials showed the presence of a R-curve behavior. 相似文献
44.
45.
In the present work, choosing a varying output weighting matrix, an optimal regulator having state feedback terms with variable gain and feed-forward terms dependent on input as well as output disturbances has been proposed. 相似文献
46.
47.
48.
49.
S. Mukhopadhyay D. K. Bhattacharyya 《European Journal of Lipid Science and Technology》1983,85(8):309-311
A colorimetric method based on the colour reaction between allyl thiourea and potassium ferricyanide solution in dilute acetic acid has been developed for the determination of allyl isothiocyanate content in mustard and rapeseed oils. The method measures the optical density of the colour complex at 600 nm and it works in the range 2.5 to 7.5 μg of allyl isothiocyanate per ml of the colour solution. Mustard and rape oil samples analysed contain 0.40 to 0.6% of allyl isothiocyanate, with standard deviation of 0.002 to 0.016. The method takes around 3 hours and permits a number of sample analysis at a time. 相似文献
50.
Mamata Mukhopadhyay 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1979,29(10):634-641
Selectivity and distribution coefficients are two important parameters required for selection of solvents and process conditions for efficient separation of aromatics from a multi-component hydrocarbon feedstock. A simple thermodynamic method is presented in this paper for the prediction of these parameters from a knowledge of physical properties of the pure components, such as vapour pressure, molar volume and critical temperature. The activity coefficients were calculated using the solubility parameter theory extended to multi-component mixtures of polar and nonpolar components. The compositions of the extract and raffinate phases were computed using an iterative search technique for simultaneous solution of the thermodynamic criterion equations and the material balance equations for each component. For testing the validity of this method, the predicted values of the selectivity at infinite dilution and the equilibrium phase compositions were compared with the corresponding experimental values from the literature and the agreement is found to be highly satisfactory. 相似文献