全文获取类型
收费全文 | 1503篇 |
免费 | 56篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 24篇 |
综合类 | 6篇 |
化学工业 | 322篇 |
金属工艺 | 70篇 |
机械仪表 | 16篇 |
建筑科学 | 58篇 |
矿业工程 | 9篇 |
能源动力 | 53篇 |
轻工业 | 100篇 |
水利工程 | 14篇 |
石油天然气 | 5篇 |
无线电 | 202篇 |
一般工业技术 | 273篇 |
冶金工业 | 201篇 |
原子能技术 | 7篇 |
自动化技术 | 200篇 |
出版年
2022年 | 30篇 |
2021年 | 22篇 |
2020年 | 21篇 |
2019年 | 24篇 |
2018年 | 25篇 |
2017年 | 28篇 |
2016年 | 29篇 |
2015年 | 18篇 |
2014年 | 53篇 |
2013年 | 107篇 |
2012年 | 72篇 |
2011年 | 81篇 |
2010年 | 44篇 |
2009年 | 42篇 |
2008年 | 77篇 |
2007年 | 66篇 |
2006年 | 59篇 |
2005年 | 62篇 |
2004年 | 38篇 |
2003年 | 47篇 |
2002年 | 37篇 |
2001年 | 25篇 |
2000年 | 27篇 |
1999年 | 18篇 |
1998年 | 31篇 |
1997年 | 19篇 |
1996年 | 32篇 |
1995年 | 13篇 |
1994年 | 19篇 |
1993年 | 19篇 |
1992年 | 13篇 |
1991年 | 20篇 |
1990年 | 25篇 |
1989年 | 20篇 |
1988年 | 12篇 |
1987年 | 11篇 |
1986年 | 17篇 |
1985年 | 14篇 |
1984年 | 11篇 |
1982年 | 12篇 |
1980年 | 18篇 |
1979年 | 9篇 |
1976年 | 10篇 |
1975年 | 10篇 |
1973年 | 19篇 |
1972年 | 17篇 |
1971年 | 11篇 |
1969年 | 9篇 |
1961年 | 10篇 |
1959年 | 9篇 |
排序方式: 共有1560条查询结果,搜索用时 0 毫秒
1.
We propose a standardization procedure that provides a convenient, quantitative and reproducible laboratory-based method for measuring the state of polarization (SOP) fluctuations produced by polarization varying devices. This method is based on the SOP distributions generated by commercial polarization scramblers. We show that these devices generate distributions of the maximum change of the SOP (in a given sample time) that follow Rayleigh statistics, which scale linearly with scrambling frequency and the sample time. We use this procedure to measure the SOP fluctuations in a short length of coiled fiber subject to mechanical perturbations. 相似文献
2.
3.
Equal Strain Consolidation by Vertical Drains 总被引:1,自引:0,他引:1
Chin Jian Leo 《Canadian Metallurgical Quarterly》2004,130(3):316-327
This paper shows the development of a series of closed-form solutions of equal strain consolidation in the presence of a vertical drain with smear and well resistance. Using an approach that considers the effects of both the radial and vertical drainage in a fully coupled fashion, solutions are obtained for the excess pore pressure and the degree of consolidation in the compressible soil subjected to a step- or ramp-loading situation. The closed-form solutions in the present paper may be evaluated in an electronic spreadsheet on a standard personal computer. 相似文献
4.
5.
6.
Kevin R. Boyle Martijn Udink Anton de Graauw Leo P. Ligthart 《Antennas and Propagation, IEEE Transactions on》2007,55(2):373-382
A dual-fed, self-diplexing planar inverted F antenna and an associated RF front-end are described. It is shown that co-design of the antenna and front-end can be used to double the operational bandwidth, without significant size or performance penalties. Indeed, the use of two feeds allows the antenna to be self-diplexing, which results in improved overall efficiency 相似文献
7.
Anil Kumar William R. Leo Lawrence Green Gene L. Woodruff 《Journal of Fusion Energy》1989,8(1-2):107-126
The neutron spectra transmitted across a fission-suppressed hybrid blanket and its components, driven by a low intensity 14 MeV Haefely neutron generator, were measured with a 2×2 NE213 detector at LOTUS facility. These experiments have been analyzed with 2D and 3D codes DOT3.5 and MCNP, respectively. The spectral integrals between 15 to 1 MeV show good agreement among the 2D, the 3D, and the NE213 for 15 cm lead, 18 cm beryllium, and 25 cm graphite slabs. However, there are large discrepancies for 6.2 cm stainless steel and 15 cm lithium carbonate slabs. The assemblies involving two or more of these slabs reflect these tendencies. We observe also considerable disagreement over pointwise spectra for a number of assemblies.Work done while on visiting assignment to Institut de Génie Atomique, E.P.F.L. 相似文献
8.
Leo Dorst 《Journal of Mathematical Imaging and Vision》2014,50(3):214-234
We fit k-spheres optimally to n-D point data, in a geometrically total least squares sense. A specific practical instance is the optimal fitting of 2D-circles to a 3D point set. Among the optimal fitting methods for 2D-circles based on 2D (!) point data compared in Al-Sharadqah and Chernov (Electron. J. Stat. 3:886–911, 2009), there is one with an algebraic form that permits its extension to optimally fitting k-spheres in n-D. We embed this ‘Pratt 2D circle fit’ into the framework of conformal geometric algebra (CGA), and doing so naturally enables the generalization. The procedure involves a representation of the points in n-D as vectors in an (n+2)-D space with attractive metric properties. The hypersphere fit then becomes an eigenproblem of a specific symmetric linear operator determined by the data. The eigenvectors of this operator form an orthonormal basis representing perpendicular hyperspheres. The intersection of these are the optimal k-spheres; in CGA the intersection is a straightforward outer product of vectors. The resulting optimal fitting procedure can easily be implemented using a standard linear algebra package; we show this for the 3D case of fitting spheres, circles and point pairs. The fits are optimal (in the sense of achieving the KCR lower bound on the variance). We use the framework to show how the hyperaccurate fit hypersphere of Al-Sharadqah and Chernov (Electron. J. Stat. 3:886–911, 2009) is a minor rescaling of the Pratt fit hypersphere. 相似文献
9.
The surface activity of spent sulphite liquor (SSL) and the separation of surface active components by foam fractionation were studied. The maximum activity (lowest surface tension) of SSL was observed at a high pH. The surface tension was found to be 42 mN/m and 38 mN/m at acidic and basic pH values, respectively, and also a maximum foaminess (Σ) of 7 min was observed at pH 10. Foam fractionation reduced the surfactant concentration by 90% at an optimum pH of 10. The surfactants were concentrated in the collapsed foam as shown by the fact that the critical micelle concentrations of the unfractionated SSL and foam were 70% (v/v) and 10% (v/v), respectively. The removed surfactants were concentrated in 20% of the original liquid volume. 相似文献
10.
Anu Harju 《Journal of chemical ecology》1996,22(4):719-728
The effect of protein and birch bark powder (BBP) content of forage on detoxification capacity of root voles (Microtus oeconomus) was studied. Young voles were fed with eight different diets for two weeks. Individuals on low (3%) protein diets had significantly lighter livers and kidneys than those on moderate (6%) or high (12%) protein diets. Birch bark powder addition did not have significant effect on organ weight. Detoxification was significantly induced, apparently due to secondary compounds in BBP. The activity of ethoxyresorufin-O-dealkylase (EROD) was high when protein content or BBP concentration in forage was high as compared to low protein diets or diets containing no BBP. Glucuronidation, on the other hand, was not induced by BBP. High BBP content caused serious physiological stress to the voles. The only individuals surviving were those capable of sufficiently allocating energy and protein to detoxification. 相似文献