全文获取类型
收费全文 | 28564篇 |
免费 | 2764篇 |
国内免费 | 1451篇 |
专业分类
电工技术 | 2037篇 |
技术理论 | 5篇 |
综合类 | 2049篇 |
化学工业 | 4583篇 |
金属工艺 | 1605篇 |
机械仪表 | 1867篇 |
建筑科学 | 2257篇 |
矿业工程 | 732篇 |
能源动力 | 766篇 |
轻工业 | 1855篇 |
水利工程 | 523篇 |
石油天然气 | 1462篇 |
武器工业 | 268篇 |
无线电 | 3362篇 |
一般工业技术 | 3440篇 |
冶金工业 | 1481篇 |
原子能技术 | 346篇 |
自动化技术 | 4141篇 |
出版年
2024年 | 141篇 |
2023年 | 522篇 |
2022年 | 914篇 |
2021年 | 1336篇 |
2020年 | 1003篇 |
2019年 | 777篇 |
2018年 | 841篇 |
2017年 | 913篇 |
2016年 | 869篇 |
2015年 | 1180篇 |
2014年 | 1459篇 |
2013年 | 1592篇 |
2012年 | 1742篇 |
2011年 | 1888篇 |
2010年 | 1641篇 |
2009年 | 1540篇 |
2008年 | 1676篇 |
2007年 | 1587篇 |
2006年 | 1517篇 |
2005年 | 1379篇 |
2004年 | 1053篇 |
2003年 | 874篇 |
2002年 | 957篇 |
2001年 | 801篇 |
2000年 | 682篇 |
1999年 | 625篇 |
1998年 | 535篇 |
1997年 | 489篇 |
1996年 | 453篇 |
1995年 | 367篇 |
1994年 | 327篇 |
1993年 | 239篇 |
1992年 | 185篇 |
1991年 | 121篇 |
1990年 | 107篇 |
1989年 | 107篇 |
1988年 | 67篇 |
1987年 | 50篇 |
1986年 | 39篇 |
1985年 | 22篇 |
1984年 | 24篇 |
1983年 | 18篇 |
1982年 | 25篇 |
1981年 | 7篇 |
1980年 | 22篇 |
1979年 | 7篇 |
1977年 | 13篇 |
1976年 | 9篇 |
1975年 | 6篇 |
1974年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
In this paper, any two of the three anticorrosion agents, that is emulsifier (OP-10), soluble glass (Na2O·nSiO2) and glycerin (C3H8O3), were treated simultaneously on the surface of amorphous (a-) MgNi+5% Ml2Mg17 (Ml denotes the lanthanum-rich mish metal) electrode and the electrolyte. Effect of the synergistic anticorrosion treatment on charging/discharging cycle stability of the electrode was investigated. Contrasted with single treatment method, the cycling stability of the electrodes was further improved. The desirable synergistic anticorrosion method was that the electrode was treated by the soluble glass, and that OP-10 was added into the electrolyte. The cyclic voltammogram (CV) results of the electrode show clearly that the anticorrosion agent can change the electrochemical activity and mechanism of the electrode. The concentration of the anticorrosion agent in the electrolyte treated by the synergistic anticorrosion method was also investigated. The appropriate concentration of the anticorrosion agents in the electrolyte is 0.143%. 相似文献
52.
Shaofeng Wang Jianwei Xu Yuejin Tong Lin Wang Chaobin He 《Polymer International》2005,54(9):1268-1274
A novel cholesterol‐imprinted polymer (CMIP‐H) was prepared by a hybrid method of covalent imprinting and non‐covalent imprinting. This approach involves the copolymerization of a template‐containing monomer, cholesteryl 2‐hydroxyethyl methacrylate carbonate, and a cross‐linker, followed by hydrolysis to afford a flexible guest‐binding site accompanied with the easy and efficient removal of a ‘sacrificial spacer’. The effect of solvent on the binding capacity of CMIP‐H towards cholesterol was studied, indicating that a good binding capacity towards cholesterol could be achieved in a less‐polar solvent. The binding experiments of CMIP‐H towards a series of structural analogues of cholesterol, including cholesterol acetate, progesterone and stigmasterol, were carried out in hexane. The results showed that CMIP‐H almost did not bind cholesterol acetate at all because the hydrogen‐bonding site is blocked. It exhibited a similar binding towards both cholesterol and stigmasterol, but much higher binding towards progesterone. Copyright © 2005 Society of Chemical Industry 相似文献
53.
54.
Dongchang Sun Liyong Tong 《International journal for numerical methods in engineering》2004,60(11):1911-1932
A novel finite element model is presented for static and dynamic analysis of composite plates integrated with a laminated piezoelectric layer, a host laminated composite plate and an adhesive layer between them. A new adhesive element is developed which includes both peel and shear effects in the adhesive layer based on first‐order shear deformation plate theory. The thin adhesive layer between the piezoelectric layer and the host plate is modelled by assuming that it carries constant shear and peel strains throughout its thickness. In addition, a weighted static shape control scheme for finding the optimal voltage distribution for static shape control is given. By selecting different weighting matrices, a variety of items such as displacements, slopes, curvatures, strains and even generalized forces, can be included in finding the optimal actuating voltage for static shape control. The present model is validated by comparing with those results available in the literature. The numerical results show that the weighted linear least method can give a satisfactory voltage distribution to best match the desired shape. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
55.
56.
57.
J. Chen J. B. Xu K. Xue J. An N. Ke W. Cao H. B. Xia J. Shi D. C. Tian 《Microelectronics Reliability》2005,45(1):137-142
Transition-metal compound TiC60 thin films were grown by co-deposition from two separated sources of fullerene C60 powder and titanium. Study of structural properties of the films, by Raman spectroscopy, atomic force microscopy, and scanning tunneling spectroscopy reveals that the films have a deformed C60 structure with certain amount of sp3 bonds and a rough surface with a large number of nanoclusters. z–V tunnelling spectroscopic measurements suggest that several charge transport mechanisms are involved in as the tip penetrates into the thin film. Conventional field electron emission (FEE) measurements show a high emission current density of 10 mA/cm2 and a low turn-on field less than 8 V/μm, with the field enhancement factors being 659 and 1947 for low-field region and high-field region, respectively. By exploiting STM tunneling spectroscopy, local FEE on nanometer scale has also been characterized in comparison with the conventional FEE. The respective field enhancement factors are estimated to be 99–355 for a gap varying from 36 to 6 nm. The enhanced FEE of TiC60 thin films can be ascribed to structural variation of C60 in the films and the electrical conducting paths formed by titanium nanocrystallites embedded in C60 matrix. 相似文献
58.
Recently, in our laboratory a closed form expression for the correlation function of the hard-sphere dimer fluid obtained
from Wertheims multidensity Ornstein-Zernike integral equation theory with Percus-Yevick approximation was presented by Kim
et al. [2001]. However, it is difficult to apply its expression to perturbation theory and vapor-liquid equilibria calculations,
since it is of very complex form. In this work, we present a simplified expression for the first shell of the radial distribution
function (RDF) of the hard-sphere dimer fluid using a series expansion of the analytical expression. The expansion is carried
out in terms of both the packing fraction and the radial distance. Expressions are also obtained for the coordination number
and its first and second derivatives as functions of radial distance and packing fraction. These expressions, which are useful
in perturbation theory, are simpler to use than those obtained from the starting equation, while giving good agreement with
the original expression results. Then we present an simplified equation of state for the square-well dimer fluid of variable
well width (λ) based on Barker-Henderson perturbation theory using its expression for the radial distribution function of
the hard-sphere dimer fluid, and test its expression with NVT and Gibbs ensemble Monte Carlo simulation data [Kim et al.,
2001]. 相似文献
59.
Nguyen An Tien I. Ya. Mittova O. V. Almjasheva S. A. Kirillova V. V. Gusarov 《Glass Physics and Chemistry》2008,34(6):756-761
Nanocrystalline LaFeO3 is prepared by the dehydration of coprecipitated lanthanum and iron(III) hydroxides. It is shown that the behavior of the samples during heating and the size distribution of LaFeO3 nanocrystals can be considerably different depending on the scheme used for coprecipitation of lanthanum and iron hydroxides; independently of the method employed for coprecipitation of the initial compounds, sintering of the samples at 950°C leads to the formation of lanthanum orthoferrite crystals up to 100 nm in size. 相似文献
60.
Hui Chen D.T.K. Tong 《Photonics Technology Letters, IEEE》2005,17(4):801-803
Symmetric interference in two-dimensional multimode silicon waveguides is experimentally investigated. For a 100/spl times/100 /spl mu/m/sup 2/ cross section, 2700-/spl mu/m-long waveguide fabricated on silicon-on-insulator substrate, an 8/spl times/8 matrix of replicated images with high contrast ratio is demonstrated for 1530-1570 nm wavelength range. Symmetric interference results in reduced device length, and the actual device length is consistent with the theoretical expectation. The device also exhibits stable imaging in terms of good loss uniformity, and low wavelength and polarization dependencies among the replicated images. 相似文献