全文获取类型
收费全文 | 761257篇 |
免费 | 8731篇 |
国内免费 | 1857篇 |
专业分类
电工技术 | 13257篇 |
综合类 | 2869篇 |
化学工业 | 117187篇 |
金属工艺 | 32902篇 |
机械仪表 | 24683篇 |
建筑科学 | 17259篇 |
矿业工程 | 5874篇 |
能源动力 | 18537篇 |
轻工业 | 57141篇 |
水利工程 | 9692篇 |
石油天然气 | 18240篇 |
武器工业 | 52篇 |
无线电 | 81637篇 |
一般工业技术 | 155400篇 |
冶金工业 | 120175篇 |
原子能技术 | 17555篇 |
自动化技术 | 79385篇 |
出版年
2021年 | 6515篇 |
2019年 | 6202篇 |
2018年 | 24155篇 |
2017年 | 23284篇 |
2016年 | 20802篇 |
2015年 | 7708篇 |
2014年 | 12271篇 |
2013年 | 31297篇 |
2012年 | 21507篇 |
2011年 | 33600篇 |
2010年 | 27534篇 |
2009年 | 27509篇 |
2008年 | 28968篇 |
2007年 | 29447篇 |
2006年 | 19534篇 |
2005年 | 18724篇 |
2004年 | 17751篇 |
2003年 | 17419篇 |
2002年 | 16246篇 |
2001年 | 15539篇 |
2000年 | 14958篇 |
1999年 | 14659篇 |
1998年 | 34848篇 |
1997年 | 25002篇 |
1996年 | 19465篇 |
1995年 | 14823篇 |
1994年 | 13331篇 |
1993年 | 13163篇 |
1992年 | 10154篇 |
1991年 | 9871篇 |
1990年 | 9633篇 |
1989年 | 9363篇 |
1988年 | 9117篇 |
1987年 | 8146篇 |
1986年 | 7997篇 |
1985年 | 9067篇 |
1984年 | 8217篇 |
1983年 | 7903篇 |
1982年 | 7119篇 |
1981年 | 7165篇 |
1980年 | 6959篇 |
1979年 | 7081篇 |
1978年 | 6958篇 |
1977年 | 7646篇 |
1976年 | 9421篇 |
1975年 | 6251篇 |
1974年 | 5987篇 |
1973年 | 6121篇 |
1972年 | 5308篇 |
1971年 | 4950篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
The main objective of this present study was to evaluate, for a standard mortar, the drying effect on its mechanical behaviour. Numerous uniaxial compression tests were thus performed with loading-unloading cycles. They were carried out on different samples previously preserved under various conditions of conservation: preserved from desiccation, air drying and rapid drying at 60°C. The obtained results showed significant influences of these conditions on the material behaviour (increase in strength, decrease in Young's modulus and Poisson's ratio) and the necessity of taking into account the coupling effects between mechanical—poromechanical behaviours and drying. 相似文献
83.
A.L. Pan H.G. ZhengZ.P. Yang F.X. Liu Z.J. Ding Y.T. Qian 《Materials Research Bulletin》2003,38(5):789-796
Small Ag particles or clusters dispersed mesoporous SiO2 composite films were prepared by a new method: First the matrix SiO2 films were prepared by sol-gel process combined with the dip-coating technique, then they were soaked in AgNO3 solutions followed by irradiation of γ-ray at room temperature and in ambient pressure. The structures of these films were examined by X-ray diffraction (XRD), high-resolution transmission electron microscope (HRTEM), and optical absorption spectroscopy. It has been shown that the Ag particles grown within the porous SiO2 films are very small, and they are isolated and dispersed from each other with very narrow size distributions. With increasing the soaking concentration and an additional annealing, an opposite peakshift effect of the surface plasmon resonance (SPR) was observed in the optical absorption measurements. 相似文献
84.
Trajectory control of incompletely restrained parallel-wire-suspended mechanism based on inverse dynamics 总被引:5,自引:0,他引:5
This paper discusses parallel wire mechanisms where an end-effector of the mechanism is suspended by multiple wires. The mechanisms enable not only three-dimensional (3-D) positioning but also 3-D orienting of the end-effector, unlike typical wire suspension-type mechanisms such as overhead crane. To discuss the parallel-wire-suspended mechanisms generally, two forms of basic dynamic equations are presented. Then the parallel wire mechanisms are classified into two types based on the basic equations. Dynamical properties of the two types of wire-suspended positioning mechanism are discussed. In this paper, one of the wire-suspended mechanism, incompletely restrained-type parallel wire mechanism, is mainly discussed on its inverse dynamics problem and its trajectory control problem. The inverse dynamics problem for the incompletely restrained-type mechanism plays an important role on its control problem, because the mechanism has low stiffness based on incomplete constraints on the suspended object which is governed by its dynamics. The paper proposes an antisway control method for the suspended object. In the method, the inverse dynamics calculation is used for nonlinear dynamics compensation to control the suspended object of the incompletely restrained parallel wire mechanism. 相似文献
85.
A method and instruments based on it are proposed for the contact measurement of surface temperature when carrying out industrial experiments and when monitoring technological parameters. 相似文献
86.
A new topology for a photonic signal processor, which overcomes the basic recursive frequency response problem that limits the passband range, is presented. The structure is based on a new multiple-wavelength offset-cavity structure that is cascaded with a series of unbalanced delay line structures. This not only can synthesize a very narrow notch response with good shape factor but also permits a multifold extension of the free spectral range (FSR) and passband width. Results on the interference mitigation filter demonstrate a stopband of 1% of center frequency and a fourfold increase in the FSR and passband width, while also having a very small shape factor, in excellent agreement with predictions. 相似文献
87.
88.
D. Vignolles D. Smirnov G. Rikken B. Raquet H. Rakoto C. Proust M. Nardone J. Léotin F. Lecouturier M. Goiran O. Drachenko J. M. Broto L. Brossard A. Audouard 《Journal of Low Temperature Physics》2003,133(1-2):97-120
An overview over past and present activities and future developments at the Toulouse pulsed magnetic field facility is given, both as far as technical developments of the infrastructure, as well as low temperature physics performed at the LNCMP are concerned. 相似文献
89.
H. Yamamoto N. Heyamoto T. Matsui N. Murayama J. Shibata 《International Journal of Thermophysics》2003,24(5):1385-1394
Polyvinylalcohol (PVA) polymer gel is a temperature sensitive polymeric gel, with a critical transition temperature (with H2O) of 310 K. At higher than 310 K, this temperature sensitive polymer gel shrinks because of discharging water, whereas at lower temperatures, the gel swelled because of absorbing water. The reversibility of the gel's volume change was confirmed by temperature swing. The adsorption behavior of an organic compound onto the PVA polymer gel in water was tested at various temperatures. The amount of adsorbed organic compound increased remarkably at temperatures higher than about 310 K. Then, it was confirmed that the organic compound in PVA polymer gel could be reversibly adsorbed and desorbed by a temperature change between 293 and 323 K. The mechanism of adsorption of the organic compound onto the PVA polymer gel could be explained by hydration and dehydration of polymer gel. 相似文献
90.
The expectation-maximization (EM) algorithm is well established as a computationally efficient method for separable signal parameter estimation. Here, a new geometric derivation and interpretation of the EM algorithm is given that facilitates the understanding of EM convergence properties. Geometric considerations lead to an alternative separable signal parameter estimator based on successive cancellation. The new generalized successive interference cancellation (GSIC) algorithm is then applied to multiuser delay and channel estimation for code-division multiple access (CDMA) radiolocation and communication. The radiolocation application uses a handshaking protocol in which multiple reference nodes transmit acknowledge (ACK) CDMA packets to a master node, which then computes round-trip travel times (RTTs). Simulation results comparing EM and GSIC are presented for the CDMA channel-estimation problem. 相似文献