全文获取类型
收费全文 | 3132篇 |
免费 | 353篇 |
国内免费 | 309篇 |
专业分类
电工技术 | 82篇 |
综合类 | 260篇 |
化学工业 | 85篇 |
金属工艺 | 52篇 |
机械仪表 | 201篇 |
建筑科学 | 125篇 |
矿业工程 | 18篇 |
能源动力 | 32篇 |
轻工业 | 43篇 |
水利工程 | 18篇 |
石油天然气 | 46篇 |
武器工业 | 11篇 |
无线电 | 283篇 |
一般工业技术 | 152篇 |
冶金工业 | 15篇 |
原子能技术 | 20篇 |
自动化技术 | 2351篇 |
出版年
2024年 | 5篇 |
2023年 | 28篇 |
2022年 | 48篇 |
2021年 | 67篇 |
2020年 | 54篇 |
2019年 | 52篇 |
2018年 | 49篇 |
2017年 | 56篇 |
2016年 | 82篇 |
2015年 | 95篇 |
2014年 | 200篇 |
2013年 | 165篇 |
2012年 | 218篇 |
2011年 | 271篇 |
2010年 | 205篇 |
2009年 | 222篇 |
2008年 | 244篇 |
2007年 | 233篇 |
2006年 | 220篇 |
2005年 | 190篇 |
2004年 | 181篇 |
2003年 | 194篇 |
2002年 | 158篇 |
2001年 | 109篇 |
2000年 | 64篇 |
1999年 | 55篇 |
1998年 | 53篇 |
1997年 | 46篇 |
1996年 | 18篇 |
1995年 | 37篇 |
1994年 | 19篇 |
1993年 | 17篇 |
1992年 | 16篇 |
1991年 | 19篇 |
1990年 | 8篇 |
1989年 | 13篇 |
1988年 | 6篇 |
1987年 | 8篇 |
1986年 | 5篇 |
1985年 | 14篇 |
1984年 | 9篇 |
1983年 | 5篇 |
1981年 | 7篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1973年 | 2篇 |
排序方式: 共有3794条查询结果,搜索用时 15 毫秒
1.
Fatigue crack propagation of multiple coplanar cracks with the coupled extended finite element/fast marching method 总被引:1,自引:0,他引:1
A numerical technique for modeling fatigue crack propagation of multiple coplanar cracks is presented. The proposed method couples the extended finite element method (X-FEM) [Int. J. Numer. Meth. Engng. 48 (11) (2000) 1549] to the fast marching method (FMM) [Level Set Methods & Fast Marching Methods: Evolving Interfaces in Computational Geometry, Fluid Mechanics, Computer Vision, and Materials Science, Cambridge University Press, Cambridge, UK, 1999]. The entire crack geometry, including one or more cracks, is represented by a single signed distance (level set) function. Merging of distinct cracks is handled naturally by the FMM with no collision detection or mesh reconstruction required. The FMM in conjunction with the Paris crack growth law is used to advance the crack front. In the X-FEM, a discontinuous function and the two-dimensional asymptotic crack-tip displacement fields are added to the finite element approximation to account for the crack using the notion of partition of unity [Comput. Meth. Appl. Mech. Engng. 139 (1996) 289]. This enables the domain to be modeled by a single fixed finite element mesh with no explicit meshing of the crack surfaces. In an earlier study [Engng. Fract. Mech. 70 (1) (2003) 29], the methodology, algorithm, and implementation for three-dimensional crack propagation of single cracks was introduced. In this paper, simulations for multiple planar cracks are presented, with crack merging and fatigue growth carried out without any user-intervention or remeshing. 相似文献
2.
基于扩展分形和CFAR特征融合的SAR图像目标识别 总被引:3,自引:0,他引:3
研究了多信息融合技术在SAR图像目标识别中的应用。将扩展分形特征(Extended Fractal)与双参数恒虚警特征(Double Parameter CFAR)形成的多信息进行融合处理。运用Dempster-Shafer证据理论,在决策层对SAR图像中的像素进行识别分类。实验结果表明通过融合对像素分类的准确性明显好于单特征的检测结果,减少了虚警概率,提高了系统的识别能力。 相似文献
3.
The draft Long-Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR) contains Cryptosporidium log-inactivation CT tables (ozone-in-water concentration [residual], “C” times contact time, T). Depending on water temperature, Cryptosporidium CT values that are listed are 15 to 25 times greater than CT values for equivalent Giardia log-inactivation credit. The elevated operating dose required for Cryptosporidium log-inactivation credit has the potential to increase disinfection by-product (DBP) formation (e.g., bromate). Calculating CT value accurately will minimize ozone dose, which will decrease operating cost and lower DBP formation, and at the same time maintain disinfection protection through implementation of scientifically based safety factors. Various methods are available for calculating CT value. The method chosen depends largely on the available information concerning ozone residual characteristics and hydrodynamic features of the ozone contactor, plus local regulatory requirements. Four methods are discussed in this paper. Each method can be used to calculate Giardia, virus, and Cryptosporidium log-inactivation credit. 相似文献
4.
WKB近似下的Fourier衍射成象方法 总被引:1,自引:0,他引:1
对于介质目标微波衍射成象,本文引入了WKB近似来模拟目标内部总场。基于这种近似,我们导出了Fourier衍射公式,并采用了广义滤波逆传播方法由目标空间谱实现目标特性的重建。计算机模拟结果表明采用WKB近似重建目标特性较Born近似有明显改善。 相似文献
5.
6.
Michael V. Antony 《Minds and Machines》1991,1(3):321-341
Fodor and Pylyshyn (1988) have argued that the cognitive architecture is not Connectionist. Their argument takes the following form: (1) the cognitive architecture is Classical; (2) Classicalism and Connectionism are incompatible; (3) therefore the cognitive architecture is not Connectionist. In this essay I argue that Fodor and Pylyshyn's defenses of (1) and (2) are inadequate. Their argument for (1), based on their claim that Classicalism best explains the systematicity of cognitive capacities, is an invalid instance of inference to the best explanation. And their argument for (2) turns out to be question-begging. The upshot is that, while Fodor and Pylyshyn have presented Connectionists with the important empirical challenge of explaining systematicity, they have failed to provide sufficient reason for inferring that the cognitive architecture is Classical and not Connectionist. 相似文献
7.
Despite its energetic interest, the use of microwaves for the thawing or temperage of food products presents a major drawback called thermal runaway. This is mainly due to the important gap between the dielectric properties of water in solid and liquid phases. A monitoring approach of the temperatures inside a foodstuff during microwave defrosting is therefore proposed to, in a first step, detect the critical phenomena of thermal runaway, and, in further work, to control it. An observer allowing to estimate the internal temperatures from the temperature of the surface has been developed. An Extended Kalman Filter, because of its simplicity of design, has been chosen, but this choice is not exclusive. The heat transfer with phase change and microwave effects is represented by a nonlinear distributed parameters system, and the observer is based on a standard finite volume scheme. The approach is experimentally carried out and validated during the defrosting of a block of tylose. 相似文献
8.
Abstract There are still many institutions of higher education in the UK, both universities and polytechnics, that have not taken on board the application of information technology to foreign language learning. Apart from considerations of cost, there is also the problem of time—deciding how best to use the limited time at one's disposal for exploring computer applications to foreign language learning. Both problems may be compounded by the mistaken belief that effective use of this 'new' technology necessarily involves learning one or more programming languages. This paper endeavours to show that recent advances in both software and hardware have produced computing tools of particular interest to translation and the translator, and that, since translation is a reality for large numbers of undergraduates in the UK, such tools represent an obvious starting point for the introduction of IT into the undergraduate curriculum. 相似文献
9.
论述了在程序设计过程中 ,使用树形控件、SQL 语句、临时表等多种手段 ,达到多个关联数据库的数据由一个可视化树形结构控件显示的方法和技巧 相似文献
10.
本文介绍一种能够解决有语言障碍的人汉语发音问题的计算机软件系统,此系统采用电报和五笔画编码方案作为汉字输入方法,自建了一套汉字录入和检索体系,并利用Microsoft公司的Speech SDK4.0和Concatenated Text-to-Speech Engine建立了专用的语音库,本系统使得有语言障碍的人可以与其他正常人之间进行正常的交流,从而避免了使用哑语带来的不便。 相似文献