全文获取类型
收费全文 | 3216篇 |
免费 | 192篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 40篇 |
综合类 | 1篇 |
化学工业 | 834篇 |
金属工艺 | 120篇 |
机械仪表 | 82篇 |
建筑科学 | 76篇 |
矿业工程 | 15篇 |
能源动力 | 128篇 |
轻工业 | 533篇 |
水利工程 | 24篇 |
石油天然气 | 9篇 |
无线电 | 153篇 |
一般工业技术 | 743篇 |
冶金工业 | 54篇 |
原子能技术 | 45篇 |
自动化技术 | 554篇 |
出版年
2024年 | 11篇 |
2023年 | 42篇 |
2022年 | 37篇 |
2021年 | 99篇 |
2020年 | 84篇 |
2019年 | 110篇 |
2018年 | 166篇 |
2017年 | 155篇 |
2016年 | 151篇 |
2015年 | 140篇 |
2014年 | 187篇 |
2013年 | 380篇 |
2012年 | 189篇 |
2011年 | 236篇 |
2010年 | 242篇 |
2009年 | 178篇 |
2008年 | 112篇 |
2007年 | 87篇 |
2006年 | 48篇 |
2005年 | 15篇 |
2004年 | 28篇 |
2003年 | 26篇 |
2002年 | 35篇 |
2001年 | 26篇 |
2000年 | 36篇 |
1999年 | 21篇 |
1998年 | 23篇 |
1997年 | 21篇 |
1996年 | 17篇 |
1995年 | 25篇 |
1994年 | 20篇 |
1993年 | 27篇 |
1992年 | 21篇 |
1991年 | 14篇 |
1990年 | 15篇 |
1989年 | 15篇 |
1988年 | 12篇 |
1985年 | 19篇 |
1984年 | 25篇 |
1983年 | 20篇 |
1982年 | 21篇 |
1981年 | 38篇 |
1980年 | 27篇 |
1979年 | 23篇 |
1978年 | 23篇 |
1977年 | 22篇 |
1976年 | 33篇 |
1975年 | 23篇 |
1974年 | 16篇 |
1973年 | 22篇 |
排序方式: 共有3411条查询结果,搜索用时 15 毫秒
31.
Petra Punčochářová-Pořízková Jiří Fürst Jaromír Horáček Karel Kozel 《Mathematics and computers in simulation》2010
This study deals with a numerical solution of a 2D unsteady flow of a compressible viscous fluid in a channel for low inlet airflow velocity. The unsteadiness of the flow is caused by a prescribed periodic motion of a part of the channel wall with large amplitudes, nearly closing the channel during oscillations. The channel is a simplified model of the glottal space in the human vocal tract and the flow can represent a model of airflow coming from the trachea, through the glottal region with periodically vibrating vocal folds, and to the human vocal tract. 相似文献
32.
33.
34.
Aleksandar Kovačević Branko Milosavljević Zora Konjović Milan Vidaković 《Multimedia Tools and Applications》2010,47(3):525-544
This paper presents a tunable content-based music retrieval (CBMR) system suitable the for retrieval of music audio clips. The audio clips are represented as extracted feature vectors. The CBMR system is expert-tunable by altering the feature space. The feature space is tuned according to the expert-specified similarity criteria expressed in terms of clusters of similar audio clips. The main goal of tuning the feature space is to improve retrieval performance, since some features may have more impact on perceived similarity than others. The tuning process utilizes our genetic algorithm. The R-tree index for efficient retrieval of audio clips is based on the clustering of feature vectors. For each cluster a minimal bounding rectangle (MBR) is formed, thus providing objects for indexing. Inserting new nodes into the R-tree is efficiently performed because of the chosen Quadratic Split algorithm. Our CBMR system implements the point query and the n-nearest neighbors query with the O(logn) time complexity. Different objective functions based on cluster similarity and dissimilarity measures are used for the genetic algorithm. We have found that all of them have similar impact on the retrieval performance in terms of precision and recall. The paper includes experimental results in measuring retrieval performance, reporting significant improvement over the untuned feature space. 相似文献
35.
36.
G. Blaževičius L. Rimkus D. Merkevičūtė J. Atkočiūnas 《Structural and Multidisciplinary Optimization》2017,55(1):25-36
Structural optimization based on the shakedown theory is a powerful and promising technique. However, due to the nonlinearities of physical materials and the number of variable loads in real structures, it is computationally complex and time-consuming. To simplify the occurring non-linear, non-convex optimization problems, the paper suggests reducing the number of yield conditions. The so-called a yield criterion of the mean (integral yield condition) is analysed and explained in detail, which allows taking into account one yield condition for the entire finite element instead of multiple point-wise conditions. This approach shows promising results in numerical application to the optimization of a circular plate, considering a possibility of employing the yield criteria of the mean or pointwise yield conditions in different areas of the plate in particular. The methods applied are based on the assumptions of perfect plasticity and small deformations. 相似文献
37.
Slow and fast diffusion effects in image processing 总被引:3,自引:0,他引:3
A mathematical model for a nonlinear image multiscale analysis is studied. Processing of an image is based on a solution of
the strongly nonlinear parabolic partial differential equation, which can degenerate depending on values of the greylevel
intensity function. The governing PDE is a generalization of the regularized (in the sense of Catté, Lions, Morel and Coll)
Perona-Malik anisotropic diffusion equation. We present numerical techniques for solving the suggested initial-boundary value
problem and also existence and convergence results. Numerical experiments are discussed.
Received: 6 May 1998 / Accepted: 27 July 2000 相似文献
38.
Attempts to carry out the hydroformylation of allyldiethylamine homogeneously catalyzed by rhodium complexes led to unexpected formation of N,N,N,N-tetraethyl-1,4-diaminobutane and 4-(diethylamino)-1-butanole as final products. The role of the catalyst on the product formation and the reaction mechanism are briefly discussed. 相似文献
39.
Using a new design of helium-methane gas-flow detector of conversion electrons for Mössbauer spectroscopy, non-uniform nucleation of the primary -Fe-Co phase on both contact and free surfaces of the Ar(+H2) annealed amorphous Fe75Co9B16 alloy was observed in its early crystallization stage. In this state the amount of crystalline phase on the contact ribbon side surpasses that on the free one by a factor of three, whereas no traces of volume crystallization were observed in the transmission spectra. By applying ion implantation to both ribbon surfaces, a slight reduction of the crystalline phase contribution was found. Magnetic domain structure observations were performed in order to evaluate the influence of surface crystallization on magnetic properties. 相似文献
40.
The paper contains a review of some results concerning probability theory on MV algebras (laws of large numbers, central
limit theorem, martingale convergence theorem). Also some algebraic and methodical aspects are discussed. 相似文献