全文获取类型
收费全文 | 26119篇 |
免费 | 2097篇 |
国内免费 | 1337篇 |
专业分类
电工技术 | 1708篇 |
技术理论 | 1篇 |
综合类 | 2945篇 |
化学工业 | 2718篇 |
金属工艺 | 1592篇 |
机械仪表 | 1619篇 |
建筑科学 | 4242篇 |
矿业工程 | 1828篇 |
能源动力 | 780篇 |
轻工业 | 1708篇 |
水利工程 | 1186篇 |
石油天然气 | 1009篇 |
武器工业 | 195篇 |
无线电 | 1401篇 |
一般工业技术 | 1668篇 |
冶金工业 | 1489篇 |
原子能技术 | 201篇 |
自动化技术 | 3263篇 |
出版年
2024年 | 78篇 |
2023年 | 257篇 |
2022年 | 501篇 |
2021年 | 528篇 |
2020年 | 573篇 |
2019年 | 523篇 |
2018年 | 495篇 |
2017年 | 613篇 |
2016年 | 745篇 |
2015年 | 841篇 |
2014年 | 1451篇 |
2013年 | 1294篇 |
2012年 | 1720篇 |
2011年 | 1951篇 |
2010年 | 1544篇 |
2009年 | 1717篇 |
2008年 | 1497篇 |
2007年 | 1911篇 |
2006年 | 1753篇 |
2005年 | 1549篇 |
2004年 | 1312篇 |
2003年 | 1159篇 |
2002年 | 976篇 |
2001年 | 843篇 |
2000年 | 662篇 |
1999年 | 587篇 |
1998年 | 417篇 |
1997年 | 395篇 |
1996年 | 336篇 |
1995年 | 293篇 |
1994年 | 228篇 |
1993年 | 161篇 |
1992年 | 133篇 |
1991年 | 101篇 |
1990年 | 78篇 |
1989年 | 71篇 |
1988年 | 49篇 |
1987年 | 53篇 |
1986年 | 30篇 |
1985年 | 17篇 |
1984年 | 24篇 |
1983年 | 15篇 |
1982年 | 12篇 |
1981年 | 8篇 |
1980年 | 15篇 |
1979年 | 8篇 |
1977年 | 4篇 |
1975年 | 3篇 |
1973年 | 3篇 |
1968年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
The proposed work involves the multiobjective PSO based adaption of optimal neural network topology for the classification of multispectral satellite images. It is per pixel supervised classification using spectral bands (original feature space). This paper also presents a thorough experimental analysis to investigate the behavior of neural network classifier for given problem. Based on 1050 number of experiments, we conclude that following two critical issues needs to be addressed: (1) selection of most discriminative spectral bands and (2) determination of optimal number of nodes in hidden layer. We propose new methodology based on multiobjective particle swarm optimization (MOPSO) technique to determine discriminative spectral bands and the number of hidden layer node simultaneously. The accuracy with neural network structure thus obtained is compared with that of traditional classifiers like MLC and Euclidean classifier. The performance of proposed classifier is evaluated quantitatively using Xie-Beni and β indexes. The result shows the superiority of the proposed method to the conventional one. 相似文献
2.
The Vehicle Routing Problem with Simultaneous Pickup and Delivery (VRPSPD) is an extension to the classical Vehicle Routing Problem (VRP), where customers may both receive and send goods simultaneously. The Vehicle Routing Problem with Mixed Pickup and Delivery (VRPMPD) differs from the VRPSPD in that the customers may have either pickup or delivery demand. However, the solution approaches proposed for the VRPSPD can be directly applied to the VRPMPD. In this study, an adaptive local search solution approach is developed for both the VRPSPD and the VRPMPD, which hybridizes a Simulated Annealing inspired algorithm with Variable Neighborhood Descent. The algorithm uses an adaptive threshold function that makes the algorithm self-tuning. The proposed approach is tested on well-known VRPSPD and VRPMPD benchmark instances derived from the literature. The computational results indicate that the proposed algorithm is effective in solving the problems in reasonable computation time. 相似文献
3.
4.
Abstract. This paper describes artificial neural network based pure significance tests for the unit root hypothesis against nonlinear alternatives. The theoretical properties of the tests are discussed and a Monte Carlo investigation of their small sample properties is undertaken. 相似文献
5.
本工艺是对原有工艺的改进,突破了原有布帮鞋不能采用无浆贴合的局限性,对原有工艺中的不足有了很大的改进,提高了生产效率,改善了鞋子外观质量,增加了鞋子的美观性。 相似文献
6.
7.
8.
带隔板底水油藏油井临界产量计算公式 总被引:25,自引:9,他引:16
本给出了带隔板底水油藏油井的监界产量计算公式,它适用于所有带隔板底水油藏的油井。 相似文献
9.
10.
María P. Albano Liliana B. Garrido 《Journal of Materials Synthesis and Processing》2002,10(4):211-218
Si3N4powders coated with 6 wt% Y2O3and 4 wt% Al2O3were prepared by coprecipitation. The resulting powders were dispersed in water at different pH values and with addition of various amounts of ammonium polyacrylate (NH4PA) to produce 32 vol% slips. The influence of the amount of NH4PA solution added and pH on the rheological properties of 32 vol% coated Si3N4slips were studied. In addition, the sintered density of cast samples was determined and related to the degree of slip dispersion. The adsorption of the NH4PA on the coated particle surface was rather high and the surface became saturated near 0.86 mg/m2at pH 9.2. High NH4PA concentrations (1.7–3 wt%) were necessary to obtain well dispersed 32 vol% coated Si3N4slips at pH 9.2. The best stabilization was obtained with the addition of 2.3 wt% NH4PA; in this condition, the viscosity reached a minimum value of 35 mPa.s at 100 s–1. The slip viscosity increased with increasing pH from 9.2 to 10.2. Slips with low viscosities gave a more dense packing of cast samples and consequently higher sintered density values. 相似文献