全文获取类型
收费全文 | 3031篇 |
免费 | 261篇 |
国内免费 | 156篇 |
专业分类
电工技术 | 109篇 |
综合类 | 230篇 |
化学工业 | 246篇 |
金属工艺 | 416篇 |
机械仪表 | 177篇 |
建筑科学 | 491篇 |
矿业工程 | 109篇 |
能源动力 | 91篇 |
轻工业 | 94篇 |
水利工程 | 256篇 |
石油天然气 | 46篇 |
武器工业 | 36篇 |
无线电 | 127篇 |
一般工业技术 | 166篇 |
冶金工业 | 124篇 |
原子能技术 | 17篇 |
自动化技术 | 713篇 |
出版年
2024年 | 10篇 |
2023年 | 36篇 |
2022年 | 76篇 |
2021年 | 75篇 |
2020年 | 89篇 |
2019年 | 62篇 |
2018年 | 61篇 |
2017年 | 80篇 |
2016年 | 106篇 |
2015年 | 115篇 |
2014年 | 194篇 |
2013年 | 204篇 |
2012年 | 223篇 |
2011年 | 265篇 |
2010年 | 215篇 |
2009年 | 228篇 |
2008年 | 199篇 |
2007年 | 226篇 |
2006年 | 200篇 |
2005年 | 167篇 |
2004年 | 125篇 |
2003年 | 93篇 |
2002年 | 73篇 |
2001年 | 73篇 |
2000年 | 41篇 |
1999年 | 46篇 |
1998年 | 31篇 |
1997年 | 25篇 |
1996年 | 25篇 |
1995年 | 17篇 |
1994年 | 14篇 |
1993年 | 11篇 |
1992年 | 6篇 |
1991年 | 6篇 |
1990年 | 7篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 8篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 4篇 |
1979年 | 1篇 |
排序方式: 共有3448条查询结果,搜索用时 15 毫秒
1.
2.
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
3.
4.
两种波长激光血管内照射生物效应比较 总被引:2,自引:0,他引:2
目的:研究同等照射条件的低强度532nm与633nm激光血管内照射生物效应的特点。方法:用532nm和633nm激光对健康大耳白家兔血管内照射,平均照射功率均设定在5mW左右,照射总能量约12J。两组家兔均于照前及照后1d、4d、7d、11d采集外周血,检测血浆ET、NO、MDA含量和SOD活性。结果:两组家兔上述各指标随照后时间的变化规律相似,经方差分析组间各指标都没有显著性差异。结论:同等照射条件下,低强度532nm与633nm激光照射血液的生物效应相似。 相似文献
5.
In Malaysia, no long-term daylight data are measured. It was only recently that the need to measure the availability of daylight became urgent when the importance of daylighting in buildings was rediscovered. The hourly daylight availability has been simulated for the Malaysian sky using daylight modelling techniques based on empirical and measured solar irradiation and cloud cover data. This paper presents the techniques involved in producing exterior illuminance data. These data were then compared with measured illuminance at Shah Alam and Bangi, Malaysia. The global illuminance levels are generally high, with values exceeding 80,000 lux at noon during the months when solar irradiation is highest. Even during the months when the ground receives less solar irradiation, the peak illuminance can reach 60,000 lux. Applications and uses of such data are in daylighting design, both for visual and thermal comfort, task illuminance and energy-conscious design of buildings. Recommendations are made at the end of the paper on the various climatic data that are required to be measured for overall daylighting design applications. 相似文献
6.
1 IntroductionThestickingpointofassociationrulealgorithmsdependsoneffectivelyfindingallcorrelationpatternsthatsatisfyvaluerequirementinthemagnanimityofdata.Butthealgorithmsalsobringanegativeef fect:thenumberofassociationrulesisverylarge.Alsoinformation… 相似文献
7.
8.
大变量逻辑函数最佳覆盖问题研究 总被引:2,自引:0,他引:2
逻辑函数的最佳覆盖,一直是逻辑综合领域的关键环节。尤其是大变量逻辑函数最佳覆盖,对复杂的逻辑综合更为重要,但也更加困难。本文在对逻辑覆盖算法研究的基础上,提出了适合大变量逻辑函数最佳覆盖的Beister改进算法。经过大量算题的测试表明,改进的列覆盖算法在时间复杂度和选择效果方面均优于Beister算法。 相似文献
9.
C R Chakravorty 《Bulletin of Materials Science》1994,17(6):733-745
Magnesium-lithium alloys are among the lowest density metallic materials. Addition of lithium, with a relative density of
0·53, in magnesium reduces the density of the alloy significantly. Furthermore, addition of nearly 11 wt.% lithium converts
hexagonal close packed structure of pure magnesium to a body centered cubic lattice, markedly improving formability of the
alloy. The development of these alloys, however, had been hampered due to the high reactivity of lithium and magnesium in
the molten state and also, due to poor creep resistance and instability of mechanical properties at room temperature. In an
attempt to indigenize these ultra light alloys for possible applications in Indian satellite programme, detailed research
work was initiated in DMRL. The difficulties associated with producing sound cast ingots have been overcome by controlling
melting and casting parameters of these alloys. Extensive work has been done on structure-property correlation of alloys with
varying lithium content and minor alloying additions. Based on these work, advanced magnesium-lithium alloys have been developed
with improved tensile properties, room temperature stability and creep resistance. Wrought products (plates/sheets) of magnesium-lithium
alloy have been supplied to ISAC, Bangalore and are being used in their INSAT-2 programme. This paper describes the systematic
studies carried out in the laboratory to indigenize these ultra light alloys. 相似文献
10.