全文获取类型
收费全文 | 346470篇 |
免费 | 25352篇 |
国内免费 | 8414篇 |
专业分类
电工技术 | 20147篇 |
技术理论 | 40篇 |
综合类 | 20124篇 |
化学工业 | 55467篇 |
金属工艺 | 18882篇 |
机械仪表 | 21019篇 |
建筑科学 | 26519篇 |
矿业工程 | 9317篇 |
能源动力 | 10160篇 |
轻工业 | 21469篇 |
水利工程 | 5877篇 |
石油天然气 | 18636篇 |
武器工业 | 2457篇 |
无线电 | 41767篇 |
一般工业技术 | 42447篇 |
冶金工业 | 16978篇 |
原子能技术 | 4026篇 |
自动化技术 | 44904篇 |
出版年
2025年 | 1032篇 |
2024年 | 7711篇 |
2023年 | 7004篇 |
2022年 | 10201篇 |
2021年 | 13816篇 |
2020年 | 11405篇 |
2019年 | 9848篇 |
2018年 | 9321篇 |
2017年 | 10517篇 |
2016年 | 10028篇 |
2015年 | 12589篇 |
2014年 | 16076篇 |
2013年 | 19672篇 |
2012年 | 19917篇 |
2011年 | 22345篇 |
2010年 | 19265篇 |
2009年 | 18808篇 |
2008年 | 18044篇 |
2007年 | 17161篇 |
2006年 | 17197篇 |
2005年 | 14996篇 |
2004年 | 10260篇 |
2003年 | 9226篇 |
2002年 | 8996篇 |
2001年 | 7926篇 |
2000年 | 7441篇 |
1999年 | 8245篇 |
1998年 | 7299篇 |
1997年 | 6000篇 |
1996年 | 5610篇 |
1995年 | 4667篇 |
1994年 | 3795篇 |
1993年 | 2951篇 |
1992年 | 2311篇 |
1991年 | 1758篇 |
1990年 | 1365篇 |
1989年 | 1166篇 |
1988年 | 925篇 |
1987年 | 641篇 |
1986年 | 521篇 |
1985年 | 416篇 |
1984年 | 287篇 |
1983年 | 254篇 |
1982年 | 223篇 |
1981年 | 184篇 |
1980年 | 178篇 |
1979年 | 112篇 |
1978年 | 67篇 |
1977年 | 68篇 |
1976年 | 81篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
ChenJianrong PengJianqin 《中国油气》2002,9(1):34-36
China has formulated a series of preferential taxation policies for the country 's petroleum enterprises. Those state policies are the important factors influencing reform and development of petroleum enterprises. The taxes turned over to the State by CNPC in 1998, 1999 and 2000 are 31.4 billion yuan, 31.7 billion yuan and 41 billion yuan respectively, accounting for 11.64 percent, 9.06 percent and 10.15 percent of the annual sales income.With China 's entry into WTO, it is necessary for t… 相似文献
92.
New insights into the noise reduction Wiener filter 总被引:3,自引:0,他引:3
93.
94.
Lei Guo Lennart Ljung Pierre Priouret 《International Journal of Adaptive Control and Signal Processing》1993,7(6):525-537
An analysis is given of the performance of the standard forgetting factor recursive least squares (RLS) algorithm when used for tracking time-varying linear regression models. Three basic results are obtained: (1) the ‘P-matrix’ in the algorithm remains bounded if and only if the (time-varying) covariance matrix of the regressors is uniformly non-singular; (2) if so, the parameter tracking error covariance matrix is of the order O(μ + γ2/μ), where μ = 1 - λ, λ is the forgetting factor and γ is a quantity reflecting the speed of the parameter variations; (3) this covariance matrix can be arbitrarily well approximated (for small enough μ) by an expression that is easy to compute. 相似文献
95.
Machine Learning - Research showed that deep learning models are vulnerable to membership inference attacks, which aim to determine if an example is in the training set of the model. We propose a... 相似文献
96.
We present a simple and efficient approach for continuous collision detection of deforming triangles based on conservative advancement. The efficiency of our approach is due to a sequence of simple collision-free conditions for deforming triangles. In our experiment, we show that our CCD algorithm achieves 2-30 times performance improvement over existing algorithms for triangle primitives. 相似文献
97.
M. Alghane Y. Q. Fu B. X. Chen Y. Li M. P. Y. Desmulliez A. J. Walton 《Microfluidics and nanofluidics》2012,13(6):919-927
This paper reports an experimental and numerical investigation on the scaling effects in the flow hydrodynamics for confined microdroplets induced by a surface acoustic wave (SAW). The characteristic parameters of the flow hydrodynamics were studied as a function of the separation height, H, between the LiNbO3 substrate and a top glass plate, for various droplets volumes and radio-frequency powers. The ratio of the gap height to attenuation length of the SAW, H/l SAW, is shown to be an important parameter affecting the streaming flow induced in this confined regime. The reported numerical and experimental results are in good agreement over the range examined in this study and demonstrate that, at a lower gap heights of H?≤?100?μm, a significant decrease in streaming velocity or Reynolds number is induced, with the velocity approaching zero when the gap height is decreased to ~50?μm. An increase in the gap height results in an increased streaming velocity; however, if the gap height exceeds 70?% of the SAW attenuation length, any further increase in the gap height induces a drop in the streaming velocity. 相似文献
98.
Catalysis Letters - Pd-based heterogeneous nanocatalysts have wide application in chemical industry. However, the traditional synthesis process contains multi-steps such as impregnation, dry,... 相似文献
99.
Predicting phase equilibrium,phase transformation,and microstructure evolution in titanium alloys 总被引:3,自引:0,他引:3
Y. -Z. Wang N. Ma Q. Chen F. Zhang S. L. Chen Y. A. Chang 《JOM Journal of the Minerals, Metals and Materials Society》2005,57(9):32-39
Phase transformation and microstructural evolution in commercial titanium alloys are extremely complex. Traditional models
that characterize microstructural features by average values without capturing the anisotropy and spatially varying aspects
may not be sufficient to quantitatively define the microstructure and hence to allow for establishing a robust microstructure-property
relationship. This article discusses recent efforts in integrating thermodynamic modeling and phase-field simulation to develop
computational tools for quantitative prediction of phase equilibrium and spatiotemporal evolution of microstructures during
thermal processing that account explicitly for precipitate morphology, spatial arrangement, and anisotropy. The rendering
of the predictive capabilities of the phase-field models as fast-acting design tools through the development of constitutive
equations is also demonstrated.
For more information, contact Y.-Z. Wang, Department of Materials Science & Engineering, Ohio State University, 2041 College
Road, Columbus, OH 43221, USA; (614) 292-0682; fax (614) 292-1537; e-mail wang.363@osu.edu. 相似文献
100.
Silicon - In this paper, an analytical model for negative capacitance double gate field effect transistor (NC-DG-FET) is proposed. This model includes interface traps and temperature effects, which... 相似文献