首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   346470篇
  免费   25352篇
  国内免费   8414篇
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
  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.
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.
93.
94.
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.
Chen  Jiyu  Guo  Yiwen  Zheng  Qianjun  Chen  Hao 《Machine Learning》2021,110(4):651-674
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.
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.
Lin  Xiao-Qi  Wang  Zhi-Qiao  Xu  Zhong-Ning  Guo  Guo-Cong 《Catalysis Letters》2021,151(11):3213-3219
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.
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.
Dong  Yibiao  Han  Ru  Wang  Danghui  Wang  Ruofei  Guo  Chenmeng 《SILICON》2021,13(9):3101-3111
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   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号