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   69910篇
  免费   5233篇
  国内免费   2784篇
电工技术   3438篇
技术理论   10篇
综合类   4071篇
化学工业   12213篇
金属工艺   3776篇
机械仪表   4315篇
建筑科学   5947篇
矿业工程   2003篇
能源动力   2059篇
轻工业   4230篇
水利工程   1103篇
石油天然气   4363篇
武器工业   534篇
无线电   8214篇
一般工业技术   8936篇
冶金工业   3586篇
原子能技术   782篇
自动化技术   8347篇
  2024年   250篇
  2023年   1122篇
  2022年   1851篇
  2021年   2520篇
  2020年   1997篇
  2019年   1762篇
  2018年   1920篇
  2017年   2215篇
  2016年   1996篇
  2015年   2631篇
  2014年   3250篇
  2013年   3895篇
  2012年   4278篇
  2011年   4516篇
  2010年   3932篇
  2009年   3722篇
  2008年   3652篇
  2007年   3645篇
  2006年   3842篇
  2005年   3325篇
  2004年   2292篇
  2003年   2001篇
  2002年   1928篇
  2001年   1751篇
  2000年   1755篇
  1999年   2026篇
  1998年   1810篇
  1997年   1485篇
  1996年   1418篇
  1995年   1081篇
  1994年   1034篇
  1993年   714篇
  1992年   549篇
  1991年   440篇
  1990年   329篇
  1989年   262篇
  1988年   238篇
  1987年   149篇
  1986年   105篇
  1985年   80篇
  1984年   38篇
  1983年   36篇
  1982年   40篇
  1981年   22篇
  1980年   14篇
  1979年   5篇
  1978年   1篇
  1976年   1篇
  1959年   2篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
The effects of coupling agents, silicone oil, and three types of polymeric modifiers on the mechanical properties of linear low density polyethylene (LLDPE) composites highly filled with aluminium hydroxide [Al(OH)3] were studied. Polymeric modifiers that contain polar groups, such as silane‐grafted polyethylene (Si‐g‐PE) and acrylic‐acid‐grafted ethylene‐vinyl acetate copolymer (AA‐g‐EVA), improve the mechanical properties dramatically, while nonpolar modifiers improve them to some extent. When Al(OH)3 was treated using a titanate coupling agent, the silicone oil increased the impact strength and elongation at break of the LLDPE/Al(OH)3 composites. Introduction of a polymeric modifier containing polar groups destroys the beneficial effects of silicone oil on film mechanical properties, while the introduction of a nonpolar elastomeric polymeric modifier retains the high impact strength and elongation at break. SEM analyses provide the indirect evidence of the encapsulation of silicone oil around the filler. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 121–128, 2002  相似文献   
82.
"互联网+"环境下,网上自主学习已成常态.文章提出一种个性化试题推荐方法,先通过认知诊断模型诊断出学生的认知状态,再采用协同过滤方法推荐试题,能给学生推荐准确且可解释性的试题.  相似文献   
83.
Zhu  Shuai  Wang  Hui  Lv  Hui  Zhang  Huisheng 《Neural Processing Letters》2021,53(2):1161-1186
Neural Processing Letters - Online sequential extreme learning machine (OS-ELM) is one of the most popular real-time learning strategy for feedforward neural networks with single hidden layer due...  相似文献   
84.
Zhang  Wei  Han  Weijie  Zhu  Zhiliang  Yu  Hai 《Multimedia Tools and Applications》2021,80(24):33429-33454
Multimedia Tools and Applications - Almost all existing image encryption algorithms are only suitable for low-resolution images in the standard image library. When they are used to encrypt...  相似文献   
85.
Zhang  Yafei  Wang  Lin  Zhu  Jonathan J. H.  Wang  Xiaofan 《World Wide Web》2021,24(2):585-606
World Wide Web - With the emergence and rapid proliferation of social media platforms and social networking sites, recent years have witnessed a surge of misinformation spreading in our daily life....  相似文献   
86.

This paper proposes a sequential design scheme for switching LPV (Linear Parameter-Varying) control, aiming to reduce the computational complexity of the associated optimization problem. Different from the traditional approach that simultaneously designs switching LPV controllers and solves a high-dimensional optimization problem, the proposed sequential design approach renders a bundle of low-dimensional optimization problems to be solved iteratively. Individual LPV controller for each subregion is synthesized by independent PLMIs (Parametric Linear Matrix Inequalities) to guarantee performance, and controller variables are interpolated on the overlapped subregions such that the performance is also guaranteed on the overlapped subregion. Numerical examples are used to demonstrate the effectiveness of this method to reduce the computational load in each design iteration and improved performance over the conventional simultaneous design method with well-tuned interpolation coefficient.

  相似文献   
87.
International Journal of Control, Automation and Systems - This paper presents a novel filtering based multi-innovation estimation algorithm for output-error autoregressive moving average (i.e.,...  相似文献   
88.
International Journal of Control, Automation and Systems - In this paper, we discuss actuator fault and sensor fault detection and isolation (FDI) problems for a class of switched nonlinear systems...  相似文献   
89.
音频大地电磁(AMT)在隧道的工程地质勘察是一种非常有效的方法,它具有不受高阻屏蔽、轻便、探测深度相对较大等优点,在宏观上可以查明隧道地层岩性分界、地质构造及其赋水性。以某隧道音频大地电磁勘察为例,分别对AMT的采集手段、工频干扰去噪、静态校正、反演方法等关键技术问题进行分析,并结合实际资料对该工作区的地层分布、断层及其破碎带的赋水情况等进行分析和解释,在其应用中取得了理想的效果。  相似文献   
90.
Runoff simulation is highly significant for hydrological monitoring, flood peak simulation, water resource management, and basin protection. Runoff simulation by distributed hydrological models, such as the soil and water assessment tool (SWAT) model which is the most widely used, is becoming a hotspot for hydrological forecasting research. However, parameter calibration is inefficient and inaccurate for the SWAT model. An automatic parameter calibration (APC) method of the SWAT model was developed by hybrid of the genetic algorithm (GA) and particle swarm optimization (PSO). Multi‐station and multi‐period runoff simulation and accuracy analysis were conducted in the basin of the Zhangjiang River on the basis of this hybrid algorithm. For example, in the Yaoxiaba Station, the calibration results produced an R2 of 0.87 and Nash Sutcliffe efficiency (NSE) index of 0.85, while verification results revealed an R2 of 0.83 and NSE of 0.83. Results of this study show that the proposed method can effectively improve the efficiency and simulation accuracy of the model parameters. It can be concluded that the feasibility and applicability of GA‐PSO as an APC method for the SWAT model were confirmed via case studies. The proposed method can provide theoretical guidance for many hydrological research fields, such as hydrological simulation, flood prevention, and forecasting.  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