全文获取类型
收费全文 | 194551篇 |
免费 | 16359篇 |
国内免费 | 8315篇 |
专业分类
电工技术 | 11559篇 |
技术理论 | 13篇 |
综合类 | 11596篇 |
化学工业 | 32394篇 |
金属工艺 | 10109篇 |
机械仪表 | 11535篇 |
建筑科学 | 14624篇 |
矿业工程 | 5438篇 |
能源动力 | 5776篇 |
轻工业 | 13566篇 |
水利工程 | 3402篇 |
石油天然气 | 10745篇 |
武器工业 | 1404篇 |
无线电 | 22368篇 |
一般工业技术 | 24043篇 |
冶金工业 | 12592篇 |
原子能技术 | 2084篇 |
自动化技术 | 25977篇 |
出版年
2024年 | 709篇 |
2023年 | 3280篇 |
2022年 | 5961篇 |
2021年 | 8502篇 |
2020年 | 6378篇 |
2019年 | 5151篇 |
2018年 | 5858篇 |
2017年 | 6468篇 |
2016年 | 5871篇 |
2015年 | 7711篇 |
2014年 | 9670篇 |
2013年 | 12258篇 |
2012年 | 12879篇 |
2011年 | 13719篇 |
2010年 | 11651篇 |
2009年 | 11014篇 |
2008年 | 10747篇 |
2007年 | 9979篇 |
2006年 | 9969篇 |
2005年 | 8671篇 |
2004年 | 5862篇 |
2003年 | 5030篇 |
2002年 | 4501篇 |
2001年 | 3930篇 |
2000年 | 3832篇 |
1999年 | 4432篇 |
1998年 | 3747篇 |
1997年 | 3218篇 |
1996年 | 3015篇 |
1995年 | 2527篇 |
1994年 | 2033篇 |
1993年 | 1579篇 |
1992年 | 1304篇 |
1991年 | 927篇 |
1990年 | 791篇 |
1989年 | 737篇 |
1988年 | 562篇 |
1987年 | 452篇 |
1986年 | 406篇 |
1985年 | 387篇 |
1984年 | 364篇 |
1983年 | 304篇 |
1982年 | 297篇 |
1981年 | 279篇 |
1980年 | 233篇 |
1979年 | 215篇 |
1978年 | 201篇 |
1977年 | 201篇 |
1975年 | 194篇 |
1974年 | 174篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
Adaptive backstepping repetitive learning control design for nonlinear discrete‐time systems with periodic uncertainties
下载免费PDF全文
![点击此处可从《International Journal of Adaptive Control and Signal Processing》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Qiao Zhu Jian‐Xin Xu Shiping Yang Guang‐Da Hu 《International Journal of Adaptive Control and Signal Processing》2015,29(4):524-535
This paper addresses a tracking problem for uncertain nonlinear discrete‐time systems in which the uncertainties, including parametric uncertainty and external disturbance, are periodic with known periodicity. Repetitive learning control (RLC) is an effective tool to deal with periodic unknown components. By using the backstepping procedures, an adaptive RLC law with periodic parameter estimation is designed. The overparameterization problem is overcome by postponing the parameter estimation to the last backstepping step, which could not be easily solved in robust adaptive control. It is shown that the proposed adaptive RLC law without overparameterization can guarantee the perfect tracking and boundedness of the states of the whole closed‐loop systems in presence of periodic uncertainties. In addition, the effectiveness of the developed controller is demonstrated by an implementation example on a single‐link flexible‐joint robot. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
92.
93.
Bing Yang Yu Zhou Wenjie Yu Song Zhang Hongxiang Chen Ju Ye 《Polymer International》2019,68(4):675-683
In order to improve the dispersity and stability of the nano‐SiO2 aqueous system with high solid content, a kind of polyacrylic acid dispersant with methoxysilicon end groups (KH590‐PAA) was synthesized by photopolymerization of acrylic acid (AA) initiated with (3‐mercaptopropyl)trimethoxysilane (KH590). After adding KH590‐PAA into the nano‐SiO2 aqueous dispersion system (20 wt% solid content), the viscosity and the curing time of the system were measured with a rotational viscometer and the inverted bottle method. Moreover, the dispersion mechanism of KH590‐PAA for the nano‐SiO2 aqueous system was researched by measuring the adsorption capacity, the particle size and the zeta potential of the nanoparticles with a conductivity meter, dynamic light scattering, SEM and TEM, respectively. The results showed that the methoxysilicon groups in KH590‐PAA could react with hydroxyl groups on the surface of nano‐SiO2 in the process of stirring, which enhanced the adsorption capacity of the dispersant and then increased the surface charge of the particles. Therefore, electrostatic repulsion and steric hindrance effects between the SiO2 nanoparticles could be further enhanced by adding the KH590‐PAA dispersant, and then the nano‐SiO2 aqueous system exhibited better dispersity and stability. Besides, the dispersion properties of SiO2 nanoparticles in water were closely related to the addition amount and the molecular weight of the KH590‐PAA dispersant. © 2018 Society of Chemical Industry 相似文献
94.
<正>悉尼理工大学工程和计算机系系馆位于市区的显赫地段,旨在重新给大学城市校区注入活力,成为悉尼商务中心南端的门户。建筑本体如同一件雕塑作品,迥然和周围的传统建筑风格相异。建筑地上14层,地下4层,设有先进的演讲厅、学术办公室、会议室、学习和研究实验室、营业咖啡厅、娱乐区、停车场,并在隔壁建筑旁设计自行车停靠处。 相似文献
95.
Emma Layton Anna-Marie Fairhurst Sam Griffiths-Jones Richard K. Grencis Ian S. Roberts 《International journal of molecular sciences》2020,21(23)
In eukaryotes, microRNAs (miRNAs) have roles in development, homeostasis, disease and the immune response. Recent work has shown that plant and mammalian miRNAs also mediate cross-kingdom and cross-domain communications. However, these studies remain controversial and are lacking critical mechanistic explanations. Bacteria do not produce miRNAs themselves, and therefore it is unclear how these eukaryotic RNA molecules could function in the bacterial recipient. In this review, we compare and contrast the biogenesis and functions of regulatory RNAs in eukaryotes and bacteria. As a result, we discovered several conserved features and homologous components in these distinct pathways. These findings enabled us to propose novel mechanisms to explain how eukaryotic miRNAs could function in bacteria. Further understanding in this area is necessary to validate the findings of existing studies and could facilitate the use of miRNAs as novel tools for the directed remodelling of the human microbiota. 相似文献
96.
97.
Anxiang Su Gaoxing Ma Minhao Xie Yang Ji Xiangfei Li Liyan Zhao Qiuhui Hu 《International Journal of Food Science & Technology》2019,54(6):2277-2287
In this study, in vitro digestion and fermentation of Flammulina velutipes -derived polysaccharides (FVP) were investigated. It was found that FVP mainly consisted of 48.45% glucose, 15.40% mannose, 14.60% xylose, 11.80% fucose and 9.90% galactose. The -human saliva, simulated gastric and small intestinal juices conditions did not break down the FVP. Based on in vitro fermentation tests, FVP modulated the composition of gut microbiota by elevating the amounts of Bifidobacteriaceae and Bacteroidaceae and reducing the numbers of genera Lachnospiraceae and Enterococcaceae. Meanwhile, FVP affected the synthesis of short-chain fatty acids derived from gut microbiota. 相似文献
98.
99.
100.