全文获取类型
收费全文 | 138012篇 |
免费 | 6373篇 |
国内免费 | 3571篇 |
专业分类
电工技术 | 4674篇 |
技术理论 | 3篇 |
综合类 | 6595篇 |
化学工业 | 19500篇 |
金属工艺 | 7905篇 |
机械仪表 | 6839篇 |
建筑科学 | 7242篇 |
矿业工程 | 2325篇 |
能源动力 | 2582篇 |
轻工业 | 8087篇 |
水利工程 | 2484篇 |
石油天然气 | 2812篇 |
武器工业 | 608篇 |
无线电 | 15736篇 |
一般工业技术 | 21796篇 |
冶金工业 | 4847篇 |
原子能技术 | 1085篇 |
自动化技术 | 32836篇 |
出版年
2024年 | 254篇 |
2023年 | 907篇 |
2022年 | 1859篇 |
2021年 | 2561篇 |
2020年 | 1829篇 |
2019年 | 1486篇 |
2018年 | 15897篇 |
2017年 | 15093篇 |
2016年 | 11583篇 |
2015年 | 2944篇 |
2014年 | 3168篇 |
2013年 | 3579篇 |
2012年 | 7015篇 |
2011年 | 13465篇 |
2010年 | 12015篇 |
2009年 | 9147篇 |
2008年 | 10304篇 |
2007年 | 11113篇 |
2006年 | 3243篇 |
2005年 | 3831篇 |
2004年 | 2958篇 |
2003年 | 2743篇 |
2002年 | 2160篇 |
2001年 | 1498篇 |
2000年 | 1347篇 |
1999年 | 1108篇 |
1998年 | 747篇 |
1997年 | 653篇 |
1996年 | 642篇 |
1995年 | 495篇 |
1994年 | 406篇 |
1993年 | 263篇 |
1992年 | 221篇 |
1991年 | 170篇 |
1990年 | 119篇 |
1989年 | 106篇 |
1988年 | 93篇 |
1987年 | 54篇 |
1986年 | 46篇 |
1968年 | 43篇 |
1966年 | 42篇 |
1965年 | 45篇 |
1962年 | 64篇 |
1961年 | 57篇 |
1960年 | 46篇 |
1959年 | 42篇 |
1958年 | 37篇 |
1957年 | 36篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Telecommunication Systems - Machine to Machine technology has a broad application prospect in the 5G network, but there is a bottleneck in the energy consumption of intelligent devices powered by... 相似文献
2.
Shanshan Li Bing Zhang Xuxiang Feng Yewei Wu 《International journal of remote sensing》2019,40(14):5635-5650
Feature-based methods have been developed in the past decades for the registration of optical satellite images. However, it is still a challenging problem to handle well the registration between medium and high spatial resolution images due to the large difference of the spatial structural features and local details for the same objects. In this study, an automated co-registration technique is proposed that integrates an improved SIFT (I-SIFT) and a novel matching strategy called spatial consistency constraints (SCC) to cope with the large difference in spatial resolutions between the image pair. Three constraints on angle, distance, and ratio are introduced to re the initial matching features obtained by I-SIFT. Three groups of experiments were conducted to validate the effectiveness of the proposed method. The experiments used high resolution multispectral and panoramic SPOT 5/6 images and Landsat 5/8 orthorectification images. Experimental results show that the registration error lies in about 1 pixel of high-resolution images and demonstrate that the proposed I-SIFT-SCC approach is suitable for fine registration of optical satellite images from medium spatial resolution to high spatial resolution with resolution ratio up to 6. 相似文献
3.
Dan Ye Kaiyu Wang Haijiao Yang Xingang Zhao 《International Journal of Adaptive Control and Signal Processing》2020,34(11):1677-1696
In this article, an adaptive fuzzy output feedback control method is presented for nonlinear time-delay systems with time-varying full state constraints and input saturation. To overcome the problem of time-varying constraints, the integral barrier Lyapunov functions (IBLFs) integrating with dynamic surface control (DSC) are applied for the first time to keep the state from violating constraints. The effects of unknown time delays can be removed by using designed Lyapunov-Krasovskii functions (LKFs). An auxiliary design system is introduced to solve the problem of input saturation. The unknown nonlinear functions are approximated by the fuzzy logic systems (FLS), and the unmeasured states are estimated by a designed fuzzy observer. The novel controller can guarantee that all signals remain semiglobally uniformly ultimately bounded and satisfactory tracking performance is achieved. Finally, two simulation examples illustrate the effectiveness of the presented control methods. 相似文献
4.
Yan Jing Zhu Rongying Wu Fan Zhao Ziyin Ye Huan Hou Mengying Liu Yong Yin Lichen 《Nano Research》2020,13(10):2706-2715
Nano Research - Insufficient intratumoral penetration greatly hurdles the anticancer performance of nanomedicine. To realize highly efficient tumor penetration in a precisely and spatiotemporally... 相似文献
5.
6.
7.
Scientometrics - In traditional research, the application of quantitative measurement on the value and influence of uncited papers is not feasible owing to the lack of data. The rapid advancement... 相似文献
8.
Loboda P. I. Minitsky A. V. Byba Ye. G. Sysoev M. O. Radchuk S. V. 《Powder Metallurgy and Metal Ceramics》2020,58(11-12):651-656
Powder Metallurgy and Metal Ceramics - The infiltration of aluminum melts into porous metal skeletons produced by powder metallurgy methods, including 3D printing, under a pressure gradient was... 相似文献
9.
Yuanyuan Zhang Haiyan Lu Bing Wang Zhuo Zhang Xiaorong Lin Zhongzheng Chen Bin Li 《International Journal of Food Science & Technology》2015,50(6):1397-1404
Removal of imidacloprid and acetamiprid in tea infusions by microfiltration membrane using dead‐end model was investigated in the present study. The results showed that microfiltration significantly promoted the removal of both pesticides (P < 0.05) in tea infusions. Furthermore, the extent of removal was strongly influenced by the pore size of membrane, operational pressure and the concentrations of tea infusions. The initial concentration of imidacloprid and acetamiprid showed no significant effect on their removal rates. The maximum removal rates were 79.7% for imidacloprid and 81.9% acetamiprid. The changes in major chemical components of tea infusions after microfiltration were evaluated. The results indicated that microfiltration caused no considerable changes in total polyphenols and total free amino acids, and small but statistically significant losses (6.3–18.0%) of eight catechins and three methylxanthines when filtration volume reached to 200 mL. The present study validated the application of microfiltration as a potentially feasible and promising method for the removal of imidacloprid and acetamiprid residues from tea infusions. 相似文献
10.
Yange Yang Xiangyang Zhou Bing Li Cunman Zhang 《International Journal of Hydrogen Energy》2021,46(5):4259-4282
Proton exchange membrane fuel cells (PEMFCs) have become the most attractive power supply units for stationary and mobile applications. The operation, design characteristics, as well as performance of PEMFCs, are closely related to the multiphase transport of mass, heat, and electricity in the cell, a critical of which is the gas diffusion layer (GDL). It is very important to guarantee the transmission of water and gasses under high current density, and which is the weakness of PEMFCs at present. Microporous layer (MPL) is considered to be the key variable for mass transfer, so varieties of works focus on modification of MPL materials and its structure design. However, there is still a lack of special review to summarize and prospect the progress of MPL in recent years. This review article therefore focuses on the insights and comprehensive understanding of four critical issues of the MPL, the porosity, pore size distribution, wettability, structural design and the durability of MPL. At last, the conclusion and recommendations section summarized the future prospects and recommendations for possible research opportunities. 相似文献