全文获取类型
收费全文 | 33733篇 |
免费 | 4221篇 |
国内免费 | 2066篇 |
专业分类
电工技术 | 2561篇 |
综合类 | 2696篇 |
化学工业 | 5578篇 |
金属工艺 | 1892篇 |
机械仪表 | 1927篇 |
建筑科学 | 2468篇 |
矿业工程 | 902篇 |
能源动力 | 1048篇 |
轻工业 | 3781篇 |
水利工程 | 777篇 |
石油天然气 | 1170篇 |
武器工业 | 463篇 |
无线电 | 3803篇 |
一般工业技术 | 3902篇 |
冶金工业 | 1448篇 |
原子能技术 | 537篇 |
自动化技术 | 5067篇 |
出版年
2024年 | 241篇 |
2023年 | 756篇 |
2022年 | 1627篇 |
2021年 | 2244篇 |
2020年 | 1572篇 |
2019年 | 1274篇 |
2018年 | 1315篇 |
2017年 | 1414篇 |
2016年 | 1227篇 |
2015年 | 1762篇 |
2014年 | 1988篇 |
2013年 | 2377篇 |
2012年 | 2589篇 |
2011年 | 2740篇 |
2010年 | 2410篇 |
2009年 | 2285篇 |
2008年 | 2130篇 |
2007年 | 1811篇 |
2006年 | 1545篇 |
2005年 | 1308篇 |
2004年 | 941篇 |
2003年 | 786篇 |
2002年 | 813篇 |
2001年 | 715篇 |
2000年 | 428篇 |
1999年 | 302篇 |
1998年 | 288篇 |
1997年 | 233篇 |
1996年 | 173篇 |
1995年 | 127篇 |
1994年 | 106篇 |
1993年 | 89篇 |
1992年 | 36篇 |
1991年 | 49篇 |
1990年 | 30篇 |
1989年 | 43篇 |
1988年 | 18篇 |
1987年 | 22篇 |
1986年 | 26篇 |
1985年 | 18篇 |
1984年 | 16篇 |
1983年 | 19篇 |
1982年 | 11篇 |
1981年 | 10篇 |
1980年 | 25篇 |
1979年 | 11篇 |
1978年 | 8篇 |
1977年 | 12篇 |
1976年 | 21篇 |
1951年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
32.
为研究古建筑木结构透榫节点的M-θ力学模型,在分析透榫节点构造特征与受力机理的基础上,建立其数值模型,用透榫节点的试验数据验证了该数值模型的正确性,并分析了节点缝隙、木材横纹弹性模量和大榫头长度对透榫节点受弯承载力的影响。根据受力分析结果,建立以弹性点、屈服点与极限点为特征点的三折线多参数M-θ力学模型,其结果与多数的试验结果基本吻合,并将该力学模型应用于木构架的受力分析。研究结果表明:透榫节点的滞回耗能能力强,节点的变形主要集中在榫头处。当榫头与卯口之间的缝隙增大时,节点的受弯承载力降低。随木材横纹弹性模量的提高和大榫头长度的增加,节点的受弯承载力有一定提高。文章建立的M-θ力学模型能较好反映透榫节点的受力过程,适用于木构架的受力分析,其荷载 位移骨架曲线与试验结果基本吻合。研究成果可为古建筑木结构的维修与保护提供参考。 相似文献
33.
34.
Xiangrong Ma Rui Dang Ning Yang Xiao Li Ya zhang Ying Gong Zhipan Liu Wei Guo Yuanyuan Zhang Chunyan Li 《International Journal of Hydrogen Energy》2021,46(44):22842-22851
The high cost of noble metal catalysts has been a great bottleneck for the catalyst industry. Using the noble metal at a single-atom level for catalytic applications could dramatically decrease the cost. The impacts of single Pt atoms on the photocatalytic performance of Ag3VO4 have been investigated and reported. In this report, single Pt atoms were anchored on the surface of Ag3VO4 (AVO) as a cocatalyst, and the resultant composite photocatalyst has been studied for photocatalytic H2 production from water driven by visible light. The as-prepared AVO particles are hollow nanospheres in the monoclinic phase with a bandgap of 2.20 eV. The light absorption edge of AVO/Pt is slightly red-shifted compared to that of the pristine AVO, indicating more visible light absorption of AVO/Pt. The XPS peaks of Ag, V, and Pt exhibit a significant shift after AVO and Pt get into contact, suggesting the strong interaction between the surface Ag and V atoms, and single Pt atoms. After 3-h illumination, the photocatalytic H2 evolution amount from AVO/Pt is improved up to 1400 μmol, which is 2.8 times that on the bare AVO. Such efficient photocatalytic H2 evolution on AVO/Pt is still maintained after five reaction cycles. The better photocatalytic performance of AVO/Pt has been attributed to the more efficient visible light utilization and the lower interfacial charge transfer resistance, as demonstrated in the DRS and EIS spectra. The presence of the surface Pt atoms also leads to a higher amount of reactive radicals, which could efficiently promote the surface redox reactions. 相似文献
35.
Rui
Zhang Junmin Li Jianmin Jiao 《International Journal of Adaptive Control and Signal Processing》2020,34(7):919-936
This article investigates an adaptive fuzzy tracking control problem for a class of nontriangular form systems with asymmetric time-varying full state constraints. Unknown functions are approximated by the fuzzy logic systems. A domination approach is employed to tackle the nontriangular form structure. Time-varying asymmetric barrier Lyapunov functions (ABLFs) are adopted to ensure full-state constraints satisfaction. Based on the backstepping technique and time-varying ABLFs, an adaptive controller is proposed and guarantees that all the signals in the closed-loop system are ultimately bounded and the time-varying full state constraints are met. Simulation examples are presented to further demonstrate the effectiveness of the proposed approach. 相似文献
36.
介绍了中国石油天然气股份有限公司大庆石化分公司地下输水管网的腐蚀现状与调查分析情况,提出了对地下输水管网实施以深井阳极地床外加电流阴极保护为主、局部欠保护区辅以镁合金牺牲阳极的阴极保护方案。经分析,采取上述防护措施后,每年可产生2488万元的经济效益。 相似文献
37.
38.
Piedade M. Sousa L. A. de Almeida T. M. Germano J. da Costa B. A. Lemos J. M. Freitas P. P. Ferreira H. A. Cardoso F. A. 《IEEE transactions on circuits and systems. I, Regular papers》2006,53(11):2384-2395
This paper presents a hand-held microsystem based on new fully integrated magnetoresistive biochips for biomolecular recognition (DNA hybridization, antibody antigen interaction, etc.). Magnetoresistive chip surfaces are chemically treated, enabling the immobilization of probe biomolecules such as DNA or antibodies. Fluid handling is also integrated in the biochip. The proposed microsystem not only integrates the biochip, which is an array of 16times16 magnetoresistive sensors, but it also provides all the electronic circuitry for addressing and reading out each transducer. The proposed architecture and circuits were specifically designed for achieving a compact, programmable and portable microsystem. The microsystem also integrates a hand-held analyzer connected through a wireless channel. A prototype of the system was already developed and detection of magnetic nanoparticles was obtained. This indicates that the system may be used for magnetic label based bioassays 相似文献
39.
表面贴装工艺流程的关键工序之一就是焊膏印刷,其工艺控制的好坏直接影响着装配的线路板的质量。通过对印刷工艺参数的分析,利用试验设计的方法来找出关键工艺参数,并加以优化设定,从而为控制工序参数奠定基础。 相似文献
40.
文章提出了一种面向XML文档的基于XMLschema并结合RDF的访问控制模型,它实现了对XML文档的细粒度的安全访问控制,同时提供了对XML文档中associationsecurityobject的安全访问控制。 相似文献