全文获取类型
收费全文 | 18786篇 |
免费 | 2230篇 |
国内免费 | 811篇 |
专业分类
电工技术 | 762篇 |
技术理论 | 1篇 |
综合类 | 1556篇 |
化学工业 | 817篇 |
金属工艺 | 925篇 |
机械仪表 | 1201篇 |
建筑科学 | 4839篇 |
矿业工程 | 2704篇 |
能源动力 | 464篇 |
轻工业 | 476篇 |
水利工程 | 698篇 |
石油天然气 | 1630篇 |
武器工业 | 114篇 |
无线电 | 1587篇 |
一般工业技术 | 1438篇 |
冶金工业 | 777篇 |
原子能技术 | 82篇 |
自动化技术 | 1756篇 |
出版年
2024年 | 48篇 |
2023年 | 216篇 |
2022年 | 517篇 |
2021年 | 500篇 |
2020年 | 559篇 |
2019年 | 458篇 |
2018年 | 427篇 |
2017年 | 670篇 |
2016年 | 727篇 |
2015年 | 698篇 |
2014年 | 1411篇 |
2013年 | 902篇 |
2012年 | 1366篇 |
2011年 | 1287篇 |
2010年 | 1061篇 |
2009年 | 1027篇 |
2008年 | 877篇 |
2007年 | 1095篇 |
2006年 | 1063篇 |
2005年 | 930篇 |
2004年 | 787篇 |
2003年 | 906篇 |
2002年 | 866篇 |
2001年 | 886篇 |
2000年 | 676篇 |
1999年 | 550篇 |
1998年 | 367篇 |
1997年 | 293篇 |
1996年 | 201篇 |
1995年 | 135篇 |
1994年 | 121篇 |
1993年 | 47篇 |
1992年 | 40篇 |
1991年 | 32篇 |
1990年 | 19篇 |
1989年 | 23篇 |
1988年 | 8篇 |
1987年 | 8篇 |
1986年 | 9篇 |
1985年 | 1篇 |
1984年 | 5篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1976年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
3.
This work is devoted to the stress–strain state of isotropic double curved shell with defect system. The construction is weakened by two non-through thickness (internal) cracks of different length and by a circular hole located between cracks. In this study we use the line-spring model. Within the framework of this model cracks are modeled as mathematical cuts of shell’s middle surface. This leads to a two-dimensional problem. The problem is reduced to a system of eight boundary integral equations. To ensure the uniqueness of solution an additional equation is added. In the numerical solution of the problem special quadrature formulas for singular integrals of Cauchy type and the finite difference method are applied. The influence of defects on each other for double curved shell has been investigated. The given theoretical results can be used for the calculation of structural elements with holes, cracks on the strength and fracture toughness in various branches of engineering. 相似文献
4.
Muntasir Hashim Farnoosh Farhad David Smyth‐Boyle Robert Akid Xiang Zhang Philip J. Withers 《工业材料与腐蚀》2019,70(11):2009-2019
The environmental performance of 316L grade stainless steel, in the form of tensile specimens containing a single corrosion pit with various aspect ratios, under cyclic loading in aerated chloride solutions is investigated in this study. Results from environmental tests were compared and contrasted with those obtained using finite element analysis (FEA). Fractography of the failed specimens obtained from experiments revealed that fatigue crack initiation took place at the base of the shallow pit. The crack initiation shifted towards the shoulder and the mouth of the pit for pits of increasing depth. This process is well predicted by FEA, as the strain contour maps show that strain is the highest around the centric strip of the pit. However, for shallow pits, local strain is uniformly distributed around that strip but begins to concentrate more towards the shoulder and the mouth region for increasingly deep pits. 相似文献
5.
In this paper, an adaptive control approach is designed for compensating the faults in the actuators of chaotic systems and maintaining the acceptable system stability. We propose a state‐feedback model reference adaptive control scheme for unknown chaotic multi‐input systems. Only the dimensions of the chaotic systems are required to be known. Based on Lyapunov stability theory, new adaptive control laws are synthesized to accommodate actuator failures and system nonlinearities. An illustrative example is studied. The simulation results show the effectiveness of the design method. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
6.
7.
介绍了一种基于高性能浮点DSP芯片TMS320C32、CPLD芯片XC95288和A/D采样芯片AD976组成的多路采集系统的工作原理以及设计方法。通过对第一路施加特殊的电压量,在CCS开发环境下读取采样缓冲区的值,并利用Matlab对采样数据进行了全波傅氏变换。此外,该系统已在继电保护中得到广泛应用,实践表明,该系统能较好地解决多路模拟量的采集,并确保了采样数据的安全可靠性。 相似文献
8.
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
9.
分析了乐滩灌区工程北干渠溯河隧洞段长约1.06 km穿合山煤矿采空区的地质情况.借鉴高速公路煤矿采空区的成功处理经验,通过科学分析,对采空区变形和区域内覆岩的稳定性做了评价,论述了输水线路穿采空区段采取全充填压力注浆法的工程处理方法. 相似文献
10.
双排桩门架—锚杆新型组合支护体系的应用研究 总被引:1,自引:0,他引:1
本文分析了双排桩门架支护结构的受力机理。针对工程实际进行变形分析,提出增设锚杆形成锚杆———双排桩门架式组合支护体系的方法,并与监测数据对比、验证。 相似文献