全文获取类型
收费全文 | 53166篇 |
免费 | 3557篇 |
国内免费 | 1210篇 |
专业分类
电工技术 | 547篇 |
综合类 | 7564篇 |
化学工业 | 5334篇 |
金属工艺 | 586篇 |
机械仪表 | 340篇 |
建筑科学 | 30260篇 |
矿业工程 | 1256篇 |
能源动力 | 580篇 |
轻工业 | 122篇 |
水利工程 | 5103篇 |
石油天然气 | 1328篇 |
武器工业 | 147篇 |
无线电 | 140篇 |
一般工业技术 | 3363篇 |
冶金工业 | 759篇 |
原子能技术 | 122篇 |
自动化技术 | 382篇 |
出版年
2024年 | 123篇 |
2023年 | 387篇 |
2022年 | 987篇 |
2021年 | 1146篇 |
2020年 | 1085篇 |
2019年 | 781篇 |
2018年 | 977篇 |
2017年 | 1316篇 |
2016年 | 1359篇 |
2015年 | 1731篇 |
2014年 | 3564篇 |
2013年 | 2257篇 |
2012年 | 3570篇 |
2011年 | 3960篇 |
2010年 | 3167篇 |
2009年 | 3818篇 |
2008年 | 3633篇 |
2007年 | 4504篇 |
2006年 | 3575篇 |
2005年 | 3079篇 |
2004年 | 2452篇 |
2003年 | 2166篇 |
2002年 | 1859篇 |
2001年 | 1453篇 |
2000年 | 1224篇 |
1999年 | 909篇 |
1998年 | 644篇 |
1997年 | 520篇 |
1996年 | 397篇 |
1995年 | 296篇 |
1994年 | 270篇 |
1993年 | 186篇 |
1992年 | 144篇 |
1991年 | 97篇 |
1990年 | 84篇 |
1989年 | 57篇 |
1988年 | 41篇 |
1987年 | 32篇 |
1986年 | 3篇 |
1985年 | 7篇 |
1984年 | 7篇 |
1983年 | 11篇 |
1982年 | 18篇 |
1980年 | 25篇 |
1979年 | 5篇 |
1975年 | 2篇 |
1967年 | 1篇 |
1964年 | 1篇 |
1962年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
11.
This DFG-funded research project aimed to gain a better understanding of the mechanisms of the W-Cl repair principle within the framework of fundamental investigations, to contribute to the creation of the necessary basis for a broader application of the repair principle in practice. The focus was on the development of a model to describe the chloride redistribution after the application of a system sealing surface protective coating. On the basis of Fick's second law of diffusion, a mathematical model with a self-contained analytical solution was developed, with the help of which the chloride redistribution after application of a system sealing surface protective coating can be calculated under the idealized assumption of complete water saturation of the concrete. Furthermore, the influence of the dehydration of the concrete, expected as a result of the application of the repair principle W-Cl, on the chloride redistribution was investigated. On the basis of laboratory tests and numerical simulations, material-specific reduction functions were developed to quantify the relationship between the chloride diffusion coefficient and the ambient humidity. 相似文献
12.
13.
The limited research on the geopolymer concrete mix design for targeting a specific strength is identified an obstacle for their effective design and wide use. In this paper, a mix design procedure has been proposed for fly-ash based geopolymer concrete and its use as infill hybrid composite beam is investigated. Then, the structural performance of geopolymer concrete filled hybrid composite beam is investigated to determine their possible application in civil infrastructure. Firstly, a detailed procedure of mix design for fly-ash based geopolymer concrete is presented. Secondly, three hybrid beams filled with geopolymer concrete were prepared and tested in a four-point bending setup to evaluate their flexural modulus and modulus of rupture. Numerical and analytical evaluation of the behaviour of hybrid beam were performed and results showed a good agreement with the experimental investigation. Thirdly, the suitability of the beam for a composite railway sleeper is evaluated and compared with existing timber and composite sleepers. Finally, the beams’ performance in a ballast railway track is analysed using Strand7 finite element simulation software and the results showed that the new concept of using geopolymer concrete as infill to pultruded composite section satisfied the stiffness and strength requirements for a railway sleeper. 相似文献
14.
Chahmi OUCIF Luthfi Muhammad MAULUDIN Farid Abed 《Frontiers of Structural and Civil Engineering》2020,14(2):299
This work presents a numerical simulation of ballistic penetration and high velocity impact behavior of plain and reinforced concrete slabs. In this paper, we focus on the comparison of the performance of the plain and reinforced concrete slabs of unconfined compressive strength 41 MPa under ballistic impact. The concrete slab has dimensions of 675 mm × 675 mm × 200 mm, and is meshed with 8-node hexahedron solid elements in the impact and outer zones. The ogive-nosed projectile is considered as rigid element that has a mass of 0.386 kg and a length of 152 mm. The applied velocities vary between 540 and 731 m/s. 6 mm of steel reinforcement bars were used in the reinforced concrete slabs. The constitutive material modeling of the concrete and steel reinforcement bars was performed using the Johnson-Holmquist-2 damage and the Johnson-Cook plasticity material models, respectively. The analysis was conducted using the commercial finite element package Abaqus/Explicit. Damage diameters and residual velocities obtained by the numerical model were compared with the experimental results and effect of steel reinforcement and projectile diameter were studies. The validation showed good agreement between the numerical and experimental results. The added steel reinforcements to the concrete samples were found efficient in terms of ballistic resistance comparing to the plain concrete sample. 相似文献
15.
16.
17.
18.
改性沥青新型磨耗层在高等级路面上的应用 总被引:1,自引:0,他引:1
从材料、适用范围、形成机理、经济分析、施工工艺五个方面,介绍了改性沥青新型磨耗层在高等级路面上的应用,并通过试验路的观察表明,改性沥青新型磨耗层具有快速排水、增加摩阻力、愈合原路面微裂缝和较强抗磨耗的功能,是处置高等级路面上常有的龟裂、网裂、脱皮、露骨、抗磨系数不足、渗水等病害较具推广价值的新型施工工艺。 相似文献
19.
简述了浇筑混凝土的施工准备工作,从滑动层的增设、配合比的配制、混凝土的浇筑及养护、后浇带的处理等方面介绍了大体积抗渗混凝土工程的施工质量控制措施,以保证混凝土的各项指标达到规范及设计要求。 相似文献
20.