全文获取类型
收费全文 | 7980篇 |
免费 | 674篇 |
国内免费 | 405篇 |
专业分类
电工技术 | 407篇 |
综合类 | 491篇 |
化学工业 | 1264篇 |
金属工艺 | 514篇 |
机械仪表 | 408篇 |
建筑科学 | 619篇 |
矿业工程 | 366篇 |
能源动力 | 176篇 |
轻工业 | 490篇 |
水利工程 | 149篇 |
石油天然气 | 667篇 |
武器工业 | 56篇 |
无线电 | 975篇 |
一般工业技术 | 976篇 |
冶金工业 | 385篇 |
原子能技术 | 58篇 |
自动化技术 | 1058篇 |
出版年
2024年 | 54篇 |
2023年 | 158篇 |
2022年 | 298篇 |
2021年 | 365篇 |
2020年 | 314篇 |
2019年 | 279篇 |
2018年 | 273篇 |
2017年 | 300篇 |
2016年 | 264篇 |
2015年 | 365篇 |
2014年 | 409篇 |
2013年 | 525篇 |
2012年 | 512篇 |
2011年 | 551篇 |
2010年 | 473篇 |
2009年 | 450篇 |
2008年 | 390篇 |
2007年 | 427篇 |
2006年 | 415篇 |
2005年 | 356篇 |
2004年 | 222篇 |
2003年 | 188篇 |
2002年 | 152篇 |
2001年 | 142篇 |
2000年 | 155篇 |
1999年 | 199篇 |
1998年 | 161篇 |
1997年 | 119篇 |
1996年 | 114篇 |
1995年 | 105篇 |
1994年 | 92篇 |
1993年 | 55篇 |
1992年 | 47篇 |
1991年 | 36篇 |
1990年 | 23篇 |
1989年 | 21篇 |
1988年 | 16篇 |
1987年 | 6篇 |
1986年 | 7篇 |
1985年 | 7篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1980年 | 4篇 |
1977年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有9059条查询结果,搜索用时 15 毫秒
11.
通过工程实例及理论分析 ,对横向风振“锁住区”问题进行了探讨 ,对《建筑结构荷载规范》(GB5 0 0 0 9— 2 0 0 1 )中有关这一方面内容存在的一些问题进行了分析 ,希望对工程设计人员能有所帮助 相似文献
12.
13.
对小型中间下料预焙电解槽技术条件摆布的原则和具体数据进行了探讨,提出了尽可能利用从大型预焙槽上得出的先进经验,并消化吸收,掌握好各种条件的平衡,以取得好经济技术指标的观点。 相似文献
14.
M.Y. Shen Z.B. ZhangX.L. Niu 《Computer Methods in Applied Mechanics and Engineering》2003,192(25):2703-2725
The generalized compact (GC) schemes and some of their important properties are presented. And a new way for constructing high order accuracy and high-resolution GC schemes is presented. The schemes constructed by using this way could satisfy some principles and demands prescribed in advance to ensure some desired properties to the schemes, such as the principle about suppression of the oscillations, the principle of stability, the order of accuracy and number of scheme points, etc. As two examples, a three-point third-order compact scheme and a three-point fifth-order GC scheme satisfying the principle about suppression of the oscillations and the principle of stability are described in this paper. Numerical results show that these schemes are shock-capturing. The time-dependent boundary conditions proposed by Thompson are well employed when the algorithm is applied to the Euler equations of gas dynamics. Fourier analysis shows that the resolution characteristics are spectral-like. 相似文献
15.
Li Jian-zhong Niu Zheng-meng Chen Gang Tan Li-xing Shaanxi Institute of Mechanical Engineering Xi''''an P.R.China 《水动力学研究与进展(B辑)》1993,(4)
This paper will introduce experimental studies and numerical calculation onturbulent boundary layer of water flow along curved surface in our country in recent years.Onthe basis of the experimental studies,the effects of curvature and roughness on velocitydistribution and pressure distribution and the change of turbulent flow boundary layer onoverflow bucket concave surface is discussed.We proposed the empirical formula of velocity,pressure and the change of turbulent flow boundary layer on outlet bucket concave.According tothe momentum principle,we have deduced the momentum integral equation full water depthboundary layer and using the element as control unit inside the boundary layer on concavesurface of bucket.Combining with continuity equation,we have computed the boundary layerdevelopment on the bucket of a spillway.Compared with the field experimental data,thecalculation results are available.Under polar coordinates,a mathematical model for simulatingtime-averaged flow characteristics in concave surface of bucket is established.The turbulent flowfield on concave surface of bucket is calculated by SIMPLE method and this mathematicalmodel.The flow velocity field,pressure field,distribution of turbulent kinetic energy,distribution of turbulent energy dissipating rate and distribution of shear stress are available.Thecalculation value is consistent with measured test data. 相似文献
16.
几种高强度钢腐蚀疲劳裂纹扩展行为的研究 总被引:2,自引:0,他引:2
本文研究了GC-4,30CrMnSiNi2A和300M超高强钢的腐蚀疲劳裂纹扩展行为。考虑了环境,热处理制度,应力比和频率对裂纹扩展的影响。研究结果表明:腐蚀环境和热处理制度对疲劳裂纹扩展有显著影响。在侵蚀性环境中随频率降低,裂纹扩展大幅度上升,随应力比提高,环境影响加剧。利用扫描电镜对试样断口形貌进行了分析,并讨论了高强钢的腐蚀疲劳机理。 相似文献
17.
18.
多属性神经网络地震反演在NB油田水平井钻探中的应用 总被引:2,自引:0,他引:2
NB油田位于渤海海域,为新近系河流相稠油油田,储层横向分布不稳定,砂体厚度薄、连通性较差,油水关系复杂,开发设计部署了大量水平井。选择神经网络反演方法,建立地震属性与储层参数的非线性关系,进而根据其关系反演得到储层参数数据体,利用该数据体沿层切片提取储层预测信息,研究储层发育规律,指导该油田水平井的部署和钻探,取得了较好的效果,降低了钻探风险。用神经网络地震反演方法进行储层预测研究,指导水平井钻探,在渤海海域尚属首次。 相似文献
19.
20.
In order to study water-gas transport processes in the gas-diffusion-layer (GDL) of a proton exchange membrane (PEM) fuel cell system, a multiphase, multiple-relaxation-time lattice Boltzmann model is presented in this work. The model is based on the mean-field diffuse interface theory and can handle the multiphase flows with large density ratios and various viscosities. By using the standard bounce back boundary condition and an approximate average scheme for the non-slip and wetting boundary walls, respectively, detailed liquid-gas transportation in the GDL, in which exact boundary condition is difficult to be implemented, can be simulated. Unlike most of lattice Boltzmann methods based on the Bhatnagar–Gross–Krook collision operator, the present model shows a viscosity-independent velocity field, which is very important in simulating multiphase flows where various viscosities coexist. We validate our model by simulating a static droplet on a wetting wall and compare with theoretical predictions. Then, we simulate a water-gas flow in the GDL of a PEM fuel cell and investigate the saturation-dependent transport properties under different conditions. The results are shown to be qualitatively consistent with the previous numerical and theoretical works. 相似文献