全文获取类型
收费全文 | 1322篇 |
免费 | 133篇 |
国内免费 | 125篇 |
专业分类
电工技术 | 82篇 |
综合类 | 159篇 |
化学工业 | 98篇 |
金属工艺 | 202篇 |
机械仪表 | 103篇 |
建筑科学 | 66篇 |
矿业工程 | 30篇 |
能源动力 | 70篇 |
轻工业 | 34篇 |
水利工程 | 27篇 |
石油天然气 | 25篇 |
武器工业 | 11篇 |
无线电 | 169篇 |
一般工业技术 | 244篇 |
冶金工业 | 120篇 |
原子能技术 | 12篇 |
自动化技术 | 128篇 |
出版年
2024年 | 1篇 |
2023年 | 20篇 |
2022年 | 24篇 |
2021年 | 36篇 |
2020年 | 48篇 |
2019年 | 44篇 |
2018年 | 34篇 |
2017年 | 49篇 |
2016年 | 34篇 |
2015年 | 48篇 |
2014年 | 65篇 |
2013年 | 62篇 |
2012年 | 69篇 |
2011年 | 90篇 |
2010年 | 76篇 |
2009年 | 81篇 |
2008年 | 70篇 |
2007年 | 90篇 |
2006年 | 87篇 |
2005年 | 70篇 |
2004年 | 69篇 |
2003年 | 65篇 |
2002年 | 51篇 |
2001年 | 47篇 |
2000年 | 40篇 |
1999年 | 31篇 |
1998年 | 26篇 |
1997年 | 26篇 |
1996年 | 21篇 |
1995年 | 27篇 |
1994年 | 16篇 |
1993年 | 17篇 |
1992年 | 15篇 |
1991年 | 9篇 |
1990年 | 6篇 |
1989年 | 6篇 |
1988年 | 6篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1982年 | 1篇 |
排序方式: 共有1580条查询结果,搜索用时 0 毫秒
1.
A size-dependent governing equation is derived to investigate the torsional static behaviors of two-dimensionally functionally graded microtubes based on the modified couple stress theory. The shear modulus is assumed to vary along the tube’s length direction according to an exponential distribute function, and varies along the tube’s radius direction according to a power-law function. A generalized differential quadrature method is developed to determine the rotational angle and shear stresses. Some illustrative examples are given to investigate the effects of applied torques, the length scale parameter and various material compositions on the torsional angle and shear stresses. 相似文献
2.
《Calphad》2021
The present work illustrates the effect of quasi-hydrostatic pressure on the positions and widths of the homogeneity ranges of the intermetallic phases TiFe and TiFe2 at high temperatures. The experiments were performed with Ti–Fe diffusion couples that were heat treated in a multi-anvil press at 2.5 GPa. The solubility limits of the phases were derived from the concentration profiles that were measured using electron probe microanalysis. It was found that the homogeneity ranges of TiFe and TiFe2 extend to higher titanium concentrations, if the pressure is applied. The positions of the phase boundaries of the intermetallics on the iron-rich side are not affected by the pressure. The accuracy of the experimental data including the homogeneity ranges and temperatures was verified by comparing the homogeneity ranges of β-Ti(Fe), α/δ-Fe(Ti) and γ-Fe measured in this study with the homogeneity ranges taken from literature. The pressure was calibrated using the pressure-induced phase transitions of bismuth. 相似文献
3.
三光子吸收效应对孤子对传输的影响 总被引:2,自引:0,他引:2
用分步傅里叶变换法求解含三光子吸收效应的光孤子NLS方程,研究了三光子吸收效应对孤子对在传输中相互作用的影响。研究发现,在特定条件下,三光子吸收效应能使孤子对无离合地平行传输。 相似文献
4.
5.
This two-part paper presents a closed-form procedure for evaluation of estimates of local thermomechanical stress fields in two-phase fibrous composites and laminates. The first part is concerned with a unidirectional elastic laminate subjected to uniform mechanical loads and to uniform changes in temperature. Both phases are assumed to be elastic, with temperature-dependent moduli and expansion coefficients; the solution reflects the influence of thermomechanical interactions. Exact solutions are not possible for any real system, because the local geometry is not known in detail. Instead, estimates of the fields are found from a modified Mori-Tanaka approximation. Examples are presented for two SiC/Ti---Al---Nb composites. Local stresses of interest are found after cooling from fabrication to room temperature. The presence of local yielding, and the influence of coupling terms on the local stress magnitudes are examined. Extension of the results to laminated plates is presented in Part II (Dvorak, G.J., Chen, T. & Teply, J., Composites Science and Technology, 43 (1992) 359–368, this issue). 相似文献
6.
7.
8.
本文基于弹塑性分叉理论研究单向纤维增强复合材料的压缩破坏模式和压缩强度对缺陷的敏感性问题。对于常见复合材料,所得结论是:无缺陷或者小缺陷情况的破坏模式为倾斜破坏带;大缺陷情况的破坏模式为水平破坏带;形成水平破坏带的压力值小于形成倾斜破坏带的压力。 相似文献
9.
A. Demoz C. Khulbe C. Fairbridge S. Petrovic 《Journal of Applied Electrochemistry》2008,38(6):845-851
Hydrogen is among the emerging energy vectors that are being developed to replace nonrenewable hydrocarbon energy sources.
The preferred method to produce hydrogen without generating greenhouse gases is the electrolysis of water using renewable
energy. The reduction of energy during the water electrolysis process is a desirable goal regardless of the source of electric
power. Similar to ferrous/ferric mediation, iodide can be used as a mediator in the electrolysis of an acidic suspension of
coke or coal. The iodide ion is oxidized at a far lower anodic potential than the alternative oxygen evolution reaction. This
reduces the cell electrolysis voltage and, consequently, reduces electricity use. The iodide consumed at the anode is continuously
regenerated by chemical reaction with the coke/coal in suspension. 相似文献
10.
Recent experiments have shown that metallic materials display significant size effects when the characteristic length scale of non-uniform plastic deformation is close to a micron. Couple stress plasticity has been developed to explain such phenomena by Fleck and Hutchinson. The mechanical behaviors of ultra-thin nickel beams in different boundary conditions were studied with the hybrid element developed for couple stress plasticity before. Strong scale effects are found when the beam's thickness is close to the material characteristic length scale. Such phenomena will disappear if the beam' s thickness is greatly larger than the material characteristic length scale. The scale effect is the beams inherent property and it does not change with the change of support conditions. 相似文献