全文获取类型
收费全文 | 4509篇 |
免费 | 39篇 |
国内免费 | 137篇 |
专业分类
电工技术 | 15篇 |
综合类 | 54篇 |
化学工业 | 1814篇 |
金属工艺 | 169篇 |
机械仪表 | 114篇 |
建筑科学 | 78篇 |
矿业工程 | 27篇 |
能源动力 | 847篇 |
轻工业 | 43篇 |
水利工程 | 4篇 |
石油天然气 | 86篇 |
武器工业 | 10篇 |
无线电 | 358篇 |
一般工业技术 | 776篇 |
冶金工业 | 151篇 |
原子能技术 | 47篇 |
自动化技术 | 92篇 |
出版年
2024年 | 8篇 |
2023年 | 77篇 |
2022年 | 130篇 |
2021年 | 145篇 |
2020年 | 142篇 |
2019年 | 135篇 |
2018年 | 147篇 |
2017年 | 137篇 |
2016年 | 98篇 |
2015年 | 82篇 |
2014年 | 214篇 |
2013年 | 281篇 |
2012年 | 222篇 |
2011年 | 439篇 |
2010年 | 263篇 |
2009年 | 275篇 |
2008年 | 277篇 |
2007年 | 267篇 |
2006年 | 257篇 |
2005年 | 197篇 |
2004年 | 164篇 |
2003年 | 178篇 |
2002年 | 142篇 |
2001年 | 69篇 |
2000年 | 63篇 |
1999年 | 36篇 |
1998年 | 44篇 |
1997年 | 48篇 |
1996年 | 23篇 |
1995年 | 28篇 |
1994年 | 20篇 |
1993年 | 20篇 |
1992年 | 14篇 |
1991年 | 3篇 |
1990年 | 9篇 |
1989年 | 6篇 |
1988年 | 6篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 7篇 |
1984年 | 2篇 |
1980年 | 1篇 |
排序方式: 共有4685条查询结果,搜索用时 15 毫秒
21.
Porous NiTi shape memory alloy (SMA) is a novel biomedical material used for human hard tissue implant .The influence of elemental titanium powder characteristics such as powder morphology, particle size and specific surface area( SSA) on the minimal ignition temperature ,combustion temperature and final product of porous Ni-Ti SMA fabricated by combustion synthesis method was investigated in this paper by scanning electron microscopy (SEM) and laser diffraction.The preliminary data indicated that the titanium powder characteristics had a strong effect on combustion synthesis of porous NiTi SMA. 相似文献
22.
23.
24.
25.
Gang Guo Guangli Liu Karsten E. Thompson 《Chemical Engineering Communications》2003,190(12):1641-1660
Many engineering problems require the estimation of mass transfer coefficients in porous materials. In heterogeneous materials or in cases where mass transfer sites are not spatially uniform, empirical equations for mass transfer coefficients vary widely, and the origin of these differences is not well understood. In this article, we use a stochastic algorithm to model mass transfer from single particles in a two-dimensional heterogeneous packed bed. The computed mass transfer coefficients are used to generate a distribution of local Peclet numbers in the bed. Detailed hydrodynamics are then used to interpret variations in the local Peclet number. The results show clear relationships between pore structure, streamline patterns, and mass transfer rates. 相似文献
26.
FLOW OF NEWTONIAN FLUIDS THROUGH SINUSOID ALLY CONSTRICTED TUBES. NUMERICAL AND EXPERIMENTAL RESULTS
J. A. Deiber Mb. Peirotti R. A. Bortolozzi R. J. Durelli 《Chemical Engineering Communications》1992,117(1):241-262
Numerical and experimental predictions of pressure drops in the flow of Newtonian fluids through sinusoidally constricted tubes (SCT) are carried out. The numerical evaluations analyzed in this work are obtained from the following methods: Geometric Iteration (GJM), Geometric Iteration with First and Second Upwinds (GIM1, GIM2), Successive Over Relaxation by Line (SORBLM), Global Galerkin Spectral Method (GGSM), Collocation (CM) and Dufort-Frankel (DFM). The GIM1, GIM2 and SORBLM are applied to SCT and explained in this work. The other methods have been previously reported in the literature with the same purpose. Experiments are accomplished for constrictions of approximately 40,60 and 80% of the average tube diameter and results compare well with numerical predictions of the steady flow. It is concluded that special attention should be given to evaluations of the friction factor ƒ for Reynolds numbers Re between the onsets of flow separation and turbulence due to flow instability. Finally, the SCT as a model for porous media (PM) is discussed. 相似文献
27.
在有壁垒膜存在的表面,多孔膜的生长在氧化初期受到延迟阻碍,这一现象在直流恒压多孔阳极氧化电流一时间曲线上反映出来。电流达到稳态氧化的时间愈长,壁垒膜愈厚。文中应用此法判断了0.5MH_3BO_3介质的pH值、温度对壁垒阳极氧化膜厚的影响,并应用记录同一介质环境壁垒恒流阳极氧化的槽压一时间曲线得到验证。 相似文献
28.
The humidity response characteristics of La doped BaTiO3 with different sintered densities and room temperature electrical conductivities were investigated using complex impedance measurement. The samples with low density and high resistivity showed the large and nearly linear sensitivity to the change of humidity. The impedance spectra of samples, when exposed to high humidity, can exhibit microstructure-related features, even though they do not give rise to a noticeable characteristic change when exposed to low humidity. The observed impedance patterns were dependent upon the density, and hence the oxidation kinetics of BaTiO3. 相似文献
29.
A. Stein 《Advanced materials (Deerfield Beach, Fla.)》2003,15(10):763-775
This report highlights developments in the fields of microporous and mesoporous materials that were published mostly during the year 2002. Selected examples are provided to illustrate new zeolite structures, porous coordination materials, mesoporous solids with new compositions, controlled morphologies, and increased hydrothermal and thermal stabilities, as well as porous solids with tunable pore openings or other structural features that can be dynamically modified. A number of applications are discussed, including stabilization of reactive guests, separations, electronic materials, and sensors. 相似文献
30.
MASS TRANSFER IN GAS-SPARGED POROUS ELECTRODES 总被引:1,自引:0,他引:1
The electrochemical limiting current method was used to measure mass transfer coefficients with cocurrent upward gas-liquid flow in packed bed electrodes. Liquid-solid and overall gas-solid coefficients were determined from limiting current data in the presence of inert or reactive gas flows with the use of a plug flow model. The presence of inert gas flow increased mass transfer coefficients over those in single-phase flow by a factor of up to 1.7. As a result of boundary layer penetration by gas bubbles, sparging with reactive gas increased mass transfer rates by a factor of up to 3.5. 相似文献