全文获取类型
收费全文 | 86622篇 |
免费 | 9064篇 |
国内免费 | 3506篇 |
专业分类
电工技术 | 1905篇 |
技术理论 | 1篇 |
综合类 | 3701篇 |
化学工业 | 29172篇 |
金属工艺 | 10630篇 |
机械仪表 | 1645篇 |
建筑科学 | 2485篇 |
矿业工程 | 2424篇 |
能源动力 | 2359篇 |
轻工业 | 10482篇 |
水利工程 | 438篇 |
石油天然气 | 4689篇 |
武器工业 | 399篇 |
无线电 | 3692篇 |
一般工业技术 | 17188篇 |
冶金工业 | 5190篇 |
原子能技术 | 372篇 |
自动化技术 | 2420篇 |
出版年
2024年 | 572篇 |
2023年 | 1933篇 |
2022年 | 2805篇 |
2021年 | 3718篇 |
2020年 | 3614篇 |
2019年 | 3047篇 |
2018年 | 3331篇 |
2017年 | 3765篇 |
2016年 | 3912篇 |
2015年 | 3965篇 |
2014年 | 5017篇 |
2013年 | 6254篇 |
2012年 | 5746篇 |
2011年 | 6832篇 |
2010年 | 4605篇 |
2009年 | 4859篇 |
2008年 | 4070篇 |
2007年 | 4532篇 |
2006年 | 4349篇 |
2005年 | 3464篇 |
2004年 | 3295篇 |
2003年 | 2868篇 |
2002年 | 2408篇 |
2001年 | 1715篇 |
2000年 | 1504篇 |
1999年 | 1205篇 |
1998年 | 1029篇 |
1997年 | 882篇 |
1996年 | 695篇 |
1995年 | 644篇 |
1994年 | 446篇 |
1993年 | 338篇 |
1992年 | 319篇 |
1991年 | 246篇 |
1990年 | 292篇 |
1989年 | 271篇 |
1988年 | 99篇 |
1987年 | 80篇 |
1986年 | 75篇 |
1985年 | 82篇 |
1984年 | 79篇 |
1983年 | 41篇 |
1982年 | 65篇 |
1981年 | 10篇 |
1980年 | 41篇 |
1979年 | 10篇 |
1978年 | 9篇 |
1976年 | 8篇 |
1974年 | 8篇 |
1951年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
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
92.
93.
碘量法测铜中物质性质和分析操作 总被引:3,自引:0,他引:3
本文讨论了碘量法测定铜量中一些有关物质的特性,以及这些性质对分析条件和操作的要求。 相似文献
94.
M. Djaeni P. Bartels J. Sanders G. van Straten A. J. B. van Boxtel 《Drying Technology》2007,25(6):1053-1067
This work discusses the potential of three multistage zeolite drying systems (counter-, co-, and cross-current) with a varying number of stages. The evaluation showed that for 2-4 stages with heat recovery the efficiency of the systems ranges between 80 and 90%. Additionally, by introducing a compressor, the latent heat in the exhaust air from the regenerator is recovered and used to heat the inlet air for an additional drying stage. As a result, for the counter-current drying system and compressor pressure 1.5-2 bar, a maximum energy efficiency of 120% is achieved, which results in halving the energy consumption compared to conventional drying systems. 相似文献
95.
The viscometric, turbidimetric and potentiometric properties of copolymers of acrylamide (AM) with 2-acrylamido-2-methylpropanedimethylammonium chloride (AMPDAC) were studied in aqueous solutions. The AMPDAC polymers exhibit poor salt tolerance and large, negative viscosity/temperature coefficients. Furthermore, the polymers were found to be sensitive to changes in pH. The AMPDAC polymers undergo phase separation in the presence of dianions as a function of temperature and AMPDAC composition. 相似文献
96.
La doping effects on intergrowth Bi2WO6–Bi3TiNbO9 ferroelectric ceramics were studied by X-ray diffraction, electron probe microanalysis and dielectric spectroscopy. It was found that the La3+ distribution, ferroelectric phase transition and dielectric relaxation behavior are apparently affected by La doping. With increasing La3+ content, the site of dopant ion varies, the grain growth of Bi5TiNbWO15 is restrained, the Curie temperature is reduced and broadened. Furthermore, two dielectric relaxation loss peaks were observed both in temperature and frequency spectra. The calculated relaxation parameters revealed the oxygen vacancy related to the relaxation process. 相似文献
97.
从水淬渣中回收镓的试验研究 总被引:5,自引:0,他引:5
对鼓风炉(ISP法)或烟化炉水淬渣中回收镓的工艺进行了研究。结果表明,利用浓硫酸恒温熟化的独特浸出工艺,克服硅对液固分离的影响;以伯胺N9123作为萃取剂在硫酸介质中萃取镓;获得了含镓品位为2.82%的富集物。 相似文献
98.
I. N. Ishchuk 《Measurement Techniques》2007,50(10):1081-1086
A three-dimensional solution of the direct problem of heat conduction when a linear pulsed heat source acts in the plane of
contact of two semibounded bodies is presented. The solution is obtained by the method of finite differences. An example of
the modeling is considered.
__________
Translated from Izmeritel’naya Tekhnika, No. 10, pp. 42–45, October, 2007. 相似文献
99.
Z. Gruba? 《Materials Letters》2007,61(3):794-798
The initial stage of copper electrodeposition on the electrochemically activated assembly of carbon microelectrodes from an acid solution of copper sulfate was investigated using cyclic voltammetry, potentiostatic pulse technique and electrochemical impedance spectroscopy. Analysis of the experimental current transients has been carried out using a non-linear fitting procedure according to the model that takes into account spherical diffusion towards a disc-shaped microelectrode. The higher values of diffusion coefficient in comparison with those observed on planar electrodes were explained with an increased diffusion caused by the electrode geometry. Impedance spectra showed two time constants, the high-frequency related to the charge transfer process and the low-frequency corresponded to the deposit morphology. 相似文献
100.
论述了普通胶辊表面不处理的性能特点和存在问题,技术措施和合理工艺参数,提高了成纱条干水平,减少缠绕和磨损。 相似文献