全文获取类型
收费全文 | 91189篇 |
免费 | 11466篇 |
国内免费 | 6421篇 |
专业分类
电工技术 | 8681篇 |
技术理论 | 3篇 |
综合类 | 10274篇 |
化学工业 | 8653篇 |
金属工艺 | 7787篇 |
机械仪表 | 9625篇 |
建筑科学 | 6792篇 |
矿业工程 | 5388篇 |
能源动力 | 5731篇 |
轻工业 | 1339篇 |
水利工程 | 3918篇 |
石油天然气 | 5336篇 |
武器工业 | 3383篇 |
无线电 | 7822篇 |
一般工业技术 | 7896篇 |
冶金工业 | 2500篇 |
原子能技术 | 1453篇 |
自动化技术 | 12495篇 |
出版年
2024年 | 393篇 |
2023年 | 1291篇 |
2022年 | 2654篇 |
2021年 | 2933篇 |
2020年 | 3174篇 |
2019年 | 2358篇 |
2018年 | 2386篇 |
2017年 | 3176篇 |
2016年 | 3850篇 |
2015年 | 4219篇 |
2014年 | 6237篇 |
2013年 | 6101篇 |
2012年 | 7625篇 |
2011年 | 8223篇 |
2010年 | 5918篇 |
2009年 | 5900篇 |
2008年 | 5531篇 |
2007年 | 6835篇 |
2006年 | 5840篇 |
2005年 | 4688篇 |
2004年 | 3939篇 |
2003年 | 3062篇 |
2002年 | 2476篇 |
2001年 | 2056篇 |
2000年 | 1612篇 |
1999年 | 1331篇 |
1998年 | 1042篇 |
1997年 | 831篇 |
1996年 | 749篇 |
1995年 | 583篇 |
1994年 | 491篇 |
1993年 | 322篇 |
1992年 | 262篇 |
1991年 | 214篇 |
1990年 | 173篇 |
1989年 | 143篇 |
1988年 | 99篇 |
1987年 | 47篇 |
1986年 | 64篇 |
1985年 | 35篇 |
1984年 | 35篇 |
1983年 | 27篇 |
1982年 | 23篇 |
1981年 | 13篇 |
1980年 | 20篇 |
1979年 | 19篇 |
1977年 | 6篇 |
1976年 | 5篇 |
1959年 | 21篇 |
1951年 | 27篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
《International Journal of Hydrogen Energy》2022,47(48):20999-21012
Micro-combustor is a portable power device that can provide energy efficiently, heat recirculating is considered to be an important factor affecting the combustion process. For enhancing the heat recirculating and improving the combustion stability, we proposed a heat-recirculating micro-combustor embedded with porous media, and the numerical simulation was carried out by CFD software. In this paper, the effect of porous media materials, thickness and inlet conditions (equivalence ratio, inlet velocity) on the temperature distribution and exhaust species in the micro combustor are investigated. The results showed that compared with the micro combustor without embedded porous media (MCNPM), micro-combustor embedded with porous media (MCEPM) can improve the temperature uniformity distribution in the radial direction and strengthen the preheating capacity. However, it is found that the embedding thickness of porous media should be reasonably arranged. Setting the thickness of porous media to 15 mm, the combustor can obtain excellent comprehensive capacity of steady combustion and heat recirculating. Compared the thermal performance of Al2O3, SiC, and ZrO2 porous media materials, indicating that SiC due to its strong thermal conductivity, its combustion stabilization and heat recirculating capacity are obviously better than that of Al2O3 and ZrO2. With the porous media embedded in the micro combustor, the combustion has a tempering limit of more than 10 m/s, and the flame is blown out of the porous media area over 100 m/s. The reasonable equivalence ratio of CH4/air combustion should be controlled within the range of 0.1–0.5, and “super-enthalpy combustion” can be realized. 相似文献
12.
Effect of heat loss on the syngas production by fuel-rich combustion in a divergent two-layer burner
《International Journal of Hydrogen Energy》2022,47(34):15270-15281
The effect of heat loss on the syngas production from partial combustion of fuel-rich in a divergent two-layer burner is numerically studied using two-dimensional model with detailed kinetics GRI-Mech 1.2. Both the radiation and wall heat losses to the surrounding are considered in the computations. It is shown that two types heat losses have different effects on the syngas production. The radiation heat loss has significant effect on the syngas temperature and the syngas temperature is dropped as radiation heat loss is increased, but it has neglected effect on the reforming efficiency and methane conversion efficiency. The wall heat loss has a comprehensive effect on the syngas production. The wall heat loss not only reduces the conversion efficiency, but also significantly decreases the syngas temperature. The effect of wall heat loss becomes weak as the equivalence is increased. The reforming efficiency drops from 0.440 to 0.424 for equivalence ratio of 2 and mixture velocity of 0.17 m/s for the predictions between adiabatic wall and non-adiabatic conditions. 相似文献
13.
14.
Amino acid modified polyaspartic acids were evaluated as calcium-scale inhibitors. Feasibility of scale inhibition experiments was analyzed by molecular dynamics simulation and Gaussian optimization, and the scale inhibition mechanism was theoretically analyzed. Scale inhibition performance was studied by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, static scale inhibition experiments, and electrochemical performance testing, which provided an experimental basis for the molecular dynamics simulation. The experimental results showed that Arg-SA-PASP has better scale inhibition and corrosion inhibition performance than His-SA-PASP. The scale inhibition effect increased with increasing concentration. Electrochemical tests indicated that Arg-SA-PASP is an excellent scale and corrosion inhibitor. 相似文献
15.
以重庆市甄子岩29号危岩体为研究对象,基于现场调查和分析解剖,建立UDEC离散元数值计算模型,对其演化变形过程进行模拟分析。研究表明,在巨大的自重作用下,由于基座岩体岩质软,岩体较破碎,且基座外侧为直立的陡崖,具有完整的临空面,从而使基座岩体易发生压缩流变及剪切流变,进而使危岩体存在滑移垮塌的危险。 相似文献
16.
目的研究蛋类礼盒包装结构的缓冲性能。方法以蛋类尺寸为基础,建立可发性聚乙烯(expandable polyethylene. EPE)缓冲单元结构和组合结构,进行静态仿真分析和实验验证,比较结构在形状、叠合层数、组合形式等参数变化时的载荷与位移。结果结构层数变化相同时,单元结构的极限载荷从143N增加到236 N,组合结构的极限载荷从224 N增加到476 N,均呈近线性增长。结论蛋类礼盒包装中,组合结构的承载能力优于单元结构,通过单元结构的组合,可满足不同蛋类的包装要求。 相似文献
17.
运用FLUENT数值模拟软件分析了平板集热器(倾角)变化对集热器传热特性的影响,保证其结构参数不变,通过对5组不同倾角(0°、30°、45°、60°、75°)的数值模型进行非稳态模拟,对模拟数据进行分析,得出了平板集热器不同倾角对集热器传热性能变化的影响。 相似文献
18.
19.
Xiaoyan Qiu Yongqiang Zhang Haitao Wu Rui Yang Jun Yang Rongjuan Liu Yong Liu Zhiping Zhou Tongfan Hao Yijing Nie 《Polymer International》2019,68(2):218-224
The crystallization of capped ultrathin polymer films is closely dependent on film thickness and interfacial interaction. Using dynamic Monte Carlo simulations, the crystallization behaviors of polymer films confined between two substrates were investigated. The crystallization rate of confined polymers is reduced with high interfacial interactions. Above a critical strength of interfacial interaction, polymer crystallization in the thin film is inhibited within the simulation time scales. An increase in film thickness leads to a rise in critical interfacial interaction. In thicker films, the chains have more space to change conformation to form crystal stems. In addition, there are fewer absorbed segments in confined chains for the thicker films, and thus the chains have stronger ability to adjust their conformation. Therefore an increase in film thickness can cause a reduction in the entropic barrier required for the formation of crystals and thus an increase in the critical interfacial interaction. © 2018 Society of Chemical Industry 相似文献
20.
水平井压裂技术在低渗透及非常规储层中得到了广泛应用,压裂后水平井的产能预测关系到油田开发方案的制定,因此,国内外学者对压后渗流模型的建立和求解方法做出了不懈的努力。本文详细回顾了国内外学者所建压裂水平井产能预测模型及求解方法,指出了不同模型和求解方法的优缺点,并展望了压裂水平井产能模型的发展方向。 相似文献