全文获取类型
收费全文 | 1711篇 |
免费 | 293篇 |
国内免费 | 116篇 |
专业分类
电工技术 | 17篇 |
综合类 | 124篇 |
化学工业 | 576篇 |
金属工艺 | 25篇 |
机械仪表 | 40篇 |
建筑科学 | 42篇 |
矿业工程 | 13篇 |
能源动力 | 396篇 |
轻工业 | 190篇 |
水利工程 | 5篇 |
石油天然气 | 69篇 |
武器工业 | 6篇 |
无线电 | 20篇 |
一般工业技术 | 192篇 |
冶金工业 | 50篇 |
原子能技术 | 330篇 |
自动化技术 | 25篇 |
出版年
2024年 | 7篇 |
2023年 | 12篇 |
2022年 | 42篇 |
2021年 | 49篇 |
2020年 | 60篇 |
2019年 | 58篇 |
2018年 | 50篇 |
2017年 | 46篇 |
2016年 | 66篇 |
2015年 | 59篇 |
2014年 | 90篇 |
2013年 | 195篇 |
2012年 | 75篇 |
2011年 | 102篇 |
2010年 | 64篇 |
2009年 | 92篇 |
2008年 | 91篇 |
2007年 | 90篇 |
2006年 | 84篇 |
2005年 | 101篇 |
2004年 | 109篇 |
2003年 | 93篇 |
2002年 | 88篇 |
2001年 | 53篇 |
2000年 | 57篇 |
1999年 | 44篇 |
1998年 | 47篇 |
1997年 | 38篇 |
1996年 | 26篇 |
1995年 | 26篇 |
1994年 | 21篇 |
1993年 | 13篇 |
1992年 | 15篇 |
1991年 | 9篇 |
1990年 | 9篇 |
1989年 | 7篇 |
1988年 | 5篇 |
1987年 | 1篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1959年 | 7篇 |
排序方式: 共有2120条查询结果,搜索用时 15 毫秒
81.
82.
Chang Ho Kim Soon Heung Chang 《International Journal of Heat and Mass Transfer》2005,48(11):2242-2249
An experimental study of the critical heat flux (CHF) using R-134a in uniformly heated vertical tube was performed and 182 CHF data points were obtained from the present work to investigate the CHF characteristics of R-134a. The investigated flow parameters in R-134a were: (1) outlet pressures of 13, 16.5, 23.9 bar, (2) mass fluxes of 285-1300 kg/m2 s, (3) subcooling temperatures of 5-40 °C. The CHF tests were performed in a 17.04 mm I.D. test section with heated length of 3 m. The parametric trends of CHF show a general agreement with previous understanding in the water. To assess the suitability of the CHF test using R-134a for modeling the CHF in water, Bowring correlation and Katto correlation were used in the present investigation. It was found that the present test results coincided well with the data predicted with both correlations. It demonstrates that the R-134a can be used as the CHF modeling fluid of water for the investigated flow conditions and geometric condition. 相似文献
83.
强化管内沸腾换热实验研究 总被引:2,自引:0,他引:2
主要研究在低过热度下微槽对流动沸腾换热特性的影响,分别以单工质甲醇和甲醇与甲苯的混合物为工质对不同流量情况下光管、直槽管和螺旋槽管的流动沸腾换热特性进行了实验研究。研究结果表明:对单工质甲醇来说,螺旋槽管可以明显起到强化传热作用,而且流量越低,强化传热效果越明显。对混合工质来说,当流量较低时,螺旋槽管强化传热效果不明显,而在流量较高时,强化传热效果比较明显。无论是单工质还是混合工质,直槽管在实验所能达到的壁面温度条件下不能起到明显的强化传热效果。还给出了螺旋槽管强化传热的定性解释。 相似文献
84.
In this study, pool boiling test results are provided for the structured enhanced tubes having pores with connecting gaps.
The surface geometry of the present tube is similar to that of Turbo-B. Three tubes with different pore size (0.20 mm, 0.23
mm and 0.27 mm) were manufactured and tested using R-11, R-123 and R-134a. The pore size which yields the maximum heat transfer
coefficient varied depending on the refrigerant. For R-134a, the maximum heat transfer coefficient was obtained for the tube
having 0.27 mm pore size. For R-11 and R-123, the optimum pore size was 0.23 mm. One novel feature of the present tubes is
that their boiling curves do not show a ‘cross-over’ characteristic, which existing pored tubes do. The connecting gaps of
the present tube are believed to serve an additional route for the liquid supply and delay the dry-out of the tunnel. The
present tubes yield the heat transfer coefficients approximately equal to those of the existing pored enhanced tubes. At the
heat flux 40 kW/m2 and saturation temperature 4.4° C, the heat transfer coefficients of the present tubes are 6.5 times larger for R-11, 6.0
times larger for R-123 and 5.0 times larger for R-134a than that of the smooth tube 相似文献
85.
86.
Jian-hua XIANG Chao ZHOU Chun-liang ZHANG Gui-yun LIU Cong-gui CHEN Wei ZHOU 《中国有色金属学会会刊》2018,28(7):1404-1412
A theoretical model of phase change heat sink was established in terms of thermal resistance network. The influence of different parameters on the thermal resistance was analyzed and the crucial impact factors were determined. Subsequently, the forming methods including ploughing–extrusion and stamping method of boiling enhancement structure at evaporation surface were investigated, upon which three-dimensional microgroove structure was fabricated to improve the efficiency of evaporation. Moreover, the crucial parameters related to the fabrication of miniaturized phase change heat sink were optimized. The heat transfer performance of the heat sink was tested. Results show that the developed phase change heat sink has excellent heat transfer performance and is suitable for high power LED applications. 相似文献
87.
After a reactor core melts accident, the solid wall of the reactor pressure vessel (RPV) will be inevitably eroded by the melting core which contains large density of heat flux. The analysis of the coupled ablation and heat transfer of the lower head for RPV is of great theoretical significance to the effectiveness demonstration of water injection in reactor pit and the confirmation of the residual wall thickness of RPV. In this work, numerical simulations were carried out based on the RPV model of CPR1000 using the CFD software FLUENT 17.2. Based on dynamic mesh model and user-defined function (UDF) redevelopment, a fully coupling calculation model considering the transient ablation and heat conduction of solid wall of RPV, the redistribution of heat flux density in RPV inner wall and the subcooled boiling of RPV outer wall was established. Both two-phase flow pattern in the reactor pit and temperature field of RPV solid wall ablation within 9 000 s were obtained and the minimum residual wall thickness and the occurrence location were determined by analysis. The results show that it is feasible to use dynamic mesh to capture wall ablation. The fully coupling calculation model has certain advantages in analyzing the transient ablation process of RPV under severe accident. 相似文献
88.
对环形通道内金属钠起始沸腾壁面过热度进行实验研究。实验段长800 mm,环形通道外径10 mm,内径6 mm。电加热元件最高热流密度为846 kW/m2,进口过冷度为63.1~287.8 ℃,质量流量为7.2~122.0 kg/h,系统压力为0.85~28.79 kPa。实验结果表明,起始沸腾壁面过热度随热流密度和进口过冷度的增加而升高,随质量流量和系统压力的增加而降低。拟合得到了关于起始沸腾壁面过热度的半经验关系式,关系式计算结果与实验数据符合良好。 相似文献
89.
基于Matlab软件开发了自动识别气液两相流界面程序,程序可获得气液界面变化、汽膜厚度、汽膜脱离周期和汽膜法向速度等特征。利用该程序对沟槽结构加热表面朝下布置时,在不同倾角、不同热流密度下的汽泡动态数据进行了处理和分析。结果表明:加热表面朝下发生核态沸腾时,汽膜厚度随热流密度的增大而增大,汽泡脱离周期随热流密度的增大先减小,而后维持在一稳定值;汽膜脱离周期随倾角的增大而减小,倾角为5°时的汽膜脱离周期稳定在0.27 s左右。当发生沸腾危机时,汽膜厚度迅速减小,这可作为动态监测加热表面沸腾状态的依据。 相似文献
90.