全文获取类型
收费全文 | 392篇 |
免费 | 10篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 16篇 |
综合类 | 12篇 |
化学工业 | 83篇 |
金属工艺 | 11篇 |
机械仪表 | 12篇 |
建筑科学 | 23篇 |
矿业工程 | 17篇 |
能源动力 | 112篇 |
轻工业 | 27篇 |
水利工程 | 3篇 |
石油天然气 | 8篇 |
无线电 | 12篇 |
一般工业技术 | 41篇 |
冶金工业 | 15篇 |
原子能技术 | 2篇 |
自动化技术 | 10篇 |
出版年
2023年 | 4篇 |
2022年 | 15篇 |
2021年 | 11篇 |
2020年 | 15篇 |
2019年 | 9篇 |
2018年 | 12篇 |
2017年 | 12篇 |
2016年 | 10篇 |
2015年 | 5篇 |
2014年 | 18篇 |
2013年 | 26篇 |
2012年 | 11篇 |
2011年 | 34篇 |
2010年 | 18篇 |
2009年 | 8篇 |
2008年 | 18篇 |
2007年 | 19篇 |
2006年 | 8篇 |
2005年 | 17篇 |
2004年 | 18篇 |
2003年 | 15篇 |
2002年 | 12篇 |
2001年 | 11篇 |
2000年 | 15篇 |
1999年 | 5篇 |
1998年 | 9篇 |
1997年 | 13篇 |
1996年 | 5篇 |
1995年 | 10篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1982年 | 1篇 |
排序方式: 共有404条查询结果,搜索用时 15 毫秒
1.
The non-uniformity of the air temperatures and the slow flow rate at the plane collector exit constitute the main cause of the limitations of the solar drying systems. In order to obtain an uniform and a variable flow rate for different uses, a hot air generator using concentrated solar radiation is proposed. To improve the thermal efficiency of the generator, a study of the influence of different shape parameters is realized. The generator is simulated in the laboratory while investigating the flow induced by a circular disc heated uniformly by Joule effect at constant temperature. This disc is placed at the entrance of an open ended vertical cylinder of a larger diameter. Thermal radiation emitted by the hot disc heats the cylinder wall. The heating of the fluid at the cylinder-inlet generates a thermosiphon flow around the one created by the hot disc. The comparison of the velocity and the temperature profiles of the resulting flow permits to determine the influence of the cylinder height, the vertical source-cylinder spacing and the radius ratio, on the resulting flow at the system exit. Thus, a judicious choice of the shape parameters entails an improvement of the flow rate as well as the thermal flux absorbed by the air and a good homogenization of the air temperature at the generator exit. 相似文献
2.
大型空分设备的工艺流程不同,采取的氪、氙预浓缩技术也不同。介绍了适用于不同流程的从液氧中提取氪-氙浓缩物和从富氧液空中提取氪-氙浓缩物的氪、氙预浓缩工艺原理、技术参数和特点。 相似文献
3.
4.
密集平行束孔落矿的底盘漏斗采矿方案的特点是:用密集严行束孔落矿;凿岩与出矿水平合二为一;实行“掘井、劈漏、落矿三位一体”的回采工艺。该方案结构简单、采切比低、工人劳动强度低,适于开采缓倾斜顶底围岩不稳固的中厚以上矿体。 相似文献
5.
The first stage of a two-step concentrated sulfuric acid process that converts softwood sawdust to sugars has been explored. The research focuses on the ability of an in-house custom fabricated corotating twin-screw reactor (TSR) to effectively break down and solubilize crystalline cellulose into low molecular weight carbohydrates. Based on design of experiment (DOE) screening results, a four-level, two-factor experimental model building DOE was undertaken. Solid sawdust conversion to liquid, screw torque, and TSR exit pressure were measured or recorded at each experimental condition to yield percent conversion of solids, processed material viscosity, and material energy requirements. Thereafter, model quadratic equations were fitted to the experimental data and found to be statistically significant. Based on data obtained in the DOE the process was optimized to establish a base case operating condition. The acid-treated product made at base case twin-screw operating conditions showed a 38.2% conversion of dry sawdust solids to soluble liquids. The dry solids conversion reduced 73.8% of all hemicellulose and 44.4% of all cellulose to soluble monomers and oligosaccharides. 相似文献
6.
7.
以浸没式超滤膜为核心的短流程净水工艺的应用与思考 总被引:1,自引:0,他引:1
以浸没式超滤膜为核心的短流程净水工艺自问世以来受到业界的广泛关注.该工艺为净水厂建设和改造提出了一条将预处理、超滤、浓水回收、污泥浓缩、排泥等工序集合在一个构筑物中运行的全新技术路线,有着广阔的应用前景.从该工艺各个环节的特点出发,进行从设计到运行的多角度思考,提出了一些自己的理解,抛砖引玉与大家共同探讨. 相似文献
8.
E. Zafari 《先进材料力学与结构力学》2017,24(9):725-736
In the present study, transverse vibrations of nanobeams with manifold concentrated masses, resting on Winkler elastic foundations, are investigated. The model is based on the theory of nonlocal elasticity in the presence of concentrated masses applied to Euler–Bernoulli beams. A closed-form expression for the transverse vibration modes of Euler–Bernoulli beams is presented. The proposed expressions are provided explicitly as the function of two integrated constants, which are determined by the standard boundary conditions. The utilization of the boundary conditions leads to definite terms of natural frequency equations. The natural frequencies and vibration modes of the concerned nanobeams with different numbers of concentrated masses in different positions under some typical boundary conditions (simply supported, cantilevered, and clamped–clamped) have been analyzed by means of the proposed closed–form expressions in order to show their efficiency. It is worth mentioning that the effect of various nonlocal length parameters and Winkler modulus on natural frequencies and vibration modes are also discussed. Finally, the results are compared with those corresponding to a classical local model. 相似文献
9.
建立HPLC法测定益肾蠲痹丸中延胡索乙素的含量。采用Kromasil色谱注,流动相为甲醇-乙腈-1%醋酸铵缓冲液(pH=5.0±0.02)(10∶30∶60),流速1.0ml/min,检测波长283nm。延胡索乙素在0.07776~1.5552ug(r=0.9999)范围内线性关系良好,平均回收率为99.6%。 相似文献
10.