全文获取类型
收费全文 | 417篇 |
免费 | 65篇 |
国内免费 | 38篇 |
专业分类
化学 | 113篇 |
晶体学 | 14篇 |
力学 | 21篇 |
综合类 | 9篇 |
数学 | 162篇 |
物理学 | 201篇 |
出版年
2023年 | 4篇 |
2022年 | 16篇 |
2021年 | 14篇 |
2020年 | 21篇 |
2019年 | 17篇 |
2018年 | 15篇 |
2017年 | 19篇 |
2016年 | 18篇 |
2015年 | 9篇 |
2014年 | 6篇 |
2013年 | 37篇 |
2012年 | 13篇 |
2011年 | 25篇 |
2010年 | 23篇 |
2009年 | 13篇 |
2008年 | 25篇 |
2007年 | 18篇 |
2006年 | 22篇 |
2005年 | 24篇 |
2004年 | 26篇 |
2003年 | 19篇 |
2002年 | 18篇 |
2001年 | 13篇 |
2000年 | 14篇 |
1999年 | 13篇 |
1998年 | 40篇 |
1997年 | 15篇 |
1996年 | 7篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1986年 | 1篇 |
1982年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有520条查询结果,搜索用时 15 毫秒
61.
Yilmaz Simsek 《Applied mathematics and computation》2010,216(10):2976-973
The main purpose of this paper is to construct a family of modified p-adic twisted functions, which interpolate the modified twisted q-Bernoulli polynomials and the generalized twisted q-Bernoulli numbers at negative integers. We also give some applications and examples related to these functions and numbers. 相似文献
62.
This study reports the comparison of heat transfer and friction factor characteristics of helical screw inserts in Al2O3–water and carbon nano-tube–water nano-fluids through a straight pipe in transition regime with constant heat flux boundary condition. Experiments were carried out by using 0.15% volume concentration of Al2O3–water and carbon nano-tube–water nano-fluid with helical tape inserts of twist ratio, TR = 1.5, 2.5, and 3. The thermal performance of helical screw tape inserts with the carbon nano-tube–water nano-fluid is found -to be higher when compared to the Al2O3–water nano-fluid. In addition, the maximum enhancement in heat transfer was obtained for the carbon nano-tube–water nano-fluid with helical tape inserts of twist ratio 1.5. The increase in pressure drop of the Al2O3–water nano-fluid with helical screw tape inserts is found to be higher compared to the carbon nano-tube–water nano-fluid helical screw tape inserts at lower value of twist ratio. 相似文献
63.
ABSTRACTPresent study investigates the heat transfer and friction characteristics of heat exchanger tube fitted with perforated twisted tape (PTT) insert having V cuts. A copper tube of 1 m length and 0.032 m inner diameter is used as test section to collect the experimental data by varying the twist ratio of PTT from 2 to 6 for the Reynolds number range of 2,700–23,400. V cuts are introduced in the PTT and the V-cut relative pitch ratio is varied from 1 to 2. The maximum thermo-hydraulic performance parameter is found to be 1.58. 相似文献
64.
This article reports an experimental investigation on the heat transfer, friction factor, and thermal enhancement factor of a tube equipped with vertical wing-cut twisted tapes, horizontal wing-cut twisted tapes, and plain twisted tapes with twist ratios of y = 2.0, 4.4, and 6.0. The obtained results reveal that the heat transfer rate, friction factor, and thermal enhancement factor in the tube equipped with horizontal wing-cut twisted tapes are significantly higher than those in the tube fitted with vertical wing-cut twisted tapes, plain twisted tapes, and a plain tube. An empirical correlation is subsequently derived from the experimental results. 相似文献
65.
Laminar Heat Transfer Augmentation through A Square Duct and Circular Tube Fitted with Twisted Tapes
Experimental studies on friction factor and heat transfer characteristics for the laminar flow of ethylene glycol in a square duct fitted with twisted tapes of different twist ratios under nearly uniform wall temperature conditions are reported in this article. The Nusselt numbers were found to be 5.44–7.49 and 2.46–4.87 times that of plain square duct forced convection values based on constant flow rate and constant pumping power criteria, respectively, for y = 2.66. The augmented friction factor and Nusselt number for a square duct is about 1.9 and 2.10 times higher than that for an augmented circular tube. 相似文献
66.
67.
Hartmut Stöcker Maximilian Rühl Anett Heinrich Erik Mehner Dirk C. Meyer 《Journal of Electrostatics》2013,71(5):905-909
The triboelectric effect describes electrical charging when bringing different materials into contact. We report on the generation of hard X-ray radiation by peeling various adhesive tapes under medium vacuum conditions. Beside vacuum housing and pumps as instrumentation only an electric motor, two rolls and a metal foil as target material are necessary. The spectral distribution of generated X-rays was analyzed using an energy-dispersive detector. Depending on peeling speed, pressure and choice of material combination, electrons with energies sufficient to excite emission in the hard X-ray region are produced. The results are discussed in terms of triboelectric separation of charge carriers. 相似文献
68.
In this paper we prove the best possible Lp estimates for the ?-b -equation on the boundaries of real ellipsoids in Cn, and provide examples to show why they cannot be improved. 相似文献
69.
70.