全文获取类型
收费全文 | 792篇 |
免费 | 16篇 |
国内免费 | 6篇 |
专业分类
化学 | 615篇 |
晶体学 | 20篇 |
力学 | 16篇 |
数学 | 37篇 |
物理学 | 126篇 |
出版年
2023年 | 3篇 |
2022年 | 3篇 |
2021年 | 6篇 |
2020年 | 6篇 |
2019年 | 3篇 |
2018年 | 3篇 |
2017年 | 6篇 |
2016年 | 15篇 |
2015年 | 7篇 |
2014年 | 19篇 |
2013年 | 35篇 |
2012年 | 29篇 |
2011年 | 44篇 |
2010年 | 25篇 |
2009年 | 19篇 |
2008年 | 33篇 |
2007年 | 42篇 |
2006年 | 57篇 |
2005年 | 59篇 |
2004年 | 43篇 |
2003年 | 35篇 |
2002年 | 35篇 |
2001年 | 19篇 |
2000年 | 19篇 |
1999年 | 18篇 |
1998年 | 12篇 |
1997年 | 8篇 |
1996年 | 8篇 |
1995年 | 8篇 |
1994年 | 10篇 |
1993年 | 9篇 |
1992年 | 12篇 |
1991年 | 16篇 |
1990年 | 5篇 |
1989年 | 12篇 |
1988年 | 10篇 |
1987年 | 7篇 |
1986年 | 9篇 |
1985年 | 16篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 14篇 |
1981年 | 6篇 |
1980年 | 11篇 |
1979年 | 9篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1975年 | 8篇 |
1974年 | 7篇 |
1973年 | 6篇 |
排序方式: 共有814条查询结果,搜索用时 31 毫秒
71.
M.A. BramantyaT. Sawada 《Journal of magnetism and magnetic materials》2011,323(10):1330-1333
Structure of magnetorheological (MR) fluids depends on the strength of the magnetic field applied and on the mode of its application. The ultrasonic wave propagation velocity changes under the effect of an external magnetic field as a result of formation of clusters arranged along the direction of the field in the MR fluids. Therefore, we propose a qualitative analysis of these clustering structures by measuring properties of ultrasonic propagation. Since the MR fluids are opaque, the non-contact inspection using this ultrasonic technique can be very useful. In this study, we measured ultrasonic propagation velocity in MR fluid influenced by an external magnetic field for different swept rate precisely. With increasing magnetic field intensity, the changes of the ultrasonic wave velocity are more pronounced. Sedimentation effect takes place in certain time for different swept rate due to magnetic particle size and it follows linear relationship in log scale. Significant differences of the ultrasonic wave velocity are established between the case when the field is swept at a constant rate and the case when it is stepped up. 相似文献
72.
73.
Journal of Sol-Gel Science and Technology - 相似文献
74.
75.
76.
Novel fluoroalkyl end‐capped vinyltrimethoxysilane oligomer/hydroxyapatite (HAp) nanocomposites were prepared by the reaction of calcium nitrate tetrahydrate and phosphoric acid in the presence of the corresponding oligomer. These fluorinated oligomer/HAp composites thus obtained are nanometer size‐controlled fine particles (83–173 nm), and were found to exhibit good dispersibility in methanol, ethanol, and isopropyl alcohol. These fluorinated HAp nanocomposites were applied to the surface modification of glass and poly(methyl methacrylate) (PMMA) to exhibit good hydro‐ and oleophobic characteristics imparted by fluorine on their surface. In addition, the surface structural changes of the modified polyethylene terephtalate and PMMA films treated with these fluorinated nanocomposites before and after soaking in a simulated body fluid (SBF) were analyzed by using SEM, XRD, and EDX to observe the formation of spherical HAp deposits on the surface. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
77.
Diogo P. Rivelli Carlos A. H. Filho Rebeca L. Almeida Cristina D. Ropke Tânia C. H. Sawada Silvia B. M. Barros 《Photochemistry and photobiology》2010,86(5):1005-1007
Chlorogenic acid is a natural potent antioxidant. It can be used in cosmetics formulations, but for this purpose its photochemical stability should be determined to ensure that the compound will not be degraded after UV radiation exposure. To evaluate this possibility, the concentration of a chlorogenic acid solution was determined by HPLC before and after UVA and UVB irradiation. The results indicate that chlorogenic acid is not degraded under UVA or UVB irradiation. 相似文献
78.
Ali Izadi-Najafabadi Takeo Yamada Don N. Futaba Hiroaki Hatori Sumio Iijima Kenji Hata 《Electrochemistry communications》2010,12(12):1678-1681
We report the energy and power voltage-dependencies of supercapacitors using single-walled carbon nanotube electrodes. The energy density was dependent on the cell-voltage cubed (up to 4 V: E = 1.43 × V3). The cubic relationship was attributed to the linear increase of the capacitance as a function of voltage, enabled by electrochemical doping. Furthermore, while up to 3.5 V, the maximum power rating of the nanotube electrodes increased as a function of the cell-voltage squared, beyond 3.5 V, a decline in power was observed as a result of depletion of the electrolyte's ions. 相似文献
79.
Journal of Sol-Gel Science and Technology - 相似文献
80.
A chromoionophore-derived calix[4]crown, 1 , possessing an effective signal-controllable function by metal ionic inputs has been newly synthesized, whose function is mainly of our interest, by transforming the process of receptor activation to one that may be detected by an optical signal (i.e. color change), the basic feature of antagonist-agonist competition may be reproduced readily and visually detected. The process would be particularly new within the field of optical read-out receptors. Further, from the standpoint of material sciences, the controllable signal function may not only be welcome for molecular information processing, but also contribute to the design of new sensory materials. 相似文献