全文获取类型
收费全文 | 376篇 |
免费 | 9篇 |
国内免费 | 4篇 |
专业分类
化学 | 316篇 |
晶体学 | 15篇 |
力学 | 8篇 |
数学 | 8篇 |
物理学 | 42篇 |
出版年
2022年 | 3篇 |
2021年 | 3篇 |
2020年 | 3篇 |
2019年 | 3篇 |
2018年 | 4篇 |
2017年 | 4篇 |
2016年 | 6篇 |
2015年 | 6篇 |
2014年 | 6篇 |
2013年 | 21篇 |
2012年 | 9篇 |
2011年 | 10篇 |
2010年 | 10篇 |
2009年 | 11篇 |
2008年 | 15篇 |
2007年 | 16篇 |
2006年 | 14篇 |
2005年 | 15篇 |
2004年 | 22篇 |
2003年 | 19篇 |
2002年 | 16篇 |
2001年 | 9篇 |
2000年 | 10篇 |
1999年 | 7篇 |
1998年 | 11篇 |
1997年 | 8篇 |
1996年 | 8篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 9篇 |
1991年 | 6篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 8篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 8篇 |
1984年 | 13篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 6篇 |
1974年 | 4篇 |
1928年 | 2篇 |
排序方式: 共有389条查询结果,搜索用时 15 毫秒
311.
Ikue Itamoto Hideshi Ishida Masahiko Higashiyama Daigo Miki Genta Kawahara 《Heat and Mass Transfer》2009,46(2):153-165
In this study surface-averaged and extremal properties of heat transfer and shear stress on the upper wall surface of Rayleigh–Bénard
convection are numerically examined. The Prandtl number was raised up to 103, and the Rayleigh number was changed between 104 and 107. As a result, average Nusselt number Nu and shear rate τ/Pr depends on Pr, Ra, and the entire numerical results are distributed between two correlation equations corresponding to small and large Pr. The small and large Pr equations are closely related to steady and unsteady flow regimes, respectively. Nevertheless, a single relation τ/Pr ~ Nu
3.0 exists to explain the entire results. Similarly the change of local maximal properties Nu
max and τ
max/Pr depends on Pr, Ra, and these values are also distributed between two correlation equations corresponding to small and large Pr cases. Despite such complicated dependence we can obtain a correlation equation as a form of τ
max/Pr ~ Nu
max2.6, which has not been obtained theoretically. 相似文献
312.
313.
Jun Komiyama Kenichi Eriguchi Yoshihisa Abe Shunichi Suzuki Hideo Nakanishi Takayoshi Yamane Hisashi Murakami Akinori Koukitu 《Journal of Crystal Growth》2008,310(1):96-100
The hydride vapor phase epitaxy (HVPE) of {0 0 0 1} AlN films on {1 1 1} Si substrates covered with epitaxial {1 1 1} cubic SiC (3C-SiC intermediate layers) was carried out. 3C-SiC intermediate layers are essential to obtain high-quality AlN films on Si substrates, because specular AlN films are obtained with 3C-SiC intermediate layers, whereas rough AlN films are obtained without 3C-SiC intermediate layers. We determined the polarities of AlN films and the underlying 3C-SiC intermediate layers by convergent beam electron diffraction (CBED) using transmission electron microscopy. For the first time, the polarities of the AlN films and the 3C-SiC intermediate layers were determined as Al and Si polarities, respectively. The AlN films were hardly etched by aqueous KOH solution, thereby indicating Al polarity. This supports the results obtained by CBED. The result is also consistent with electrostatic arguments. An interfacial structure was proposed. The 3C-SiC intermediate layers are promising for the HVPE of AlN films on Si substrates. 相似文献
314.
Hideshi YAMANE 《Frontiers of Mathematics in China》2013,8(5):1077-1083
We report our recent result about the long-time asymptotics for the defocusing integrable discrete nonlinear Schr?dinger equation of Ablowitz- Ladik. The leading term is a sum of two terms that oscillate with decay of order t -1/2 相似文献
315.
316.
Isabella G. Alonso Lais T. Yamane Verônica S. de Freitas-Blanco Luiz F.T. Novaes Michelle Franz-Montan Eneida de Paula Marili V.N. Rodrigues Rodney A.F. Rodrigues Julio C. Pastre 《Tetrahedron》2018,74(38):5192-5199
A 5-step synthesis of spilanthol (affinin) is reported, where the route features complete control of alkene geometry during the assembling of the double bonds, with the use of a Sonogashira cross-coupling reaction, a Z-selective alkyne semi-reduction and a HWE olefination reaction as the key steps. A simplified analogue was also prepared in 4 steps. Both compounds were found to permeate dermatomed pig ear skin through an in vitro Franz-type diffusion cell. The simplified analogue presented a superior anesthetic effect in vivo, using the tail flick model, when compared to spilanthol and to the commercial standard EMLA®. These results suggest that both spilanthol and its analogue could be useful as a topical anesthetic in clinical practice. 相似文献
317.
A simple method for the synthesis of amides has been developed by molybdenum-mediated carbamoylation of aryl halides. Whereas the conventional palladium-catalyzed three-component coupling reaction requires a large excess of gaseous carbon monoxide, the incorporation of carbon monoxide in this Mo-mediated carbamoylation reaction is so efficient that it requires only a slight excess amount of carbon monoxide in the form of its molybdenum complex, Mo(CO)(6). The reaction is applicable for the synthesis of a wide variety of not only secondary and tertiary amides but also primary amides by using aqueous ammonia. 相似文献
318.
This paper treats the generalized quantum group with a bi-homomorphism χ for which the corresponding generalized root system is a finite set. We establish a Harish-Chandra type theorem describing the (skew) centers of U. 相似文献
319.
320.
Synthesis and asymmetric anionic polymerization of substituted 7‐aryl‐2,6‐dimethyl‐1,4‐benzoquinone methides
下载免费PDF全文
![点击此处可从《Journal of polymer science. Part A, Polymer chemistry》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Takahiro Uno Hiroshi Ohta Atsushi Yamane Masataka Kubo Takahito Itoh 《Journal of polymer science. Part A, Polymer chemistry》2015,53(3):437-444
Substituted 7‐aryl‐2,6‐dimethyl‐1,4‐benzoquinone methides which have an electron‐donating methoxy substituent at the para‐position (p‐OMe, 2a ) or an electron‐withdrawing chloro one at the para‐ (p‐Cl, 2b ), meta‐ (m‐Cl, 2c ) , and ortho‐positions (o‐Cl, 2d ) of the benzene ring were synthesized, and their asymmetric anionic polymerizations using the complex of lithium 4‐isopropylphenoxide with (?)‐sparteine were carried out in toluene at 0 °C. The polymers with negative specific rotation were obtained for all of four monomers, and the polymer obtained from 2a showed smaller specific rotation value than that of polymer having no substituent (p‐H, 1 ) on the phenyl group and the polymers obtained from 2b–d showed larger ones. It was found that the kind of a substituent and its substitution position on the phenyl group affect significantly the optical activity of polymers. The largest specific rotation value of [α]435= ?153.2° was obtained in the polymerization of 2d with an ortho‐chloro substituent. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 437–444 相似文献