全文获取类型
收费全文 | 3233篇 |
免费 | 100篇 |
国内免费 | 17篇 |
专业分类
化学 | 2581篇 |
晶体学 | 32篇 |
力学 | 37篇 |
数学 | 217篇 |
物理学 | 483篇 |
出版年
2023年 | 19篇 |
2022年 | 21篇 |
2021年 | 21篇 |
2020年 | 45篇 |
2019年 | 46篇 |
2018年 | 29篇 |
2017年 | 26篇 |
2016年 | 61篇 |
2015年 | 60篇 |
2014年 | 96篇 |
2013年 | 201篇 |
2012年 | 153篇 |
2011年 | 196篇 |
2010年 | 127篇 |
2009年 | 120篇 |
2008年 | 193篇 |
2007年 | 183篇 |
2006年 | 199篇 |
2005年 | 207篇 |
2004年 | 182篇 |
2003年 | 153篇 |
2002年 | 150篇 |
2001年 | 59篇 |
2000年 | 56篇 |
1999年 | 35篇 |
1998年 | 39篇 |
1997年 | 30篇 |
1996年 | 27篇 |
1995年 | 25篇 |
1994年 | 37篇 |
1993年 | 17篇 |
1992年 | 30篇 |
1991年 | 21篇 |
1990年 | 13篇 |
1989年 | 12篇 |
1988年 | 21篇 |
1987年 | 16篇 |
1986年 | 19篇 |
1985年 | 36篇 |
1984年 | 52篇 |
1983年 | 29篇 |
1982年 | 39篇 |
1981年 | 45篇 |
1980年 | 29篇 |
1979年 | 29篇 |
1978年 | 21篇 |
1977年 | 26篇 |
1976年 | 19篇 |
1975年 | 18篇 |
1974年 | 21篇 |
排序方式: 共有3350条查询结果,搜索用时 46 毫秒
991.
A study by computer simulation is reported of the behavior of a quantized vortex line at a very low temperature when there is continuous excitation of low-frequency Kelvin waves. There is no dissipation except by phonon radiation at a very high frequency. It is shown that nonlinear coupling leads to a net flow of energy to higher wave numbers and to the development of a simple spectrum of Kelvin waves that is insensitive to the strength and frequency of the exciting drive. The results are likely to be relevant to the decay of turbulence in superfluid 4He at very low temperatures. 相似文献
992.
Lasing at resonantly coupled whispering-gallery mode frequencies is observed in photonic molecules consisting of bispheres of 4.2 and 5.1 microm in diameter placed in a silicon V-groove. We examine spatial profiles of photonic molecule modes by use of frequency-resolved imaging and reveal bonding and antibonding mode features. From the lasing threshold characteristics, we quantitatively measure the quality factor and the spontaneous-emission coupling ratio of the photonic molecule modes and confirm that strong coherent coupling leads to photonic molecule modes. 相似文献
993.
M. Asai K. Tsukada S. Ichikawa M. Sakama H. Haba Y. Nagame I. Nishinaka K. Akiyama A. Toyoshima T. Kaneko Y. Oura Y. Kojima M. Shibata 《The European Physical Journal A - Hadrons and Nuclei》2003,16(1):17-19
A new neutron-deficient berkelium isotope 241Bk produced in the 239Pu(6Li, 4n) reaction has been identified using a gas-jet coupled on-line isotope separator. Cm K and L X-rays associated with the EC decay of 241Bk were observed in the mass-241 fraction, and three γ transitions were attributed to the EC decay of 241Bk through X-γ coincidences. The half-life of 241Bk was determined to be 4.6±0.4 min which is 1/2-1/4 of that of theoretical predictions. The half-life value and the observed
γ transitions can be consistently explained as a consequence of the allowed EC transition of π7/2+[633] → ν7/2+[624].
Received: 14 October 2002 / Accepted: 6 November 2002 / Published online: 17 January 2003
RID="a"
ID="a"e-mail: asai@tandem.tokai.jaeri.go.jp
Communicated by J. ?yst? 相似文献
994.
A novel gold(III) complex with a monodentate 5,5-dimethylhydantoin ligand, [Au(dmh)4]-, is square planar in geometry, inert and highly stable in alkaline solutions because of soft acid-base interactions, and electrochemically reduced near -0.3 V vs Ag/AgCl to give a gold(0) film with a high current efficiency. 相似文献
995.
Pd-catalyzed C3-selective allylation of indoles with allyl alcohols promoted by triethylborane 总被引:1,自引:0,他引:1
Kimura M Futamata M Mukai R Tamaru Y 《Journal of the American Chemical Society》2005,127(13):4592-4593
Under palladium catalysis, Et3B nicely promotes allyl alcohols to undergo C3-selective allylation of indoles and tryptophan; the yields range 75-95%. 相似文献
996.
Kajitani T Masu H Kohmoto S Yamamoto M Yamaguchi K Kishikawa K 《Journal of the American Chemical Society》2005,127(4):1124-1125
Achiral rodlike molecules possessing an ester group generated a chiral smectic liquid crystal phase. 相似文献
997.
A new tricyclo[4.2.0.0(2,8)]octane-type neolignan, 6-allyl-7-(3,4-dimethoxyphenyl)- 2,3-dimethoxy-8-methyl-tricyclo[4.2.0.0(2,8)]oct-3-en-5-one, together with 15 known lignan and neolignan derivatives have been isolated from the flower buds of Magnolia denudata DESR. and the structures of these compounds have been elucidated based on the 1H- and 13C-NMR spectra and two-dimensional NMR methods such as HMBC, HMQC, and NOESY. 相似文献
998.
Kuwata-Gonokami M Saito N Ino Y Kauranen M Jefimovs K Vallius T Turunen J Svirko Y 《Physical review letters》2005,95(22):227401
We examine the spectral dependence in the visible frequency range of the polarization rotation of two-dimensional gratings consisting of chiral gold nanostructures with subwavelength features. The gratings, which do not diffract, are shown to exhibit giant specific rotation (approximately 10(4) degrees/mm) of polarization in direct transmission at normal incidence. The rotation is the same for light incident on the front and back sides of the sample. Such reciprocity indicates three dimensionality of the structure arising from the asymmetry of light-plasmon coupling at the air-metal and substrate-metal interfaces. The structures thus enable polarization control with quasi-two-dimensional planar objects. However, in contradiction with recently suggested interpretation of experiments on larger scale but otherwise similar structures, the observed polarization phenomena violate neither reciprocity nor time-reversal symmetry. 相似文献
999.
H.?IimuraEmail author M.?Asai S.?Ichikawa J.?Katakura M.?Magara A.?Osa M.?Oshima N.?Shinohara H.?Yamamoto 《The European Physical Journal A - Hadrons and Nuclei》2005,23(1):33-39
The low-lying levels in 127La have been studied through the -decay of 127Ce ( T1/2 = 29s) produced by bombarding a natMo target with a 185-MeV 35Cl beam. Reaction products were on-line mass-separated, and -ray singles and - coincidence measurements were performed. Conversion electrons were also measured and multipolarities of transitions have been derived. The half-life of the 210.9-keV level was determined to be (1.9±0.3)ns by the - delayed coincidence technique. The level scheme obtained has been compared with calculations based on the Nilsson model. 相似文献
1000.