全文获取类型
收费全文 | 43282篇 |
免费 | 172篇 |
国内免费 | 293篇 |
专业分类
化学 | 31198篇 |
晶体学 | 18篇 |
力学 | 218篇 |
综合类 | 14篇 |
数学 | 275篇 |
物理学 | 12024篇 |
出版年
2023年 | 21篇 |
2022年 | 24篇 |
2021年 | 13篇 |
2020年 | 14篇 |
2019年 | 22篇 |
2018年 | 26篇 |
2017年 | 15篇 |
2016年 | 25篇 |
2015年 | 24篇 |
2014年 | 44篇 |
2013年 | 37篇 |
2012年 | 4366篇 |
2011年 | 5838篇 |
2010年 | 950篇 |
2009年 | 171篇 |
2008年 | 4277篇 |
2007年 | 4197篇 |
2006年 | 4201篇 |
2005年 | 4028篇 |
2004年 | 3192篇 |
2003年 | 2439篇 |
2002年 | 2020篇 |
2001年 | 1281篇 |
2000年 | 1607篇 |
1999年 | 363篇 |
1998年 | 148篇 |
1997年 | 122篇 |
1996年 | 580篇 |
1995年 | 429篇 |
1994年 | 495篇 |
1993年 | 661篇 |
1992年 | 550篇 |
1991年 | 251篇 |
1990年 | 242篇 |
1989年 | 204篇 |
1988年 | 137篇 |
1987年 | 165篇 |
1986年 | 179篇 |
1985年 | 144篇 |
1984年 | 33篇 |
1983年 | 18篇 |
1982年 | 20篇 |
1981年 | 15篇 |
1979年 | 9篇 |
1977年 | 8篇 |
1975年 | 14篇 |
1972年 | 12篇 |
1957年 | 7篇 |
1956年 | 7篇 |
1948年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 687 毫秒
91.
92.
93.
94.
95.
96.
97.
Alam MS Katayama N Kim IJ Li WC Lou XC Sun CR Bortoletto D Goldberg M Horwitz N Mestayer MD Moneti GC Sharma V Shipsey IP Skwarnicki T Csorna SE Letson T Brock IC Ferguson T Artuso M Bebek C Berkelman K Blucher E Byrd J Cassel DG Cheu E Coffman DM Crawford G DeSalvo R DeWire JW Drell PS Ehrlich R Galik RS Gittelman B Gray SW Halling AM Hartill DL Heltsley BK Kandaswamy J Kowalewski R Kreinick DL Kubota Y Lewis JD Mistry NB Mueller J Namjoshi R Nandi S Nordberg E O'Grady C Peterson D Pisharody M 《Physical review D: Particles and fields》1989,40(11):3790
98.
Abachi S Derrick M Kooijman P Musgrave B Price LE Repond J Sugano K Blockus D Brabson B Brom J Jung C Ogren H Rust DR Akerlof C Chapman J Errede D Ken MT Meyer DI Neal H Nitz D Thun R Tschirhart R Baringer P Bylsma BG DeBonte R Koltick D Low EH McIlwain RL Miller DH Ng CR Shibata EI 《Physical review D: Particles and fields》1989,40(3):902-905
99.
Keggin heteropolyanions [XM(12)O(40)](n-) have various isomeric structures, alpha and beta being the most common. Conventionally, the alpha structure appears to be the most stable, but calculations carried out at the DFT level for X = P(V), Si(IV), Al(III), As(V), Ge(IV), and Ga(III) and M = W(VI) and Mo(VI) show that this stability depends on several factors, particularly on the nature of the heteroatom (X) and the total charge of the cluster. In this paper, we apply the clathrate model to the Keggin molecule to carry out a fragment-interaction study to elucidate when and why the traditional relative stability of various isomers can be inverted. The fully oxidized anions that have inverted the traditional stability trend in this series are [AlW(12)O(40)](5-) and [GaW(12)O(40)](5-), both of which contain a third-group heteroatom and an overall charge of -5. beta-isomers are always more easily reduced than alpha-isomers. This experimental observation suggests that reduction favors the stability of beta-isomers and one of the most important results of this study is that the alpha/beta inversion is achieved in most cases after the second reduction. The alpha- and beta-isomers may have different properties because the energy of the LUMO, a symmetry-adapted d(xy)-metal orbital, is different. 相似文献
100.
Sun S Szakal C Winograd N Wucher A 《Journal of the American Society for Mass Spectrometry》2005,16(10):1677-1686
The ion bombardment-induced release of particles from a metal surface is investigated using energetic fullerene cluster ions as projectiles. The total sputter yield as well as partial yields of neutral and charged monomers and clusters leaving the surface are measured and compared with corresponding data obtained with atomic projectile ions of similar impact kinetic energy. It is found that all yields are enhanced by about one order of magnitude under bombardment with the C60+ cluster projectiles compared with Ga+ ions. In contrast, the electronic excitation processes determining the secondary ion formation probability are unaffected. The kinetic energy spectra of sputtered particles exhibit characteristic differences which reflect the largely different nature of the sputtering process for both types of projectiles. In particular, it is found that under C60+ impact (1) the energy spectrum of sputtered atoms peaks at significantly lower kinetic energies than for Ga+ bombardment and (2) the velocity spectra of monomers and dimers are virtually identical, a finding which is in pronounced contrast to all published data obtained for atomic projectiles. The experimental findings are in reasonable agreement with recent molecular dynamics simulations. 相似文献