全文获取类型
收费全文 | 1656篇 |
免费 | 51篇 |
国内免费 | 7篇 |
专业分类
化学 | 929篇 |
晶体学 | 8篇 |
力学 | 22篇 |
数学 | 220篇 |
物理学 | 535篇 |
出版年
2021年 | 11篇 |
2020年 | 25篇 |
2019年 | 18篇 |
2018年 | 17篇 |
2017年 | 11篇 |
2016年 | 32篇 |
2015年 | 21篇 |
2014年 | 21篇 |
2013年 | 67篇 |
2012年 | 64篇 |
2011年 | 90篇 |
2010年 | 42篇 |
2009年 | 41篇 |
2008年 | 67篇 |
2007年 | 54篇 |
2006年 | 55篇 |
2005年 | 57篇 |
2004年 | 58篇 |
2003年 | 44篇 |
2002年 | 80篇 |
2001年 | 37篇 |
2000年 | 28篇 |
1999年 | 23篇 |
1998年 | 18篇 |
1997年 | 17篇 |
1996年 | 40篇 |
1995年 | 40篇 |
1994年 | 32篇 |
1993年 | 42篇 |
1992年 | 47篇 |
1991年 | 33篇 |
1990年 | 32篇 |
1989年 | 35篇 |
1988年 | 18篇 |
1987年 | 17篇 |
1986年 | 21篇 |
1985年 | 29篇 |
1984年 | 22篇 |
1983年 | 24篇 |
1982年 | 17篇 |
1981年 | 20篇 |
1980年 | 22篇 |
1979年 | 20篇 |
1978年 | 20篇 |
1977年 | 16篇 |
1975年 | 19篇 |
1974年 | 25篇 |
1973年 | 26篇 |
1972年 | 10篇 |
1970年 | 13篇 |
排序方式: 共有1714条查询结果,搜索用时 218 毫秒
41.
Ian L. Cooper Christopher N. M. Pounder 《International journal of quantum chemistry》1983,23(1):257-270
Local Coulomb correlation hole distribution functions may be used to assess the extent to which electron correlation effects are present in large scale SCF + CI wave functions. From a set of modified virtual orbitals, ordered according to their interaction with the SCF configuration, we have constructed a limited SCF + CI wave function with improved convergence characteristics with respect to that formed from the canonical virtual orbital set. These wave functions, of the same size yet with different energies, have been used to examine the range and depth of local Coulomb correlation holes in FCN. In all cases, the depth of the local Coulomb hole is no more than 10% or so of that of the corresponding Fermi hole, and the range Fermi correlation is generally less than that of Fermi correlation. This is particularly marked in the high density regions around the nuclei. The significance of our results is discussed in relation to a recent proposal for the incorporation of Coulomb correlation into the local exchange method. 相似文献
42.
Cooper TJ Talaty ER Van Stipdonk MJ 《Journal of the American Society for Mass Spectrometry》2005,16(8):1305-1310
We report a new fragmentation pathway for the CID of (b3 - 1 + Cat)+ product ions derived from the model peptide AXAG, where X = beta-alanine, gamma-aminobutyric acid, epsilon-amino-n-caproic acid, or 4-aminomethylbenzoic acid. By changing the amino acid to the C-terminal side of the amino acid X, and incorporating 15N and 13C labeled residues at the same position, we conclude that the dissociation pathway most likely leads to a metal cationized nitrile. With respect to the various amino acids at position X, the putative nitrile product becomes more prominent, relative to the conventional (a3 - 1 + Cat)+ species, in the order beta-alanine < gamma-aminobutyric acid < epsilon-aminocaproic acid < 4-aminomethylbenzoic acid. The pathway is not observed for peptides with alpha-amino acids at position X. The product ion is observed most prominently during the CID of Li+ and Na+ cationized peptides, only to a small extent for Ag+ cationized peptides, and not at all from protonated analogues. 相似文献
43.
Long-lived metastable negative ions of CO2 have been observed in the gas phase as direct products of electron and cesium collisions with organic molecules which contain “bent” CO2 as a basic unit. The long autodetachment life-times are attributed to two related factors - first, the potential energy curve of CO−2(2A1) lies below that of CO2(1A1) at 134°, and, second, an unfavorable Franck-Condon overlap exists between the bent ion (134°) and the linear neutral parent. 相似文献
44.
Abachi S Abbott B Abolins M Acharya BS Adam I Adams DL Adams M Ahn S Aihara H Alitti J Álvarez G Alves GA Amidi E Amos N Anderson EW Aronson SH Astur R Avery RE Baden A Balamurali V Balderston J Baldin B Bantly J Bartlett JF Bazizi K Bendich J Beri SB Bertram I Bezzubov VA Bhat PC Bhatnagar V Bhattacharjee M Bischoff A Biswas N Blazey G Blessing S Boehnlein A Bojko NI Borcherding F Borders J Boswell C Brandt A Brock R Bross A Buchholz D Burtovoi VS Butler JM Casey D Castilla-Valdez H 《Physical review letters》1995,75(6):1023-1027
45.
46.
Abachi S Abbott B Abolins M Acharya BS Adam I Adams DL Adams M Ahn S Aihara H Alitti J Álvarez G Alves GA Amidi E Amos N Anderson EW Aronson SH Astur R Avery RE Baden A Balamurali V Balderston J Baldin B Bantly J Bartlett JF Bazizi K Bendich J Beri SB Bertram I Bezzubov VA Bhat PC Bhatnagar V Bhattacharjee M Bischoff A Biswas N Blazey G Blessing S Boehnlein A Bojko NI Borcherding F Borders J Boswell C Brandt A Brock R Bross A Buchholz D Burtovoi VS Butler JM Casey D Castilla-Valdez H 《Physical review letters》1995,75(4):618-623
47.
48.
49.
50.