全文获取类型
收费全文 | 1843篇 |
免费 | 70篇 |
国内免费 | 13篇 |
专业分类
化学 | 1233篇 |
晶体学 | 26篇 |
力学 | 30篇 |
数学 | 395篇 |
物理学 | 242篇 |
出版年
2023年 | 11篇 |
2021年 | 28篇 |
2020年 | 25篇 |
2019年 | 14篇 |
2018年 | 35篇 |
2017年 | 24篇 |
2016年 | 65篇 |
2015年 | 35篇 |
2014年 | 55篇 |
2013年 | 104篇 |
2012年 | 87篇 |
2011年 | 88篇 |
2010年 | 58篇 |
2009年 | 58篇 |
2008年 | 92篇 |
2007年 | 72篇 |
2006年 | 74篇 |
2005年 | 73篇 |
2004年 | 62篇 |
2003年 | 47篇 |
2002年 | 56篇 |
2001年 | 24篇 |
2000年 | 37篇 |
1999年 | 34篇 |
1998年 | 34篇 |
1997年 | 23篇 |
1996年 | 19篇 |
1995年 | 24篇 |
1994年 | 26篇 |
1993年 | 12篇 |
1991年 | 19篇 |
1990年 | 12篇 |
1989年 | 15篇 |
1988年 | 23篇 |
1987年 | 29篇 |
1986年 | 14篇 |
1984年 | 17篇 |
1983年 | 17篇 |
1982年 | 17篇 |
1981年 | 26篇 |
1980年 | 25篇 |
1978年 | 19篇 |
1977年 | 20篇 |
1976年 | 19篇 |
1975年 | 16篇 |
1974年 | 15篇 |
1973年 | 29篇 |
1972年 | 14篇 |
1970年 | 16篇 |
1962年 | 11篇 |
排序方式: 共有1926条查询结果,搜索用时 15 毫秒
1.
2.
It is known that under resonance conditions, a group of strongly interacting bosonic atoms, trapped in a double-well potential, mimics a single particle, performing Rabi oscillations between the wells. By implication, all atoms need to tunnel at roughly the same time, even though the Bose–Hubbard Hamiltonian accounts only for one-atom-at-a-time transfers. The mechanism of this collective behavior is analyzed, the Rabi frequencies in the process are evaluated, and the limitation of this simple picture is discussed. In particular, it is shown that the small rapid oscillations superimposed on the slow Rabi cycle result from splitting the transferred cluster at the sudden onset of tunnelling, and disappear if tunnelling is turned on gradually. 相似文献
3.
Mark Edgar Dee Hayward Fatemeh Zeinali Shahzad Riaz George W. Weaver 《Magnetic resonance in chemistry : MRC》2020,58(2):170-185
A simple to use nuclear magnetic resonance analysis method has been tested on complex 1H, 19F, and 13C multiplets. This open-source line-shape analysis method analysis of total lineshape (ANATOLIA)1 provides some significant advantages over traditional assign-iterate methods of NMR spectral analysis by avoiding false minima and progressing optimisation to the global minimum. The target molecules are 1-perfluorotol-4-yl-2-perfluorotol-4-yl-oxymethyl-1H-benzimidazole (molecule-I) and 1-tetrafluoropyrid-4-yl-2-tetrafluoropyrid-4-yl-thio-1H-benzimidazole (molecule-II) which were produced as part of a family of fluorinated drug scaffolds prepared for anticancer and antiparasitic screening. Spectra display significant second-order effects with 1H Δδ = 3.68 and 4.67 Hz for the aromatic hydrogen “triplets”, with 19F 4JAA', 4JBB', 4JXX', and 4JYY' coupling constants range from +4.8 to −14.0 Hz and for 13C-isotopomers 19F Δδ of up to 111.56 Hz. A spin-system of six coupling nuclei (HaHbHcHd FYFY') was analysed in 12 s, a spin-system of nine coupling fluorine nuclei (AA'BB'CCC-YY') was analysed within 2 min, and 10 coupling nuclei (XX'YY'ZZZ-BB'-Hd) was optimised in 6 min using a laptop computer. ANATOLIA was also robust enough to be able to yield accurate spectral values from inaccurate input values. In both compounds, a fluorine–fluorine coupling constant was identified between the two fluoro-aromatic rings (FBB' and FYY') of +4.05 and +4.67 Hz and attributed to a through-space interaction. Ab initio structure optimisations and coupling constant calculations provided useful input data for spectral analysis. A modern 19F nuclear magnetic resonance spectrum of perfluorotoluene (octafluorotoluene) and analysis from 1975 was used as a test data set to assess ANATOLIA. 相似文献
4.
ABSTRACT A new density functional for the study of associating inhomogeneous fluids based on Wertheim's first-order thermodynamic perturbation theory is presented and compared to the most currently used associating density functionals. This functional is developed using the weighted density approximation in the range of association of hard spheres. We implement this functional within the framework of classical density functional theory together with modified fundamental measure theory to account for volume exclusion of hard spheres. This approach is tested against molecular simulations from literature of pure associating hard spheres and mixtures of non-associationg and associating hard spheres with different number of bonding sites close to a hard uniform wall. Furthermore, we compare and review our results with the performance of associating functionals from literature, one based on fundamental measure theory and the inhomogeneous version of Wertheim's perturbation theory. Results obtained with classical DFT and the three functionals show excellent agreement with molecular simulations in systems with one hard wall. For the cases of small pores where only one or two layers of fluid are allowed discrepancies between results with classical DFT and molecular simulations were found. 相似文献
5.
6.
7.
8.
Tom Edgar 《Journal of Algebraic Combinatorics》2007,26(3):357-362
Twisted Bruhat orders are certain partial orders on a Coxeter system (W,S) associated to initial sections of reflection orders, which are certain subsets of the set of reflections T of a Coxeter system. We determine which subsets of T give rise to a partial order on W in the same way. 相似文献
9.
10.