全文获取类型
收费全文 | 2400篇 |
免费 | 95篇 |
国内免费 | 14篇 |
专业分类
化学 | 1741篇 |
晶体学 | 10篇 |
力学 | 40篇 |
数学 | 396篇 |
物理学 | 322篇 |
出版年
2022年 | 14篇 |
2021年 | 26篇 |
2020年 | 54篇 |
2019年 | 37篇 |
2018年 | 31篇 |
2017年 | 21篇 |
2016年 | 72篇 |
2015年 | 60篇 |
2014年 | 64篇 |
2013年 | 99篇 |
2012年 | 95篇 |
2011年 | 100篇 |
2010年 | 90篇 |
2009年 | 76篇 |
2008年 | 100篇 |
2007年 | 102篇 |
2006年 | 119篇 |
2005年 | 103篇 |
2004年 | 91篇 |
2003年 | 80篇 |
2002年 | 94篇 |
2001年 | 45篇 |
2000年 | 49篇 |
1999年 | 52篇 |
1998年 | 46篇 |
1997年 | 54篇 |
1996年 | 55篇 |
1995年 | 53篇 |
1994年 | 49篇 |
1993年 | 38篇 |
1992年 | 37篇 |
1991年 | 36篇 |
1990年 | 26篇 |
1989年 | 41篇 |
1988年 | 22篇 |
1987年 | 15篇 |
1986年 | 24篇 |
1985年 | 25篇 |
1984年 | 28篇 |
1983年 | 32篇 |
1981年 | 20篇 |
1980年 | 24篇 |
1979年 | 30篇 |
1978年 | 26篇 |
1977年 | 20篇 |
1976年 | 20篇 |
1975年 | 15篇 |
1974年 | 13篇 |
1973年 | 18篇 |
1971年 | 17篇 |
排序方式: 共有2509条查询结果,搜索用时 0 毫秒
111.
112.
113.
114.
Exciton‐Vibrational Couplings in Homo‐ and Heterodimer Stacks of Perylene Bisimide Dyes within Cyclophanes: Studies on Absorption Properties and Theoretical Analysis
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
David Bialas Christoph Brüning Dr. Felix Schlosser Dr. Benjamin Fimmel Johannes Thein Prof. Dr. Volker Engel Prof. Dr. Frank Würthner 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(42):15011-15018
The optical properties of a series of three cyclophanes comprising either identical or different perylene bisimide (PBI) chromophores were studied by UV/Vis absorption spectroscopy and their distinctive spectral features were analyzed. All the investigated cyclophanes show significantly different absorption features with respect to the corresponding constituent PBI monomers indicating strong coupling interactions between the PBI units within the cyclophanes. DFT calculations suggest a π‐stacked arrangement of the PBI units at close van der Waals distance in the cyclophanes with rotational displacement. Simulations of the absorption spectra based on time‐dependent quantum mechanics properly reproduced the experimental spectra, revealing exciton‐vibrational coupling between the chromophores both in homo‐ and heterodimer stacks. The PBI cyclophane comprising two different PBI chromophores represents the first example of a PBI heterodimer stack for which the exciton coupling has been investigated. The quantum dynamics analysis reveals that exciton coupling in heteroaggregates is indeed of similar strength as for homoaggregates. 相似文献
115.
116.
We study the perturbation theory for the eigenvalue problem of a formal matrix product A
1
s
1 ··· A
p
s
p, where all A
k are square and s
k {–1, 1}. We generalize the classical perturbation results for matrices and matrix pencils to perturbation results for generalized deflating subspaces and eigenvalues of such formal matrix products. As an application we then extend the structured perturbation theory for the eigenvalue problem of Hamiltonian matrices to Hamiltonian/skew-Hamiltonian pencils. 相似文献
117.
Based on detailed theoretical analyses, we present, for the first time, direct evidence that the significant interface dipole commonly observed for atoms and molecules physisorbed on metal surfaces originates from exchangelike effects. In the case of Xe, previously proposed contributions from chemical interactions do not play a significant role. 相似文献
118.
Gain-guided diode lasers usually have emission wavelengths determined by the manufacturing process, with typically 0.5-1-nm bandwidth. Furthermore, their beam quality is rather poor. We show that external cavities allow for tunable narrow-bandwidth operation of gain-guided diode lasers. At the same time the beam quality is drastically improved; almost diffraction-limited light of more than 200 mW has been achieved over the whole tuning range from 910 to 942 nm with narrow bandwidth. 相似文献
119.
Volker Prautzsch Stefan Ibach 《Journal of inclusion phenomena and macrocyclic chemistry》1999,33(4):427-458
Very large ring systems, containing more than 50 ring members, are becoming increasingly important in different topics in natural sciences. These so-called gigantocycles differ from smaller macrocycles in physical properties, special structural features and chemical behaviour. This article is meant to be the first summary of such ring systems and a synopsis of the most remarkable examples with their fascinating nano-scaled structures and ingenious synthesis. To restrict the scope of the article, only isolated and completely characterized, monodisperse compounds are presented. Furthermore, attention is mainly directed at organic gigantocycles. Some ultracycles with more than 100 ring members, mainly occurring in polymer chemistry and nature, will also be described. 相似文献
120.