全文获取类型
收费全文 | 2848篇 |
免费 | 38篇 |
国内免费 | 6篇 |
专业分类
化学 | 2052篇 |
晶体学 | 9篇 |
力学 | 44篇 |
综合类 | 1篇 |
数学 | 460篇 |
物理学 | 326篇 |
出版年
2016年 | 32篇 |
2015年 | 30篇 |
2014年 | 34篇 |
2013年 | 96篇 |
2012年 | 76篇 |
2011年 | 71篇 |
2010年 | 49篇 |
2009年 | 46篇 |
2008年 | 76篇 |
2007年 | 93篇 |
2006年 | 71篇 |
2005年 | 69篇 |
2004年 | 58篇 |
2003年 | 62篇 |
2002年 | 49篇 |
2001年 | 28篇 |
2000年 | 26篇 |
1999年 | 28篇 |
1998年 | 25篇 |
1997年 | 36篇 |
1996年 | 32篇 |
1995年 | 38篇 |
1994年 | 49篇 |
1993年 | 31篇 |
1992年 | 28篇 |
1991年 | 35篇 |
1990年 | 29篇 |
1989年 | 40篇 |
1988年 | 32篇 |
1987年 | 37篇 |
1986年 | 37篇 |
1985年 | 50篇 |
1984年 | 58篇 |
1983年 | 30篇 |
1982年 | 53篇 |
1981年 | 50篇 |
1980年 | 43篇 |
1979年 | 37篇 |
1978年 | 64篇 |
1977年 | 60篇 |
1976年 | 45篇 |
1975年 | 38篇 |
1974年 | 34篇 |
1973年 | 47篇 |
1972年 | 31篇 |
1971年 | 46篇 |
1970年 | 30篇 |
1969年 | 20篇 |
1968年 | 19篇 |
1966年 | 24篇 |
排序方式: 共有2892条查询结果,搜索用时 31 毫秒
1.
Synthesis and Photophysical Properties of a Sc3N@C80‐Corrole Electron Donor–Acceptor Conjugate
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)
Bin Liu Hongyun Fang Prof. Xiaofang Li Wenting Cai Lipiao Bao Marc Rudolf Fabian Plass Prof. Louzhen Fan Prof. Xing Lu Prof. Dirk M. Guldi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(2):746-752
Embedding endohdedral metallofullerenes (EMFs) into electron donor–acceptor systems is still a challenging task owing to their limited quantities and their still largely unexplored chemical properties. In this study, we have performed a 1,3‐dipolar cycloaddition reaction of a corrole‐based precursor with Sc3N@C80 to regioselectively form a [5,6]‐adduct ( 1 ). The successful attachment of the corrole moiety was confirmed by mass spectrometry. In the electronic ground state, absorption spectra suggest sizeable electronic communications between the electron acceptor and the electron donor. Moreover, the addition pattern occurring at a [5,6]‐bond junction is firmly proven by NMR spectroscopy and electrochemical investigations performed with 1 . In the electronically excited state, which is probed in photophysical assays with 1 , a fast electron‐transfer yields the radical ion pair state consisting of the one‐electron‐reduced Sc3N@C80 and of the one‐electron‐oxidized corrole upon its exclusive photoexcitation. As such, our results shed new light on the practical work utilizing EMFs as building blocks in photovoltaics. 相似文献
2.
P. Rudolf R. Raval P. Dumas G.P. Williams 《Applied Physics A: Materials Science & Processing》2002,75(1):147-153
Infrared (IR) spectroscopy of chemisorbed C60 on Ag (111), Au (110) and Cu (100) reveals that a non-IR-active mode becomes active upon adsorption, and that its frequency
shifts proportionally with the charge transferred from the metal to the molecule by about 5 cm-1 per electron. The temperature dependence of the frequency and the width of this IR feature have also been followed for C60/Cu (100) and were found to agree well with a weak anharmonic coupling (dephasing) to a low-frequency mode, which we suggest
to be the frustrated translational mode of the adsorbed molecules.
Additionally, the adsorption is accompanied by a broadband reflectance change, which is interpreted as due to the scattering
of conduction electrons of the metal surface by the adsorbate. The reflectance change allows determination of the friction
coefficient of the C60 molecules, which results in rather small values (∼2×109 s-1 for Ag and Au, and ∼1.6×109 s-1for Cu), consistent with a marked metallic character of the adsorbed molecules.
Pre-dosing of alkali atoms onto the metal substrates drastically changes the IR spectra recorded during subsequent C60 deposition: anti-absorption bands, as well as an increase of the broadband reflectance, occur and are interpreted as due
to strong electron–phonon coupling with induced surface states.
Received: 6 June 2001 / Accepted: 23 October 2001 / Published online: 3 April 2002 相似文献
3.
4.
5.
Sufficient conditions which guarantee that certain linear integro-differential equation cannot have a positive solution are
established. 相似文献
6.
7.
8.
Holger Poths Erik Wischerhoff Rudolf Zentel Axel Sch nfeld Guido Henn Friedrich Kremer 《Liquid crystals》1995,18(5):811-818
Two new ferroelectric oligosiloxanes, a cyclic tetramer and a twin, have been synthesized. By a comparative study with their corresponding monomer and side chain polysiloxanes, the influence of oligo- and polymerization on the liquid crystalline and ferroelectric properties have been investigated. Polymerization leads to a stabilization of LC phases through increase of the clearing temperatures and suppression of crystallization. Oligomerization also leads to mesophase broadening, but, due to the low degree of polymerization, the effect is inferior to the linear polysiloxanes. The low viscosity of the oligosiloxanes ensures response times in the microsecond region, thus being comparable with their monomer and conventional LMWFLCs. It is found that polymerization increases the spontaneous polarization Ps. This is attributed to the density increase after polymerization, enhancing the inter-mesogenic interactions. The collective and local dynamics of the OFLCs are influenced differently with respect to their molecular structures. Each oligomer is already a good model for its corresponding polymer concerning the soft mode dynamics. For the local β-relaxation a similar temperature dependence of the relaxation times τ for the cyclic tetramer and for the side chain polysiloxanes is observed. The long axial rotation of the twin, having a very efficient decoupling, is significantly faster, thus resembling the monomer. 相似文献
9.
Experimental and theoretical investigations of the spectroscopy of molecules in superfluid helium droplets provide evidence for the key role of the first helium layer surrounding the dopant molecule in determining the molecule's spectroscopic features. Recent investigations of emission spectra of phthalocyanine in helium droplets revealed a doubling of all transitions. Herein, we present the emission spectra of Mg-phthalocyanine and of phthalocyanine-argon clusters in helium droplets, which confirm the splitting as a general effect of the helium environment. A scheme of levels is deduced from the emission spectra and attributed to quantized states of the first helium layer surrounding the dopant molecule. 相似文献
10.