全文获取类型
收费全文 | 569篇 |
免费 | 82篇 |
国内免费 | 136篇 |
专业分类
化学 | 618篇 |
晶体学 | 15篇 |
力学 | 2篇 |
综合类 | 5篇 |
数学 | 7篇 |
物理学 | 140篇 |
出版年
2024年 | 2篇 |
2023年 | 6篇 |
2022年 | 6篇 |
2021年 | 22篇 |
2020年 | 20篇 |
2019年 | 18篇 |
2018年 | 13篇 |
2017年 | 19篇 |
2016年 | 25篇 |
2015年 | 28篇 |
2014年 | 27篇 |
2013年 | 60篇 |
2012年 | 37篇 |
2011年 | 31篇 |
2010年 | 17篇 |
2009年 | 21篇 |
2008年 | 40篇 |
2007年 | 35篇 |
2006年 | 36篇 |
2005年 | 31篇 |
2004年 | 31篇 |
2003年 | 32篇 |
2002年 | 57篇 |
2001年 | 31篇 |
2000年 | 19篇 |
1999年 | 24篇 |
1998年 | 15篇 |
1997年 | 20篇 |
1996年 | 24篇 |
1995年 | 14篇 |
1994年 | 17篇 |
1993年 | 6篇 |
1992年 | 2篇 |
1990年 | 1篇 |
排序方式: 共有787条查询结果,搜索用时 15 毫秒
31.
Julien Iehl Thi Le Anh Nguyen Stéphane Frein Uwe Hahn Joaquín Barberá Jean-François Nierengarten 《Liquid crystals》2017,44(12-13):1852-1860
ABSTRACTLiquid-crystalline [60]fullerodendrimers were constructed via click chemistry based on the reaction between hexa-adducts of [60]fullerene (C60) bearing 12 azide groups and alkyne-terminated cyanobiphenyl dendrons of first- and second-generation. The structure of all the new compounds was confirmed by IR, UV, 1H and 13C NMR spectroscopies and mass spectrometry. The mesomorphic properties were studied by polarised optical microscopy, differential scanning calorimetry and small-angle X-ray scattering. The hexa-adduct of C60 functionalised with the first-generation dendrons gave rise to the formation of a smectic A phase and a rectangular columnar phase (c2mm symmetry) while the hexa-adduct of C60 decorated with the second-generation dendrons displayed only a rectangular columnar phase (c2mm symmetry). Our results show that the hexa-adduct of C60 is a unique synthetic platform for the design of fullerodendrimers and dendronised materials. 相似文献
32.
Side chain engineering of naphthalene diimide–bithiophene‐based polymer acceptors in all‐polymer solar cells 下载免费PDF全文
Xia Wu Yumin Tang Yuxi Wang Xiaoyuan Liu Changmei Liu Xiaonan Zhang Yingguo Yang Xingyu Gao Fei Chen Xugang Guo Zhi‐Kuan Chen 《Journal of polymer science. Part A, Polymer chemistry》2017,55(22):3679-3689
Two novel polymeric acceptors based on naphthalene diimide (NDI) and 2.2′‐bithiophene, named as P(NDI2THD‐T2) and P(NDI2TOD‐T2), were designed and synthesized for all polymer solar cells application. The structural and electronic properties of the two acceptors were modulated through side‐chain engineering of the NDI units. The optoelectronic properties of the polymers and the morphologies of the blend films composed of the polymer acceptors and a donor polymer PTB7‐Th were systemically investigated. With thiophene groups introduced into the side chains of the NDI units, both polymers showed wider absorption from 350 nm to 900 nm, compared with the reference polymer acceptor of N2200. No redshift of absorption spectra from solutions to films indicated reduced aggregation of the polymers due to the steric hindrance effect of thiophene rings in the side chains. The photovoltaic performance were characterized for devices in a configuration of ITO/PEDOT:PSS/PTB7‐Th:acceptors/2,9‐bis(3‐(dimethylamino)propyl)anthra[2,1,9‐def:6,5,10‐def]diisoquinoline‐1,3,8,10(2H,9H)‐tetraone (PDIN)/Al. With the addition of diphenyl ether as an additive, the power conversion efficiencies (PCEs) of 2.73% and 4.75% for P(NDI2THD‐T2) and P(NDI2TOD‐T2) based devices were achieved, respectively. The latter showed improved Jsc, Fill Factor (FF), and PCE compared with N2200 based devices. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3679–3689 相似文献
33.
Water is the most important liquid on earth. Clusters of water have been investigated extensively in an effort to understand the bulk property of water. But the behavior of single water molecule without H‐bond has been rarely studied. Open‐cage [60]fullerenes have been shown to trap a single water molecule selectively over molecules with comparable size and act as the smallest “water bottle”. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
34.
The 1H decoupled Phosphorus NMR lineshape of DPPC-water dispersions shows characteristic changes when passing through the three thermotropic phase transitions: subtransition (Lσ′ - Lβ′), pretransition (Lβ′ - Pβ′) and main transition (Pβ -Lα). At the subtransition the spectrum changes from a non-axial-symmetric powder spectrum (Lσ′) to an axial-symmetric one (Lβ′). The two higher phase transitions are characterized by decreases in the intrinsic 31P line widths and the chemical shift anisotropy. Proton-enhanced 13C-spectra of the same compound, with natural isotope abundance, recorded at 76 MHz permit the resolved observation of different carbon-positions in the headgroup. In particular the N-(CH3)3-carbon nuclei exhibit a narrow isotropic lineshape throughout the entire observed temperature range (-20°C … 50°C). This implies that rotational motion in this moiety does not cease below the subtransition. To summarize, the headgroup mobility in the Lσ'-phase can be described as follows: The rotation of the entire choline group about the chemical bonds between the phosphate group and the glycerol-backbone is slow on the 31P-NMR timescale, the N-(CH3)3 end of the choline moiety, however, still undergoes rapid rotational motion. This picture is in accordance with recent interpretations of our ‘H-NMR second moment analysis. 相似文献
35.
36.
Zi‐Yi Yu Han Lai Wen‐Juan Zhao Rui Wu Xue‐Sen Liu Li‐Hua Gan 《International journal of quantum chemistry》2017,117(19)
To elucidate the structure of a compound is a necessary step for its practical applications. To study the structure and properties of metal sulfide fullerene Sc2S@C88 detected by mass spectrometry, 11 194 isomers of C88 and 33 isomers of Sc2S@C88 were systematically examined by density functional theory calculations. The calculations show that the two lowest‐energy isomers are Sc2S@C88:81 738 (IPR‐35) and Sc2S@C88:81 735 (IPR‐32), followed by Sc2S@C88:81 729 (IPR‐26), Sc2S@C88:81 712 (IPR‐9), and Sc2S@C88:81 733 (IPR‐30). Structural analysis shows that the first two energetically favored isomers are bridged by the third and fifth energetically favored isomers, which can transfer into each other via direct Stone–Wales rotation. The calculations of temperature effect show that the first two favored isomers become dominant forms of Sc2S@C88 with decreasing temperature and may coexist in the soot. This structural convertibility among favored isomers of Sc2S@C88 suggest a hidden rule that birds of a feather flock together in metal sulfide fullerenes. This rule may decrease the range of candidate cages for the structural identification of a metal sulfide fullerene. IR spectra are simulated for helping the future experimental identification of Sc2S@C88. 相似文献
37.
《Journal of computational chemistry》2017,38(3):144-151
An increasing number of observations show that non‐classical isomers may play an important role in the formation of fullerenes and their exo‐ and endo‐derivatives. A quantum‐mechanical study of all classical isomers of C58, C60, and C62, and all non‐classical isomers with at most one square or heptagonal face, was carried out. Calculations at the B3LYP/6‐31G* level show that the favored isomers of C58, C60, and C62 have closely related structures and suggest plausible inter‐conversion and growth pathways among low‐energy isomers. Similarity of the favored structures is reinforced by comparison of calculated ring currents induced on faces of these polyhedral cages by radial external magnetic fields, implying patterns of magnetic response similar to those of the stable, isolated‐pentagon C60 molecule. © 2016 Wiley Periodicals, Inc. 相似文献
38.
Xitong Liu Wei Wang Zhenqiang Fan Wanning Huang Lixing Luo Canglei Yang Prof. Dr. Jing Zhang Prof. Dr. Jianfeng Zhao Prof. Dr. Lei Zhang Prof. Dr. Wei Huang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(40):10448-10455
Fullerene host-guest constructs have attracted increasing attention owing to their molecular-level hybrid arrangements. However, the usage of simple carbazolic derivatives to bind with fullerenes is rare. In this research, three novel carbazolic derivatives, containing a tunable bridging linker and carbazole units for the capturing of fullerenes, are rationally designed. Unlike the general concave-convex interactions, fullerenes could interact with the planar carbazole subunits to form 2-dimensional hexagonal/quadrilateral cocrystals with alternating stacking patterns of 1 : 1 or 1 : 2 stoichiometry, as well as the controllable fullerene packing modes. At the meanwhile, good electron-transporting performances and significant photovoltaic effects were realized when a continuous C60⋅⋅⋅C60 interaction channel existed. The results indicate that the introduction of such carbazolic system into fullerene receptor would provide new insights into novel fullerene host-guest architectures for versatile applications. 相似文献
39.
Effect of additive length and chemistry on the morphology of blends of conjugated thiophenes and fullerene derivative acceptor molecules 下载免费PDF全文
Small molecule additives have been shown to increase the device efficiency of conjugated polymer (donor) and fullerene derivative (acceptor) based organic solar cells by modifying the morphology of the device active layer. In this paper we conduct a systematic study of how additives affect the donor‐acceptor morphology using molecular dynamics simulations of blends of thiophene‐based oligomers, mimicking poly(3‐dodecylthiophene) (P3DDT) or poly(2,2′:5′,2”‐3,3”‐didocyl‐terthiophene) (PTTT), and fullerene derivatives with additives of varying length and chemical functionalization, mimicking experimentally used additives like methyl ester additives, diiodooctane, and alkanedithiols. We find that functionalization of additives with end groups that are attracted to acceptor molecules are necessary to induce increased donor‐acceptor macrophase separation. In blends where acceptors intercalate between oligomer alkyl side chains, functionalized additives decrease acceptor intercalation. Functionalized additives with shorter alkyl segments increase acceptor macrophase separation more than additives with same chemical functionalization but longer alkyl segments. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1046–1057 相似文献
40.
Wen‐Jing Shi Dr. Mohamed E. El‐Khouly Dr. Kei Ohkubo Prof. Shunichi Fukuzumi Prof. Dennis K. P. Ng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(34):11332-11341
An efficient functional mimic of the photosynthetic antenna‐reaction center has been designed and synthesized. The model contains a near‐infrared‐absorbing aza‐boron‐dipyrromethene (ADP) that is connected to a monostyryl boron‐dipyrromethene (BDP) by a click reaction and to a fullerene (C60) using the Prato reaction. The intramolecular photoinduced energy and electron‐transfer processes of this triad as well as the corresponding dyads BDP‐ADP and ADP‐C60 have been studied with steady‐state and time‐resolved absorption and fluorescence spectroscopic methods in benzonitrile. Upon excitation, the BDP moiety of the triad is significantly quenched due to energy transfer to the ADP core, which subsequently transfers an electron to the fullerene unit. Cyclic and differential pulse voltammetric studies have revealed the redox states of the components, which allow estimation of the energies of the charge‐separated states. Such calculations show that electron transfer from the singlet excited ADP (1ADP*) to C60 yielding ADP.+‐C60.? is energetically favorable. By using femtosecond laser flash photolysis, concrete evidence has been obtained for the occurrence of energy transfer from 1BDP* to ADP in the dyad BDP‐ADP and electron transfer from 1ADP* to C60 in the dyad ADP‐C60. Sequential energy and electron transfer have also been clearly observed in the triad BDP‐ADP‐C60. By monitoring the rise of ADP emission, it has been found that the rate of energy transfer is fast (≈1011 s?1). The dynamics of electron transfer through 1ADP* has also been studied by monitoring the formation of C60 radical anion at 1000 nm. A fast charge‐separation process from 1ADP* to C60 has been detected, which gives the relatively long‐lived BDP‐ADP.+C60.? with a lifetime of 1.47 ns. As shown by nanosecond transient absorption measurements, the charge‐separated state decays slowly to populate mainly the triplet state of ADP before returning to the ground state. These findings show that the dyads BDP‐ADP and ADP‐C60, and the triad BDP‐ADP‐C60 are interesting artificial analogues that can mimic the antenna and reaction center of the natural photosynthetic systems. 相似文献