全文获取类型
收费全文 | 971篇 |
免费 | 194篇 |
国内免费 | 31篇 |
专业分类
化学 | 1123篇 |
晶体学 | 3篇 |
力学 | 1篇 |
综合类 | 1篇 |
物理学 | 68篇 |
出版年
2023年 | 7篇 |
2022年 | 2篇 |
2021年 | 18篇 |
2020年 | 32篇 |
2019年 | 29篇 |
2018年 | 22篇 |
2017年 | 22篇 |
2016年 | 60篇 |
2015年 | 63篇 |
2014年 | 66篇 |
2013年 | 92篇 |
2012年 | 75篇 |
2011年 | 71篇 |
2010年 | 52篇 |
2009年 | 73篇 |
2008年 | 66篇 |
2007年 | 65篇 |
2006年 | 56篇 |
2005年 | 71篇 |
2004年 | 46篇 |
2003年 | 52篇 |
2002年 | 25篇 |
2001年 | 21篇 |
2000年 | 11篇 |
1999年 | 8篇 |
1998年 | 10篇 |
1997年 | 25篇 |
1996年 | 18篇 |
1995年 | 26篇 |
1994年 | 7篇 |
1993年 | 3篇 |
1992年 | 2篇 |
排序方式: 共有1196条查询结果,搜索用时 15 毫秒
951.
圆顶建筑、病毒衣壳和C60分子·笼的生成机制和尺寸差别很大,但都属二十面体壳层,遵循同一几何规律。圆顶建筑和病毒衣壳由近似全等的三角面构成,有12个五键连35顶,10(T-1)个六键连36顶,其中三角面数T=h2+hk十k2是二十面体的一个三角中的小三角面数,h,k是六角坐标系中35顶的坐标。另一方面,全碳分子笼Cn(包括其原型C60)由12个五角面与10(T-1)个六角面围成,全是三键连顶(h,k是一个五角面中心的坐标)。显然,这两类二十面体壳层是对偶的,也就是它们的面、顶有互换关系。本文讨论这些二十面体壳层的几何特征及富勒烯的多样性,强调不同学科间的联系和科学研究的继承与发展的关系。 相似文献
952.
Dr. Sara Vidal Dr. Marta Izquierdo Dr. Salvatore Filippone Dr. Israel Fernández Seckin Akin Dr. Ji-Youn Seo Dr. Shaik M. Zakeeruddin Prof. Michael Grätzel Prof. Nazario Martín 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(13):3224-3228
We report on the site-selective synthesis of PCBM-like [70]fullerene site-isomers, where the elusive β-site-isomers are, for the first time, the major product in a (cyclo)addition chemical reaction involving [70]fullerene. The reaction involves an straightforward cyclopropanation of [70]fullerene from sulfonium salts, affording a mixture of α and β site-isomers in good yields. Amazingly, the preference for the α- or β-site-isomer can be efficiently controlled by means of the solvent polarity! DFT theoretical calculations (DMF and toluene) nicely predict that, although the formation of the α-adduct is, as expected, thermodynamically favored, the selectivity of the process is determined by the energy difference of the respective transition states. Furthermore, the employ of α or/and β site-isomers, as pure materials or as a mixture of them, used as templating agent, has been evaluated in perovskite solar cells. The positive influence of the [70]fullerenes by passivating the voids/pin-holes and/or deep slits, is reflected in highly efficient and stable bulk heterojunction perovskite solar cells, whose performance (around 20 %) is slightly but consistently depending on the isomeric fullerene composition. These experimental findings pave the way to investigate a new reactivity on C70 and to explore the properties of the less-known β-derivatives. 相似文献
953.
Dr. Anaïs Mairena Dr. Laura Zoppi Dr. Samuel Lampart Prof. Dr. Kim K. Baldridge Prof. Dr. Jay S. Siegel Prof. Dr. Karl-Heinz Ernst 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(49):11555-11559
The modification of metal electrode surfaces with functional organic molecules is an important part of organic electronics. The interaction of the buckminsterfullerene fragment molecule pentaindenocorannulene with a Cu(100) surface is studied by scanning tunneling microscopy, dispersion-enabled density functional theory, and force field calculations. Experimental and theoretical methods suggest that two adjacent indeno groups become oriented parallel to the surface upon adsorption under mild distortion of the molecular frame. The binding mechanism between molecule and surface is dominated by strong electrostatic interaction owing to Pauli repulsion. Two-dimensional aggregation at room temperature leads to a single lattice structure in which all molecules are oriented unidirectionally. Their relative arrangement in the lattice suggests noncovalent intermolecular interaction through C−H⋅⋅⋅π bonding. 相似文献
954.
Dr. Dmitri V. Konarev Dr. Alexey A. Popov Dr. Leokadiya V. Zorina Dr. Salavat S. Khasanov Prof. Dr. Rimma N. Lyubovskaya 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(65):14858-14869
A series of compounds with Sc3N@Ih-C80 in the neutral, monomeric, and dimeric anion states have been prepared in the crystalline form and their molecular structures and optical and magnetic properties have been studied. The neutral Sc3N@Ih-C80 ⋅ 3 C6H4Cl2 ( 1 ) and (Sc3N@Ih-C80)3(TPC)2 ⋅ 5 C6H4Cl2 ( 2 , TPC=triptycene) compounds both crystallized in a high-symmetry trigonal structure. The reduction of Sc3N@Ih-C80 to the radical anion resulted in dimerization to form diamagnetic singly bonded (Sc3N@Ih-C80−)2 dimers. In contrast to {[2.2.2]cryptand(Na+)}2(Sc3N@Ih-C80−)2 ⋅ 2.5 C6H4Cl2 ( 3 ) with strongly disordered components, we synthesized new dimeric phases {[2.2.2]cryptand- (K+)}2(Sc3N@Ih-C80−)2 ⋅ 2 C6H4Cl2 ( 4 ) and {[2.2.2]cryptand- (Cs+)}2(Sc3N@Ih-C80−)2 ⋅ 2 C6H4Cl2 ( 5 ) in which only one major dimer orientation was found. The thermal stability of the (Sc3N@Ih-C80−)2 dimers was studied by EPR analysis of 3 to show their dissociation in the 400–460 K range producing monomeric Sc3N@Ih-C80.− radical anions. This species shows an EPR signal with a hyperfine splitting of 5.8 mT. The energy of the intercage C−C bond was estimated to be 234±7 kJ mol−1, the highest value among negatively charged fullerene dimers. The EPR spectra of crystalline (Bu3MeP+)3(Sc3N@Ih-C80.−)3 ⋅ C6H4Cl2 ( 6 ) are presented for the first time. The salt shows an asymmetric EPR signal, which could be fitted by three lines. Two lines were attributed to Sc3N@Ih-C80.−. Hyperfine splitting is manifested above 180 K due to the hyperfine interaction of the electron spin with the three scandium atoms (a total of 22 lines with an average splitting of 5.32 mT are observed at 220 K). Furthermore, each of the 22 lines is additionally split into six lines with an average separation of 0.82 mT. The large splitting indicates intrinsic charge and spin density transfer from the fullerene cage to the Sc3N cluster. Both the monomeric and dimeric Sc3N@Ih-C80− anions show an intrinsic shift of the IR bands attributed to the Sc3N cluster and new bands corresponding to these species appear in the NIR range of their UV/Vis/NIR spectra, which allows these anions to be distinguished from neutral species. 相似文献
955.
Dr. Ziqi Hu Aman Ullah Dr. Helena Prima-Garcia Sang-Hyun Chin Dr. Yuanyuan Wang Dr. Juan Aragó Prof. Zujin Shi Dr. Alejandro Gaita-Ariño Prof. Eugenio Coronado 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(52):13242-13248
To design molecular spin qubits with enhanced quantum coherence, a control of the coupling between the local vibrations and the spin states is crucial, which could be realized in principle by engineering molecular structures via coordination chemistry. To this end, understanding the underlying structural factors that govern the spin relaxation is a central topic. Here, we report the investigation of the spin dynamics in a series of chemically designed europium(II)-based endohedral metallofullerenes (EMFs). By introducing a unique structural difference, i. e. metal-cage binding site, while keeping other molecular parameters constant between different complexes, these manifest the key role of the three low-energy metal-displacing vibrations in mediating the spin-lattice relaxation times (T1). The temperature dependence of T1 can thus be normalized by the frequencies of these low energy vibrations to show an unprecedentedly universal behavior for EMFs in frozen CS2 solution. Our theoretical analysis indicates that this structural difference determines not only the vibrational rigidity but also spin-vibration coupling in these EMF-based qubit candidates. 相似文献
956.
Dr. Luis Martín-Gomis Rocío Díaz-Puertas Sairaman Seetharaman Prof. Dr. Paul A. Karr Prof. Dr. Fernando Fernández-Lázaro Prof. Dr. Francis D'Souza Prof. Dr. Ángela Sastre-Santos 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(21):4822-4832
A multimodular donor–acceptor conjugate featuring silicon phthalocyanine (SiPc) as the electron donor, and two electron acceptors, namely tetrachloroperylenediimide (PDI) and C60, placed at the opposite ends of the SiPc axial positions, was newly designed and synthesized, and the results were compared to the earlier reported PDI-SiPc-C60 triad. Minimal intramolecular interactions between the entities was observed. Absorption, fluorescence, computational and electrochemical studies were performed to evaluate the excitation energy, geometry and electronic structure, and energy levels of different photoevents. Steady-state absorption, fluorescence and excitation spectral studies revealed efficient singlet–singlet energy transfer from 1PDI* to SiPc in the PDI-SiPc dyad and the PDI-SiPc-C60 triad. The measured rates for these photochemical events were found to be much higher than those reported earlier for the triad, due to closer proximity between the PDI and SiPc entities. The distance also affected the charge separation path in which involvement of PDI, and not C60, in charge separation in the present triad was witnessed. The present investigation brings out the importance of donor–acceptor distances in channeling photochemical events in a multimodular system. 相似文献
957.
Prof. Dr. Tomokazu Umeyama Tomoya Ohara Dr. Yusuke Tsutsui Shota Nakano Prof. Dr. Shu Seki Prof. Dr. Hiroshi Imahori 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(29):6726-6735
Few-layered antimonene (FLSb) nanosheets were noncovalently functionalized with fullerene C60 clusters by quick addition of a poor solvent (i.e., acetonitrile) into a mixed dispersion of FLSb and C60 in a good solvent (i.e., toluene). In a flash-photolysis time-resolved microwave conductivity (FP-TRMC) measurement, the FLSb-C60 composite, (FLSb+C60)m, showed a rapid rise in transient conductivity, whereas no conductivity signal was observed in the single components, FLSb and C60. This demonstrated the occurrence of photoinduced charge separation between FLSb and C60 in (FLSb+C60)m. Furthermore, a photoelectrochemical device with an electrophoretically deposited (FLSb+C60)m film exhibited an enhanced efficiency of photocurrent generation, compared to those of the single-components, FLSb and C60, due to the photoinduced charge separation between FLSb and C60. This work provides a promising approach for fabrication of antimonene–organic molecule composites and paves the way for their application in optoelectronics. 相似文献
958.
Yajing Hu Albert Solé-Daura Dr. Yang-Rong Yao Xuechen Liu Dr. Sijie Liu Ao Yu Dr. Ping Peng Prof. Josep M. Poblet Dr. Antonio Rodríguez-Fortea Prof. Luis Echegoyen Prof. Fang-Fang Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(8):1748-1753
The chemistry of cationic forms of clusterfullerenes remain less explored than that of the corresponding neutral or anionic species. In the present work, M3N@Ih-C80 (M=Sc or Lu) cations were generated by both electrochemical and chemical oxidation methods. The as-obtained cations successfully underwent the typical Bingel–Hirsch reaction that fails with neutral Sc3N@Ih-C80. Two isomeric Sc3N@Ih-C80 cation derivatives, [5,6]-open and [6,6]-open adducts, were synthesized, and the former has never been prepared by means of a Bingel–Hirsch reaction with neutral clusterfullerenes. In the case of the Lu3N@Ih-C80 cation, however, only a [6,6]-open adduct was obtained. Density functional theory (DFT) calculations indicated that the oxidized M3N@Ih-C80 was much more reactive than the neutral compound upon addition of the diethyl bromomalonate anion. The Bingel–Hirsch reaction of M3N@Ih-C80 cations occurred by means of an unusual outer-sphere single-electron transfer (SET) process from the diethyl bromomalonate anion to the stable intermediate [M3N@C80(C2H5COO)2CBr].. Remarkably, the diethyl bromomalonate anion was found to act as both a nucleophile and an electron donor. 相似文献
959.
Jesús Antonio Luque-Urrutia Dr. Albert Poater Prof. Dr. Miquel Solà 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(4):804-808
From the analysis of the polarizability of carbon nano-onions (CNOs), it was concluded that CNOs behave as near perfect nanoscopic Faraday cages. If CNOs behave as ideal Faraday cages, the reactivity of the C240 cage should be the same in Li+@C240 and Li+@C60@C240. In this work, the Diels–Alder reaction of cyclopentadiene to the free C240 cage and the C60@C240 CNO together with their Li+-doped counterparts were analyzed using DFT. It was found that in all cases the preferred cycloaddition is on bond [6,6] of type B of C240. Encapsulation of Li+ results in lower enthalpy barriers due to the decrease of the energy of the LUMO orbital of the C240 cage. When the Li+ is placed inside the CNO C60@C240, the decrease in enthalpy barrier is similar to that of Li+@C240. However, the location of Li+ in Li+@C240 (off-centered) and Li+@C60@C240 (centered) is quite different. When Li+ was placed in the center of the C240 cage in Li+@C240, the barriers increased significantly. Taking into account this effect, the barriers in Li+@C240 and Li+@C60@C240 differ by about 4 kcal mol−1. This result can be attributed to the shielding effect of C60 in Li+@C60@C240. As a result, we conclude that this CNO does not act as a perfect Faraday cage. 相似文献
960.
Reaction Mechanism and Regioselectivity of the Bingel–Hirsch Addition of Dimethyl Bromomalonate to La@C2v‐C82
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)
Juan Pablo Martínez Dr. Marc Garcia‐Borràs Dr. Sílvia Osuna Dr. Jordi Poater Prof. Dr. F. Matthias Bickelhaupt Prof. Dr. Miquel Solà 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(17):5953-5962
We quantum chemically explore the thermodynamics and kinetics of all 65 possible mechanistic pathways of the Bingel–Hirsch addition of dimethyl bromomalonate to the endohedral metallofullerene La@C2v‐C82 that result from the combination of 24 nonequivalent carbon atoms and 35 different bonds present in La@C2v‐C82 by using dispersion‐corrected DFT calculations. Experimentally, this reaction leads to four singly bonded derivatives and one fulleroid adduct. Of these five products, only the singly bonded derivative on C23 could be experimentally identified unambiguously. Our calculations show that La@C2v‐C82 is not particularly regioselective under Bingel–Hirsch conditions. From the obtained results, however, it is possible to make a tentative assignment of the products observed experimentally. We propose that the observed fulleroid adduct results from the attack at bond 19 and that the singly bonded derivatives correspond to the C2, C19, C21, and C23 initial attacks. However, other possibilities cannot be ruled out completely. 相似文献