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131.
Michael Yuan Ming Huang Chi Kong LawWeikun Ge Jacky W.Y LamBen Zhong Tang 《Journal of luminescence》2002,99(2):161-168
Poly{n-[((4′-cyano-4-biphenylyl)oxy)carbonyl]-1-alkynes} (PAnCN, where n=2, 8), which is a class of monosubstituted polyacetylenes with biphenyl mesogens and cyano tails in their pendants, can emit strong deep-blue photoluminescence (PL). In this paper we have investigated their optical absorptions, PL evolutions with excitation power and excitation wavelength, electronic structures, and the electric-field effect on the PL of a moderately concentrated PAnCN solution that had been treated by electric fields. Having been treated by an electric-field pulse (6×105 V/m) for about 3 s, the originally featureless PL spectrum of the PAnCN solution becomes structured and transient, which evolves with time and external electric field. Our results have demonstrated that both the absorption and the deep-blue PL originate from the biphenyl mesogens in the side chains rather than from the distorted backbones. 相似文献
132.
Isolde Bachert Irene Bartusseck Pierre Braunstein Emmanuel Guillon Jacky Ros Guido Kickelbick 《Journal of organometallic chemistry》1999,580(2):3016
Heterometallic triangular platinum–cobalt, palladium–cobalt and palladium–molybdenum clusters stabilized by one or two bridging diphosphine ligands such as Ph2PNHPPh2 (dppa) or (Ph2P)2NMe (dppaMe) or by mixed ligand sets Ph2PCH2PPh2 (dppm)/dppa have been prepared with the objectives of comparing the stability and properties of the clusters as a function of the short-bite diphosphine ligand used and of the metal carbonyl fragment they contain. Ligand redistribution reactions were observed during the purification of [Co2Pd(μ3-CO)(CO)4(μ-dppa)(μ-dppm)] (4) by column chromatography with the formation of [Co2Pd(μ3-CO)(CO)4(μ-dppm)2] and the dinuclear complex [(OC)2
Cl] (5). The latter was independently prepared by reaction of [Pd(dppa-P,P′)2](BF4)2 with Na[Co(CO)4]. Attempts to directly incorporate the ligand (Ph2P)2N(CH2)3Si(OMe)3 (dppaSi) into a cluster or to generate it by N-functionalization of coordinated dppa were unsuccessful, in contrast to results obtained recently with related clusters. The crystal structure of [Co2Pt(μ3-CO)(CO)6(μ-dppa)] (1) has been determined by X-ray diffraction. 相似文献
133.
He Benzhao Huang Jiachang Zhang Jing Liu Xinyue Wang Dong Sung Herman H. Y. Liu Yajun Qin Anjun Lam Jacky W. Y. Tang Ben Zhong 《中国科学:化学(英文版)》2022,65(4):789-795
Science China Chemistry - The development of new polymerization routes to afford N-heterocyclic polymers is of vital importance and highly desired for various practical applications. Herein, a... 相似文献
134.
Zikai He Liang Shan Ju Mei Hong Wang Jacky W. Y. Lam Herman H. Y. Sung Ian D. Williams Xiao Gu Qian Miao Ben Zhong Tang 《Chemical science》2015,6(6):3538-3543
Reported herein is a new class of pure polycyclic hydrocarbon molecules, designed through a novel aggregation-induced emission (AIE) strategy, with unexpected photochromic properties. The restriction of intramolecular motion was found as a comprehensive mechanism for the AIE effect. The photochromism mechanism study revealed that the photocyclization reaction of cis-stilbene, the molecular conformation in the single crystal and the tetracene backbone should contribute to the unique photo behavior. In particular, the fast responsive, photo-reversible and thermo-irreversible photochromic effect facilitated in the solid state opens a new field of aggregation-promoted photochromism. 相似文献
135.
136.
The steric requirements of leaving groups for 14 bridgehead derivatives have been examined using MM2 calculations. The strain varies almost monotonously throughout the series upon variation of the leaving group from H to C1, OH, CH3, CH3CH2O, (CH3)3CO, (CH3)3C and no significant trends for differential F-strain effects are detected expect for the perhydrophenalene derivative 13 . The experimental rates of solvolysis of bridgehead derivatives correlate well with the calculated steric energy differences between substrate R-X and the corresponding carbenium ion R⊕. However, the strain calculations using the more recent force-fields ( MM2 ) disagree, in part, with those reported in the literature: chloride and p-toluenesulfonate leaving groups correlate with identical slopes, and the perhydrotriquinacene derivative 10 shows no anomalous behavior. The calculations suggest that F-strain and C,C-hyperconjugation should not play any dominant role in bridgehead solvolysis. 相似文献
137.
Designing Efficient and Ultralong Pure Organic Room‐Temperature Phosphorescent Materials by Structural Isomerism
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Dr. Yu Xiong Dr. Zheng Zhao Dr. Weijun Zhao Dr. Huili Ma Prof. Qian Peng Prof. Zikai He Dr. Xuepeng Zhang Dr. Yuncong Chen Xuewen He Prof. Jacky W. Y. Lam Prof. Ben Zhong Tang 《Angewandte Chemie (International ed. in English)》2018,57(27):7997-8001
Pure organic materials with ultralong room‐temperature phosphorescence (RTP) are attractive alternatives to inorganic phosphors. However, they generally show inefficient intersystem crossing (ISC) owing to weak spin–orbit coupling (SOC). A design principle based on the realization of small energy gap between the lowest singlet and triplet states (ΔEST) and pure ππ* configuration of the lowest triplet state (T1) via structural isomerism was used to obtain efficient and ultralong RTP materials. The meta isomer of carbazole‐substituted methyl benzoate exhibits an ultralong lifetime of 795.0 ms with a quantum yield of 2.1 %. Study of the structure–property relationship shows that the varied steric and conjugation effects imposed by ester substituent at different positions are responsible for the small ΔEST and pure ππ* configuration of T1. 相似文献
138.
Using a scheme given by Marco, we prove that partially hyperbolic tori along resonant surfaces of near-integrable Hamiltonian systems possess the obstruction property in Arnold's terminology. The proof is based on a specific lambda lemma for these tori. 相似文献
139.
Marie Haïdopoulo Marcel Bertault Jacky Even Loïc Toupet 《Macromolecular theory and simulations》2000,9(5):257-262
In this paper, we developed two types of programs in order to simulate the polymerization reaction of a fully deuterated crystal of diacetylene 2,4‐hexadiynylene bis(p‐toluenesulfonate) (pTS‐D). The first simulation is based on a modification of Baughman's model, a classical model for simulating the polymerization of diacetylene crystals. The agreement between the simulated and experimental results concerning the reaction kinetics is satisfactory. With this simulation algorithm, we take into account the experimental observation that the polymerization of pTS‐H and pTS‐D crystals is really a random process of formation of polymer chains along the crystallographic axis b . The second simulation is based on the Monte Carlo method, which permits not only to simulate the kinetics of the reaction, but also the chain‐length distribution in the hydrogenated and deuterated compounds. These two types of simulations were already developed for the hydrogenated crystal of diacetylene, named pTS‐H. Two main modifications are applied in the case of pTS‐D for taking into account experimental results: in the first the rate constants of chain‐terminating microscopic processes are different in pTS‐H and pTS‐D which must be considered. The second modification concerns the evolution of the lattice deformation during the course of polymerization. The experimental variation of the b parameter as a function of polymer content X in pTS‐D is different from that in pTS‐H; this result is important to consider when calculating the activation energy of the initiation and propagation microscopic processes. 相似文献
140.
Jacky Wing Yip Lam Junwu Chen Charles Chi Wang Law Han Peng Zhiliang Xie Kevin Ka Leung Cheuk Hoi Sing Kwok Ben Zhong Tang 《Macromolecular Symposia》2003,196(1):289-300
Linear polyacetylenes and hyperbranched polyphenylenes carrying 1,2,3,4,5-pentaphenylsilolyl (PS) pendants are designed and synthesized. Homo-polymerization of HC≡CPS, HC≡C(CH2)9OPS, and C6H5C≡C(CH2)9OPS and (co)polycyclotrimerization of (HC≡C)2PS with 1-octyne are effected by NbCl5-, WCl6-, MoCl5-, and TaCl5-based catalysts. High molecular weight linear ( 1-3 ) and hyperbranched polymers (6) are obtained in high yields (Mw up to ∼70 × 103 and yield up to 85%). All the polymers are thermally stable, losing little weight when heated to 350°C. Whereas all the polymers emit faint light when molecularly dissolved, polymers 2 , 3 , and 6 become emissive when aggregated in poor solvents or when cooled to low temperatures. Restricted intramolecular rotations of the phenyl rings upon the axes of the single bonds linked to the silole cores may be responsible for the aggregation- or cooling-induced emission. A multilayer electroluminescent device using 3 as an active layer emits a blue light of 496 nm with maximum brightness, current efficiency, and external quantum yield of 1118 cd/m2, 1.45 cd/A, and 0.55%, respectively. Polymers 6 are non-linear optically active and strongly attenuate the optical power of intense laser pulses, whose optical limiting performances are superior to that of C60, a best-known optical limiter. 相似文献