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71.
Sabyasachi Sinha Ray Achintya K. Kundu Malay Ghosh Sukumar Maiti 《Journal of polymer science. Part A, Polymer chemistry》1986,24(4):603-612
A comparative evaluation of triphenylphosphine–polyhalocompound-activated polycondensation of amino carboxylic acid as well as amino carboxylic acid containing an imidogroup with thionyl chloride activated polycondensation of the above two types of acids has been discussed. The role of different polyhalocompounds, acid acceptors, sequence of addition of reactants, temperature of reaction, etc. has been studied. It was observed that the molecular weight of the polyamide and polyamideimide, as evident from their inherent viscosity data, is generally higher, but the yield is lower than those obtained by thionyl chloride method. The reaction by the former method appears to be faster than the latter. The influence of various reaction conditions and possible mechanism of the polycondensation have been discussed. 相似文献
72.
Mohamed A. Ali Wessel M. W. Winters Moushira A. Mohamed Dezhi Tan Guojun Zheng Rasmus S. K. Madsen Oxana V. Magdysyuk Maria Diaz-Lopez Biao Cai Nan Gong Yijue Xu Ivan Hung Zhehong Gan Sabyasachi Sen Hong-Tao Sun Thomas D. Bennett Xiaofeng Liu Yuanzheng Yue Jianrong Qiu 《Angewandte Chemie (International ed. in English)》2023,62(14):e202218094
Metal coordination compound (MCC) glasses [e.g., metal-organic framework (MOF) glass, coordination polymer glass, and metal inorganic-organic complex (MIOC) glass] are emerging members of the hybrid glass family. So far, a limited number of crystalline MCCs can be converted into glasses by melt-quenching. Here, we report a universal wet-chemistry method, by which the super-sized supramolecular MIOC glasses can be synthesized from non-meltable MOFs. Alcohol and acid were used as agents to inhibit crystallization. The MIOC glasses demonstrate unique features including high transparency, shaping capability, and anisotropic network. Directional photoluminescence with a large polarization ratio (≈47 %) was observed from samples doped with organic dyes. This crystallization-suppressing approach enables fabrication of super-sized MCC glasses, which cannot be achieved by conventional vitrification methods, and thus allows for exploring new MCC glasses possessing photonic functionalities. 相似文献
73.
Effect of screened Coulomb (Yukawa) potentials on the doubly excited meta‐stable bound states and the resonance states with unnatural parities of the helium atom have been investigated in the framework of stabilization method using CI‐type basis functions. A total of 54 resonances (6 each of 1Do and 3Do states, 12 each of 1Fe and 3Fe states, 9 each of 1Go and 3Go states) below the He+(3P) thresholds have been estimated by calculating the density of resonance states using a stabilization method. The resonances belong to the different 3lnl′ (n ≥ 3) series. We have also calculated the doubly excited 1,3Fe and 1,3Go meta‐stable bound states of He atom below the He+ (2P) thresholds. The resonance energies and widths along with the meta‐stable bound states energies are reported for various screening parameters. In free atom case, some of the F‐wave resonance states and most of the cases, F‐ and G‐wave resonance widths are reported for the first time. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 相似文献
74.
Structure and dynamics of room temperature ionic liquids with bromide anion: results from 81Br NMR spectroscopy
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Takatsugu Endo Mamoru Imanari Yuki Hidaka Hiroko Seki Keiko Nishikawa Sabyasachi Sen 《Magnetic resonance in chemistry : MRC》2015,53(5):369-378
We report the results of a comprehensive 81Br NMR spectroscopic study of the structure and dynamics of two room temperature ionic liquids (RTILs), 1‐butyl‐3‐methylimidazolium bromide ([C4mim]Br) and 1‐butyl‐2,3‐dimethylimidazolium bromide ([C4C1mim]Br), in both liquid and crystalline states. NMR parameters in the gas phase are also simulated for stable ion pairs using quantum chemical calculations. The combination of 81Br spin‐lattice and spin‐spin relaxation measurements in the motionally narrowed region of the stable liquid state provides information on the correlation time of the translational motion of the cation. 81Br quadrupolar coupling constants (CQ) of the two RTILs were estimated to be 6.22 and 6.52 MHz in the crystalline state which were reduced by nearly 50% in the liquid state, although in the gas phase, the values are higher and span the range of 7–53 MHz depending on ion pair structure. The CQ can be correlated with the distance between the cation–anion pairs in all the three states. The 81Br CQ values of the bromide anion in the liquid state indicate the presence of some structural order in these RTILs, the degree of which decreases with increasing temperature. On the other hand, the ionicity of these RTILs is estimated from the combined knowledge of the isotropic chemical shift and the appropriate mean energy of the excited state. [C4C1mim]Br has higher ionicity than [C4mim]Br in the gas phase, while the situation is reverse for the liquid and the crystalline states. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
75.
Elucidating the Thermal Decomposition of Dimethyl Methylphosphonate by Vacuum Ultraviolet (VUV) Photoionization: Pathways to the PO Radical,a Key Species in Flame‐Retardant Mechanisms
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Shuyu Liang Dr. Patrick Hemberger Dr. N. Matthias Neisius Dr. Andras Bodi Prof. Dr. Hansjörg Grützmacher Prof. Dr. Joelle Levalois‐Grützmacher Dr. Sabyasachi Gaan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(3):1073-1080
The production of phosphoryl species (PO, PO2, HOPO) is believed to be of great importance for efficient flame‐retardant action in the gas phase. We present a detailed investigation of the thermal decomposition of dimethyl methylphosphonate (DMMP) probed by vacuum ultraviolet (VUV) synchrotron radiation and imaging photoelectron photoion coincidence (iPEPICO) spectroscopy. This technique provides a snapshot of the thermolysis process and direct evidence of how the reactive phosphoryl species are generated during heat exposure. One of the key findings of this work is that only PO is formed in high concentration upon DMMP decomposition, whereas PO2 is absent. It can be concluded that the formation of PO2 needs an oxidative environment, which is typically the case in a real flame. Based on the identification of products such as methanol, formaldehyde, and PO, as well as the intermediates O?P?CH3, H2C?P?OH, and H2C?P(?O)H, supported by quantum chemical calculations, we were able to describe the predominant pathways that lead to active phosphoryl species during the thermal decomposition of DMMP. 相似文献
76.
Using an effective lattice gas-like model for B-B′ site ordering we study order-disorder transitions in double perovskite
materials A2BB′O6. We motivate this effective model from a microscopic hamiltonian. Using this model, we are able to address several experimentally
observed issues including nonmonotonic dependence of the degree of order on annealing temperature, and the rapid decrease
of order upon overdoping with either B or B′ species. We also study ordering in the ‘ternary’ compounds A2BB′1−yB″yO6, using a variant of the Blume-Emery-Griffiths model. Several issues related to structural and magnetic ordering are discussed. 相似文献
77.
A new route is developed for the synthesis of molybdenum and tungsten porphyrins using [M(NO)(2)py(2)Cl(2)] (M = Mo, W) as the metal source and TPP (dianion of 5,10,15,20-meso-tetraphenylporphyrin) in the benzoic acid melt. Complexes [Mo(V)O(TPP)(OOCPh)] (1) and [W(V)O(TPP)(OOCPh)] (2) are isolated in almost quantitative yield. These are characterized by single-crystal X-ray structure analysis, electron paramagnetic resonance, electronic and IR spectroscopy, and magnetic moment measurements. Benzenethiol substitutes for PhCOO(-) in 1, forming an intermediate thiolato complex that responds to the intramolecular redox reaction across the Mo(V)-SPh bond to yield [Mo(IV)O(TPP)] (3). Under an excess of benzenethiol, PhS(-) is coordinated to the vacant site in 3, which under aerial oxidation is oxidized to benzenesulfonate to form [Mo(V)O(TPP)(O(3)SPh)] (4). 2 undergoes similar aerial oxidation chemistry albeit slowly. 相似文献
78.
Exploiting powerful computational aspects and highly correlated exponential wave functions for two‐electron atoms, we have investigated the effects of screened Coulomb interaction on the hexadecapole polarizability of Li+(11S), and the dispersion coefficients C6, C8, C10, and C12 for interaction of Li+ with H and He atoms in their ground states. The dispersion coefficients and hexadecapole polarizability for different screening parameters ranging from 0 to 1.0 a are reported. In the unscreened case, the hexadecapole polarizability of Li+, and the dispersion C12 coefficients for Li+–H and Li+–He system are reported for the first time in the literature. The C6, C8, and C10 coefficients for the unscreened cases are comparable with the reported results. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 相似文献
79.
Samanta S Sengupta K Mittra K Bandyopadhyay S Dey A 《Chemical communications (Cambridge, England)》2012,48(61):7631-7633
An iron porphyrin catalyst with four electron donor groups is reported. The porphyrin ligand bears a distal hydrogen bonding pocket which inverts the normal axial ligand binding selectivity exhibited by porphyrins bearing sterically crowded distal structures. This catalyst specifically reduces O(2) by four electrons under both fast and slow electron fluxes at pH 7. 相似文献
80.
Zishi Jiang Sabyasachi Kar Y.K. Ho 《Journal of Quantitative Spectroscopy & Radiative Transfer》2012,113(1):75-81
Doubly-excited 1,3Pe and 1,3Do states of Li II, Be III, B IV, C V are calculated using highly correlated exponential wave functions within the framework of Ritz variational principle. The wavelengths for the 2pnp 1Pe→2pn′d 1Do (n, n′≤7) and 2pnp 3Pe→2pn′d 3Do (n, n′≤7) transitions are reported. Our present results for the 2pnp 1,3Pe and 2pnd 1,3Do states energies are accurate in precision compared to the results of previous calculations. Comparisons are also made with the experimental results. The effective quantum numbers (n?) for the 2pnp 1,3Pe and 2pnd 1,3Do states are also reported. 相似文献