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161.
Color-tunable, aggregation-induced emission of a butterfly-shaped molecule comprising a pyran skeleton and two cholesteryl wings 总被引:1,自引:0,他引:1
Tong H Hong Y Dong Y Ren Y Häussler M Lam JW Wong KS Tang BZ 《The journal of physical chemistry. B》2007,111(8):2000-2007
A chiral pyran derivative containing two cholesteryl groups (1) is synthesized, and its optical properties are investigated. Whereas the isolated molecule of 1 is virtually nonluminescent in dilute solutions, it becomes highly emissive with a 2 orders of magnitude increase in fluorescence quantum yield upon aggregation in poor solvents or in solid state, showing a novel phenomenon of aggregation-induced emission (AIE). The color and efficiency of the AIE of 1 can be tuned by varying the morphology of its aggregates: photoluminescence of its aggregates formed in a tetrahydrofuran/water mixture progressively red-shifts (green --> yellow --> red) with increasing water content of the mixture, with the crystalline aggregates emitting bluer lights in higher efficiencies than their amorphous counterparts. 相似文献
162.
Aggregation-induced and crystallization-enhanced emissions of 1,2-diphenyl-3,4-bis(diphenylmethylene)-1-cyclobutene 总被引:1,自引:0,他引:1
Dong Y Lam JW Qin A Sun J Liu J Li Z Sun J Sung HH Williams ID Kwok HS Tang BZ 《Chemical communications (Cambridge, England)》2007,(31):3255-3257
1,2-Diphenyl-3,4-bis(diphenylmethylene)-1-cyclobutene can be induced to emit efficiently by aggregate formation, with the crystalline aggregates emitting brighter, bluer lights than their amorphous counterparts. 相似文献
163.
Layered hybrid organic perovskites (HOPs) structures are a class of low‐cost two‐dimensional materials that exhibit outstanding optical properties, related to dielectric and quantum confinement effects. Whereas modeling and understanding of quantum confinement are well developed for conventional semiconductors, such knowledge is still lacking for 2D HOPs. In this work, concepts of effective mass and quantum well are carefully investigated and their applicability to 2D HOPs is discussed. For ultrathin layers, the effective‐mass model fails. Absence of superlattice coupling and importance of non‐parabolicity effects prevents the use of simple empirical models based on effective masses and envelope function approximations. An alternative method is suggested in which 2D HOPs are treated as composite materials, and a first‐principles approach to the calculation of band offsets is introduced. These findings might also be relevant for other classes of layered 2D functional materials. 相似文献
164.
Changmin Xing Jacky W. Y. Lam Keqing Zhao Ben Zhong Tang 《Journal of polymer science. Part A, Polymer chemistry》2008,46(9):2960-2974
Triphenylene‐containing 1‐decynes with different alkyl chain lengths and their polymers are synthesized and the effects of the structural variables on their mesomorphic properties are investigated. The monomers [HC?C(CH2)8CO2C18H6 (OCmH2m+1)5; m = 4–9] are prepared by consecutive etherization, coupling, and esterification reactions. The monomers form columnar phases at room temperature. The polymerizations of the monomers are effected by [Rh(nbd)Cl]2, producing soluble polymers in high yields (up to 84%). The structures and properties of the polymers are characterized and evaluated by IR, NMR, TGA, DSC, POM, and XRD analyses. All the polymers are thermally stable, losing little of their weights when heated to 300 °C. The isotropization temperature of the polymers increases initially with the length of alkyl chain but decreases on further extension. Although the polymers with shorter and longer alkyl chain lengths adopt a homogeneous hexagonal columnar structure, those with intermediate ones form mesophases with mixed structures. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2960–2974, 2008 相似文献
165.
We define an operator which extends classical differentiation from smooth deterministic functions to certain stochastic processes. Based on this operator, we define a procedure which associates a stochastic analog to standard differential operators and ordinary differential equations. We call this procedure stochastic embedding. By embedding Lagrangian systems, we obtain a stochastic Euler–Lagrange equation which, in the case of natural Lagrangian systems, is called the embedded Newton equation. This equation contains the stochastic Newton equation introduced by Nelson in his dynamical theory of Brownian diffusions. Finally, we consider a diffusion with a gradient drift, a constant diffusion coefficient and having a probability density function. We prove that a necessary condition for this diffusion to solve the embedded Newton equation is that its density be the square of the modulus of a wave function solution of a linear Schrödinger equation. To cite this article: J. Cresson, S. Darses, C. R. Acad. Sci. Paris, Ser. I 342 (2006). 相似文献
166.
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168.
Jianli Hua Jacky Wing Yip Lam Xiaoming Yu Lijun Wu Hoi Sing Kwok Kam Sing Wong Ben Zhong Tang 《Journal of polymer science. Part A, Polymer chemistry》2008,46(6):2025-2037
Perylene (Py)‐containing polyacetylenes with different skeleton structures ? [HC?C(C6H4)CO2? Py]n? (P 1 ), ? [HC?C(CH2)8CO2? Py]n? (P 2 ), and ? {[(C6H5) C?C(CH2)9NH2]? co? [(C6H5)C?C(CH2)9? Py]}n? (P 3 ) are synthesized in satisfactory yields by Rh‐catalyzed polymerization (for P 1 and P 2 ) and polymer reaction (for P 3 ). All the polymers are soluble and possess high molecular weights (Mw up to 2.8 × 105). Their structures and properties are characterized and evaluated by IR, NMR, UV, TGA, PL, and photovoltaic (PV) analyses. The polymers are thermally stable, losing little of their weights when heated to 330 °C. When their solutions are irradiated, their perylene pendants emit intense red fluorescence at 610 nm. PV cells with a configuration of ITO/PEDOT:PSS/polymer/LiF/Al are fabricated, which show maximum current density of 10.3 μA/cm2. The external quantum efficiency is sensitive to the polymer structure, with P 3 exhibiting the highest value of 0.23%. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2025–2037, 2008 相似文献
169.
Chan JC Lam WH Wong HL Zhu N Wong WT Yam VW 《Journal of the American Chemical Society》2011,133(32):12690-12705
The synthesis, characterization, electrochemistry, photophysics and photochromic behavior of a new class of cyclometalated platinum(II) complexes [Pt(C(∧)N)(O(∧)O)] (1a-5a and 1b-5b), where C(∧)N is a cyclometalating 2-(2'-thienyl)pyridyl (thpy) or 2-(2'-thienothienyl)pyridyl (tthpy) ligand containing the photochromic dithienylethene (DTE) unit and O(∧)O is a β-diketonato ligand of acetylacetonato (acac) or hexafluoroacetylacetonato (hfac), have been reported. The X-ray crystal structures of five of the complexes have also been determined. The electrochemical studies reveal that the first quasi-reversible reduction couple, and hence the nature of lowest unoccupied molecular orbital (LUMO) of the complexes, is sensitive to the nature of the ancillary O(∧)O ligands. Upon photoexcitation, complexes 1a-3a and 1b-3b exhibit drastic color changes, ascribed to the reversible photochromic behavior, which is found to be sensitive to the substituents on the pyridyl ring and the extent of π-conjugation of the C(∧)N ligand as well as the nature of the ancillary ligand. The thermal bleaching kinetics of complex 1a has been studied in toluene at various temperatures, and the activation barrier for the thermal cycloreversion of the complex has been determined. Density functional theory (DFT) calculations have been performed to provide an insight into the electrochemical, photophysical and photochromic properties. 相似文献
170.
Y Liu X Chen Y Lv S Chen J W Y Lam F Mahtab HS Kwok X Tao BZ Tang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(32):9929-9938
By employing a new synthetic strategy, a series of oligomers and a polymer composed of different number of tetraphenylethene and triphenylamine units was designed and synthesised. The optical physics properties and electroluminescence behaviours were studied comparatively. All the molecules demonstrate an aggregation-induced emission (AIE) phenomenon and bear very high quantum yields in the solid state. The emission wavelengths and quantum efficiencies alternate with the change of the molecular configurations and achieve their maximum at the largest oligomer. The thermal stabilities also become higher along with the increase in the molecular weight. The molecules have suitable HOMO levels that match the work function of the indium tin oxide (ITO) anode. They can act as both light-emitting and hole-transporting materials in OLEDs. Thus the present strategy combines the intrinsic emissive nature of AIE materials and the good hole-transport capability of aromatic amines, thereby achieving a win-win for both optical and electrical properties. 相似文献