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991.
Joanna Krakowiak 《The Journal of chemical thermodynamics》2011,43(6):882-894
The densities of tetra-n-butylammonium bromide in 1-propanol, 1-butanol, acetone at (288.15, 293.15, 298.15, 303.15, 308.15, 313.15, and 323.15) K and sound velocities at 298.15 K have been measured. From these data apparent molar volumes VΦ at (288.15, 293.15, 298.15, 303.15, 308.15, 313.15, and 323.15) K and the apparent molar isenotropic compressibility KS,Φ, at T = 298.15 K of tetrabutylammonium bromide in nonaqueous solvents have been determined. The apparent molar volumes and the apparent molar isenotropic compressibilities were fitted to the Redlich, Rosenfeld, and Mayer equation as well as to the Pitzer equation yielding infinite dilution data, which were compared to the similar quantities for tetrabutylphosphonium bromide. Moreover, the acoustical parameters such as intermolecular free length (Lf), relative association (RA), Rao’s molar sound function (Rm), and salvation number (Sn) were calculated using the experimental data of density and sound velocity at T = 298.15 K for ammonium and phosphonium bromides. The obtained data suggest the penetration of the acetone molecule within the intraionic free space of the tetrabutyl-ammonium and phosphonium cations. 相似文献
992.
The intermolecular potentials for the X 2σ and A2Π states of Li… Ar were studied by a variety of multiconfiguration, single-configuration, and perturbation methods (CASPT 2). The A 2Π excited state was calculated to have a well depth of 811 cm?1 at an internuclear separation of 2.59 Å, in excellent agreement with the 810 cm?1 derived from experimental data. A smaller well of 77 cm?1 was found for the X 2σ ground state at an intermolecular separation of 4.8 Å. These results are in better agreement with experimental results than were the previously reported pseudopotential calculations. The comparison of CI calculation with the CAPST 2 results shows that the latter is able to give good results for interacting metal–rare gas systems. © 1995 John Wiley & Sons, Inc. 相似文献
993.
Franklin A. Davis Bin Chao Yemane W. Andemichael Pradyumna K. Mohanty Tianan Fang David M. Burns Ashwin Rao Joanna M. Szewczyk 《Heteroatom Chemistry》2002,13(5):486-492
Enantiopure N‐sulfinyl‐δ‐amino‐β‐ketoesters and isoquinolones, prepared from sulfinimines (N‐sulfinyl imines) are a new class of polyfunctionalized chiral building blocks. These building blocks provide easy access to enantiomerically pure, functionalized piperidines and tetrahydroisoquinolines with a minimum of chemical manipulation and protecting‐group chemistry. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:486–492, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/hc.10090 相似文献
994.
Joanna Kulesza Marcin GuzinskiVeronique Hubscher-Bruder Francoise Arnaud-NeuMaria Bocheńska 《Polyhedron》2011,30(1):98-105
The synthesis, characterisation and X-ray crystal structures of p-tert-butyl-calix[4]arene-thioamide L and its complex with lead L-Pb2+ is reported. The cation-binding properties in solution have been assessed by liquid-liquid extraction of the metal picrates from water into dichloromethane and by stability constants determination in acetonitrile using UV-absorption spectrophotometry or potentiometry. The compound was used as active material in Pb-ion-selective membrane electrodes. The characteristics of these electrodes as well as the selectivity coefficients for Pb2+ cation versus many metal ions tested were obtained. Complex formation constants within the electrode membranes were determined using the sandwich membrane method and were compared to those obtained in acetonitrile. The lead concentration in the scrap-lead was determined with the use of electrodes incorporating the ligand studied. 相似文献
995.
Mononuclear, five-coordinate lanthanide amido and aryloxide complexes bearing tetradentate (N2O2) Schiff bases 总被引:2,自引:0,他引:2
Schuetz SA Silvernail CM Incarvito CD Rheingold AL Clark JL Day VW Belot JA 《Inorganic chemistry》2004,43(20):6203-6214
Two monomeric, five-coordinate lanthanide complexes, [bis-5,5'-(1,3-propanediyldiimino)-2,2-dimethyl-4-hexene-3-onato]samarium[2,6-bis(tert-butyl)-4-methylphenoxide] and [bis-5,5'-(1,3-propanediyldiimino)-2,2-dimethyl-4-hexene-3-onato]erbium[2,6-bis(tert-butyl)-4-methylphenoxide], were isolated from the reactions of 2,6-bis(tert-butyl)-4-methylphenol with [bis-5,5'-(1,3-propanediyldiimino)-2,2-dimethyl-4-hexene-3-onato]lanthanide[bis(trimethylsilyl)amido] (lanthanide = Er(3+) and Sm(3+)). The purified phenoxides were recovered in excellent yields and analytical purity, and the reactions proceeded cleanly without Schiff-base degradation or cluster formation. Analogously, [bis-3,3'-(1,3-propanediyldiimino)-1-phenyl-2-butene-1-onato]erbium[bis(trimethylsilyl)amido] was also directly converted to [bis-3,3'-(1,3-propanediyldiimino)-1-phenyl-2-butene-1-onato]erbium[2,6-bis(tert-butyl)-4-methylphenoxide]; however, a less sterically demanding alcohol (i.e., ethanol) yielded a neutral trinuclear oxo alkoxide species with each dianionic Schiff base asymmetrically bridging through micro-oxo interactions. In this polynuclear cluster, each symmetry-related, seven-coordinate erbium(III) ion exhibits monocapped trigonal prismatic geometry, which assembles by sharing triangular capped faces. Single-crystal X-ray diffraction revealed square-pyramidal metal coordination in each five-coordinate lanthanide ion with varied S(4) ruffling of the "square base" donor atoms and the six-membered propylene diamine chelate ring adopting the boat conformation. To contrast the effect of subtle ligand changes, we also report the synthesis and characterization of [bis-5,5'-(2,2-dimethyl-1,3-propanediyldiimino)-2,2-dimethyl-4-hexene-3-onato]samarium[bis(trimethylsilyl)amido], having gem-dimethyl substituents appended to the propylene bridge central carbon. The six-membered diamine chelate ring in this compound adopts the chair conformation without metal-hydrocarbon interaction. Also presented are qualitative activity observations and polymerization data for the polymerization of rac-lactide and epsilon-caprolactone using the five-coordinate lanthanide amidos and phenoxides. 相似文献
996.
Jamróz MH Rode JE Ostrowski S Lipiński PF Dobrowolski JC 《Journal of chemical information and modeling》2012,52(6):1462-1479
To measure molecular chirality, the molecule is treated as a finite set of points in the Euclidean R(3) space supplemented by k properties, p(1)((i)), p(2)((i)), ..., p(k)((i)) assigned to the ith atom, which constitute a point in the Property P(k) space. Chirality measures are described as the distance between a molecule and its mirror image minimized over all its arbitrary orientation-preserving isometries in the R(3) × P(k) Cartesian product space. Following this formalism, different chirality measures can be estimated by taking into consideration different sets of atomic properties. Here, for α-amino acid zwitterionic structures taken from the Cambridge Structural Database and for all 1684 neutral conformers of 19 biogenic α-amino acid molecules, except glycine and cystine, found at the B3LYP/6-31G** level, chirality measures have been calculated by a CHIMEA program written in this project. It is demonstrated that there is a significant correlation between the measures determined for the α-amino acid zwitterions in crystals and the neutral forms in the gas phase. Performance of the studied chirality measures with changes of the basis set and computation method was also checked. An exemplary quantitative structure–activity relationship (QSAR) application of the chirality measures was presented by an introductory model for the benchmark Cramer data set of steroidal ligands of the sex-hormone binding globulin. 相似文献
997.
Metallic elements such as Ag, Al, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Rb, Sr, and Zn were determined using ICP-OES in a representative set of fifteen fruiting bodies of the edible fungus Suillus variegatus. Fruiting bodies were collected from unpolluted areas near the village of Lubichowo of the Bory Tucholskie forest complex in northern Poland in 2007?C2008. The caps were richer in Ag, Al, Cd, Cr, Cu, Fe, K,Mg, Ni, Rb, and Zn, and the stipes in Ba, Ca, Mn, Na, Pb, and Sr. Cobalt concentration in the caps and stipes was similar. In the caps, the content of the elements decreased in the order (mg per kg of dry weight): K 29000 ± 3700, Fe 1600 ± 80, Mg 990 ± 110, Rb 320 ± 86, Zn 90 ± 19, Ca 75 ± 34, Al 68 ± 32, Na 40 ± 18, Cu 19 ± 7, Mn 13 ± 7, Cd 1.0 ± 0.5, Ni 0.64 ± 0.32, Ag 0.40 ± 0.20, Cr 0.33 ± 0.06, Pb 0.20 ± 0.17, Ba 0.19 ± 0.11, Sr 0.15 ± 0.09, and Co 0.070 ± 0.050. Apparently, S. variegatus collected from background areas are relatively low in Pb and Cd and so are suitable for human consumption. 相似文献
998.
Carbon Paste Electrodes Modified with Graphene Oxides – Comparative Electrochemical Studies of Thioguanine 下载免费PDF全文
Sylwia Smarzewska Joanna Pokora Andrzej Leniart Natalia Festinger Witold Ciesielski 《Electroanalysis》2016,28(7):1562-1569
The voltammetric study of thioguanine (TG) was comparatively investigated on bare, graphene oxide and reduced graphene oxide modified carbon paste electrodes using cyclic (CV) and square wave stripping (SWSV) voltammetric techniques. Depending on the working electrode and pH of supporting electrolyte, characteristic electrochemical behaviour of thioguanine was established and the mechanism of TG oxidation was suggested. Based on the obtained results, the new voltammetric method for TG determination in buffer solutions and pharmaceutical formulation was developed. Atomic force microscopy was used to characterize electrodes surfaces. 相似文献
999.
1000.
Smetana AB Wang JS Boeckl J Brown GJ Wai CM 《Langmuir : the ACS journal of surfaces and colloids》2007,23(21):10429-10432
By lowering the reaction temperature during metal ion reduction in a reverse micelle system, gold nanoparticle size can be subtly tuned from 6.6 to 2.2 nm in diameter. Under these reaction conditions, the water-to-surfactant ratio (W value) also plays an important role in controlling the particle size, enabling a wide range of products obtainable via a simple, quick, reproducible synthesis. Particle sizes were measured by HRTEM, and size trends were supported by UV-vis spectroscopy. 相似文献