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71.
J. L. Lundberg E. J. Mooney C. E. Rogers 《Journal of Polymer Science.Polymer Physics》1969,7(5):947-962
Diffusion coefficients and solubilities of methane in polyisobutylene have been measured at four temperatures between 102 and 188°C. in the pressure range 23–341 atm. Diffusion coefficients extrapolated to atmospheric pressure range from 1.72 × 10?6 cm.2/sec. at 102°C. to 1.5 × 10?5 cm.2/sec. at 188°C. corresponding to an activation energy for diffusion of 8.7 ± 0.4 kcal./mole. Solubilities are small, about one molecule of methane for every forty carbon atoms in the polyisobutylene at 300 atm. partial pressure of methane. Solubilities vary little with temperature, but show an apparent minimum between 127 and 188°C. With improved methods of data analysis, diffusion coefficients and solubilities have been recalculated from previously reported studies on nitrogen in branched polyethylene and methane in branched polyethylene, linear polyethylene, and polystyrene. Recalculated diffusion coefficients are essentially the same as those reported previously, but the recalculated solubilities are decreased from 2 to 30%. The solubilities of all five systems show strong deviations from Henry's law, i.e., increases in partial pressure of methane and nitrogen with respect to solubility exceed linearity. The partial pressure (or fugacity)—solubility data may be interpreted in terms of a sorption model in which sorbed molecules are accommodated in widely dispersed, unoccupied volumes or sites in the polymer. An almost equivalent, solution model in which the first sorbed molecules to enter the polymer are accommodated to a large extent in existing volumes in the polymer, with successively sorbed molecules swelling the polymer to a greater extent (i.e., partial molal volume of sorbed molecules, V 1, increasing with concentration) can also account for these data. 相似文献
72.
Leucine aminopeptidase activity was measured using l-[U-14C]leucinamide as substrate. The leucine freed by hydrolysis was separated by high voltage electrophoresis and estimated in a scintillation counter. The method was especially useful for studying the production of LAP during the molting of infective juveniles of the nematodes, H. contortus, because activity could be measured without purifying or concentrating the enzyme. 相似文献
73.
The heats of combustion of 95 samples of oil shale from the Nevis Valley have been determined from DTA peak areas obtained by combustion in 1.5 atm oxygen. The heats of combustion of the oil shale ranged from 0.2 to 8.5 MJ kg−1, with an average of 2.6 MJ kg−1, while that of the kerogen was calculated to be 34.2 MJ kg−1. Up to four peaks were obtained in the DTA combustion curve, suggesting that different parts of the kerogen molecule were being oxidised at different temperatures.
In nitrogen, DTA endotherms were observed due to decarbonation of siderite (ca. 455°C), and dehydroxylation of kaolinite (ca. 570°C) and chlorite (ca. 760°C), and an exotherm due to formation of mullite (ca. 980°C). 相似文献
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Many of the proprietary additive formulations that have been proposed to control the properties of metal electrodeposits include water soluble macromolecules. Among these are the hydrodynamically interesting polyethylene glycols ‘Polyox’. In the course of a rotating disk electrode study of the effects of additives in copper electrodeposition the present authors had cause to try the effects of low concentrations of Polyox in an acid copper sulphate plating solution. In the presence of an essential trace of chloride ion Polyox very strongly inhibited deposition below a critical overpotential at which current density rises extremely rapidly with increasing overpotential. These results suggest that below the critical overpotential chloride ions hold a film of Polyox onto the electrode surface and may also give the film some lateral cohesion. The film may be a Polyox-cuprous chloride complex. Striking spiral patterns form at the critical overpotential. Their characteristics are explained as the consequences of electrodeposition on a surface containing submicroscopic protrusions and depressions in conditions where current density increases very rapidly with potential. 相似文献
79.
Lee GW Gangopadhyay AK Kelton KF Hyers RW Rathz TJ Rogers JR Robinson DS 《Physical review letters》2004,93(3):037802
New short-range order data are presented for equilibrium and undercooled liquids of Ti and Ni. These were obtained from in situ synchrotron x-ray diffraction measurements of electrostatically levitated droplets. While the short-range order of liquid Ni is icosahedral, consistent with Frank's hypothesis, significantly distorted icosahedral order is observed in liquid Ti. This is the first experimental observation of distorted icosahedral short-range order in any liquid, although this has been predicted by theoretical studies on atomic clusters. 相似文献
80.
Menard E Bilhaut L Zaumseil J Rogers JA 《Langmuir : the ACS journal of surfaces and colloids》2004,20(16):6871-6878
Nanotransfer printing represents an additive approach for patterning thin layers of solid materials with nanometer resolution. The surface chemistries, thin film deposition techniques, and stamp designs are all important for the proper operation of this method. This paper presents some details concerning processing procedures and other considerations needed for patterning two- and three-dimensional nanostructures with low density of defects and minimal distortions. 相似文献