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991.
Kell Mortensen Y. Tomkiewicz T.D. Schultz E.M. Engler V.V. Patel A.R. Taranko 《Solid State Communications》1981,40(10):915-918
We report on transport and EPR studies of (TMTSF)2-PF6, both in its pristine form and when doped with the sulfur analog TMTTF. All samples undergo a single phase transition which can be seen in both the transport and magnetic data and which, in the undoped material, occurs at ~11.5 K. The effects of a 3% dopant concentration are dramatic: a 40% rise in the transition temperature, a 130% rise in the room- temperature spin susceptibility and a 30% fall in the low-temperature g shift. Possible causes are discussed. 相似文献
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A numerical technique and a computer program based on the method of orthogonal collocation on finite elements for solving steady state carrier-mediated transport problems is presented. The method is especially suitable in solving boundary layer type of problems as arise in carrier-mediated transport. The method uses an efficient LU decomposition of a blockdiagonal matrix. A residual criterion is used for the placement of elements which can be easily implemented using an interactive feature in the computer program. Numerical results for three different systems; a system with simple kinetics and equal diffusivities for carrier and its complex, a system with simple kinetics and unequal diffusivities and a system with complex kinetics and equal diffusivities, indicate that the method is very versatile and has very good convergence properties. The method can be used very easily for all these systems by making minor modifications to the computer program. 相似文献
996.
J. M. Schultz E. W. Fischer O. Schaumburg H. A. Zachmann 《Journal of Polymer Science.Polymer Physics》1980,18(2):239-245
The course of melting of melt-crystallized polyethylene fractions and of a poly(ethylene oxide)-polystyrene-poly(ethylene oxide) triblock copolymer has been followed by small-angle x-ray scattering (SAXS). Changes in the intensity and shape of the SAXS curves indicated that both surface melting and melting over the full crystallite thickness (full-strand melting) take place. Full strand melting is the final, irreversible process. Comparison with an analytical model indicates that in the earlier stages of the irreversible, full-strand process the crystallites melt out randomly throughout the bulk. Later stages may occur by the simultaneous melting of a larger stack of crystallites. 相似文献
997.
J. Petermann R. M. Gohil J. M. Schultz R. W. Hendricks J. S. Lin 《Journal of Polymer Science.Polymer Physics》1982,20(3):523-534
Polypropylene films were produced by solidification during high-rate (>104s?1) melt drawing. Small-angle x-ray scattering (SAXS) data were collected during interruptions of the annealing of these films. Fibrillar crystallization took place during the melt-drawing process. The fibrils exhibit an axial density modulation as determined by SAXS and transmission electron microscopy. Annealing increases the amplitude of the density modulation. Detailed examination of the SAXS curves shows that the modulation is approximately sinusoidal and that the amplification of the density modulation occurs with no change in periodicity. Comparison of SAXS curves taken at different times during annealing suggests a process similar to spinodal decomposition. It is proposed that the microstructural change within a fibril takes place by the axial motion and clustering of chain defects. 相似文献
998.
Park HS Blewitt G Cortez BG Foster GW Gajewski W Haines TJ Kielczewska D LoSecco JM Bionta RM Bratton CB Casper D Chrysicopoulou P Claus R Errede S Ganezer KS Goldhaber M Jones TW Kropp WR Learned JG Lehmann E Reines F Schultz J Seidel S Shumard E Sinclair D Sobel HW Stone JL Sulak LR Svoboda R van der Velde JC Wuest C 《Physical review letters》1985,54(1):22-25
999.
1000.
Schultz MJ Adler RS Zierkiewicz W Privalov T Sigman MS 《Journal of the American Chemical Society》2005,127(23):8499-8507
The experimental and computational mechanistic details of the Pd(OAc)(2)/TEA-catalyzed aerobic alcohol oxidation system are disclosed. Measurement of various kinetic isotope effects and the activation parameters as well as rate law derivation support rate-limiting deprotonation of the palladium-coordinated alcohol. Rate-limiting deprotonation of the alcohol is contrary to the majority of related kinetic studies for Pd-catalyzed aerobic oxidation of alcohols, which propose rate-limiting beta-hydride elimination. This difference in the rate-limiting step is supported by the computational model, which predicts the activation energy for deprotonation is 3 kcal/mol higher than the activation energy for beta-hydride elimination. The computational features of the similar Pd(OAc)(2)/pyridine system were also elucidated. Details of the study illustrate that the use of TEA results in an active catalyst that has only one ligand bound to the Pd, resulting in a significant lowering of the activation energy for beta-hydride elimination and, therefore, a catalyst that is active at room temperature. 相似文献