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991.
A promising method for the elimination of undesired capacitive currents in view of realizing a potentially calibration free coulometric ion detection system is presented. The coulometric cell is composed of a porous polypropylene tube doped with a liquid calcium-selective membrane and a silver/silver chloride wire as an inner electrode, forming a thin layer sample between wire and tubing. The total charge passed through the system during potential controlled electrolysis of the thin layer sample is indeed found to be proportional to the amount of calcium present, but non-Faradaic processes do contribute to the obtained signal. We introduce here a multi-pulse procedure that allows one to perform a second excitation pulse at the same excitation potential after exhaustive ion transfer voltammetry of calcium has taken place. The intercept of the calibration curve after background subtraction is found as 20.6 ± 0.6 μC, significantly lower than the value of 54.1 ± 0.8 μC for the uncorrected curve. Changes in sample temperature (from 23 °C to 38 °C) did equally not affect the background corrected coulometric readings, supporting that the procedure renders the readout principle more robust. 相似文献
992.
993.
B. Mears P. R. Pine H. W. Doughty B. Freeman J. Guzmán A. Rancano T. L. Kelley J. J. Melloy H. A. Fales T. Callan R. T. P. Jones B. Tougarinov H. Hölemann C. Frick H. Engemann A. Schleicher W. T. Schrenk Ph. H. Delano J. L. Merrill A. S. Russell S. W. Rowell K. S. Jackson N. H. Furman M. I. Schubin K Anderson H. Swett Ella M. Collin H. J. S. Sand L. F. Yntema und D. D. Peirce 《Fresenius' Journal of Analytical Chemistry》1932,87(5-6):214-224
Ohne Zusammenfassung 相似文献
994.
995.
Corey L. Jones Colan E. Hughes Hamish H.-M. Yeung Alison Paul Kenneth. D. M. Harris Timothy L. Easun 《Chemical science》2021,12(4):1486
The formation processes of metal–organic frameworks are becoming more widely researched using in situ techniques, although there remains a scarcity of NMR studies in this field. In this work, the synthesis of framework MFM-500(Ni) has been investigated using an in situ NMR strategy that provides information on the time-evolution of the reaction and crystallization process. In our in situ NMR study of MFM-500(Ni) formation, liquid-phase 1H NMR data recorded as a function of time at fixed temperatures (between 60 and 100 °C) afford qualitative information on the solution-phase processes and quantitative information on the kinetics of crystallization, allowing the activation energies for nucleation (61.4 ± 9.7 kJ mol−1) and growth (72.9 ± 8.6 kJ mol−1) to be determined. Ex situ small-angle X-ray scattering studies (at 80 °C) provide complementary nanoscale information on the rapid self-assembly prior to MOF crystallization and in situ powder X-ray diffraction confirms that the only crystalline phase present during the reaction (at 90 °C) is phase-pure MFM-500(Ni). This work demonstrates that in situ NMR experiments can shed new light on MOF synthesis, opening up the technique to provide better understanding of how MOFs are formed.A new in situ NMR methodology for studying the formation processes of MOFs is reported, supported by SAXS and PXRD experiments. Synthesis of a phosphonate-based MOF is described, from molecular aggregation through to nucleation and crystallisation. 相似文献
996.
Gunjan Verma V. K. Aswal S. K. Kulshreshtha C. Manohar P. A. Hassan Eric W. Kaler 《Pramana》2008,71(5):997-1002
Structural parameters of micelles formed by Triton X-100 in the presence of solubilized anthranilic acid at different pH values
was investigated using light scattering and small angle neutron scattering. Analysis of the SANS data indicate that micelles
are oblate ellipsoidal in nature with little variation in the dimensions, in the investigated pH range (from 0.5 to 6.0).
The interaction potential of the micelles shows a minimum closer to the isoelectric point of anthranilic acid. A similar variation
is observed in the cloud point of the micelles with pH. The observed variation in the interaction potential with pH of the
micellar solution can be explained in terms of the reversal of charge on anthranilic acid due to shift in the acid-base equilibrium.
The variation in interaction potential and cloud point with pH is modelled using Coulombic repulsion of charged molecules
at the micelle interface.
相似文献
997.
998.
Eric Rosen 《Israel Journal of Mathematics》2008,166(1):239-284
We develop the theory of higher prolongations of algebraic varieties over fields in arbitrary characteristic with commuting
Hasse-Schmidt derivations. Prolongations were introduced by Buium in the context of fields of characteristic 0 with a single
derivation. Inspired by work of Vojta, we give a new construction of higher prolongations in a more general context. Generalizing
a result of Buium in characteristic 0, we prove that these prolongations are represented by a certain functor, which shows
that they can be viewed as ‘twisted jet spaces.’ We give a new proof of a theorem of Moosa, Pillay and Scanlon that the prolongation
functor and jet space functor commute. We also prove that the m-th prolongation and m-th jet space of a variety are differentially isomorphic by showing that their infinite prolongations are isomorphic as schemes. 相似文献
999.
John C. Graham Xinmin Xu Lonnie Jones Margarita Orticochea 《Journal of polymer science. Part A, Polymer chemistry》1990,28(5):1179-1183
The reaction of bis(ethyl-3-oxo-butanolato-O1,O3)-bis(2-propanolato)titanium(Tyzor DCR and 2-isocyanatoethyl methacrylate (IEM) in refluxing hexane produced a mixture of trimer and polymers of 2-isocyanatoethyl methacrylate which varied considerably from 23 to 92% polymer as the molar ratio of bis(ethyl-3-oxo-butanolato-O1,O3)-bis(2-propanolato)titanium(Tyzor DCR) to 2-isocyanatoethyl methacrylate (IEM) varied from 1:4 to 1:32. The IEM 1-nylon polymer which was soluble in cresol and phenol was characterized by FTIR, 1H-NMR, and 13C-NMR. This analysis also showed that the methacrylate carbon–carbon double bond survived our reaction conditions intact. Based on atomic absorption determination of titanium, the molecular weight of the polymer ranged between 3000 and 4000 g/mol. Thermal gravimetric analysis (TGA) showed the polymer to be stable in air to approximately 250°C. 相似文献