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91.
Stig Veibel A. K. Dhamoon und Inger Grete Krogh Andersen 《Fresenius' Journal of Analytical Chemistry》1964,200(6):439-443
Zusammenfassung Acetylaceton und Benzoylaceton bilden mit elektronegativ substituierten Phenylhydrazinen, selbst mit 2,4-Dinitrophenylhydrazin, und selbst wenn die Reaktion bei Zimmertemperatur durchgeführt wird, 1,3,5-tri-substituierte Pyrazole ohne nachweisbare Mengen von Zwischenprodukten (Monophenylhydrazone).5-Methoxypentan-2,4-dion bildet mit p-Nitrophenylhydrazin bei Zimmertemperatur ein Monophenylhydrazon. Bei höherer Temperatur wird aber auch hier das entsprechende Pyrazol gebildet.
Wir möchten nicht unterlassen, dem Carlsbergfond unseren Dank für eine finanzielle Unterstützung auszusprechen. 相似文献
Summary Acetylacetone and benzoylacetone react with electro-negatively substituted phenylhydrazines to form 1,3,5-trisubstituted pyrazoles, also with 2,4-dinitrophenylhydrazine and even if the reaction is performed at room temperature. There are no detectable quantities of intermediate products (monophenylhydrazones).5-Methoxypentane-2,4-dione is forming with p-nitrophenylhydrazine at room temperature a monophenylhydrazone, but at higher temperature the corresponding pyrazole is also formed.
Wir möchten nicht unterlassen, dem Carlsbergfond unseren Dank für eine finanzielle Unterstützung auszusprechen. 相似文献
92.
The paper describes an interactice, computer based procedure for solving the variant of the vehicle loading problem encountered when loading containers and pallets into an aircraft. The procedure is heuristic and practical oriented; it is presently being implemented by Scandinavian Airlines. 相似文献
93.
The spin polarization of the conduction electrons of a doped semiconductor (e.g. EuO + x%Gd) is calculated using a moment method together with an alloy analogy. It is shown to be caused by a complicated temperature- and carrier concentration-dependence of the quasiparticle spectrum of the s-f model. Obtained polarization agrees very well with recent photoemission experimental data. 相似文献
94.
The influence of surface polaritons (SPs), excited on the external (fast mode) and internal (slow mode) surfaces of a gold film, on the tunneling current of a STM is investigated. The role of the surface polaritons is directly demonstrated by the angular excitation spectra of the induced tunneling current. Possible mechanisms which might give rise to the SP induced change in the tunneling current are discussed. An electromagnetic field of SPs within a tunneling gap is estimated to be surface enhanced in order to explain the value of the induced tunneling current. Images of the polariton induced signal distribution over the sample surface taken by means of different SP modes are compared in order to obtain information on the structure of the internal surface of the film. 相似文献
95.
The local approach for the intraatomic correlation is applied to study the ground state phase diagram of the extended Hubbard model with a half-filled band. The long-range orders are not destroyed by the correlation effect in the limit of weak interaction, though the values of the order parameters are reduced from those of the Hartree-Fock approximation, especially for the antiferromagnetic-state. We find that the antiferromagnetic-charge order phase boundary is only slightly shifted towards the charge ordered state, while the phase boundary between the singlet superconducting and the charge ordered phases remains the same as that derived from the Hartree-Fock approximation. 相似文献
96.
Simultaneous use of large standard molecules and small particles of the product examined gives rise to errors in pore size determination by size exclusion chromatography. This error is calculated for packings of spherical particles, thus making corrections possible. 相似文献
97.
By combining ab initio results for the electronic structure and phonon spectrum with the group theory, we establish the origin of the Verwey transition in Fe3O4. Two primary order parameters with X3 and Delta5 symmetries are identified. They induce the phase transformation from the high-temperature cubic to the low-temperature monoclinic structure. The on-site Coulomb interaction U between 3d electrons at Fe ions plays a crucial role in this transition--it amplifies the coupling of phonons to conduction electrons and thus opens a gap at the Fermi energy. 相似文献
98.
99.
We study systems with a continuous phase transition that tune their parameters to maximize a quantity that diverges solely at a unique critical point. Varying the size of these systems with dynamically adjusting parameters, the same finite-size scaling is observed as in systems where all relevant parameters are fixed at their critical values. This scheme is studied using a self-tuning variant of the Ising model. It is contrasted with a scheme where systems approach criticality through a target value for the order parameter that vanishes with increasing system size. In the former scheme, the universal exponents are observed in naïve finite-size scaling studies, whereas in the latter they are not. 相似文献
100.