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71.
We present a piecewise- linear map of the unit interval in which the resolvent of the Frobenius- Perron operator, considered in a polynomial basis, has an essen-tial singularity at the origin. Associated with the essential singularity are polynomial shift states, which are obtained from creation and annihilation operators in non- self- dual function spaces. Correlation functions of general polynomial observables have decay components that vanish in a finite time.  相似文献   
72.
The pyrolyses of four alkyl allyl sulfides with substituents on the α? C atom of the alkyl moiety have been studied in a stirred-flow system over the temperature range 340-400°C and pressures between 2 and 12 torr. The only products formed are propene and thioaldehydes. The reactions showed first-order kinetics with the rate coefficients following the Arrhenius equations: Chloromethyl allyl sulfide: Cyanomethyl allyl sulfide: 1-cyanoethyl allyl sulfide: Neopentyl allyl sulfide: The effects of these and other substituents on the reactivity is discussed in relation with the stabilization of a polar six-centered transition state. The results support a non-concerted mechanism where the 1–5 α? H atom shift is assisted by its acidic character.  相似文献   
73.
74.
We study the properties of a causal quantum theory in phase space for which phase space classical mechanics is obtained as a limit. The causal quantum theory is obtained from a generalized coherent state representation. The behavior for the one particle case and the manyparticle case are illustrated for the harmonic oscillator. We also answer to the arguments against the possibility of constructing causal theories in phase space.  相似文献   
75.
Formation enthalpy of self-association of indoles in non-polar solvents is obtained from the behaviour of their fluorescence spectra areas with temperature. Formation enthalpy of skatole self-association thus obtained is in agreement with that found by another method. This supports the hypothesis that the spectral anomalies observed are due to self-association. The method can be extended to other molecules and it is independent of the spectral structure.  相似文献   
76.
Photocatalytic coatings for environmental applications   总被引:3,自引:0,他引:3  
A series of nano- and micronparticle-grade anatase and rutile titanium dioxide pigments have been prepared with various densities of surface treatments, particle size and surface area. Their photocatalytic activites have been determined in a series of paint films by FTIR, chalking, color, gloss change and weight loss after artifical weathering. The pigments have also been examined by rapid assessment methodologies using photodielectric microwave spectroscopy, 2-propanol oxidation and hydroxyl analysis. The microwave response under light and dark cycles provides an extended timescale probe of charge-carrier dynamics in the pigments. Pigment particle size, surface area and properties clearly play an important role in dispersion and any polymer-pigment interactions. Photooxidation studies on several types of paint films show a clear demarcation between nanoparticle- and pigmentary-grade titanium dioxide, with the former being more active because of their greater degree of catalytic surface activity. The photosensitivity of titanium dioxide is considered to arise from localized sites on the crystal surface (i.e. acidic OH), and occupation of these sites by surface treatments inhibits photoreduction of the pigment by ultraviolet radiation; hence, the destructive oxidation of the binder is inhibited. Coatings containing 2-5% by weight alumina or alumina and silica are satisfactory for general-purpose paints. If greater resistance to weathering is desired, the pigments are coated more heavily to about 7-10% weight. The coating can consist of a combination of several materials, e.g. alumina, silica, zirconia, aluminum phosphates of other metals. For example, the presence of hydrous alumina particles lowers van der Waals forces between pigments particles by several orders of magnitude, decreasing particle-particle attractions. Hydrous aluminum oxide phases appear to improve dispersibility more effectively than most of the other hydroxides and oxides. Coated nanoparticles are shown to exhibit effective light stabilization in various water- and oil-based paint media in comparison with conventional organic stabilizers. Hindered piperidine stabilizers are shown to provide no additional benefits in this regard, often exhibiting strong antagonism. The use of photocatalytic titania nanoparticles in the development of self-cleaning paints and microbiological surfaces is also demonstrated in this study. In the former case, surface erosion is shown to be controlled by varying the ratio of admixture of durable pigmentary-grade rutile (heavily coated) and a catalytic-grade anatase nanoparticle. For environmental applications in the development of coatings for destroying atmospheric pollutants such as nitrogen oxide gases (NO(X)), stable substrates are developed with photocatalytic nanoparticle-grade anatase. In this study, porosity of the coatings through calcium carbonate doping is shown to be crucial in the control of the effective destruction of atmospheric NO(X) gases. For the development of microbiological substrates for the destruction of harmful bacteria, effective nanoparticle anatase titania is shown to be important, with hydrated high surface area particles giving the greatest activity.  相似文献   
77.
This paper reports that the directional temperature is used to present a scheme for deducing the velocity of the reference frame where the black-body which produces the 2.7 K radiation background is at rest.The new renormalized relativistic thermodynamics lays the foundations of the method.  相似文献   
78.
We prove that for a uniformly convex Lagrangian system L on a compact manifold M, almost all energy levels contain a periodic orbit. We also prove that below Mañé's critical value of the lift of the Lagrangian to the universal cover, c u (L), almost all energy levels have conjugate points. We in addition prove that if an energy level is of contact type, projects onto M and $M\ne{\mathbb T}^2We prove that for a uniformly convex Lagrangian system L on a compact manifold M, almost all energy levels contain a periodic orbit. We also prove that below Ma?é's critical value of the lift of the Lagrangian to the universal cover, c u (L), almost all energy levels have conjugate points.We in addition prove that if an energy level is of contact type, projects onto M and , then the free time action functional of L+k satisfies the Palais-Smale condition.Partially supported by Conacyt, Mexico, grant 36496-E.  相似文献   
79.
Highly photoconductive properties are reported for organic-inorganic hybrid sol-gel thin film materials composed of a classical poly(vinylcarbazole)/2,4,7-trinitro-9-fluorenone (PVK/TNF) polymeric mixture, entrapped in a SiO(2) matrix, whose pores have been chemically modified by organic functional groups. The highest photosensitivity obtained, 3.4 x 10(-10) cm Omega(-1) W(-1) at E 22 V microm(-)1, at the optimum molar ratio between the active components, TNF, PVK, and SiO(2), is in the range of the highest values ever reported for any PVK/TNF-based classical photoconductive material. It is demonstrated that the PVK/TNF-based sol-gel films follow Onsager's classical charge-generation model. The analysis of the photocurrent efficiency (Phi) of PVK/TNF-based sol-gel films by such a model provides the primary quantum yield of thermalized pair formation and the initial thermalized pair distance, phi(0) = 0.12 and r(0) = 66.1 Angstrom, respectively, for the optimized sample. As a result of Onsager's analysis, a notorious improvement of the photocurrent generation process was achieved for low TNF concentrations.  相似文献   
80.
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