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211.
A new, one-pot, efficient, three-component condensation of benzaldehyde derivatives, enolizable ketones, acetyl chloride, and acetonitrile or benzonitrile in the presence of silica-supported perchloric acid as an effective catalyst for the synthesis of β-amido carbonyl compounds is described. The present methodology offers several advantages, such as good yields, short reaction times, and simple workup procedure. 相似文献
212.
Asghar Bodaghi 《先进技术聚合物》2020,31(3):355-367
This review is about the reactive plasticizer. Plasticizers are small molecules with low molecular weight. These compounds typically have an esteric structure. The plasticizers reduce the glass transition temperature, and the viscosity of the polymer also enhances the flexibility and processability of polymer materials. The main problem of these additives is that, over time, they migrate from the polymeric matrix and exude to the surface of polymeric matrix. As a result, the physical and mechanical properties of the polymer are affected. Various strategies, such as increasing molecular weight of plasticizer, selection of oligomeric structure for plasticizer, and adding nanoparticles of minerals, have been investigated to reduce and eliminate migration. An approach that has recently been of great interest to researchers is the use of reactive plasticizers. In this approach, plasticizers covalently bond to the polymeric chains and prevent migration. 相似文献
213.
Morad Moataz Habeebullah Turki M. Althagafi Ismail Asghar Basim H. Bayazeed Abrar A. Bawazeer Tahani M. Al-Solimy Amerah M. El-Metwaly Nashwa 《Research on Chemical Intermediates》2020,46(10):4543-4562
Research on Chemical Intermediates - Novel copper complexes were prepared from acetanilide derivatives and deliberately characterized. The molar ratio obtained was 1:1 through neutral bi-dentate... 相似文献
214.
The solvent effect on a nucleophilic substitution reaction of 2‐ and 4‐chloro‐3,5‐dinitrobenzotrifluoride with substituted anilines was studied in methanol, acetonitrile, and toluene at 25°C. This reaction is of second order, except 2‐chloro‐3,5‐dinitrobenzotrifluoride in toluene shows third order. The kA values are found to be dependent on the substituent in aniline and give good Hammett correlations. The obtained ρ values are ?4.07 and ?4.62, for the reaction of anilines with 2‐chloro‐3,5‐dinitrobenzotrifluoride in methanol and acetonitrile, respectively. The ρ values for the reaction of the anilines with 4‐chloro‐3,5‐dinitrobenzotrifluoride are ?3.38, ?4.11, and ?4.34 in methanol, acetonitrile, and toluene, respectively. The reaction of the former compound with anilines in toluene shows a second order in aniline. The dependence of the reaction on the external base such as DABCO suggests a proton transfer controlling step. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 777–786, 2009 相似文献
215.
S. Issmer M. Fruneau J.A. Pinston M. Asghar D. Barnéoud J. Genevey Th. Kerscher K.E.G. Löbner 《The European Physical Journal A - Hadrons and Nuclei》1998,2(2):173-177
Direct mass measurements of A=80 isobars were performed using the second cyclotron of SARA (Système Accélérateur Rh?ne-Alpes)
of the ISN (Institut des Sciences Nucléaires) in Grenoble as a time-of-flight mass spectrometer. Using the 300 MeV 58Ni +27Al reaction, the isobars 80Rb, 80Sr, 80Y, and 80Zr (only one event!) were measured. For 80Y we found a mass value of 79.934320(180) u, corresponding to a decay energy Q (80Y →80Sr) of (9120 ± 170) keV. Comparing this value to the former experiments of Lister et al. and Della Negra et al. results in
a difference of about 2.2 MeV. However, it does agree with the recommended value of Audi and Wapstra, which is derived from
systematic trends. For 80Zr the single event was identified with a probability of 0.999975 and a mass value of 79.940400(1600) u could be deduced from
our experiment.
Received: 22 Juli 1997 / Revised version: 3 February 1998 相似文献
216.
S. Asghar Tasawar Hayat M. Ayub 《International Journal of Infrared and Millimeter Waves》1997,18(9):1821-1836
The diffraction of anE-polarized and anH-polarized wave by an imperfectly conducting slit (on which impedance boundary conditions are imposed) in an infinite metallic
plane is investigated. The two independent problems are solved by using integral transforms, the Wiener-Hopf technique and
asymptotic approximations. It is found that the diffracted field consists of the sum of fields produced by the two edges of
the planes formed by the slit and a field due to the interaction of the two edges. 相似文献
217.
It has been argued that Chebyshev polynomials are ideal to use as approximating functions to obtain solutions of integral
equations and convolution integrals on account of their fast convergence. Using the standard deviation as a measure of the
accuracy of the approximation and the CPU time as a measure of the speed, we find that for reasonable accuracy Legendre polynomials
are more efficient. 相似文献
218.
This study aims to investigate electrohydrodynamics of two superimposed fluids that are confined between a pair of two-dimensional flat plates and are exposed to a sinusoidal electric field in zero gravity. The goal is to identify the parameters that affect the flow structure and interface deformation using a simple closed form solution. The governing electrohydrodynamic equations are solved analytically for Newtonian and immiscible fluids in the framework of leaky-dielectric theory and in the limit of small electric field and fluid inertia. A detailed analysis of the electric and flow fields is presented and it is shown that the electric field induces sinusoidal electrical stresses at the interface, which lead to periodic convection cells. The parameters affecting the sense of flow circulation and strength are investigated and it is shown that the former depends on the relative magnitude of the electric permittivity and conductivity ratios while the latter is controlled by the relative thicknesses of the fluid layers and the ratio of the electric conductivities and viscosities of the fluids. The maximum flow strength is achieved at a relative thickness that is set by the competition between the electric and hydrodynamic effects. For small deformation, the distortion of the interface is examined using a normal stress balance at the interface, and it is shown that the degree of interface deformation scales with the square of the amplitude of the electric potential nonuniformity, while its wavenumber is twice that of the imposed potential nonuniformity. Furthermore, a zero-deformation curve is found, which delineates the region in the permittivity-conductivity space according to the sense of interface deformation. The results show that for certain ranges of fluid layer thicknesses and permittivity ratios, the interface will remain flat, despite the action of the nonuiform field. 相似文献
219.
We investigate the effects of accretion of phantom energy onto primordial black holes. Since Hawking radiation and phantom
energy accretion contribute to a decrease of the mass of the black hole, the primordial black hole that would be expected to decay now due to the Hawking process would
decay earlier due to the inclusion of the phantom energy. Equivalently, to have the primordial black hole decay now it would have to be
more massive initially. We find that the effect of the phantom energy is substantial and the black holes decaying now would
be much more massive—over ten orders of magnitude! This effect will be relevant for determining the time of production and hence
the number of evaporating black holes expected in a universe accelerating due to phantom energy. 相似文献
220.
The boundary layer flow of a second grade fluid over a permeable stretching surface with arbitrary velocity and appropriate wall transpiration is investigated. The fluid is electrically conducting in the presence of a constant applied magnetic field. An exact solution to the nonlinear flow problem is presented. 相似文献