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排序方式: 共有1333条查询结果,搜索用时 390 毫秒
131.
Carbon ionic liquid electrode (CILE) has been modified with a new synthesized mediator i.e. N,N′‐dimethyl‐4,4′‐azopyridinium hexafluorophosphate (MAZPHP) via sol process and the electron transfer mediating characteristics of this mediator has been evaluated. 4,4′‐Azopyridine (AZP) did not show any electrocatalytic activity toward the selected probe, NADH, while its synthesized methylated derivative, MAZPHP, is a very efficient mediator for the electrocatalytic NADH oxidation. Cyclic voltammetry of MAZPHP/Sol/CILE exhibited a pair of reversible peaks corresponding to incorporated mediator with a formal potential of about 221 mV vs. Ag/AgCl. MAZPHP/Sol/CILE is free from fouling effects by the oxidation products of NADH which generally give hindrance to amperometric detection of NADH. Using amperometric technique, NADH can be determined in the range of 1.0×10?5 M to 1.4×10?3 M with a detection limit of 2.0×10?6 M. 相似文献
132.
133.
The effect of heat treatment on the Fe2+/Fe3+ ratio in some alkali phosphate glasses containing antimony and iron oxides has been investigated. Differential thermal analysis, Mossbauer spectroscopy, magnetic susceptibility and density measurements as well as the molar volume calculations were used in this study. The obtained data indicate that all glasses show approximately unchangeable stability. It is found, from the area under the Mossbauer absorption spectra that ferrous transformed gradually to ferric ions and the transformation rate constant was found to be 48 min−1. The elapsed time was found to be 160 min. This transformation represents a first-order solid state reaction. The molar magnetic susceptibility measurements confirm the above results. 相似文献
134.
Real life reaction–diffusion problems are characterized by their inherent or externally induced uncertainties in the design parameters. This paper presents a finite element solution of reaction–diffusion equations of Wick type. Using the Wick-product properties and the Wiener–Itô chaos expansion, the stochastic variational problem is reformulated to a set of deterministic variational problems. To obtain the chaos coefficients in the corresponding deterministic reaction–diffusion, we implement the usual Galerkin finite element method using standard techniques. Once this representation is computed, the statistics of the numerical solution can be easily evaluated. Computational results are shown for one- and two-dimensional test examples. 相似文献
135.
Maghsoodlou MT Habibi-Khorassani SM Heydari R Hassankhani A Marandi G Nassiri M Mosaddeg E 《Molecular diversity》2007,11(2):87-91
A new one-pot, simple and effective procedure is presented for the preparation of O-containing phosphorus ylides by the Michael
addition reaction of N-methylpyrrole-2-carbaldehydoxime, pyridin-2-carbaldehydoxime or acetophenonoxime with acetylenic esters. 相似文献
136.
S. Elghobashi T. Abou-Arab M. Rizk A. Mostafa 《International Journal of Multiphase Flow》1984,10(6):697-710
A two-equation turbulence model for two-phase flows has recently been proposed by Elghobashi & Abou-Arab (1983). They derived the exact equations of the kinetic energy of turbulence and the rate of dissipation of that energy, and modeled the turbulent correlations, resulting from time-averaging, up to third order. In order to validate the proposed model, a turbulent axisymmetric gaseous jet laden with spherical uniform-size solid particles is studied here. The predictions of the mean flow properties of the two-phases and the turbulence kinetic energy and shear stress of the carrier phase show good agreement with the experimental data. 相似文献
137.
Mostafa A. Abdelkader 《Applied Scientific Research》1968,18(1):112-115
Summary The family of trajectories (in the phase plane) of van der Pol's equation is a one parameter family of curves; no explicit analytical expression for it is known. The same is true for the orthogonal trajectories of this family. The differential equation of the orthogonal curves is solved here exactly in terms of modified Bessel functions. Two curves of the orthogonal family are found to be especially simple, and a graph is given which would permit plotting the solutions of van der Pol's equation with an accuracy higher than that attainable with the usual methods. 相似文献
138.
139.
Mostafa Hossein Beyki Hassan Alijani Yousef Fazli 《Research on Chemical Intermediates》2017,43(11):6245-6257
An efficient adsorption system was developed for removal of hazardous Direct Blue 71 as a sample azo dye. The γ-Fe2O3@CuO adsorption system was synthesized based on a sol–gel combustion route and characterized by energy-dispersive X-ray (EDX) analysis, X-ray diffraction (XRD) analysis, vibrating-sample magnetometry (VSM), and field-emission scanning electron microscopy (FESEM) techniques. The response surface methodology with Box–Behnken design was used to evaluate the effects of pH, shaking time, and adsorbent dose on dye adsorption. The results showed that solution pH was the parameter with greatest effect on dye adsorption. Adsorption equilibrium was reached quickly, within 8 min. Study of isotherms revealed adsorption capacity of 45.7 mg g?1 according to the Freundlich model. Sorbent regeneration could be performed using methanol–NaOH (0.1 mol L?1) solution. 相似文献
140.
In this work a facile hydrothermal route has been employed to prepare a multiwall carbon nanotube wrapped in a chelating resin. 8-Hydroxyquinoline and p-formaldehyde were used as monomer and linker for polymer synthesis. The prepared composite was employed as an efficient adsorbent for lead adsorption and preconcentration from various matrices. Effective parameters on lead adsorption have been optimized by central composite design. Results showed that equilibrium adsorption was obtained at pH = 4, with a shacking time of 15 min and adsorbent dosage of 15 mg. Isotherm study showed that the sorbent has adsorbent capacity of 250 mg g?1; moreover, the process followed a Langmuir isotherm model. Thermodynamic investigation confirmed that lead adsorption is spontaneous, as well as follows endothermic path. 相似文献