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121.
Using fast confocal microscopy we image the three-dimensional dynamics of particles in a yielded hard-sphere colloidal glass under steady shear. The structural relaxation, observed in regions with uniform shear, is nearly isotropic but is distinctly different from that of quiescent metastable colloidal fluids. The inverse relaxation time tau(alpha)(-1) and diffusion constant D, as functions of the local shear rate gamma*, show marked shear thinning with tau(alpha)(-1) proportional to D proportional to gamma*(0.8) over more than two decades in gamma*. In contrast, the global rheology of the system displays Herschel-Bulkley behavior. We discuss the possible role of large scale shear localization and other mechanisms in generating this difference. 相似文献
122.
123.
Tractable analytic expressions are developed for a variety of basic statistical quantities involving a Gaussian-beam wave propagating through a random medium confined to a portion of the propagation path between input and output planes, the limiting case of which defines a thin random phase screen. For a plane wave incident on a phase screen located midway between input and output planes, it is well known that the statistics in the receiver plane are in close agreement with those associated with a plane wave propagating through an extended random medium between input and output planes. For a similar comparison between a phase screen and extended turbulence in the case of a Gaussian-beam wave at the input plane, the present analysis reveals that the phase screen must be positioned between input and output planes differently from the plane-wave case, the position being dependent upon the Fresnel ratio of the Gaussian beam. The analytic results developed in this paper for the thin phase screen model are based on the Kolmogorov power-law spectrum for refractive-index fluctuations and the Rytov approximation. Extension of these results to multiple phase screens is also discussed. 相似文献
124.
A model to price default free bonds, similar to ones developed by Cox, Ingersoll and Ross, Langetieg, and Richard, is empirically examined. Calculation of model prices involves three disjoint tasks: (1) estimation of the values of the real interest rate and the inflation rate (which we will refer to as state variables or sources of uncertainty) as well as the parameters of the state stochastic differential equations, (2) estimation of the market prices of risk associated with the two state variables, and (3) the solution of the valuation partial differential equation. Task 1 is accomplished by using a Kalman Filter algorithm, task 2 uses a Fama/MacBeth approach, and task 3 utilizes an Alternating Direction Implicit finite difference technique. Model prices are compared to actual prices. The model performs better during a period of relatively stable economic conditions compared to a period associated with more volatile conditions. Pricing errors are smaller at short maturities, and increase as time to maturity increases. 相似文献
125.
We have measured the angular distribution of photoemitted electrons from c(2 × 2)O, c(2 × 2)S, and CO adsorbed on a Ni(100) substrate for various independently set angles of incidence of unpolarized light at 21.2 eV. We have found that these systems have very different dependence on angle of incidence, depending upon which components of the vector potential of the light () are responsible for emission. Because the incident and reflected light combine to form a standing wave at a metal surface, the phase relationships between components of parallel and perpendicular to the surface play an important role in determining the effective orientation and magnitude of A at the emission site. We compare our measurements with macroscopic fields, calculated via the Fresnel relations, which lead to a general understanding of the effects. We further propose a method for expediting photoemission calculations by projecting out components of which preserve their phase relationships. 相似文献
126.
The 5-dimensional quasispin formalism is used to evaluate the (n, T)-dependent factors of the matrix elements of abnormal parity operators of relevance for yrast-band spectroscopy. The formalism allows the leading pseudo-SU(3) representation of the normal (N) parity part of a shell-model configuration to be coupled to low-seniority states of the abnormal (A) parity high-j intruder part of the configuration. To illustrate the importance of the nA, TA dependence of the (A) to (N) space-coupling matrix elements this model is applied to the negative-parity yrast spectra of 127La and 127Ba, using hamiltonian parameters which give a reasonable fit for 126Ba. The 127La spectrum is reproduced with a seniority-one truncation of the h configuration; the 127Ba spectrum indicates a need for higher-seniority admixtures. 相似文献
127.
Type III silica samples were implanted with O using a multi-energy process that produced a layer of constant concentration to within ± 5% beginning ~ 80 nm from the surface and extending to ~ 640 nm below the surfaces of samples. The concentrations in the layer ranged from 0.035 atomic percent to ~ 2.1 atomic percent. The optical absorption was measured from 2 to 6.5 eV. The absorption due to the implanted ions was analyzed using the difference spectra of the various samples. These difference spectra showed that optical bands at ~ 4.7 eV, 5.35 eV, and ~ 6.2 eV were a primary result of O implantation. Based on these data, we attribute these bands to O-related centers. Comparison of the difference spectra of the O samples with those of Si samples implanted to approximately the same concentrations showed that bands at the three energies in the spectra of the O samples were not observed in the spectra of the Si samples. Based on the spin concentrations of peroxy radicals, spin concentrations of E′γ, and optical absorption coefficients at 4.8-5.0 eV and at 5.83 eV, the oscillator strengths of the peroxy band (~ 4.8 eV) was estimated, from the oscillator strength of the absorption band at 5.83 eV to be < 0.014. 相似文献
128.
A wide range of products are produced in the chemical producing industry such as textile dyes, chemicals, printing dyes and chemicals, paper chemicals, electrostatic powder dyes, and optical brighteners. The aim of this study is to investigate the treatability of chemical oxygen demand (COD), aromaticity, and color in the wastewater of this sector, where highly complex chemicals are used. Most of the studies in the literature are related to the treatment of synthetically prepared dyed wastewater. This study is important as it is carried out with real wastewater and gives results of many treatment methods. In the study, COD, UV-vis absorbance, and color values were attempted to be removed from the wastewater of a chemical producing industry that was pretreated by coagulation-flocculation. The COD value of the pretreated wastewater discharged to the central treatment system was restricted as 1000 mg/L. Pretreated wastewater characterization is as follows: COD: 2117 mg/L, UV-vis absorbance values at; 254 nm: 9.91, 280 nm: 8.65, 341 nm: 12.77, 436 nm: 5.01, 525 nm: 2.24, and 620 nm: 1.59. In the study, adsorption, ozonation, and advanced oxidation processes (Fenton and persulfate oxidation) were used to remove COD and UV-vis absorbance values (aromaticity, organics, and color). The method by which the best removal efficiency was obtained for all parameters was the adsorption process using powdered activated carbon (PAC). The equilibrium PAC dose was found as 6 g/L. At this adsorbent dose, the removal efficiencies of UV-vis absorbance values were all around 99% and the efficiency of COD removal was 77%. The Langmuir isotherm constants were found to be qmax= 30.4 mg/g and KL = 487.9 (L/mg). The COD concentration at this adsorbent dose was 486 mg/L and wastewater was suitable for discharge to the central wastewater treatment plant in that region. 相似文献
129.
The reflectance spectra of ion implanted SiO2 glasses has been measured from 5000 cm−1 to 400 cm−1. The silica was implanted with Ti, Cr, Mn, Fe, Cu and Bi to nominal doses ranging from 1×1015 ions/cm2 to 1.2×1017 ions/cm2 at an energy of 160 keV and currents of approximately 2.6 μA/cm2. Changes in the intensity of the 1232 cm−1 and 1015 cm−1 vibrational modes are attributed to changes in the intermediate range order (IRO) and to changes in the concentration of non-bridging oxygen (NBO) defects in the implanted layer. These changes are ion and dose dependent. The differing effects on IRO and NBO are attributed to the chemical interaction of the implanted ions with the substrate. 相似文献
130.