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181.
We report the tunable electromagnetic (EM) wave absorption properties of Fe-deficient SrFe9.6-xCo1.2Ti1.2O19 hexaferrite–epoxy composites. SrFe9.6-xCo1.2Ti1.2O19 hexaferrite powders were prepared via solid-state reaction routes. It was observed that Sr–Ti-rich second phases were formed as x increased, i.e., the Fe content decreased. The ferromagnetic resonance (FMR) frequency of the composites gradually decreased from 8.8 GHz to 4.8 GHz with increasing x, and accordingly, the EM absorption frequency range also gradually changed. The gradual FMR frequency shift was attributed to the compositional shift in the mother phase. It is predicted that the Fe deficiency caused a decrease in the magnetocrystalline anisotropy, and in turn, it shifted the FMR frequency and modified the corresponding EM absorbing properties. All the samples demonstrated a high EM absorption performance with the lowest reflection loss of < −40 dB at the optimized frequency and thickness. 相似文献
182.
Albert Giraud Richard Giot Françoise Homand Amine Koriche 《Transport in Porous Media》2007,69(2):259-280
The present paper deals with the determination of permeability in partially saturated conditions for weakly permeable porous
continua such as argillites or deep clayey formations. The permeability can be deduced from measurements of transient weight
loss of a sample submitted to a laboratory drying test: a decrease of relative humidity is imposed by saline solution in an
hermetic chamber. Assumptions of constant gas pressure equal to atmospheric pressure and of negligible Fickean diffusive transport
of vapour are adopted. The only transport phenomenon taken into account inside the sample is the Darcean advective transport
of the water liquid. The forward problem is solved by following two modelling approaches: a linear one and a nonlinear one.
The parameter identification procedure is based upon the solution of corresponding inverse problems. In the two cases, the
Levenberg–Marquardt algorithm has been used for the minimization problem. In the linear approach, the solution of the forward
problem is explicit. In the non linear approach, finite volume method for the spatial discretization combined with a Newton–Raphson
algorithm has been used to solve the non linear forward problem. The identification method enables variations of permeability
and capillary capacity to be estimated. Comparisons between linear and non linear approaches show that the first one is useful
to give mean values and order of magnitude of permeability and capacity. A more complete information is deduced from the non
linear approach as variations of equivalent capacity and permeability during a test are significant in most cases. The analysis
of the obtained results shows that the basic modelling assumption of constant gas pressure inside the sample would not be
relevant for lower range of relative humidities and liquid permeability than those investigated. 相似文献
183.
岩体裂隙三轴应力渗透规律的试验研究 总被引:1,自引:0,他引:1
利用三轴应力渗透仪分别对煤矿底板的硬岩和软岩进行三轴应力渗透试验 ,观测渗水量、围压、轴压及水压的变化。 相似文献
184.
185.
《Arabian Journal of Chemistry》2020,13(12):8979-8994
Mixed matrix membranes (MMMs) fabricated with porous metal organic frame works have enhanced the separation performance of polymer membranes. In this context microporous 3D Tb(BTC)(H2O).(DMF)1.1 MOF was incorporated into pristine Matrimid® with loadings of 10, 20 and 30 weight percentages. SEM micrographs indicated proper distribution of filler in the Matrimid and no interfacial voids were observed. Gas permeation studies evidenced the CO2 permeability to be 13.2 (82.32%) and 18.34 (153.31%) and 25.86 Barrer for 10, 20 and 30 wt% MMMs respectively. The 257.18% increase in CO2 permeability of 30 wt% MMM than methane was attributed to polar nature of CO2, its smaller kinetic diameter, condensability, and larger solubility within the Matrimid matrix than non – polar and larger CH4 molecules.Addition of filler influenced the pure gas selectivity of all MMMs positively. So, 30 wt% MMM exhibited the highest 58.04% increase in selectivity that was attributed to the molecular sieving property of the filler and the size exclusion phenomena as followed by CH4 and CO2. The high values of mixed and pure gas selectivity were obtained upon increasing filler concentration. The commercial applicability of these MMMs was tested by checking their selectivity under increased feed concentrations of CO2 and checking permeability and selectivities at high temperatures. The study depicted that, competitive sorption of gases, prevalence of size exclusion phenomena and polymer chains relaxation at higher temperature were responsible for low gas selectivity. MMM with 30 wt% of MOF lied close to Robson’s Upper bound 2008 that indicated its good separation potential. 相似文献
186.
The effect of hot air exposure at 150 °C for up to 12 weeks (ca. 2000 h) on the properties of hydrogenated nitrile butadiene rubber (HNBR) compounds with varying degrees of carbon black content was investigated and reported in this paper. The composition of the HNBR was varied with 0, 10, 30 or 50 PHR carbon black. The tensile properties, hardness, density, solvent saturation swelling and carbon dioxide permeability of these specimens was investigated before and after exposure in a hot air oven. Correlations between these results are reported for the compounds considered in this work. These correlations illustrate how the changes in performance which would require test samples of specific geometries (such as tensile modulus or gas permeation) might in some cases be predicted by tests which do not require exact geometries (such as density or surface hardness), for the materials investigated in this paper. 相似文献
187.
壳聚糖-纤维素硫酸钠聚电解质复合物膜对药物表观渗透系数的测试 总被引:1,自引:0,他引:1
药物渗透系数是考察复合物膜的药物释放性能的重要参数. 本文以溶解性不同的两种药物扑热息痛和5-氨基水杨酸(5-ASA)为模型药物研究了其在壳聚糖-纤维素硫酸钠聚电解质复合物膜中的渗透性能. 结果表明:壳聚糖-纤维素硫酸钠聚电解质复合物膜的渗透性能与其溶胀性能密切相关;复合物膜中壳聚糖和纤维素硫酸钠的配比、相对分子量和pH值对膜的渗透性能和溶胀性能影响显著,以扑热息痛作为模型药物研究了壳聚糖-纤维素硫酸钠聚电解质复合物膜在模拟胃肠液中对药物的渗透性能. 通过调整该复合物膜的配方,可以使该膜分别实现胃、小肠和结肠定位释药的目的. 相似文献
188.
Shear Rate and Permeability in Water Flooding 总被引:1,自引:0,他引:1
Water breakthrough during oil recovery can be inhibited by the use of novel shear-induced structure additives. These affect
the shear rate experienced by fluid inside the rock matrix. We relate this to the permeability for the purpose of applying
these novel non-Newtonian materials which thicken viscosity only in the shear range associated with the permeability of the
reservoir while maintaining base fluid properties outside this range. 相似文献
189.
190.
Permeability is one of the reservoir fundamental properties, which relate to the amount of fluid contained in a reservoir
and its ability to flow. These properties have a significant impact on petroleum fields operations and reservoir management.
The most reliable data of local permeability are taken from laboratory analysis of cores. Extensive coring is very expensive
and this expense becomes reasonable in very limited cases. Thus, the proper determination of the permeability is of paramount
importance because it affects the economy of the whole venture of development and operation of a field. In this study, we
introduce a new hybrid network based on Coactive Neuro-Fuzzy Inference System (CANFIS). CANFIS is a dependable and robust
network that developed to identify a non-linear relationship and mapping between petrophysical data and core samples. Then
to improve the system performance, genetic algorithm (GA) was integrated in order to search of optimal network parameters
and decrease of noisy data in training samples. An Iranian offshore gas field is located in the Persian Gulf, has been selected
as the study area in this paper. Well log data are available on substantial number of wells. Core samples are also available
from a few wells. It was shown that the new proposed strategy is an effective method in predicting permeability from well
logs. 相似文献