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排序方式: 共有119条查询结果,搜索用时 0 毫秒
21.
P. Rajec P. Gerhart F. Macášek I. S. Shaban P. Bartoš 《Journal of Radioanalytical and Nuclear Chemistry》1999,241(1):37-43
The high-performance size-exclusion chromatography (HPSEC) and radiochromatography (HPSERC) was used for the identification
of radiocesium and radiostrontium interaction with humic acid. It was found that the behavior of humic acid on size-exclusion
chromatography is sensitive to the salt concentration and pH of the mobile phase. At lower ionic strength and in acidic region
of pH, the Aldrich humic acid exhibited three main fraction within the ranges >760 kDa, 25–100 kDa and <5 kDa. Radiocesium
was found in the low-molecular fractions (<1 kDa) of humic acids but radiostrontium interacts preferably with the fractions
of humic acid of molecular weight within the range 2–5 kDa. 相似文献
22.
R. Mahnken A. Shaban H. Potente L. Wilke 《International Journal of Solids and Structures》2008,45(17):4615-4628
Glassy polymers such as polycarbonate exhibit different behaviours in different loading scenarios, such as tension and compression. To this end a flow rule is postulated within a thermodynamic consistent framework in a mixed variant formulation and decomposed into a sum of weighted stress mode related quantities. The different stress modes are chosen such that they are accessible to individual examination in the laboratory, where tension and compression are typical examples. The characterisation of the stress modes is obtained in the octahedral plane of the deviatoric stress space in terms of the Lode angle, such that stress mode dependent scalar weighting functions can be constructed. Furthermore the numerical implementation of the constitutive equations into a finite element program is briefly described. In a numerical example, the model is used to simulate the laser transmission welding process. 相似文献
23.
Flotation-separation of aluminum from some water samples using powdered marble waste and oleic acid.
Shaban el-Sayed Ghazy Salem el-Sayed Samra Abd el-Fattah Mohammed Mahdy Sherin Mohammed el-Morsy 《Analytical sciences》2003,19(10):1401-1406
Bench-scale experiments were conducted in the laboratory, aiming to remove aluminum from water. They were based on the use of powdered marble wastes (PMW), which are inexpensive and produced in large quantity, and thus potentially cause environmental problems, as an effective inorganic sorbent and oleic acid (HOL) as surfactant. The main parameters (solution pHs, sorbent, surfactant and aluminum concentrations, shaking time, ionic strength and the presence of foreign ions) that influence the sorptive-flotation process were examined. Good results were obtained under the optimum conditions, for which nearly 100% of aluminum at pH 7 and at room temperature (approximately 25 degrees C) was removed. The procedure was successfully applied to the recovery of aluminum spiked to some natural water samples. Moreover, a sorption and flotation mechanism is suggested. 相似文献
24.
Polycarbonate is an amorphous polymer which exhibits nonlinear deformation before failure. It shows a pronounced strength-differential effect between compression and tension. Strain rate influences the mechanical response of the polycarbonate. In particular, the yield stress is increased with increasing strain rate. The concept of stress mode dependent weighting function is used in the proposed model to simulate the asymmetric effects for different loading speeds. In this concept, an additive decomposition of the flow rule is assumed into a sum of weighted stress mode related quantities. The characterization of the stress modes is obtained in the octahedral plane of the deviatoric stress space in terms of the mode angle, such that stress mode dependent scalar weighting functions can be constructed. The resulting evolution equations are updated using a backward Euler scheme and the algorithmic tangent operator is derived for the finite element equilibrium iteration. The numerical implementation of the resulting set of constitutive equations is used in a finite element program for parameter identification. The proposed model is verified by showing a good agreement with the experimental data. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
25.
Mohammed A. E. Shaban Ali Morgaan Hyungphil Chun Ivan Bernal 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(10):e472-e473
Oxidative cyclization of 5‐ethyl‐3‐(4‐methoxybenzylidene)hydrazino‐1,2,4‐triazino[5,6‐b]indole gave the linearly annelated title compound, C19H16N6O. The skeleton is approximately planar, except for the ethyl group. 相似文献
26.
H. A. Shaban A. A. Shaltout M. Abdou E. A. Al Ashker M. Elgohary 《Journal of Applied Spectroscopy》2011,77(6):771-777
Cu, Zn, and Se were successfully determined in a few microliters (<100 μl) of biological samples using discrete injection
atomic absorption spectrometry. Different factors were investigated in order to obtain a biological sample volume which is
valid for analysis. Among them are the effect of microsampling volume variations (starting from 40 to 200 μl), nebulization
efficiency, detection limits, precision, and finally the calibration and sensitivity of the proposed method. It was found
that 60 μl of the biological sample was adequate for the quantitative analysis with reasonable precision. The advantages of
the proposed method are not only rapidity, simplicity, sensitivity, and good precision, but also, contrary to conventional
flame atomic absorption spectrometry, the capability of analyzing microvolumes of samples. 相似文献
27.
28.
Shaban E. A. Saad Donald J. L. Jones Leonie M. Norris Emma Horner‐Glister Ketan R. Patel Robert G. Britton William P. Steward Andreas J. Gescher Karen Brown Stewart Sale 《Biomedical chromatography : BMC》2012,26(12):1559-1566
3′,4′,5′‐Trimethoxyflavonol (TMFol) is a synthetic flavonol with preclinical cancer chemopreventive properties. The hypothesis was tested that, in mice, p.o. administration of TMFol results in measureable levels of the parent in target tissues. A single oral dose (240 mg/kg) was administered to mice (n = 4 per time point) with time points ranging from 5 to 1440 min. TMFol and its metabolites were identified and quantitated in all tissues by high‐performance liquid chromatography (HPLC). Plasma levels of TMFol were at the limit of quantification or below, although metabolites were identified. Peak levels of TMFol in the gastrointestinal tract and the prostate averaged 1671 ± 265 µg/g (5.3 µmol/g) and 6.0 ± 1.6 µg/g (18.4 nmol/g), and occurred 20 and 360 min post‐dose, respectively. The area under the tissue concentration–time curve (AUC) for TMFol was greater than those of the metabolites, indicating that TMFol is relatively metabolically stable. Micromolar TMFol levels are easily achieved in the prostate and gastrointestinal tract, suggesting that TMFol might exert chemopreventive efficacy at these tissue sites. Further investigations are warranted to elucidate the potential chemopreventive potency of TMFol. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
29.
A. Taleshian M. Shaban Nataj B. Pourhassan 《International Journal of Theoretical Physics》2014,53(11):3943-3947
In this paper, we consider effective Hamiltonian of 2D dilatonic black hole adding Axion field and calculate closed 2-form by using geometric prequantization method. It yields to the Schrödinger equation which may be solved to obtain wave function. We obtained a condition on the cosmological constant to obtain appropriate Hamilton equation of motions. 相似文献
30.
Han Xu Muhammad Shaban Sui Wang Anas Alkayal Dingxin Liu Michael G. Kong Felix Plasser Benjamin R. Buckley Felipe Iza 《Chemical science》2021,12(40):13373
Due to increasing concentrations in the atmosphere, carbon dioxide has, in recent times, been targeted for utilisation (Carbon Capture Utilisation and Storage, CCUS). In particular, the production of CO from CO2 has been an area of intense interest, particularly since the CO can be utilized in Fischer–Tropsch synthesis. Herein we report that CO2 can also be used as a source of atomic oxygen that is efficiently harvested and used as a waste-free terminal oxidant for the oxidation of alkenes to epoxides. Simultaneously, the process yields CO. Utilization of the atomic oxygen does not only generate a valuable product, but also prevents the recombination of O and CO, thus increasing the yield of CO for possible application in the synthesis of higher-order hydrocarbons.Selective formation of atomic oxygen to form epoxides in a waste free process is reported. Simultaneously generating carbon monoxide from carbon dioxide for further use. 相似文献