全文获取类型
收费全文 | 164篇 |
免费 | 3篇 |
国内免费 | 2篇 |
专业分类
化学 | 109篇 |
晶体学 | 4篇 |
力学 | 1篇 |
数学 | 16篇 |
物理学 | 39篇 |
出版年
2023年 | 1篇 |
2022年 | 5篇 |
2021年 | 4篇 |
2020年 | 2篇 |
2019年 | 2篇 |
2018年 | 5篇 |
2017年 | 1篇 |
2016年 | 3篇 |
2015年 | 2篇 |
2014年 | 5篇 |
2013年 | 6篇 |
2012年 | 12篇 |
2011年 | 12篇 |
2010年 | 12篇 |
2009年 | 5篇 |
2008年 | 6篇 |
2007年 | 10篇 |
2006年 | 11篇 |
2005年 | 11篇 |
2004年 | 4篇 |
2003年 | 3篇 |
2002年 | 3篇 |
2001年 | 1篇 |
2000年 | 10篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 5篇 |
1995年 | 1篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1982年 | 1篇 |
1978年 | 2篇 |
1976年 | 2篇 |
1975年 | 1篇 |
排序方式: 共有169条查询结果,搜索用时 359 毫秒
71.
The oxidative catalytic degradation of the cationic dye methylene blue (MB) with NaOCl in aqueous solutions was studied using
individual and iron modified Ni- and Co-oxide systems as catalysts. The adsorption extent and the contribution of the uncatalyzed
oxidation on the overall degree of MB were determined. The results indicate that methylene blue—a representative of a class
of dyestuffs resistant to biodegradation—could be successfully decolorized and degraded using nickel and cobalt oxide catalysts
at room temperature. The highest catalytic activity manifests in the Co-oxide system which is consistent with the adsorption
data. The oxidative degradation reaction proceeds via first-order kinetics. Temperature has a relatively small effect on the
methylene blue degradation kinetics. The results obtained reveal that the catalysts investigated are suitable for oxidative
destruction of methytlene blue dye in wastewaters.
相似文献
72.
Koleva V Zhecheva E Stoyanova R 《Dalton transactions (Cambridge, England : 2003)》2011,40(28):7385-7394
Dittmarite-type compound KMnPO(4)·H(2)O was used as a new precursor for the synthesis of nanostructured LiMnPO(4) phospho-olivines with a plate-like morphology at low temperature (about 200 °C) and a short reaction time (90-180 min). The dehydration of KMnPO(4)·H(2)O was studied by DTA and TG analysis. Structural and morphological characterization of both KMnPO(4)·H(2)O and LiMnPO(4) was performed by powder XRD, SEM and TEM analyses. The formation of nanostructured LiMnPO(4) was examined by electron paramagnetic resonance spectroscopy and TEM. It was found that the reaction between KMnPO(4)·H(2)O with the LiCl-LiNO(3) mixture includes a fast ionic exchange of K(+) with Li(+) in the framework of the dittmarite structure, followed by H(2)O release and the formation of the olivine-type structure. The morphology and texture of the dittmarite-type precursor results in a plate-like morphology of LiMnPO(4) with a preferred orientation along the [100] direction. The plate-like morphology of LiMnPO(4) is stable after annealing at 500 °C. The plates are composed of nanocrystallites, with various sizes in the range 10-20 nm. The EPR signal of LiMnPO(4) is due to the exchange-coupled Mn(2+) ions. It was demonstrated that the EPR line-width correlates with the Scherrer crystallite size. 相似文献
73.
Stoyanov ES Gunbas G Hafezi N Mascal M Stoyanova IV Tham FS Reed CA 《Journal of the American Chemical Society》2012,134(1):707-714
Oxatriquinanes are tricyclic oxonium ions which are known to possess remarkable solvolytic stability compared to simple alkyl oxonium salts. Their rigid, hemispherical structure presents an oxygen at the apex of three fused five-membered rings. While trivalent oxygen species like these have been well described in the literature, the ability of oxygen to enter into a fourth covalent bonding relationship has been visited in theory and suggested by the outcome of certain reactions conducted in superacidic media, but has never been established by the characterization of a stable, persistent R(3)OH(2+) or R(4)O(2+) ion. In this study, the nucleophilicity of the oxatriquinane oxygen was evaluated first by a series of protonation studies using the Br?nsted superacid H(CHB(11)Cl(11)) both in the solid state and in liquid HCl solution. The interaction of the oxatriquinane oxygen with a bridging carbocation was also examined. A strong case could be made for the occurrence of hydrogen bonding between H(CHB(11)Cl(11)) and oxatriquinane using IR spectroscopy. Under the most forcing protonation conditions, the oxatriquinane ring is cleaved to give a bridged, dicationic, protonated tetrahydrofuran-carbenium ion. 相似文献
74.
AbstractTwo biomaterials based on the abundant Bulgarian medicinal plants Mentha spicata L. (denoted as MS) and Ruta graveolens L. (denoted as RG) were investigated as environmentally friendly biosorbents for Cu(II) removal from aqueous solutions. Grain size distribution, slurry pH, texture parameters, thermal behavior and mineralogical composition of MS and RG were determined. Instrumental methods such as scanning electron microscopy (SEM), X-ray-diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Brunauer–Emmett–Teller (BET) analysis, differential thermal analysis (DTA), and thermogravimetric analysis (TGA) were used for their characterization. It was demonstrated that the surface morphology of both materials is rough and contains pores that could entrap different pollutants, as well as functional groups that can attach metal ions. In order to examine the feasibility of these materials for use as biosorbents for heavy metals, adsorption experiments were performed. The results for the removal of Cu(II) ions from aqueous solution reveal capabilities suggesting that both materials have potential to be used as promising, efficient and low-cost biosorbents. 相似文献
75.
G. A. Akopdzhanov V. B. Anikeev V. A. Bezzubov I. A. Vasilyev Yu. V. Gilitsky S. N. Gurzhiev S. P. Denisov A. A. Durum S. A. Zvyagintsev A. V. Kozelov E. A. Kozlovsky V. M. Korablev V. I. Koreshev V. I. Kurbakov V. V. Lipaev V. A. Onuchin A. M. Rybin Yu. M. Sapunov M. M. Soldatov D. A. Stoyanova K. I. Trushin A. A. Schukin V. I. Yakimchuk 《Physics of Atomic Nuclei》2008,71(12):2074-2086
K ± → e ± νπ 0 decays have been studied using the KMN setup at the Institute for High Energy Physics (Protvino). The experiment has been performed in the 36-GeV/c hadron beams of the IHEP accelerator. The accumulated data allow us to select ~1.08M candidates for K e3 decays. Analyzing the Dalitz plot of these events, we estimate the linear slope of the charge form factor to be λ + = [30.44 ± 0.83(stat.) ± 0.74(syst.)] × 10?3. 相似文献
76.
V. P. Antonovich N. A. Chivireva I. V. Stoyanova V. F. Zinchenko N. P. Efryushina O. N. Lasovskaya N. N. Golik 《Journal of Analytical Chemistry》2003,58(11):1042-1048
It was found that the major constituents (F– and S2–) in fluorides, sulfides, and sulfofluorides of rare-earth elements, and europium(II) in europium fluoride, can be determined titrimetrically. Peculiarities of the decomposition and analysis of initial samples of these compounds and samples after high-temperature treatment in vacuum were considered. The analytical procedures are based on the combination of the decomposition of the test materials using solutions of iodine (determination of S2–), boric acid (determination of F–), and vanadium(V) salts (determination of europium(II) salts) and the final titration of excess reagents that selectively reacted with a chemical form of the analyte. Potentiometry with an ion-selective electrode was also used in the determination of fluoride ions. The total concentration of rare-earth elements was determined by chelatometry. 相似文献
77.
Radostina Palcheva Alla Spojakina Georgi Tyuliev Kveta Jiratova Lachezar Petrov 《Reaction Kinetics and Catalysis Letters》2006,89(2):285-292
Summary Hydrotreating nickel tungsten catalysts have been prepared by impregnation of g-alumina with solutions of H3PW12O40 acid and its Ni salt. It is shown that the initial heteropolyanion, its lacunar analog, nickel substituted heteropolyanion
and other new formed phases are present on the surface. The thiophene conversion is related to the presence of mixed NiWS
phase and to the close cooperation between WS2 and NiSx phases. 相似文献
78.
Georgieva R Moya S Donath E Bäumler H 《Langmuir : the ACS journal of surfaces and colloids》2004,20(5):1895-1900
The permeability of ions and small polar molecules through polyelectrolyte multilayer capsules templated on red blood cells was studied by means of confocal microscopy and electrorotation. Capsules were obtained by removing the cell after polyelectrolyte multilayer formation by means of NaOCl treatment. This procedure results in cross-linking of poly(allylamine hydrochloride) (PAH) molecules and destroying poly(styrene sulfonate) (PSS) within the multilayer. Capsules are obtained being remarkably different from layer-by-layer (LbL) capsules. These capsules are rather permeable for low as well as for high molecular weight species. However, upon adsorption of extra polyelectrolyte layers the permeability decreased remarkably. The assembly of six supplementary layers of PAH and PSS rendered the capsule almost impermeable for fluorescein. Resealing by supplementary layers is a potential means for filling and release control. By means of electrorotation measurements, it was shown that the capsule walls obtained isolating properties in electrolyte solutions. Conclusions are drawn concerning the mechanism of permeability through cell templated polyelectrolyte multilayer capsules. 相似文献
79.
Golubina E. V. Lokteva E. S. Lazareva T. S. Kostyuk B. G. Lunin V. V. Simagina V. I. Stoyanova I. V. 《Kinetics and Catalysis》2004,45(2):183-188
The hydrodechlorination of CCl4 in the presence of Pd–Fe/Sibunit catalysts of different composition was studied. An optimum concentration of the metals (2.5% at the ratio Pd/Fe = 1 : 4) was determined, which corresponds to the highest stability of catalysts and selectivity of C2–C4 olefin and paraffin formation. With the use of TPR and magnetic measurements, it was found that the metals occurred in an oxidized state in the course of the reaction; it is likely that this resulted in the formation of C2–C4 hydrocarbons. 相似文献
80.
We demonstrate that fluorescence of single molecules in the nanometric vicinity of a thin gold film can be effectively excited and detected through the film with an epi-illumination scanning confocal microscope. A full theoretical treatment of the fluorescence signal indicates that both excitation and emission are surface-plasmon mediated. Remarkably, the number of photons detectable from chromophores perpendicular to the interface is enhanced by the presence of the metal. 相似文献