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21.
Arkosi Z Szabó-Plánka T Rockenbauer A Nagy NV Lázár L Fülöp F 《Inorganic chemistry》2003,42(16):4842-4848
We have studied the complex equilibria of copper(II) with a series of beta-substituted beta-amino acids (R: H, Me, Et, iBu, iPr, cHex, 1-EtPr, and tBu) in aqueous solution by pH potentiometry and electron paramagnetic resonace (EPR) spectroscopy in the range pH = 2-8 at various metal and ligand concentrations. The basicities of the corresponding donor groups differed only slightly in the series of ligands. A purely mathematical method, the matrix rank analysis carried out on the EPR spectrum package recorded in the presence of copper(II), indicated the formation of 6 independent paramagnetic species. Accordingly, Cu(2+) (aqua complex) and the complexes [CuLH](2+), [CuL](+), [CuL(2)H(2)](2+), [CuL(2)H](+), and [CuL(2)] were considered in the subsequent analysis of series of spectra, and also two isomers of [CuL(2)] were identified. The formation constants and the EPR parameters, e.g. the isotropic g-factors and the copper and nitrogen hyperfine couplings for the above species, were determined in the same optimization procedure by the simultaneous evaluation of spectra. The ligands "LH" are suggested to bind in equatorial positions through their carboxylate groups, while the amino acids in the L protonation state are likely to occupy two equatorial sites via the amino and carboxylate groups. For the isomers of [CuL(2)], the donors of the same kind are in the cis or trans position. As far as we know, this is the first reported case in which a strong correlation has been found between the steric effects of substituents characterized by Meyer's steric parameter V(a) and the protonation constants of metal complexes. The observed trend for the preference for nonprotonated complexes [CuL](+) and [CuL(2)] to increase with the steric demand of the substituent was explained by the increasing shielding effect of the substituent hindering protonation of the nonprotonated complex. 相似文献
22.
Zsolt?Ajtony Norbert?Szoboszlai Zsuzsanna?Bella Szilvia?Bolla Pál?Szakál László?BencsEmail author 《Mikrochimica acta》2005,150(1):1-8
A flow injection hydride generation graphite furnace atomic absorption spectrometric (FI-HG-GFAAS) method was applied to the determination of Se in Se-doped and undoped cereals and bakery products. For the purpose of doping, the soils used for the cultivation of the cereals were dosed with Se-doped foliar fertilizers. The samples were dissolved in a mixture of HNO3 and H2O2 solutions using microwave-assisted digestion. The decomposition of H2Se generated from the sample solutions and the trapping of elemental Se were performed at a temperature of 300°C on an Ir-pretreated integrated graphite platform of a transversally heated graphite atomizer (THGA). For release of the trapped Se within a fairly short atomization time (5s), an atomization temperature of 2200°C was observed to be optimal. The overall efficiency of hydride generation, transport and trapping was 86%.The upper limit of the linear dynamic range of calibration was 10µgL–1, which corresponds to 0.5µgg–1 for solid samples. Recovery of the samples spiked with SeVI solutions was found to be 93±6% on average. The relative standard deviation of the determinations was less than 8%. The limit of detection was found to be 0.06µgL–1, corresponding to 3ngg–1 for solid samples. The accuracy of the method was verified with the use of IAEA-155 (whey powder) certified reference material. End-capped THGA tubes resulted in an extension of the linear calibration range compared to that of standard THGAs.The Se content in bakery products made of undoped cereals ranged from 7.7 to 68ngg–1 (wet weight) in 18 samples, whereas the Se content of the corresponding cereals was found to be below 100ngg–1 (wet weight). The Se level of cereals grown on soils treated with Se-doped fertilizers ranged from 128 to 1046ngg–1 (wet weight), and it depended linearly on the Se concentration of the corresponding foliar fertilizer. 相似文献
23.
Tolonen A György Z Jalonen J Neubauer P Hohtola A 《Biomedical chromatography : BMC》2004,18(8):550-558
Cinnamyl alcohol was added to the media of compact callus aggregates (CCA) of Rhodiola rosea for stimulating the production of cinnamyl glycosides. The biotransformation reaction produced high amounts of rosin, while only a very low amount of rosavin was produced. As the consumption rate of cinnamyl alcohol was much higher than production of rosin, the aqueous methanol extracts of compact callus aggregates were studied by liquid chromatography-mass spectrometric methods and four new unexpected biotransformation products of cinnamyl alcohol were identified. 相似文献
24.
Kerekes Zsuzsanna Restás Ágoston Lublóy Éva 《Journal of Thermal Analysis and Calorimetry》2020,139(2):775-787
Journal of Thermal Analysis and Calorimetry - Electric wiring is part of the fire protection systems; therefore, it must work reliably for a given period of time. Cable is in the first place among... 相似文献
25.
Journal of Thermal Analysis and Calorimetry - During the development of the carbon fibres and oxidized fibres, the aim was to get a material with extraordinary mechanical properties. Nowadays, it... 相似文献
26.
27.
Dario Duca Zsuzsanna Varga Gianfranco La Manna Tamás Vidóczy 《Theoretical chemistry accounts》2000,104(3-4):302-311
The hydrogenation mechanism of acetylene–ethylene mixtures on Pd catalysts under different experimental conditions was studied
by employing a time-dependent Monte Carlo approach set to use a fixed series of event probabilities. The dependence of the
catalyst activity and selectivity on the sizes of the metal particles was simulated at microscopic level and the results,
also refined by fitting procedures, suggested proper explanations for the apparent nonuniformity of the related experimental
findings. The use of the steric hindrance parameter of the surface species and the available surface energy on the metallic
catalyst sites was decisive for reproducing the experimental results.
Received: 16 September 1999 / Accepted: 3 February 2000 / Published online: 2 May 2000 相似文献
28.
D. Lőrinczy Zsuzsanna Vértes Franciska Könczöl J. Belágyi 《Journal of Thermal Analysis and Calorimetry》2009,95(3):713-719
Actin is one of the main components in the eukaryote cells which plays significant role in many cellular processes, like force-generation,
maintenance of the shape of cells, cell-division cycle and transport processes.
In this study the thermal transitions of monomer and polymerized actins were studied to get information about the changes
induced by polymerization and binding of myosin to actin using DSC and EPR techniques. The main thermal transition of F-actin
was at 67.5°C by EPR using spin-labeled actin (the relative viscosity change was around 62°C), while the DSC denaturation
T
ms were at 60.3d°C for G-actin and at 70.5°C for F-actin.
Applying the Lumry-Eyring model to obtain the parameters of the kinetic process and calculate the activation energy, a ‘break’
was found for F-actin in the function of first-order kinetic constant vs. 1/T. This indicates that an altered interdomain interaction is present in F-actin. The addition of myosin or heavy meromyosin
(HMM) in different molar ratio of myosin to actin has changed significantly the EPR spectrum of spin-labeled F-actin, indicating
the presence of the supramolecular complex. Analyzing the DSC traces of the actomyosin complex it was possible to identify
the different structural domains of myosin and actin. 相似文献
29.
The volatile oil compositions of Thymus pannonicus All. from nineteen different localities of Hungary were analyzed by GC/MS. The essential oil content of the Hungarian thyme samples varied between very low (0.14 mL/100 g DW) and fairly high (1.9 mL/100 g DW) values. Significant essential oil polymorphism was found: altogether twelve chemovarieties may have been determined, representing a way of adaptation to different habitat conditions. The main volatile compound of chemotype 1 was thymol (24.6-67.5%), while in the case of chemotype 2, thymol (36.5-63.7%) and p-cymene (11.5-27.3%) predominated. Thymol (28.4-63.7%), p-cymene (11.5-31.8%) and gamma-terpinene (9.7-20.9%) were identified as the chief monoterpenes of chemotype 3, while chemotype 4 contained thymol (36.5%), p-cymene (27.3%) and neral (11.2%). Chemotype 5 accumulated thymol (38.5%), p-cymene (20.6%), gamma-terpinene (12.0%) and beta-bisabolene (10.3%) as its main volatiles. The oil of chemotype 6 can be characterized by thymol (41.9%), p-cymene (20.2%), isoborneol (10.3%) and gamma-terpinene (9.9%), while that of chemotype 7 consisted of thymol (27.7%), linalyl acetate (18.8%), gamma-terpinene (18.6%) and alpha-cubebene (13.9%). In the oil of chemotype 8, p-cymene (45.0%), geraniol (13.6%) and linalyl acetate (9.9%) were found in higher percentages, while chemotype 9 mainly produced linalyl acetate (36.2%) and geranyl acetate (20.2%). Chemotype 10 accumulated germacrene-D (43.4) and beta-caryophyllene (15.0%), while the oil of chemotype 11 contained caryophyllene oxide (45.2%), alpha-cubebene (15.7%) and linalool (13.8%) in high proportions. Germacrene-D (29.7%), beta-caryophyllene (22.0%) and farnesol (10.4%) were identified as main essential oil compounds of chemotype 12. The last nine chemotypes were new for the literature, while the first seven contained thymol as their chief compound. The role of certain sesquiterpenes was found to be considerable. 相似文献
30.
Victor G. Mihucz Zsolt Varga István Virág Zsuzsanna Koleszár 《Microchemical Journal》2008,90(1):44-49
During the recultivation of the uranium mining area of K?vágósz?l?s (Hungary), the tailings were covered with clay and loess soil layers having a thickness of 30 cm and 100 cm, respectively. In the loess covering layer, acacia (Robinia pseudoacacia), poplars (Populus × albus, Populus × canescens), oak (Quercus pubescens), silver tree (Eleagnus angustifolia) were planted between 1996 and 2004. In order to establish the extent of the uranium and thorium transport from the sludge to the leaves by uptake and translocation processes through roots with a length higher than 1.3 m results in a remarkable redistribution of these pollutants, a gray poplar tree, growing spontaneously in the last uncovered tailing, being selected as reference tree. The U and Th concentrations in the leaves of the above-mentioned trees, in the covering layers as well as in the original sludge were determined by inductively coupled plasma sector field mass spectrometry (ICP-SF-MS). Generally, the Th concentration of the soils was about 4 times higher than that of uranium, while uranium concentration was about 10-130 times higher than that of thorium in the leaf samples and its concentration ranged from 28 to 1045 ng g− 1, the last value belonging to the poplar tree growing on the last uncovered tailing. In order to assume the mobility and bioavailability of uranium if the dry leaves fall down, the uranium species in the leaves of the poplar tree growing in the uncovered reservoir were determined applying ultrasound-assisted extraction with distilled water and ammonium acetate as well as high performance liquid chromatographic (HPLC)-ICP-SF-MS technique. About 20% of total uranium could be extracted in form of uranyl cations and a presumably negatively charged uranium compound. Estimations revealed that the annual increment of U in the soil surface layer due to the dead fallen leaves in case of the investigated gray poplar (Populus × canescens) is about 1.2%. 相似文献