全文获取类型
收费全文 | 427篇 |
免费 | 3篇 |
国内免费 | 2篇 |
专业分类
化学 | 206篇 |
晶体学 | 13篇 |
力学 | 13篇 |
数学 | 83篇 |
物理学 | 117篇 |
出版年
2023年 | 3篇 |
2021年 | 6篇 |
2020年 | 4篇 |
2019年 | 4篇 |
2018年 | 12篇 |
2017年 | 7篇 |
2016年 | 13篇 |
2015年 | 12篇 |
2014年 | 10篇 |
2013年 | 22篇 |
2012年 | 24篇 |
2011年 | 22篇 |
2010年 | 17篇 |
2009年 | 19篇 |
2008年 | 26篇 |
2007年 | 19篇 |
2006年 | 20篇 |
2005年 | 26篇 |
2004年 | 11篇 |
2003年 | 16篇 |
2002年 | 13篇 |
2001年 | 11篇 |
2000年 | 5篇 |
1999年 | 5篇 |
1998年 | 11篇 |
1997年 | 6篇 |
1996年 | 2篇 |
1994年 | 2篇 |
1992年 | 5篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1985年 | 2篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1977年 | 2篇 |
1975年 | 2篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1962年 | 1篇 |
1961年 | 1篇 |
1960年 | 2篇 |
1959年 | 8篇 |
1958年 | 10篇 |
1957年 | 9篇 |
1956年 | 2篇 |
1955年 | 8篇 |
1954年 | 4篇 |
排序方式: 共有432条查询结果,搜索用时 15 毫秒
91.
Peter Kopčanský Martina Koneracká Milan Timko Ivana Potočová Ladislav Tomčo Natália Tomašovičová Vlasta Závišová Jan Jadzyn 《Journal of magnetism and magnetic materials》2006
The paper presents an overview of the observations of structural transitions in ferronematic based on thermotropic nematic 6CHBT (4-trans-4′-n-hexyl-cyclohexyl-isothiocyanato-benzene) and in ferronematic droplets. The type of anchoring was determined using the results of the capacitance measurements. The ferronematic droplets were observed in solutions of nematogenic 6CHBT with fine magnetic particles and phenyl isocyanate. The phase diagram of the transitions between isotropic and nematic phases was found. The magneto-dielectric measurements of various structural transitions in this new system enabled to estimate the type of anchoring of nematic molecules on magnetic particles surfaces in droplets. 相似文献
92.
93.
NAD+ is degraded by horse liver alcohol dehydrogenase in a reaction with p-methylbenzyl hydroperoxide, which acts as a pseudo-substrate. An unstable intermediate product (called compound I) is formed, and this is converted into the final product NADX. The reaction can be monitored by capillary electrophoresis. NADX migrates as two well resolved peaks (NADX1 and NADX2), which belong probably to the tautomers of the same substance. The intermediate product, compound I, has the same effective mobility as the conformer NADX2 and it was impossible to separate compound I from NADX2. The spectra taken during the separation show clearly that the “9-min” peak contains different compounds during the course of the reaction and the NADX2 is not identical with compound I. 相似文献
94.
Ladislav Habala Ferdinand Devínsky Alexander E. Egger 《Journal of Coordination Chemistry》2018,71(7):907-940
Urease plays a significant role in the pathogenesis of several diseases and also has practical implications in other fields, such as agriculture or chemical analysis. Among the multitude of chemical species known to inhibit urease, metal complexes stand out as a special category due to their specific mechanism of action, distinct from purely organic substances. Their inhibitory activity seems to depend on the type of metal and its oxidation state as well as on the coordination environment of the central atom. Furthermore, the study of the interaction between metal ions and their complexes with urease renders valuable insights into detailed catalytic mechanisms of this enzyme. This brief survey attempts to provide an overview of the published research on urease inhibition by metal complexes. 相似文献
95.
Structure and properties of titanium-zinc borophosphate glasses 总被引:1,自引:0,他引:1
Ladislav Koudelka Petr Mos?ner Lionel Montagne 《Journal of solid state chemistry》2005,178(6):1837-1843
The structure of 50ZnO-10B2O3-40P2O5+xTiO2 glasses prepared by slow cooling (for x=0-24 mol% TiO2) or by quenching (for x=28-64 mol% TiO2) was studied by Raman, 31P and 11B MAS NMR spectroscopy. TiO2 incorporates into the glass structure, which results in a decrease in the molar volume and an increase in the glass transition temperature. According to Raman spectra Ti atoms form distorted TiO6 octahedra and their incorporation into the structural network results in the depolymerization of phosphate chains. 11B NMR spectra of the glasses with increasing TiO2 content show gradual changes from one symmetrical signal of B(OP)4 units to a broad complex signal which was separated into five signals ascribed to four different types of BO4 units and one BO3 unit. With increasing TiO2 content a part of boron atoms changes from tetrahedral BO4 to trigonal BO3 units, which is ascribed to the formation of TiO6 units in the glass structure. 相似文献
96.
Silvia Ružičková Jolana Bajuszová Ladislav Koller Mikuláš Matherny Karol Flórián 《Mikrochimica acta》2006,156(1-2):115-120
The evaporation as a part of the spectrochemical excitation process is a complicated procedure during which different thermo-chemical
reactions connected mainly to the formation of carbides are overshot. This one is accelerated namely at the 4000 K on the
top of the carrier electrode. The carbide creation markedly affects the evaporation process of single elements of the given
matrix and modifies this process. In spite of this it is evident that the intensity of the DC arc has a significant impact
on the evaporation of all elements.
The evaporation capability of two optical methods, the classical non-controlled direct current (DC) arc spectrography and
the PC controlled DC arc optical emission spectrometry, have been compared for the determination of some environmental important
elements (Al, Cr, Ni, and V). The experiments were carried out using grating spectrograph PGS-2 and simultaneous multi-channel
LECO 750 spectrometer which is connected to a separated evaporation cell and adjusted to the Marinković plasma source. Standardized
evaporation curves were designed and the half-time (t50%) values and the total (t100%) evaporation time values were calculated. The basic statistical evaluation was done and the main figures of the merit were
calculated. 相似文献
97.
Butorphanol tartrate is a synthetic opioid agonist-antagonist used as analgesic, possessing three chiral centres in the basic part of the molecule. Its chiral purity is routinely controlled only by optical rotation. A new capillary zone electrophoresis method, capable to separate the enantiomers of butorphanol and intermediate of its synthesis, cycloamine, was developed. Different electrolyte composition (type and concentration of carrier ion, pH, and organic solvent addition), and type and concentration of several chiral selectors (natural and modified cyclodextrins) were tested. Using the optimized conditions (acidic electrolyte with the addition of highly sulphated gamma-cyclodextrin) as low as 0.05% of undesirable enantiomers can be detected. Selected method characteristics, i.e., linearity (0-50 mg/l), precision (2.5% at 20 mg/l), and accuracy (101 +/- 2% at 20 mg/l) were evaluated. The optimized method was applied for the analysis of real batches of butorphanol and cycloamine. It was found that butorphanol tartrate manufactured by IVAX Pharmaceuticals contains less than 0.05% of undesirable enantiomer. 相似文献
98.
Andrea?TuroňováEmail author Miriam?Gálová Magdaléna??upicová Ladislav?Lux 《Journal of Solid State Electrochemistry》2003,7(10):689-693
The composition of a two-component Ni-Cu coating and the efficiency of its electrochemical deposition on Fe powder was studied
by constant current electrolysis. A fluidized bed arrangement was applied. The variable parameters were: the particle size
fraction, the density of the suspension of the Fe powder in the plating bath, and the intensity of the stirring of the fluidized
bed. Both the Cu and Ni contents in the deposit decrease with increase in the particle size, and with decrease in the suspension
density. Thus, the surface area available for the electrochemical process proved to be of high importance. Another important
factor is the quality of the contacts of the powder particles with the current carrying compact electrode during which the
deposition of Ni is preferred. This influence is manifested in a decrease of the Ni-Cu ratio in the deposit with an increase
in the particle size and rotation speed and, consequently, with a decrease in the suspension density. The current efficiency
values on the powder for optimum conditions reached 80%. 相似文献
99.
Pyrolysis-capillary gas chromatography (Py-cGC) represents important method to identify the analytes in the mixture after thermal degradation. This combines high effective analyte separation on-line coupled with thermal degradation process that depends on analyte structure. System of retention indices has been used for identification of the analytes after on-line pyrolysis and chromatographic separation. The pyrolysate composition has been studied during thermal degradation of polymethylmethacrylate (PMMA) at different pyrolysis temperatures and chromatographic column conditions. Homologues series of n-alkanes have been used for calculation of pyrolysate Kováts retention indices (I) and compared with mass spectrometric (MS) data of pyrolysate model mixture. To identify PMMA thermal degradation products the high density polyethylene (HDPE) as additive standard producing triplets of the olefin homologous series during co-pyrolysis has been used. These homologous series enable to calculate programmed temperature retention indices (ITPGC) to identify the analytes present in the pyrolysate. Calculated I values were compared with published I values databases to identify analytes yielded at different pyrolysis temperatures. 相似文献
100.
Alexander A. Kaminskii Ladislav Bohatý Hanjo Rhee Andr Kaltenbach Oliver Lux Hans J. Eichler Reinhard Rückamp Petra Becker 《Laser \u0026amp; Photonics Reviews》2013,7(3):425-431
Orthorhombic PbCO3, known as natural crystal cerussite, is presented as a new Stimulated Raman Scattering (SRS)‐active crystal. With picosecond laser pumping high‐order Raman‐induced χ(3) generation is observed. All registered Stokes and anti‐Stokes sidebands in the visible and near‐IR are identified and attributed to the SRS‐promoting phonon mode A1g of the carbonate group, with ωSRS ≈ 1054 cm−1. The first Stokes steady‐state Raman gain coefficient in the visible spectral range is estimated as well to a value not less than 4.6 cm·GW−1. 相似文献