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491.
Zimnicka M Wileńska B Sekiguchi O Uggerud E Danikiewicz W 《Journal of mass spectrometry : JMS》2012,47(4):425-438
Gas-phase reactions of isomeric nitrophenide ions and p-halonitrophenide ions with acrylonitrile, methyl acrylate, and ethyl acrylate have been studied using mass spectrometry and computational methods. Depending on the structure of the α,β-unsaturated compound, formation of adducts to the carbonyl group of the acrylate (for methyl acrylate and ethyl acrylate) and β-adducts (adducts of p-halonitrophenide ions to α,β-unsaturated compounds in β position) was observed. Further transformations of these adducts lead to the products of elimination of an alcohol molecule and the anionic products of intramolecular substitution of a halogen atom, respectively. 相似文献
492.
493.
Beata Sweryda-Krawiec Jeffery L. Coffer Shubhra Gancopadhahay 《Journal of Cluster Science》2002,13(4):637-645
Visible light emission emanating from nanostructured porous silicon is sensitive to adsorption of a number of small molecules, suggesting its utility as a chemical sensor. In this work we investigate the mechanistic origin of the diminution of the luminescence by n-propyl amine adsorption and restoration by trifluoroacetic acid, most sensitively by an examination of the changes in observed lifetime of the porous Si luminescence. This is quantified in terms of a stretched exponential model that is consistent with a distribution of luminescent centers in this nanophase material. 相似文献
494.
Syntheses, modifications and properties of latexes containing polyacrolein, suitable for the covalent immobilization of proteins, are described. Results of the studies of physical adsorption and covalent attachment of human serum albumin and gamma globulins are discussed. Procedures allowing immobilization of the enzyme, horseradish peroxidase, are described. Changes in protein molecules, owing to their contact with latex particles, are analyzed. Applicability of polyacrolein containing latexes for diagnostic purposes is discussed. 相似文献
495.
This article presents a selection of the relevant issues that emerge at the interface between chromatography and chemometrics. In the first part, we present advantages and drawbacks of applying signal-enhancement, warping and mixture-analysis methods. In the second part, we discuss typical examples of misuse and abuse of chemometrics that can occur with those less familiar with the data-processing approaches. Finally, we conclude that close collaboration between the communities of chromatographers and chemometricians will allow a deeper insight into the chromatographic systems being analyzed and permit new chromatographic problems to be solved in an efficient, elegant manner. 相似文献
496.
The applicability of the subtractive anodic stripping voltammetry (SASV) using the square‐wave mode at the silver‐gold alloy electrode has been studied for thallium determination in the presence of large amount of lead and cadmium in natural samples. 10 mmol L?1 perchloric acid was found as the most suitable supporting electrolyte for determination in synthetic solutions. The thallium peak was separated about 200 mV from Cd+Pb peak. Diethylenetriaminepentaacetic acid addition was necessary to determine thallium at the silver‐gold alloy electrode in digested plant and sediment. The determination limit was equal to 1.4 μg L?1. The method was validated by the inter‐method comparison (ICP‐MS). 相似文献
497.
Ilík P Kouril R Kruk J Myśliwa-Kurdziel B Popelková H Strzałka K Naus J 《Photochemistry and photobiology》2003,77(1):68-76
The origin of heat-induced chlorophyll fluorescence rise that appears at about 55-60 degrees C during linear heating of leaves, chloroplasts or thylakoids (especially with a reduced content of grana thylakoids) was studied. This fluorescence rise was earlier attributed to photosystem I (PSI) emission. Our data show that the fluorescence rise originates from chlorophyll a (Chl a) molecules released from chlorophyll-containing protein complexes denaturing at 55-60 degrees C. This conclusion results mainly from Chl a fluorescence lifetime measurements with barley leaves of different Chl a content and absorption and emission spectra measurements with barley leaves preheated to selected temperatures. These data, supported by measurements of liposomes with different Chl a/lipid ratios, suggest that the released Chl a is dissolved in lipids of thylakoid membranes and that with increasing Chl a content in the lipid phase, the released Chl a tends to form low-fluorescing aggregates. This is probably the reason for the suppressed fluorescence rise at 55-60 degrees C and the decreasing fluorescence course at 60-75 degrees C, which are observable during linear heating of plant material with a high Chl a/lipid ratio (e.g. green leaves, grana thylakoids, isolated PSII particles). 相似文献
498.
Wiesława Ferenc Beata Bocian J. Sarzyński 《Journal of Thermal Analysis and Calorimetry》2006,84(2):377-383
Four new complexes of 2,3,4-trimethoxybenzoic acid
anion with manganese(II), cobalt(II), nickel(II) and copper(II) cations were
synthesized, analysed and characterized by standard chemical and physical
methods. 2,3,4-Trimethoxybenzoates of Mn(II), Co(II), Ni(II) and Cu(II) are
polycrystalline compounds with colours typical for M(II) ions. The carboxylate
group in the anhydrous complexes of Mn(II), Co(II) and Ni(II) is monodentate
and in that of Cu(II) monohydrate is bidentate bridging one. The anhydrous
complexes of Mn(II), Co(II) and Ni(II) heated in air to 1273 K are stable
up to 505–517 K. Next in the range of 505–1205 K they decompose
to the following oxides: Mn3O4,
CoO, NiO. The complex of Cu(II) is stable up to 390 K, and next in the range
of 390–443 K it loses one molecule of water. The final product of its
decomposition is CuO. The solubility in water at 293 K is of the order of
10–3 mol dm–3
for the Mn(II) complex and 10–4 mol dm–3
for Co(II), Ni(II) and Cu(II) complexes. The magnetic moment values of Mn2+,
Co2+, Ni2+ and Cu2+
ions in 2,3,4-trimethoxybenzoates experimentally determined in the range of
77–300 K change from 5.64–6.57 μB (for Mn2+),
4.73–5.17 μB (for Co2+), 3.26–3.35 μB
(for Ni2+) and 0.27–1.42 μB (for Cu2+).
2,3,4-Trimethoxybenzoates of Mn(II), Co(II) and Ni(II) follow the Curie–Weiss
law, whereas that of Cu(II) forms a dimer. 相似文献
499.
Günter Grampp Stephan Landgraf Tomasz Wesierski Beata Jankowska Ewa Kalisz Dana-Maria Sabou Boryana Mladenova 《Monatshefte für Chemie / Chemical Monthly》2002,133(10):1363-1372
Summary. The kinetics of the CrO(O2)2 formation by H2O2 and Cr2O7
2− in aqueous acidic media was measured at 293 ± 2 K in a pH range between 2.5 and 3.3. Using the stopped-flow method with rapid scan UV-VIS detection, the rate law of the formation
of CrO(O2)2 was determined. For the media HClO4, HNO3 and CH3COOH, the reaction order in the Cr2O7
2− concentration was found to be 0.5. For [H2O2] as well as for [H+], the reaction was first order in all acids used. In HCl and H2SO4 media the reaction was first order in Cr2O7
2−. At T = 293 ± 2 K the rate constant for the formation of Cr(O)(O2)2 was found to be (7.3 ± 1.9) · 102 M−3/2 s−1 in HClO4.
Corresponding author. E-mail: grampp@ptc.tu-graz.ac.at
Received January 30, 2002; accepted (revised) June 5, 2002 相似文献
500.
Günter Grampp Stephan Landgraf Tomasz Wesierski Beata Jankowska Ewa Kalisz Dana-Maria Sabou Boryana Mladenova 《Monatshefte für Chemie / Chemical Monthly》2002,212(4):1363-1372
The kinetics of the CrO(O2)2 formation by H2O2 and Cr2O7
2− in aqueous acidic media was measured at 293 ± 2 K in a pH range between 2.5 and 3.3. Using the stopped-flow method with rapid scan UV-VIS detection, the rate law of the formation
of CrO(O2)2 was determined. For the media HClO4, HNO3 and CH3COOH, the reaction order in the Cr2O7
2− concentration was found to be 0.5. For [H2O2] as well as for [H+], the reaction was first order in all acids used. In HCl and H2SO4 media the reaction was first order in Cr2O7
2−. At T = 293 ± 2 K the rate constant for the formation of Cr(O)(O2)2 was found to be (7.3 ± 1.9) · 102 M−3/2 s−1 in HClO4. 相似文献