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41.
Ana Đurović Zorica Stojanović Dušan Rakić Nada Grahovac 《International journal of environmental analytical chemistry》2018,98(4):369-385
In this paper, a chronopotentiometric method for the determination of herbicide metamitron (MTM) using a glassy carbon electrode (GCE) and a thin film mercury electrode (TFME) as working electrodes is presented. MTM provided a well-defined reductive peak in the Britton–Robinson buffer on both working electrodes. Instrumental and chemical factors such as pH of the buffer, initial potential and reduction current influencing MTM chronopotentiometric response were optimised with the Box–Behnken experimental design. Under the optimal combination of factors, the analytical signal was linear in the MTM concentration range of 0.8–30 mg/L, with a detection limit of 68.53 µg/L using a TFME, and in the concentration range of 1–30 mg/L, with a detection limit of 92.91 µg/L using a GCE. The precision of the method was estimated as a function of repeatability and reproducibility, with the value of relative standard deviation lower than 2.6%. The applicability of the method was verified by direct analysis of MTM in spiked water samples and commercial pesticide formulations. The obtained results were in good agreement with those obtained using liquid chromatography/tandem mass spectrometry (LC-MS/MS) method, or with those labelled by the manufacturer. By using chronopotentiometry, neither extraction nor preconcentration procedures are necessary, thus making this method simple, cost-effective and more feasible for analytical routine analysis. 相似文献
42.
Vesna Kuntić Dusěan Malesěev Zorica Radović Vladana Vukojević 《Monatshefte für Chemie / Chemical Monthly》2000,131(7):769-777
Summary. In the present work, rutin (3,3′ ,4′ ,5,7-pentahydrohyflavone-3-rhamnoglucoside) was determinated via a complexing reaction with a titanyloxalate anion. K2[TiO(C2O4)2] and rutin react in 50% ethanol forming a 1:2 complex in a pH range from 4.00 to 11.50, in which the TiO(C2O4)2
2− ion is linked to rutin through the 4-carbonyl and 5-hydroxyl group. The thermodynamic stability constant log β2
0 of the complex is determined to 10.80 at pH = 6.50. The change of the standard Gibbs free energy Δ G0 amounts to −61 kJċ mol−1, indicating that the process of complex formation is spontaneous. The optimal conditions for the spectrophotometric determination
of microconcentrations of rutin are at pH=6.40 and λ= 430 nm, where the complex shows an absorption maximum with a molar absorption coefficient a
430=(60±2)ċ103 dm3ċ mol−1ċ cm−1. The method is applied rutin determination from tablets.
Received January 4, 2000. Accepted (revised) February 17, 2000 相似文献
43.
In this paper we present two new heuristic approaches to solve the Discrete Ordered Median Problem (DOMP). Described heuristic methods, named HGA1 and HGA2 are based on a hybrid of genetic algorithms (GA) and a generalization of the well-known Fast Interchange heuristic (GFI). In order to investigate the effect of encoding on GA performance, two different encoding schemes are implemented: binary encoding in HGA1, and integer representation in HGA2. If binary encoding is used (HGA1), new genetic operators that keep the feasibility of individuals are proposed. Integer representation keeps the individuals feasible by default, so HGA2 uses slightly modified standard genetic operators. In both methods, caching GA technique was integrated with the GFI heuristic to improve computational performance. The algorithms are tested on standard ORLIB p-median instances with up to 900 nodes. The obtained results are also compared with the results of existing methods for solving DOMP in order to assess their merits. 相似文献
44.
45.
U. Lavrenčič Štangar B. Orel A. Régis Ph. Colomban 《Journal of Sol-Gel Science and Technology》1997,8(1-3):965-971
A novel low-temperature electrochromic and photochromic material in the form of gels and thin solid films composed of H3PW12O40·nH2O (WPA) incorporated in titanium oxide gel issued of Ti(OPr
i
)4 with addition of acetic acid were made via the sol-gel route by the dip-coating technique. Gels in bulk and thin film forms
have been studied with the help of FT-IR transmission, reflection absorption and Raman spectroscopy. Similarity of the characteristic
band frequencies with pure WPA confirmed that entrapped Keggin salt is well preserved inside the gel. Photochromism of WPA/TiO2 gels which appears after short exposure to UV (λ=366 nm) radiation is related to the excitation effect of branched alcohol
leading to formation of carbonyl modes due to the alcohol transformation to aldehyde. Electrochromic properties of WPA/TiO2 gel films were tested in aqueous 0.001M HClO4 and 0.1M LiClO4 electrolytes as well as in the sol-gel electrochromic device (ECD) composed of LiClO4 doped ormolyte and Sb:Mo:SnO2 counter electrode film with optically passive response. Slight improvement of the WPA/TiO2 intercalation/deintercalation kinetics was obtained with the films exhibiting one order of magnitude higher electronic conductivity
which were made with addition of in situ polymerized pyrrole with Fe(NO3)3. 相似文献
46.
47.
B. Orel U. Opara Krašovec U. Lavrenčič Štangar P. Judeinstein 《Journal of Sol-Gel Science and Technology》1998,11(1):87-104
This paper reports on the development of all sol-gel EC devices, having the configuration WO3/ormolyte/SnO2:Mo, WO3/ormolyte/SnO2:Sb and WO3/ormolyte/SnO2:Sb:Mo, where all three internal layers, including the ionically conductive inorganic-organic hybrid (ormolyte), are prepared via the sol-gel route. The electrochemical and optical properties of EC devices are presented and their cycling stability and reversibility of their optical modulation assessed. The transmission modulation of the devices depends on the thickness of the active electrochromic, counter-electrode and ormolyte layer. The electrochemical and optical properties of individual films and the structural properties of the ormolyte are described and correlated with the stability of the all sol-gel EC devices. 相似文献
48.
Santiago Gómez-Ruiz Beatriz Gallego Željko Žižak Evamarie Hey-Hawkins Zorica D. Juranić Goran N. Kaluđerović 《Polyhedron》2010
Four titanium(IV) carboxylate complexes [Ti(η5-C5H5)2(O2CCH2SMes)2] (1), [Ti(η5-C5H4Me)2(O2CCH2SMes)2] (2), [Ti(η5-C5H5)(η5-C5H4SiMe3)(O2CCH2SMes)2] (3) and [Ti(η5-C5Me5)(O2CCH2SMes)3] (4; Mes = 2,4,6-Me3C6H2) have been synthesised by the reaction of the corresponding titanium derivatives [Ti(η5-C5H5)2Cl2], [Ti(η5-C5H4Me)2Cl2], [Ti(η5-C5H5)(η5-C5H4SiMe3)Cl2] and [Ti(η5-C5Me5)Cl3] and two (for 1–3) or three (for 4) equivalents of mesitylthioacetic acid. Complexes 1–4 have been characterized by spectroscopic methods and the molecular structure of the complexes 1, 2 and 4 have been determined by X-ray diffraction studies. The cytotoxic activity of 1–4 was tested against tumor cell lines human adenocarcinoma HeLa, human myelogenous leukemia K562, human malignant melanoma Fem-x, and normal immunocompetent cells, that is peripheral blood mononuclear cells PBMC and compared with those of the reference complexes [Ti(η5-C5H5)2Cl2] (R1), [Ti(η5-C5H4Me)2Cl2] (R2), [Ti(η5-C5H5)(η5-C5H4SiMe3)Cl2] (R3) and cisplatin. In all cases, the cytotoxic activity of the carboxylate derivatives was higher than that of their corresponding dichloride analogues, indicating a positive effect of the carboxylato ligand on the final anticancer activity. Complexes 1–4 are more active against K562 (IC50 values from 72.2 to 87.9 μM) than against HeLa (IC50 values from 107.2 to 142.2 μM) and Fem-x cells (IC50 values from 90.2 to 191.4 μM). 相似文献
49.
The electrocatalysed oxidation of histamine on a thin film nickel electrode was investigated for the purpose of its chronopotentiometric determination. The oxidation mechanism implies complex and combined processes of histamine physical adsorption and consequent oxidation via joined oxidation potency of a constant current and electrochemically generated nickel‐oxihydroxide, which played a role of an electron transfer catalyst. Experimental parameters affecting the oxidation process, including type and concentration of supporting electrolyte, initial potential, oxidation current, temperature and concentration time, were optimised. Using a 240 s accumulation time, limit of detection and quantitation were 0.11 mg L?1 and 0.29 mg L?1 of histamine, respectively. 相似文献
50.
Angela Šurca Vuk Sandra Benčič Boris Orel Franco Decker 《Journal of Sol-Gel Science and Technology》2002,23(1):53-66
Electrochemical properties of amorphous and crystalline V2O5 films, dip-coated from V-oxoisopropoxide sols and thermally treated at various temperatures (100, 150, 200 and 300°C), have been studied in extended potential range, i.e. from 1.4 to –1.6 V vs. Ag/AgCl in 1M LiClO4/propylen carbonate (PC) electrolyte. The formation of various lithiated (-, -, - and -Li
x
V2O5) phases was correlated with the values of insertion coefficient x obtained from cyclic voltammograms (CV) of crystalline V2O5 films (300°C). Reversible charging was observed when films were cycled up to –1.0 V vs. Ag/AgCl, while the extension of the potential to –1.3 V vs. Ag/AgCl change the CV of films irreversibly. Charging of crystalline V2O5 films was followed by the help of in-situ UV-visible spectroscopy, that revealed the intensity variations of the polaron absorption above 600 nm and the presence of the absorbing V3+ species between 550 and 650 nm. Ex-situ IR spectra of the crystalline films charged/discharged at –1.6V/1.4V vs. Ag/AgCl confirmed the amorphisation of the films' structure. 相似文献