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111.
Mona Mouallem-Bahout Sarah Bertrand Octavio Peña 《Journal of solid state chemistry》2005,178(4):1080-1086
Nanocrystalline single-phase samples of Zn1−xNixFe2O4 ferrites (0<x<1) have been obtained via a soft-chemistry method based on citrate-ethylene glycol precursors, at a relatively low temperature (650 °C). The influence of the nickel and zinc contents as well as that of heat treatments were investigated by means of X-ray powder diffraction, Brunauer-Emmett-Teller (BET) surface area, scanning electron microscopy (SEM) and Fourier Transform Infrared (FTIR) Spectroscopy. Higher Ni content increases the surface areas, the largest one (∼20 m2/g) being obtained for NiFe2O4 annealed at 650 °C for 15 h. For all compositions, the surface area decreases for prolonged annealing at 650 °C and for higher annealing temperatures. Those results were correlated to the particle size evolution; the smallest particles (∼50 nm) observed in the NiFe2O4 sample (650 °C, 15 h) steadily increase as Ni ions were replaced by Zn, reaching ∼100 nm in the ZnFe2O4 sample (650 °C, 15 h). For all the Zn1−xNixFe2O4 samples and, whatever the heat treatments was, the FTIR spectra show two fundamental absorption bands in the range 650-400 cm−1, characteristics of metal vibrations, without any superstructure stating for cation ordering. The highest ν1-tetrahedral stretching, observed at ∼615 cm−1 in NiFe2O4, shifts towards lower values with increasing Zn, whereas the ν2-octahedral vibration, observed at 408 cm−1 in NiFe2O4, moves towards higher wavenumbers, reaching 453 cm−1 in ZnFe2O4. 相似文献
112.
Ohne Zusammenfassung
An den Versuchen war auch Herr stud. Franz Jandraschitsch beteiligt. 相似文献
113.
Yvonne Syha Charlene Valmalle Jan W. Bats Michael Kock Mona Abdel-Tawab Manfred Schubert-Zsilavecz 《Monatshefte für Chemie / Chemical Monthly》2006,58(2):1357-1364
Although various thiazoles are known in literature for their biological and pharmacological properties only a few multi-step
synthesis pathways for the preparation of thiazolo[3,2-a]pyrimidinones have been reported, which are tedious and time-consuming. An alternative synthesis pathway is described, which
allows the preparation of 2,3-dihydrothiazolo[3,2-a]pyrimidin-5-ones in a one-step process based on a Michael-type tandem reaction. By heating of 2-thiobarbituric acid with ethyl 4-bromocrotonate in ethanol at 60°C for 2 h, a 2,3-dihydrothiazolo[3,2-a]pyrimidin-5-one was obtained in 73% yield, whereas carrying out the reaction at room temperature results in the formation
of an unstable unsaturated ester. The structures of both, the α,β-unsaturated ester as well as the 2,3-dihydrothiazolo[3,2-a]pyrimidin-5-one were confirmed by NMR spectroscopy. Additionally, the structure of the 2,3-dihydrothiazolo[3,2-a]pyrimidin-5-one was investigated by single-crystal X-ray analysis. The described approach offers a significant improvement
over previously reported synthesis pathways because it allows the simple preparation of 2,3-dihydrothiazolo[3,2-a]pyrimidin-5-ones with good yields in a one-step reaction. 相似文献
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115.
Liquid chromatography/electrospray tandem mass spectrometric analysis of incurred ractopamine residues in livestock tissues 总被引:1,自引:0,他引:1
Churchwell MI Holder CL Little D Preece S Smith DJ Doerge DR 《Rapid communications in mass spectrometry : RCM》2002,16(13):1261-1265
Ractopamine HCl is a beta-adrenergic agonist (beta-agonist) recently approved by the U.S. Food and Drug Administration, but not other governmental agencies, for use in finishing swine. For these reasons, it was important to develop and validate mass spectrometric methods for the detection and confirmation of ractopamine residues in livestock marker tissues. Incurred tissues in cattle, sheep, turkeys, and ducks were generated during 7-day ractopamine feeding (20 ppm in diets) periods. Disposition of ractopamine residues in liver and pigmented retinal epithelium was determined in animals slaughtered with withdrawal periods of 0, 3, and 7 days. Ractopamine residues, purified using solid-phase extraction, were measured using liquid chromatography (LC) and electrospray with detection by tandem mass spectrometry (MS/MS) in the multiple reaction-monitoring (MRM) mode. Total ractopamine residues (parent ractopamine + hydrolyzed conjugates) in liver were detected in all species on withdrawal day 0 (2-97 ppb) and were greatly diminished in all species by withdrawal day 7 (<1 ppb). Bovine and ovine retina had lower levels of ractopamine (0.5-3 ppb) than liver, and occular residues increased with withdrawal time, suggesting redistribution into this tissue. Lower limits of quantification were found to be approximately 0.1 ppb in liver and retina. Incurred ractopamine residues were confirmed by the precise and accurate agreement of MRM intensity ratios of diagnostic fragment ions (m/z 284, 164, and 121) from the protonated molecule between ractopamine residues in incurred samples and an authentic ractopamine standard. The limits of confirmation in liver and retina using recognized acceptance criteria were below 1 ppb. The high sensitivity and specificity for measurement and confirmation of ractopamine residues suggests this method will be applicable for regulatory residue surveillance programs. 相似文献
116.
Summary: Hyperbranched polyesteramides were prepared using phethalic anhydride (Ph An) or maleic anhydride (M An) as an A2 monomer and diethanol amine (DEA) as B′B2 monomer. Bulk condensation technique was used to synthesize polymers with both OH and modified polymers with long alkyl chain end groups. The prepared polymers were characterized using 1H-NMR, FTIR and TGA. Solution viscosity for hyperbranched polyester amide with hydroxyl end groups was measured as well. Dielectric and electric properties of the modified samples were investigated over a range of frequency and temperatures. No relaxation peak is noticed in the dielectric spectrum ε(ν) at various temperatures. The illustration of the imaginary part of the electric modulus M″ versus frequency shows a peak which is shifted towards higher frequency in increasing temperature. 相似文献
117.
118.
Felora Heshmatpour Saeed Rayati Mona Afghan Hajiabbas Bernhard Neumüller 《无机化学与普通化学杂志》2011,637(9):1224-1228
A tetrahedrally‐distorted square‐planar nickel(II) complex of tetradentate Schiff base ligand derived from 2‐hydroxypropiophenone and 2,2′‐dimethylpropandiamine [bis(2‐hydroxypropiophenone)2,2′‐dimethylpropylenediimine] ( H2L ) was prepared and used as catalyst for oxidation of styrene and α‐methyl styrene with tert‐butylhydroperoxide (TBHP). Oxidation of styrene with TBHP gave benzaldehyde and styrene oxide, but in the case of α‐methylstyrene a mixture of α‐methylstyrene oxide and acetophenone was obtained. The structure of nickel(II) complex ( NiL ) was determined by X‐ray crystallography. Crystal data for NiL at –173 °C: orthorhombic, space group P212121, a = 907.7(1), b = 1289.4(1), c = 1752.4(1) pm, Z = 4, R1 = 0.0454. 相似文献
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120.