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41.
Boris F. Minaev Valentina A. Minaeva Yurij V. Evtuhov 《International journal of quantum chemistry》2009,109(3):500-515
Intensity distribution in rotational lines of the 0–0 band of the a1Δg → X3Σ transition in the oxygen molecule at λ = 1270 nm is studied by quadratic response (QR) method in a framework of multiconfiguration self‐consisted field (MCSCF) theory. The distance dependence of the transition magnetic moment and the (0–0)/(0–1) bands intensity ratio are calculated. A short review of previous theory of the red and infrared atmospheric oxygen bands and of their enhancement by collisions is presented to analyze and compare the new results. Enhancement of these bands in O2 collisions with Li2 and N2 molecules is calculated by QR method. Diamagnetic species simulate solvent molecules of different optical polarizability. Specific influence of collisions on vibronic bands is stressed. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 相似文献
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Inna P. Tsypysheva Alexander N. Lobov Alena V. Kovalskaya Valentina I. Vinogradova Kyrill Yu. Suponitsky Sergey L. Khursan Marat S. Yunusov 《Tetrahedron: Asymmetry》2013,24(20):1318-1323
The Diels–Alder adducts of the quinolizidine alkaloids N-methylcytisine, (?)-leontidine, and (?)-thermopsine with N-phenylmaleimide have been synthesized. The structures and absolute configurations of the new asymmetric centers of the products were determined by NMR spectroscopy experiments, QC-calculations, and X-ray data. 相似文献
45.
Rosário Monteiro Gil Faria Manuela Meireles Luísa Correia‐Sá Diana Teixeira Ana Faria Conceição Calhau Valentina F. Domingues Cristina Delerue‐Matos 《Biomedical chromatography : BMC》2012,26(12):1494-1501
Scientific evidence has shown an association between organochlorine compounds (OCC) exposure and human health hazards. Concerning this, OCC detection in human adipose samples has to be considered a public health priority. This study evaluated the efficacy of various solid‐phase extraction (SPE) and cleanup methods for OCC determination in human adipose tissue. Octadecylsilyl endcapped (C18‐E), benzenesulfonic acid modified silica cation exchanger (SA), poly(styrene‐divinylbenzene (EN) and EN/RP18 SPE sorbents were evaluated. The relative sample cleanup provided by these SPE columns was evaluated using gas chromatography with electron capture detection (GC–ECD). The C18‐E columns with strong homogenization were found to provide the most effective cleanup, removing the greatest amount of interfering substance, and simultaneously ensuring good analyte recoveries higher than 70%. Recoveries > 70% with standard deviations (SD) < 15% were obtained for all compounds under the selected conditions. Method detection limits were in the 0.003–0.009 mg/kg range. The positive samples were confirmed by gas chromatography coupled with tandem mass spectrometry (GC‐MS/MS). The highest percentage found of the OCC in real samples corresponded to HCB, o,p′‐DDT and methoxychlor, which were detected in 80 and 95% of samples analyzed respectively. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
46.
Mikhail I. Smushkin Valentina G. Kharchenko Boris I. Drevko 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1):621-624
It is shown using 1H NMR spectroscopy that 2,4,6-triphenyl-4H-seleno(thio)pyrans can be isomerized into 2H-isomers by the action of lithium perchlorate or lithium chloride in DMF or only by DMF. The reaction time is found to depend on the Lewis acidity of used salt. It is supposed that isomerization in presence of Lewis acids proceeds as endocyclic 1,3-proton transfer or as a series of two 1,2-hydride shifts. 相似文献
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Valeria van Axel Castelli Antonella Dalla Cort Luigi Mandolini Valentina Pinto David N. Reinhoudt Fabrizio Ribaudo 《Supramolecular chemistry》2013,25(2-3):211-219
The complexation of the salophen-uranyl metallocleft 2 and of its half-cleft analogue 3 with enones and other carbonyl compounds was assessed in chloroform by UV-Vis titration and, occasionally, by FT-IR measurements. Complexes with receptors 2 and 3 are in all cases more stable than those with the control unsubstituted uranyl-salophen 1 , showing that in addition to the primary binding force provided by coordination of the carbonyl oxygen to the uranium, a significant driving force for complexation, typically in the range of 2-3 kcal/mol, results from van der Waals interactions of the guest with the aromatic walls. Replacement of the phenyl group in 3 with larger aromatic residues to give 4 and 5 , led to enhanced complex stabilities, due to more extended contact surfaces between host and guest. 相似文献
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Valentina Ljubomirova Rumyana Djingova Johannes T. van Elteren Marjan Veber Tomasz Kowalkowski Boguslaw Buszewski 《International journal of environmental analytical chemistry》2013,93(7):499-512
A sequential extraction procedure (three-step), proposed by the Standards, Measurements and Testing Programme (formerly BCR) of the European Union, was applied to street dust and spiked soil samples for the determination of PGEs. Analyses were carried out using inductively coupled plasma-mass spectrometry (ICP-MS). The results indicate that up to 5% from Pt, 70% from Pd and 14% from Rh are in mobile forms in street dust. The results for the soil samples spiked with crushed catalytic converter are significantly lower indicating that PGEs are oxidised more efficiently in natural conditions. Additionally Pt and Pd bound to humic acids were investigated. 相似文献
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Prof. Tiziana Benincori Dr. Valentina Bonometti Dr. Roberto Cirilli Prof. Patrizia R. Mussini Dr. Andrea Marchesi Prof. Marco Pierini Dr. Tullio Pilati Dr. Simona Rizzo Prof. Francesco Sannicolò 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(1):165-181
A series of tris‐aryl phosphane oxides existing as residual enantiomers or diastereoisomers with substituents on the aryl rings differing in size and electronic properties were synthesized and characterized. Their electronic properties were evaluated on the basis of their electrochemical oxidation and reduction potentials together with those of the corresponding “blade bromides” (i.e., the naphthalene derivatives displaying the same substitution pattern of the tris‐naphthyl phosphane oxide blades, with a bromo substituent where the phosphorus atom is located) determined by CV. The residual stereoisomeric phosphane oxides were isolated in a stereochemically pure state and were found to be highly configurationally stable at room temperature (stereoisomerization barriers of about 27 kcal mol?1). The chiroptical properties of the residual stereoisomers and the assignments of absolute configuration are discussed. The configurational stability of residual tris‐aryl phosphane oxides was found to be scarcely influenced by the electronic properties of the substituents present on the aromatic rings constituting the blades, while steric effects play the most relevant role. Detailed theoretical calculations are in agreement with the experimental results and also contribute to a rational interpretation of the stereodynamics of these systems. 相似文献