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441.
Murahashi T Mino Y Chiyoda K Ogoshi S Kurosawa H 《Chemical communications (Cambridge, England)》2008,(34):4061-4063
Two haptotropic isomers of [Pd(3)(mu(3)-DMVC)(2)(CH(3)CN)(2)][BF(4)](2) (DMVC = 1,2-di-(E)-carbomethoxyvinylcyclopentene) were structurally determined by X-ray crystallographic analyses; a monoclinic crystal contained a symmetric sandwich complex (mu(3)-eta(2):eta(2):eta(2)-coordination of DMVC ligands) and a triclinic crystal contained an unsymmetric sandwich complex (mu(3)-eta(2):eta(3):eta(1)-coordination of DMVC ligands), where the latter are connected to each other by C-HO hydrogen bonds. 相似文献
442.
Tatsumi Y Murahashi T Okada M Ogoshi S Kurosawa H 《Chemical communications (Cambridge, England)》2008,(4):477-479
A surprisingly stable homoleptic Pd(0)(4) chain complex of non-activated olefins was isolated and structurally characterized by X-ray crystallographic analysis, and the unique structure and bonding are compared to those of the corresponding dicationic [Pd(4)](2+) chain sandwich complex. 相似文献
443.
Sakaguchi K Ayabe M Watanabe Y Okada T Kawamura K Shiada T Ohfune Y 《Organic letters》2008,10(23):5449-5452
The stereoselective total synthesis of the marine alkaloid (-)-amathaspiramide F (1) was achieved from the alpha-hydoxy-alpha-ethynylsilane 2. The crucial steps in this synthesis involved not only the enolate Claisen rearrangement of the alpha-acyloxy-alpha-alkenylsilane 6 for the construction of the nitrogen-containing quaternary carbon center, but also the chemoselective formation of the azaspirohemiaminal 12 using heptamethyldisilazane as the methylamine equivalent and the regioselective dibromination of the phenol moiety of 12 using n-Bu(4)NBrCl(2). 相似文献
444.
Hollow piezoelectric cylindrical shell transducers may be made directional for underwater acoustic applications by the use of suitable acoustical baffles and the operational bandwidth may be extended by using multiple resonant modes. A theoretical and experimental investigation was performed for circumferentially baffled piezoelectric cylindrical shell transducers operating in the zero and one modes of extensional vibration. The frequency responses and directivity patterns were analyzed under various conditions of energizing separate halves of electrodes. It was found that the broadest frequency response with nearly constant beamwidth can be obtained when the two halves of the piezoelectric ring are electromechanically excited 90 deg out-of-phase. The experimental results obtained with a proof-of-concept transducer were in good agreement with the theoretical predictions. 相似文献
445.
446.
Tetsuro Yuzawa Chuichi Watanabe Shin Tsuge Robert R. Freeman Ron Matherly 《Journal of chromatography. A》2009,1216(27):5292-5295
The determination of trace organophosphonates which are used in cooling towers as a scale inhibitor usually involves extraction and/or concentration of the target components prior to analysis. The extracts are analyzed using chromatographic or spectroscopic methods. This methodology is not only cumbersome but also results in poor data quality. This work presents a novel approach for the rapid and sensitive determination of trace amounts of an organophosphonate: 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) in aqueous solution. This method is based upon reactive pyrolysis-GC/MS in the presence of tetramethyl ammonium hydroxide (TMAH). Approximately 10 μL of the aqueous sample containing a trace amount of HEDP and 1 μL of 25% a methanol TMAH solution was placed in the sample cup. The cup was then dropped into the furnace which was at 350 °C. The heat initiated the hydrolysis of the organophosphonate followed by the methylation of the hydrolysates. Trimethylphosphate (TMP) was detected by GC/MS. The level of TMP is related to the level of the phosphonate, HEDP in the aqueous sample. Using an external standard calibration curve, it was possible to make a rapid estimation of mg/L levels of organophosphate. 相似文献
447.
Jörg Richter Peter Holtappels Thomas Graule Tetsuro Nakamura Ludwig J. Gauckler 《Monatshefte für Chemie / Chemical Monthly》2009,140(9):985-999
Abstract This article focuses on perovskite materials for application as cathode material in solid oxide fuel cells. In order to develop
new promising materials it is helpful to classify already known perovskite materials according to their properties and to
identify certain tendencies. Thereby, composition-dependent structural data and materials properties are considered. Structural
data under consideration are the Goldschmidt tolerance factor, which describes the stability of perovskites with respect to
other structures, and the critical radius and lattice free volume, which are used as geometrical measures of ionic conductivity.
These calculations are based on the ionic radii of the constituent ions and their applicability is discussed. A potential
map of perovskites as a tool to classify simple ABO3 perovskite materials according to their electrical conduction behavior is critically reviewed as a structured approach to
the search for new cathode materials based on more complex perovskites with A and/or B-site substitutions. This article also
covers the approaches used to influence electronic and the ionic conductivity. The advantage of mixed ionic electronic conductors
in terms of the oxygen exchange reaction is addressed and their important properties, namely the oxygen-exchange coefficient
and the oxygen diffusion coefficient, and their effect on the oxygen reduction reaction are presented.
Graphical abstract
相似文献
448.
Two C-glucosides of resveratrol dimers (uliginoside A (1) and hemsleyanoloside B (2)) consisting of enantiomeric aglycones and two C-glucosides of resveratrol trimers (uliginosides B (3) and C (4)) consisting of diastereomeric aglycones were isolated from Shorea uliginosa (Dipterocarpaceae). These structures were elucidated by spectroscopic analysis including NMR experiments, and their absolute configurations were determined based on circular dichroism data. Resveratrol oligomers of C-glucosides with a 1,2-diaryldihydrobenzofuran ring are produced with specific biogenetic routes. 相似文献
449.
Novel sulfur-linked squaryl group-containing glutamate analogs were synthesized via addition and mono-substitution reactions of thiols to t-butyl methyl squarate (BMSQ: 7) in two steps. A glutamate analog prepared from Boc-l-Cys showed a potent binding affinity to KA/AMPA receptors. 相似文献
450.
Park MJ Fujitsuka M Kawai K Majima T 《Journal of the American Chemical Society》2011,133(39):15320-15323
Charge transfer in DNA is an essential process in biological systems because of its close relation to DNA damage and repair. DNA is also an important material used in nanotechnology for wiring and constructing various nanomaterials. Although hole transfer in DNA has been investigated by various researchers and the dynamic properties of this process have been well established, the dynamics of a negative charge, that is, excess electron, in DNA have not been revealed until now. In the present paper, we directly measured the rate of excess electron transfer (EET) through a consecutive thymine (T) sequence in nicked-dumbbell DNAs conjugated with a tetrathiophene derivative (4T) as an electron donor and diphenylacetylene (DPA) as an electron acceptor at both ends. The selective excitation of 4T by a femtosecond laser pulse caused the excess electron injection into DNA, and led to EET in DNA by a consecutive T-hopping mechanism, which eventually formed the DPA radical anion (DPA(?-)). The rate constant for the process of EET through consecutive T was determined to be (4.4 ± 0.3) × 10(10) s(-1) from an analysis of the kinetic traces of the ΔO.D. during the laser flash photolysis. It should be emphasized that the EET rate constant for T-hopping is faster than the rate constants for oxidative hole transfers in DNA (10(4) to 10(10) s(-1) for A- and G-hopping). 相似文献