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41.
Regioselective generation of the C(2)-carbocation a of tricyclo[4.2.2.01,5]decane ( 1 ) by treatment of both corresponding epimeric alcohols 5 and 6 with BF3 and trapping the rearranged tricyclo[5.3.0.04,8]decan-7-yl carbocation b with Et3SiH as hydride-ion donor (ionic hydrogenation) gives the corresponding hydrocarbon 3 as sole product in almost quantitative yield. The latter is a known intermediate in the Lewis-acid-catalyzed rearrangement of 1 to adamantane ( 4 ). 相似文献
42.
Electrical conductivity and thermoelectric power of liquid-quenched Bi-Sb tapes with Sb concentration in the range 8 to 18
at.% are reported between 77K and room temperature. Analysis of the data shows that the total electrical conductivity of these
tapes is determined by a temperature-independent component due to band conduction, and a strongly temperature-dependent part
due to carrier transport across or through the defect states. These defect states which appear to originate from structural
imperfections and disorders due to rapid cooling, are formed close to the mobility edge within a small energy range. 相似文献
43.
Summary We study the subband energies in quantum wells and quantum wires in the presence of a parallel magnetic field in non-parabolic
semiconductors, on the basis of a generalized dispersion relation considering all types of anisotropies of the energy-band
parameters within the framework ofk·p formalism, by formulating the respective electron energy spectra. It is found, by takingn-Cd3As2 as an example, that the subband energies are greater for quantum wires and smaller for quantum wells, respectively. The magnetic
field diminishes the above values and the corresponding well-known results for quantum-confined parabolic semiconductors have
also been obtained from our generalized expressions under certain limiting conditions. 相似文献
44.
An attempt is made to formulate the Einstein relation for the diffusivity-mobility ratio of the carriers in degenerate semiconductors having Kane-type energy bands in the presence of a quantizing magnetic field, taking degenerate n-InAs as an example. It is found on the basis of the three-band Kane model, which is the most valid model for n-InAs, that the same ratio oscillates with changing magnetic field only under degenerate conditions and remains unaffected otherwise. The corresponding results for parabolic semiconductors are also obtained from the expressions derived. 相似文献
45.
Two alternate synthetic routes to endo-6-aryl-2-oxobicyclo 3.3.1 nonan [3a-d] by sterespecific catalytic hydrogenetion of the easily accessible 6-arylbicyclo 3.3.1 nona-3,6-dien-2-ones [2a-d], and regioselective oomologation of endo-2-aryl-6-oxobicycle 3.2.1 octanes [4a-d] are described. 相似文献
46.
Differently substituted cyclopropylcarbinols underwent ring cleavage with easily accessible cyanuric chloride–N,N-dimethylformamide adduct to produce homoallylic chlorides or dienes depending on the nature and location of the substituents. A mechanistic explanation of the aforesaid observations has been provided. A promising antioxidant compound was prepared following this protocol and studied against Fenton’s reagent. This methodology was utilized to construct hitherto unreported vinylcyclopropane frameworks bearing homoallylic chloride and diene moieties. 相似文献
47.
Moumita Majumdar Arup Sinha Tapas Ghatak Sanjib K. Patra Nabanita Sadhukhan S. M. Wahidur Rahaman Jitendra K. Bera Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(8):2574-2585
The complete sequence of reactions in the base‐promoted reduction of [{RuII(CO)3Cl2}2] to [RuI2(CO)4]2+ has been unraveled. Several μ‐OH, μ:κ2‐CO2H‐bridged diruthenium(II) complexes have been synthesized; they are the direct results of the nucleophilic activation of metal‐coordinated carbonyls by hydroxides. The isolated compounds are [Ru2(CO)4(μ:κ2‐C,O‐CO2H)2(μ‐OH)(NPF‐Am)2][PF6] ( 1 ; NPF‐Am=2‐amino‐5,7‐trifluoromethyl‐1,8‐naphthyridine) and [Ru2(CO)4(μ:κ2‐C,O‐CO2H)(μ‐OH)(NP‐Me2)2][BF4]2 ( 2 ), secured by the applications of naphthyridine derivatives. In the absence of any capping ligand, a tetranuclear complex [Ru4(CO)8(H2O)2(μ3‐OH)2(μ:κ2‐C,O‐CO2H)4][CF3SO3]2 ( 3 ) is isolated. The bridging hydroxido ligand in 1 is readily replaced by a π‐donor chlorido ligand, which results in [Ru2(CO)4(μ:κ2‐C,O‐CO2H)2(μ‐Cl)(NP‐PhOMe)2][BF4] ( 4 ). The production of [Ru2(CO)4]2+ has been attributed to the thermally induced decarboxylation of a bis(hydroxycarbonyl)–diruthenium(II) complex to a dihydrido–diruthenium(II) species, followed by dinuclear reductive elimination of molecular hydrogen with the concomitant formation of the RuI? RuI single bond. This work was originally instituted to find a reliable synthetic protocol for the [Ru2(CO)4(CH3CN)6]2+ precursor. It is herein prescribed that at least four equivalents of base, complete removal of chlorido ligands by TlI salts, and heating at reflux in acetonitrile for a period of four hours are the conditions for the optimal conversion. Premature quenching of the reaction resulted in the isolation of a trinuclear RuI2RuII complex [{Ru(NP‐Am)2(CO)}{Ru2(NP‐Am)2(CO)2(μ‐CO)2}(μ3:κ3‐C,O,O′‐CO2)][BF4]2 ( 6 ). These unprecedented diruthenium compounds are the dinuclear congeners of the water–gas shift (WGS) intermediates. The possibility of a dinuclear pathway eliminates the inherent contradiction of pH demands in the WGS catalytic cycle in an alkaline medium. A cooperative binuclear elimination could be a viable route for hydrogen production in WGS chemistry. 相似文献
48.
We present a simplified theoretical formulation of the thermoelectric power (TP) under magnetic quantization in quantum wells (QWs) of nonlinear optical materials on the basis of a newly formulated magneto-dispersion law. We consider the anisotropies in the effective electron masses and the spin–orbit constants within the framework of k.p formalism by incorporating the influence of the crystal field splitting. The corresponding results for III–V materials form a special case of our generalized analysis under certain limiting conditions. The TP in QWs of Bismuth, II–VI, IV–VI and stressed materials has been studied by formulating appropriate electron magneto-dispersion laws. We also address the fact that the TP exhibits composite oscillations with a varying quantizing magnetic field in QWs of n- Cd3As2, n- CdGeAs2, n-InSb, p-CdS, stressed InSb, PbTe and Bismuth. This reflects the combined signatures of magnetic and spatial quantizations of the carriers in such structures. The TP also decreases with increasing electron statistics and under the condition of non-degeneracy, all the results as derived in this paper get transformed into the well-known classical equation of TP and thus confirming the compatibility test. We have also suggested an experimental method of determining the elastic constants in such systems with arbitrary carrier energy spectra from the known value of the TP. 相似文献
49.
Ajoy Ghatak 《Indian Journal of Physics》2010,84(8):1075-1082
The one dimensional wave equation
$
\frac{{d^2 \Psi }}
{{dx^2 }} + \Gamma ^2 (x)\Psi (x) = 0
$
\frac{{d^2 \Psi }}
{{dx^2 }} + \Gamma ^2 (x)\Psi (x) = 0
相似文献
50.
UV–vis absorption, steady state and time resolved fluorescence studies on the photo physical behavior of indomethacin, a traditional NSAID in binary water ethanol mixtures have been presented. Our results reveal that indomethacin can sense the micro heterogeneity in the binary mixtures forming ground state fluorescent complex with two predominant types of clusters viz. ethanol self-association clusters and hydrogen bonded water clusters. 相似文献
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