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101.
Mamoci E Cavoski I Simeone V Mondelli D Al-Bitar L Caboni P 《Molecules (Basel, Switzerland)》2011,16(3):2609-2625
F. communis and D. viscosa are perennial Mediterranean weeds that have been used for different therapeutic purposes in traditional pharmacopeia. Plant extracts were obtained from air dried D. viscosa young shoots (DvA) and F. communis aerial part (FcA) and roots (FcR) with n-hexane. The chemical compositions of the extracts were analyzed by HPLC-DAD, LC-MS (ESI) and LC-Q-TOF techniques. Two sesquiterpene lactones (inuviscolide, tomentosin) and three sesquiterpene acids (costic acid, hydroxycostic acid, ilicic acid) were identified from the D. viscosa extract, while in F. communis extracts three daucane sesquiterpenes (acetoxyferutinin, oxojaeskeanadioyl anisate, fertidin) and one coumarin (ferulenol) derivates were found. Biological activities of plant extracts were studied in in vitro experiments on the colonies and conidia of Botryotinia fuckeliana, Penicillium digitatum, P. expansum, Monilinia laxa, M. fructigena and Aspergillus spp. Extracts showed varying degree of antifungal activities on colony growth and conidia germination. The extract from FcA showed the least effect, while DvA extract had the strongest fungitoxic effects. FcR extract presented a fungitoxic effect on the colony growth, but it was not able to inhibit the conidia germination. These distinctions can be attributed to the differences in chemical composition of plant extracts. 相似文献
102.
The mechanism of the degenerate 1,5-hydride shift in 2,6-dimethyl-2-heptyl cations has been investigated using ab initio MP2 and density functional theory (DFT) hybrid (B3LYP) calculations. The potential-energy profile for the 1,5-hydride shift consists of three minima corresponding to two equivalent acyclic carbocations and one symmetrically mu-hydrido-bridged carbocation, while two equivalent unsymmetrically hydrido-bridged carbocations were located as transition-state structures. The calculated relative energy differences between acyclic carbocations and symmetrically mu-hydrido-bridged structure are significantly affected by introduction of alkyl and (CH2)n-substituents at the C4 position of the 2,6-dimethyl-2-heptyl cation structure. DFT self-consistent isodensity polarizable continuum method (SCI-PCM) and MP2 PCM continuum methods have been used to calculate the effect of solvation on geometries and relative energies of the species involved in the 1,5-hydride shift. It is found that relative energies of acyclic and mu-hydrido-bridged carbocation structures as well as the energy barriers for 1,5-hydride shifts are in accord with experimental data if solvation effects are taken into account. 相似文献
103.
104.
In this paper we report the first chemoselective asymmetric hydrogenation of (1-bromo-1-alkenyl)boronic esters, which constitutes a new route to (α-bromoalkyl)boronic esters. The study demonstrates that excellent chemoselectivities along with full conversions can be obtained for hydrogenation of alkyl substituted derivatives with iridium–PˆN complexes. Moreover, acyclic alkyl derivatives afford (α-bromoalkyl)boronic esters in good enantioselectivities ranging from 64 to 73% ee. A cyclic alkyl derivative was obtained only in a nearly racemic form. The (1-bromo-1-alkenyl)boronic esters appear to be less reactive towards homogenous hydrogenation conditions than their chloro analogues as demonstrated by the higher catalyst loadings required to achieve full conversions for alkyl derivatives and lower conversions observed for the aryl substituted derivatives. 相似文献
105.
Dr. Martin Kamlar Dr. Ivana Císařová Prof. Jan Veselý 《European journal of organic chemistry》2023,26(32):e202300400
We report a Brønsted acid-catalyzed synthesis of tetrasubstituted allenyl compounds decorated with heterocyclic sulfenyl group. The reaction proceeds readily from available propargylic alcohols in the presence of pentacarboxycyclopenatadienes (PCCPs) as organocatalysts. The developed strategy provides tetrasubstituted allene derivatives in high yields (from 55 to 98 %) and under mild reaction conditions. 相似文献
106.
Ivana Pultarova 《Applications of Mathematics》2005,50(3):323-329
We estimate the constant in the strengthened Cauchy-Bunyakowski-Schwarz inequality for hierarchical bilinear finite element spaces and elliptic partial differential equations with coefficients corresponding to anisotropy (orthotropy). It is shown that there is a nontrivial universal estimate, which does not depend on anisotropy. Moreover, this estimate is sharp and the same as for hierarchical linear finite element spaces.This research was supported by the Grant Agency of Czech Republic under the contract No. 201/02/0595. 相似文献
107.
Ivana Lula Maria F. Gomes Dorila Piló-Veloso Antonio L.O. de Noronha Hélio A. Duarte Robson A.S. Santos Rubén D. Sinisterra 《Journal of inclusion phenomena and macrocyclic chemistry》2006,56(3-4):293-302
In the present work, inclusion complexes of spironolactone (SP) with β-cyclodextrin (β-CD) in solid phase and aqueous solution were studied by solubility methods, NMR spectroscopy and thermal analysis. The results
showed different kinds of complexations when freeze-drying and kneading methods were used. The freeze-drying product (1:1,
SP:β-CD) showed lower degree of complexation and stability than the (1:2, SP:β-CD) compound obtained by kneading method. The spironolactone molecule was also studied by NMR spectroscopy at 400 MHz. The
chemical shifts of all spironolactone atoms and their inclusion compounds were assigned. Extensive use of 1D and 2D NMR techniques,
including ROESY experiment, allowed verifying the position of the spironolactone molecule inside the cyclodextrin cavity in
both situations. In addition, DFTB-SCC quantum mechanical calculations of the inclusion compounds were performed. The predicted
structural properties are in good agreement with ROESY NMR results. 相似文献
108.
The crystal structure of the cyclopentadienyl vanadocene complex (η5‐C5H5)2V(N3)2 was determined. The molecule has a typical bent metallocene structure in which two η5‐bonded cyclopentadienyl rings and two nitrogen atoms of azide ligands occupy the pseudotetrahedral coordination sites around the vanadium(IV) center. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
109.
The stabilization method provides an efficient approach to many problems in atomic and molecular dynamics. Real avoided crossings
and smoothing techniques provide the relevant information to compute real density of states. The aim of this letter is to
present an extension of the stabilization method that allows for a direct determination of full Green functions and resonance
energies. The method is based on the use of optical potentials and perturbation theory. Real avoided crossings of the original
stabilization method become complex and resonance energies appear to stabilize in the complex-energy plane. A numerical illustration
is presented for a simple model of shape resonance. Accurate results are obtained with a small number of real square-integrable
functions as in the original stabilization method. The computational efficiency of the approach and its generality are emphasized. 相似文献
110.
The crystal structure of the first cyclopentadienyl vanadium(IV) pseudohalide complex, (η5‐C5H4CH3)2V(NCO)2, was determined. The molecule has a typical bent metallocene structure in which two η5‐bonded methyl‐cyclopentadienyl rings and two nitrogen atoms of cyanato ligands occupy the pseudotetrahedral coordination sites around the vanadium(IV) center. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献