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71.
S?ren Krach Isabelle Blümel Dominic Marjoram Tineke Lataster Lydia Krabbendam Jochen Weber Jim van Os Tilo Kircher 《BMC neuroscience》2009,10(1):1-11
Background
Oxidative stress plays a key role in the neuropathogenesis of Human Immunodeficiency Virus-1 (HIV-1) infection causing apoptosis of astroglia cells and neurons. Recent data have shown that oxidative stress is also responsible for the acceleration of human fibroblast telomere shortening in vitro. In the present study we analyzed the potential relations occurring between free radicals formation and telomere length during HIV-1 mediated astroglial death.Results
To this end, U373 human astrocytoma cells have been directly exposed to X4-using HIV-1IIIB strain, for 1, 3 or 5 days and treated (where requested) with N-acetylcysteine (NAC), a cysteine donor involved in the synthesis of glutathione (GSH, a cellular antioxidant) and apoptosis has been evaluated by FACS analysis. Quantitative-FISH (Q-FISH) has been employed for studying the telomere length while intracellular reduced/oxidized glutathione (GSH/GSSG) ratio has been determined by High-Performance Liquid Chromatography (HPLC). Incubation of U373 with HIV-1IIIB led to significant induction of cellular apoptosis that was reduced in the presence of 1 mM NAC. Moreover, NAC improved the GSH/GSSG, a sensitive indicator of oxidative stress, that significantly decreased after HIV-1IIIB exposure in U373. Analysis of telomere length in HIV-1 exposed U373 showed a statistically significant telomere shortening, that was completely reverted in NAC-treated U373.Conclusion
Our results support the role of HIV-1-mediated oxidative stress in astrocytic death and the importance of antioxidant compounds in preventing these cellular damages. Moreover, these data indicate that the telomere structure, target for oxidative damage, could be the key sensor of cell apoptosis induced by oxidative stress after HIV infection. 相似文献72.
73.
Equilibrium sorption of methionine on carboxyl cation exchangers from solutions of various acidities
D. V. Ovsyannikova L. P. Bondareva V. F. Selemenev S. I. Karpov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2009,83(5):839-843
The influence of the acidity of solutions of methionine on methionine interaction with KB-2 and KB-4 carboxyl cation exchangers
in the protonated and deprotonated forms was studied by the calorimetric, sorption, and spectroscopic methods. It was found
that nonexchange methionine absorption occurred from acid solutions, and mixed ion exchange and nonexchange sorption, from
alkaline solutions. The enthalpies of sorption of methionine at various external solution pH values were determined.
Original Russian Text ? D.V. Ovsyannikova, L.P. Bondareva, V.F. Selemenev, S.I. Karpov, 2009, published in Zhurnal Fizicheskoi
Khimii, 2009, Vol. 83, No. 5, pp. 961–966. 相似文献
74.
P. Sangeetha P. Jayaprakash M. Nageshwari M. Peer Mohamed G. Vinitha M. Lydia Caroline 《Chinese Journal of Physics (Taipei)》2018,56(2):721-739
We synthesized noncentrosymmetric single crystals of L-phenylalanine nitrate (LPN) and tris L-(phenylalanine) L-phenylalaninium nitrate (TPLPN) by slow solvent evaporation technique. Both crystallized in monoclinic system with different acentric space groups namely P21 (LPN) and C2 (TPLPN) respectively. The IR and Raman spectral investigation was done for LPN and TPLPN and discussed. The UV-vis-studies accomplished the excitation wavelength of the grown crystals suitable to exhibit second harmonic generation signal. From the absorption data, remarkable optical properties such as direct band gap energy, Urbach energy, extinction coefficient were evaluated. The mechanical strength of the grown crystal was examined by Vickers micro hardness test. The temperature of decomposition was confirmed by TG/DSC analysis. Fluorescence emission spectrum of LPN and TPLPN were recorded and lifetime was also studied. The dielectric constant and dielectric loss of LPN and TPLPN has been determined as a function of frequency and temperature. Also the surface topologies of the crystallized salts were assessed by SEM studies. The third-order nonlinearities of LPN and TPLPN were determined by Z-scan technique with Nd: YAG at 532?nm and thereby from closed and open Z-scan data, third-order susceptibilities were calculated to be χ(3)?=?8.826?×?10?6 esu for LPN and χ(3)?=?2.552?×?10?7 esu for TPLPN. 相似文献
75.
Alonso E Fuwa H Vale C Suga Y Goto T Konno Y Sasaki M LaFerla FM Vieytes MR Giménez-Llort L Botana LM 《Journal of the American Chemical Society》2012,134(17):7467-7479
Gambierol is a potent neurotoxin that belongs to the family of marine polycyclic ether natural products and primarily targets voltage-gated potassium channels (K(v) channels) in excitable membranes. Previous work in the chemistry of marine polycyclic ethers has suggested the critical importance of the full length of polycyclic ether skeleton for potent biological activity. Although we have previously investigated structure-activity relationships (SARs) of the peripheral functionalities of gambierol, it remained unclear whether the whole polycyclic ether skeleton is needed for its cellular activity. In this work, we designed and synthesized two truncated skeletal analogues of gambierol comprising the EFGH- and BCDEFGH-rings of the parent compound, both of which surprisingly showed similar potency to gambierol on voltage-gated potassium channels (K(v)) inhibition. Moreover, we examined the effect of these compounds in an in vitro model of Alzheimer's disease (AD) obtained from triple transgenic (3xTg-AD) mice, which expresses amyloid beta (Aβ) accumulation and tau hyperphosphorylation. In vitro preincubation of the cells with the compounds resulted in significant inhibition of K(+) currents, a reduction in the extra- and intracellular levels of Aβ, and a decrease in the levels of hyperphosphorylated tau. In addition, pretreatment with these compounds reduced the steady-state level of the N-methyl-D-aspartate (NMDA) receptor subunit 2A without affecting the 2B subunit. The involvement of glutamate receptors was further suggested by the blockage of the effect of gambierol on tau hyperphosphorylation by glutamate receptor antagonists. The present study constitutes the first discovery of skeletally simplified, designed polycyclic ethers with potent cellular activity and demonstrates the utility of gambierol and its synthetic analogues as chemical probes for understanding the function of K(v) channels as well as the molecular mechanism of Aβ metabolism modulated by NMDA receptors. 相似文献
76.
The atmospherically relevant reactions between dimethyl selenide (DMSe) and the molecular halogens (X(2) = Cl(2), Br(2), and I(2)) have been studied with ab initio calculations at the MP2/aug-cc-pVDZ level of theory. Geometry optimization calculations showed that the reactions proceed from the reagents to the products (CH(3)SeCH(2)X + HX) via three minima, a van der Waals adduct (DMSe:X(2)), a covalently bound intermediate (DMSeX(2)), and a product-like complex (CH(3)SeCH(2)X:HX). The computed potential energy surfaces are used to predict what molecular species are likely to be observed in spectroscopic experiments such as gas-phase photoelectron spectroscopy and infrared matrix isolation spectroscopy. It is concluded that, for the reactions of DMSe with Cl(2) and Br(2), the covalent intermediate should be seen in spectroscopic experiments, whereas, in the DMSe + I(2) reaction, the van der Waals adduct DMSe:I(2) should be observed. Comparison is made with previous related calculations and experiments on dimethyl sulfide (DMS) with molecular halogens. The relevance of the results to atmospheric chemistry is discussed. The DMSeX(2) and DMSe:X(2) intermediates are likely to be reservoirs of molecular halogens in the atmosphere which will lead on photolysis to ozone depletion. 相似文献
77.
Aline Maisse-François Laurine Azor Anne-Laure Schmitt Ariane Coquel Lydia Brelot Richard Welter Stéphane Bellemin-Laponnaz Samuel Dagorne 《Journal of organometallic chemistry》2012,696(26):4248-4256
The present contribution describes the synthesis and structural characterization of structurally diverse organoaluminum species supported by variously substituted aminophenolate-type ligands: these Al complexes are all derived from the reaction of AlMe3 with aminophenols 2-CH2NH(R)-C6H3OH (1a, R = mesityl (Mes); 1b, R = 2,6-di-isopropylphenyl (Diip)) and 2-CH2NH(R)-4,6-tBu2-C6H2OH (1c, R = Mes; 1d, R = Diip). The low temperature reaction of AlMe3 with 1a–b readily affords the corresponding Al dimeric species [μ-η1,η1-N,O-{2-CH2NH(R)-C6H4O}]2Al2Me4 (2a–b), consisting of twelve-membered ring aluminacycles with two μ-η1,η1-N,O-aminophenolate units, as determined by X-ray crystallographic studies. Heating a toluene solution of 2a (80 °C, 3 h) affords the quantitative and direct formation of the dinuclear aluminium complex Al[η2-N; μ,η2-O-{2-CH2N(Mes)-C6H4O}](AlMe2) (4a) while species 2b, under the aforementioned conditions, affords the formation of the Al dimeric species [η2-N,O-{2-CH2N(Dipp)-C6H4O}AlMe]2 (3b), as deduced from X-ray crystallography for both 3b and 4a. In contrast, the reaction of bulky aminophenol pro-ligands 1c–d with AlMe3 afford the corresponding monomeric Al aminophenolate chelate complexes η2-N,O-{2-CH2NH(R)-4,6-tBu2-C6H2O}AlMe2 (5c–d; R = Mes, Diip; Scheme 3) as confirmed by X-ray crystallographic analysis in the case of 5d. Subsequent heating of species 5c–d yields, via a methane elimination route, the corresponding Al-THF amido species η2-N,O-{2-CH2N(R)-4,6-tBu2-C6H2O}Al(Me)(THF) (6c–d; R = Mes, Diip). Compounds 6c–6d, which are of the type {X2}Al(R)(L) (L labile), may well be useful as novel well-defined Lewis acid species of potential use for various chemical transformations. Overall, the sterics of the aminophenol backbone and, to a lesser extent, the reaction conditions that are used for a given ligand/AlMe3 set essentially govern the rather diverse “structural” outcome in these reactions, with a preference toward the formation of mononuclear Al species (i.e. species 5c–d and 6c–d) as the steric demand of the chelating N,O-ligand increases. 相似文献
78.
Baxter PN Al Ouahabi A Gisselbrecht JP Brelot L Varnek A 《The Journal of organic chemistry》2012,77(1):126-142
An isomeric series of dehydro[m]pyrido[n]annulenes incorporating strained 1,4-buta-1,3-diyne units have been synthesized, where m = 2, n = 14 (1a-d); m = 2, n = 15 (2a,b); and m = 3, n = 15 (3). The number of pyridine rings and annulene ring π-electrons are denoted by m and n, respectively. The X-ray crystal structures of 1b and 1c confirmed their cyclic formulation. All macrocycles were found to be luminescent chromophores with differing isomer-dependent proton and metal ion-sensory emission responses, which appear collectively as analyte-specific color patterns. Within the series studied, 1a was singular in displaying the highest luminescence quantum yield and sharing the strongest emission energy and molar absorption changes upon protonation and Hg(II) binding. Spectroscopic and electrochemical results were supported by density functional theory calculations in showing 1a, 2a, and 3 to be low bandgap materials with lowest unoccupied molecular orbitals delocalized over the 1,4-di(pyridin-4-yl)buta-1,3-diyne bridges that provide a pathway for electronic communication between the nitrogens. Overall, the investigations suggest that 1a, 2a, and 3 would be excellent ligands for the construction of novel conjugated hybrid metallosupramolecular nanostructures, polymers, and ion-sensory systems. 相似文献
79.
Rhodium-catalyzed reactions of 2-aryl-substituted 2H-chromenes with α-diazo esters prepared from dimethyl and tert-butyl methyl malonates were investigated, and the results were compared with reactions carried out with phenyliodonium ylides prepared from the same esters. The phenyliodonium ylide prepared from dimethyl malonate was found to give superior yields of cyclopropane products compared to the corresponding α-diazo equivalent. However, this result was reversed with tert-butyl methyl malonate when Rh2(S-TBSP)4 was used to decompose the diazo compound. All reactions gave 1,1-cyclopropane diesters as single diastereomers. 相似文献
80.
The sorption and structural parameters and thermal stability of montmorillonite pillared by Cr(III) polyhydroxocomplexes and heteronuclear Cr(III)–Cu(II) polyhydroxocomplexes were investigated. It was shown that the introduction of intercalating Cr(III) and Cr(III)–Cu(II) agents into the montmorillonite increased the value of the first basal reflection (d
001) up to 1.85 nm in the first case and up to 1.98 nm, in the second. The dependence of the values of d
001and specific surface area on the OH–/Cr3+ratio was found, which is retained during the calcination of the samples up to 500–800°C. The sorption ability of the prepared samples with respect to acetone, ethanol, benzene, toluene, and water was investigated. 相似文献