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1.
Binding of bis-picolylamine-naphthalene diimide-peptide nucleic acid conjugates to complementary DNA is strongly dependent upon Zn2+; ultimately, hybridization is switched ON in the presence muM Zn2+. 相似文献
2.
19F and 31P NMR spectroscopy were used to study the kinetics of the hydrolysis of LiPF6 in the homogenous solvent system propylene carbonate (PC)—dimethyl carbonate (DMC)—H2O. It was found that the main products of the hydrolysis are HF, LiPO2F2 and Li2PO3F. The content of POF3 and PF5 was negligibly low. We set up a hypothesis that the main factor determining the rate of the process is the so-called ‘secondary’ catalytic effect, caused by solvated H+ ions. 相似文献
3.
The three-dimensional reference interaction site model (3D-RISM) theory is applied to the analysis of hydration effects on the partial molar volume of proteins. For the native structure of some proteins, the partial molar volume is decomposed into geometric and hydration contributions using the 3D-RISM theory combined with the geometric volume calculation. The hydration contributions are correlated with the surface properties of the protein. The thermal volume, which is the volume of voids around the protein induced by the thermal fluctuation of water molecules, is directly proportional to the accessible surface area of the protein. The interaction volume, which is the contribution of electrostatic interactions between the protein and water molecules, is apparently governed by the charged atomic groups on the protein surface. The polar atomic groups do not make any contribution to the interaction volume. The volume differences between low- and high-pressure structures of lysozyme are also analyzed by the present method. 相似文献
4.
The rare-earth intermetallic compounds (RE)12Co5Bi (RE = Y, Gd, Tb, Dy, Ho, Er, Tm) were prepared by arc-melting and annealing at 600 degrees C. These compounds extend the previously known (RE)6M2+xX1-x (M = Co, Ni; X = Ga, In, Sn, Pb) series with the Ho6Co2Ga-type structure to X = Bi. The crystal structure of Ho12Co5Bi was refined by the Rietveld method from powder X-ray diffraction data obtained using synchrotron radiation (Pearson symbol oI36, orthorhombic, space group Immm, Z = 2, a = 9.37598(14) A, b = 9.37871(14) A, c = 9.85465(13) A). Unlike other Ho6Co2Ga-type compounds, the 2a site in Ho12Co5Bi is exclusively occupied by Co atoms. Four-probe electrical resistivity measurements on sintered polycrystalline samples of (RE)12Co5Bi indicated metallic behavior. Magnetic measurements revealed behavior ranging from frequency-dependent maxima in the ac susceptibility for Y12Co5Bi to possible ferrimagnetic ordering for Gd12Co5Bi to antiferromagnetic ordering with metamagnetic transitions for the remaining compounds. As confirmed by band structure calculations using Y12Co5Bi as a model compound, Y-Y and Y-Co interactions are the most important bonding components, but matrix effects are likely responsible for anomalously short Co-Co contacts in the structure. 相似文献
5.
6.
Andriy B. Zaborovskiy Ruslan E. Prystansky Vitaliy I. Timokhin 《Journal of organometallic chemistry》2004,689(18):2912-2919
The interaction of (Me3Si)3SiH with O2 is known to afford (Me3SiO)2Si(H)SiMe3 in which the two oxygen atoms arise from the same oxygen molecule. In order to investigate the mechanism of this unusual reaction, the oxidation rates were measured in the temperature range 30-70 °C by following oxygen uptake in the presence and absence of hydroquinone as inhibitor. The rate constant for the spontaneous reaction of (Me3Si)3SiH with O2 was determined at 70 °C to be ∼3.5 × 10−5 M−1 s−1. A sequence of the propagation steps is proposed by combining the previous and present experimental findings with some theoretical results obtained at the semiempirical level. These calculations showed that the silylperoxyl radical (Me3Si)3SiOO undergoes three consecutive unimolecular steps to give (Me3SiO)2Si()SiMe3. Evidence has been obtained that the rate determining step is the rearrangement of silylperoxyl radical to a dioxirand-like pentacoordinated silyl radical. Our findings are of considerable importance for the understanding of the oxidation of hydrogen-terminated silicon surfaces. 相似文献
7.
Andriy V. Tkachuk 《Journal of solid state chemistry》2004,177(11):3939-3943
The isostructural ternary transition-metal silicides Zr3Mn4Si6 and Hf3Mn4Si6 can be prepared by direct reaction of the elemental components or by arc-melting. The single-crystal structure of Zr3Mn4Si6 was determined by X-ray diffraction (Pearson symbol tP104, tetragonal, space group P42/mbc, Z=8, , ). Zr3Mn4Si6 is isostructural to Nb3Fe3CrSi6 and contains an essentially ordered arrangement of the transition-metal atoms. Square antiprismatic clusters with Zr and Mn atoms at the corners and Si atoms at the center share opposite faces to form one-dimensional columns extending along the c direction. These columns occupy channels that are outlined by a framework of edge- and face-sharing MnSi6 octahedra. The extensive metal-metal interactions in the structure are complemented by Si-Si bonding in the form of dumbbells, linear chains, and zigzag chains. 相似文献
8.
Andrii Lozynskyi Julia Senkiv Iryna Ivasechko Nataliya Finiuk Olga Klyuchivska Nataliya Kashchak Danylo Lesyk Andriy Karkhut Svyatoslav Polovkovych Oksana Levytska Olexandr Karpenko Assyl Boshkayeva Galiya Sayakova Andrzej Gzella Rostyslav Stoika Roman Lesyk 《Molecules (Basel, Switzerland)》2022,27(21)
A series of 11-substituted 3,5,10,11-tetrahydro-2H-benzo[6,7]thiochromeno[2,3-d][1,3]thiazole-2,5,10-triones were obtained via hetero-Diels-Alder reaction of 5-alkyl/arylallylidene/-4-thioxo-2-thiazolidinones and 1,4-naphthoquinones. The structures of newly synthesized compounds were established by spectral data and a single-crystal X-ray diffraction analysis. According to U.S. NCI protocols, compounds 3.5 and 3.6 were screened for their anticancer activity; 11-Phenethyl-3,11-dihydro-2H-benzo[6,7]thiochromeno[2,3-d]thiazole-2,5,10-trione (3.6) showed pronounced cytotoxic effect on leukemia (Jurkat, THP-1), epidermoid (KB3-1, KBC-1), and colon (HCT116wt, HCT116 p53-/-) cell lines. The cytotoxic action of 3.6 on p53-deficient colon carcinoma cells was two times weaker than on HCT116wt, and it may be an interesting feature of the mechanism action. 相似文献
9.
Apparent two-dimensional behavior of TiO2 nanotubes revealed by light absorption and luminescence 总被引:1,自引:0,他引:1
Bavykin DV Gordeev SN Moskalenko AV Lapkin AA Walsh FC 《The journal of physical chemistry. B》2005,109(18):8565-8569
Optical absorption and photoluminescence (PL) properties of colloidal TiO(2) nanotubes, produced by the alkali hydrothermal method, were studied at room temperature in the range 300-700 nm. Nanotubes having an internal diameter in the range 2.5-5 nm have very similar optical properties, in contrast to the expected behavior for quasi-1-D systems. This is explained by the complete thermal smearing of all 1-D effects, due to the large effective mass of charge carriers in TiO(2), resulting in an apparent 2-D behavior of TiO(2) nanotubes. 相似文献
10.
A concept of fluorescent metal ion sensing with an easily tunable emission wavelength is presented and its principle demonstrated by detection of Cu(2+). A fluorescein dye was chemically modified with a metal chelating group and then attached to the terminus of ss-DNA. This was combined with a complementary ss-DNA modified with another fluorescent dye (ATTO 590), emitting at a longer wavelength. In the assembled duplex, fluorescence resonance energy transfer (FRET) between the fluorescein donor (excited at 470 nm) and the ATTO 590 acceptor (emitting at 624 nm) is observed. Proper positioning within the rigid DNA double helix prevents intramolecular contact quenching of the two dyes. Coordination of paramagnetic Cu(2+) ions by the chelating unit of the sensor results in direct fluorescence quenching of the fluorescein dye and indirect (by loss of FRET) quenching of the ATTO 590 emission at 624 nm. As a result, emission of the acceptor dye can be used for monitoring of the concentration of Cu(2+), with a 20 nM detection limit. The emission wavelength is readily tuned by replacement of ATTO-DNA by other commercially available DNA-acceptor dye conjugates. Fluorescent metal ion sensors emitting at >600 nm are very rare. The possibility of tuning the emission wavelength is important with respect to the optimization of this sensor type for application to biological samples, which usually show broad autofluorescence at <550 nm. 相似文献