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81.
A highly sensitive flow-injection method is proposed for the catalytic determination of vanadium(V) at sub-nanogram per milliliter levels using a new indicator reaction. The method is based on the catalytic effect of vanadium(V) on the bromate oxidation of N,N′-bis(2-hydroxyl-3-sulfopropyl)-tolidine. 1,2-Dihydroxybenzene-3,5-disulfonate was used as an activator in the vanadium(V)-catalyzed reaction and significantly enhanced the sensitivity of the method. Vanadium(V) in the range 0.01-3.0 ng ml−1 was easily determined with sampling rate of about 30 h−1. Vanadium(IV) could be also determined. The limit of detection (S/N=3) was 0.008 ng ml−1 and the relative standard deviations were 1.4 and 1.6% for ten determinations of 0.2 ng ml−1 vanadium(IV) and vanadium(V), respectively. Interferences from metal ions could be suppressed by the addition of ethylenediamine-N,N,N′,N′-tetrakis(methylenephosphonic acid) as a masking agent. The proposed method was successfully applied to the determination of vanadium in water samples. 相似文献
82.
Miwatashi S Arikawa Y Naruo K Igaki K Watanabe Y Kimura H Kawamoto T Ohkawa S 《Chemical & pharmaceutical bulletin》2005,53(4):410-418
A novel series of 4-phenyl-5-pyridyl-1,3-thiazole analogues possessing potent in vitro inhibitory activity against p38 mitogen-activated protein kinase and the release of tumor necrosis factor-alpha (TNF-alpha) from human monocytic THP-1 cells stimulated by lipopolysaccharide has been identified. Subsequent structure-activity relationship (SAR) studies and optimization for absorption, distribution, metabolism, and elimination (ADME) profiles led to the identification of compounds 7 g and 10b as orally active lead candidates that block the in vivo production of proinflammatory cytokine (TNF-alpha). In pharmacokinetic studies, compound 10b showed good oral administration in mice and demonstrated significant in vivo anti-inflammatory activity in an anti-collagen monoclonal antibody-induced arthritis mouse model (minimum effective dose (MED)=30 mg/kg). Further elucidation of this class of compounds may provide novel anti-inflammatory agents, such as anti-rheumatoid arthritis drugs. 相似文献
83.
Iwata T Fukuzawa K Nakajima K Aida-Hyugaji S Mochizuki Y Watanabe H Tanaka S 《Computational Biology and Chemistry》2008,32(3):198-211
The hemagglutinin (HA) protein of the influenza virus binds to the host cell receptor in the early stage of viral infection. A change in binding specificity from avian 2-3 to human 2-6 receptor is essential for optimal human-to-human transmission and pandemics. Therefore, it is important to reveal the key factors governing the binding affinity of HA-receptor complex at the molecular level for the understanding and prediction of influenza pandemics. In this work, on the basis of ab initio fragment molecular orbital (FMO) method, we have carried out the interaction energy analysis of HA-receptor complexes to quantitatively elucidate the binding specificity of HAs to avian and human receptors. To discuss the binding property of influenza HA comprehensively, a number of HAs from human H1, swine H1, avian H3 and avian H5 viruses were analyzed. We performed detailed investigations about the interaction patterns of complexes of various HAs and receptor analogues, and revealed that intra-molecular interactions between conserved residues in HA play an important role for HA-receptor binding. These results may provide a hint to understand the role of conserved acidic residues at the receptor binding site which are destabilized by the electrostatic repulsion with sialic acid. The calculated binding energies and interaction patterns between receptor and HAs are consistent with the binding specificities of each HA and thus explain the receptor binding mechanism. The calculated results in the present analysis have provided a number of viewpoints regarding the models for the HA-receptor binding specificity associated with mutated residues. Examples include the role of Glu190 and Gln226 for the binding specificity of H5 HA. Since H5 HA has not yet been adapted to human receptor and the mechanism of the specificity change is unknown, this result is helpful for the prediction of the change in receptor specificity associated with forthcoming possible pandemics. 相似文献
84.
Furutachi H Hashimoto K Nagatomo S Endo T Fujinami S Watanabe Y Kitagawa T Suzuki M 《Journal of the American Chemical Society》2005,127(13):4550-4551
A mononuclear iron(III) complex containing a peroxocarbonate ligand, [Fe(qn)2(O2C(O)O)]- (qn = quinaldinate), underwent the reversible O-O bond cleavage and reformation of the peroxo group via the formation of FeIV=O or FeV=O species, which was confirmed by the resonance Raman and ESI-TOF/MS measurements. 相似文献
85.
Mengmeng Zhao Shigenori Kuga Shidong Jiang Min Wu Yong Huang 《Cellulose (London, England)》2016,23(5):2809-2818
The nanoscale structural changes of crystalline cellulose by mechanical milling was studied by high-resolution microscopy (AFM, SEM, TEM). We examined influence of environment [dry, water, silicone oil (PDMS)] on cellulose milling, finding their characteristic effects on microscopic morphology of the products. Dry milling of cellulose gave aggregated globular particles with fast decrystallization. Milling with water or PDMS caused partial dispersion of nanofibers. Milling with PDMS formed micro-platelets <1 µm thick with slight decrystallization. Remarkably, nanoscale particles isolated from PDMS-milled cellulose by sonication in ethanol contained cellulose nanosheets, typically 0.1–10 µm wide and 4.2 nm thick, apparently formed by monolayer association of elementary fibrils. TEM and electron diffraction revealed crystalline nature of nanosheets, with specific orientation of (110) plane or (200) plane perpendicular to the sheet plane. A possible mechanism of the nanosheets formation is proposed, in which the elementary fibrils are aligned parallel by mechanical impacts. 相似文献
86.
A new molecule-based magnetic material [Mn2(Saloph)2(μ-OH)][Ni(bdt)2](CH3CN)2 was prepared by the metathesis of [Mn(Saloph)(H2O)(ClO4)] (S = 2) and TBA[Ni(bdt)2] (S = 1/2). In the crystal, [Ni(bdt)2]? anions form square lattices which are separated from each other by the layers of antiferromagnetically coupled binuclear cations [Mn2(Saloph)2(μ-OH)]+. The magnetic susceptibility of the material coincides with the sum of the S = 2 van Vleck dimer model and S = 1/2 Heisenberg ferromagnetic square lattice model with 2J = ?92.4 and +4.5 K, respectively. The origin of the ferromagnetic interaction can be explained by the T-shaped intermolecular overlap mode of SOMOs which spreads to the ends of [Ni(bdt)2]? molecules. 相似文献
87.
Toshio Nakayama Shigenori Tanaka Shin-Ya Aoki 《Molecular Crystals and Liquid Crystals》2013,570(1-2):267-271
Abstract Strained lattice organic thin film which possessed distinct lattice structure from the bulk crystal was formed by molecular beam epitaxy (MBE). In situ infrared (IR) spectroscopic characterization was carried out to clarify the as-grown film structure under several growth conditions. The growth condition for parallel orientation of the flat molecules was discussed under the interrelation between the molecule-substrate interactions and the intermolecular interactions. 相似文献
88.
Dae-Young Kim Yoshiharu Nishiyama Masahisa Wada Shigenori Kuga 《Cellulose (London, England)》2001,8(1):29-33
The carbonization of cellulose with sulfuric acid impregnation was studied by thermogravimetric analysis and scanning electron microscopy. The mass yield of carbon after 800°C treatment in nitrogen increased to 2–3 times by addition of small amounts of sulfuric acid. The sulfuric acid is considered to work as dehydration catalyst, thus suppressing the release of volatile organic substances. The shrinkage of the sample during carbonization was also significantly reduced by the addition of sulfuric acid. 相似文献
89.
Xiaobo Su Satoshi Kimura Masahisa Wada Shigenori Kuga 《Cellulose (London, England)》2011,18(3):531-537
Highly crystalline cellulose samples from green algae (cellulose I) and mercerized ramie (cellulose II) were treated with
anhydrous hydrazine and the resulting complexes were analyzed by synchrotron X-ray diffraction and thermogravimetry. Cellulose
I-hydrazine complex could be fully described by a two-chain monoclinic unit cell, a = 0.879 nm, b = 1.076 nm, c = 1.038 nm, and γ = 122.0°, with space group P21. Cellulose II-hydrazine complex prepared from mercerized ramie gave a different two-chain monoclinic unit cell, a = 1.042 nm, b = 1.046 nm, c = 1.038 nm, γ = 129.7°, also with space group P21. Though having different crystal structures, the number of hydrazine molecules per glucopyranoside residue was 0.82 for cellulose
I-complex and 0.93 for cellulose II-complex, probable stoichiometric value of 1.0. Hydrazine could be extracted from the complexes
by organic solvents retaining the crystalline orders, resulting in the allomorphic conversion to cellulose IIII and cellulose IIIII, both having non-staggered chain arrangements. These features are similar to those of cellulose-ethylenediamine complexes. 相似文献
90.
Kouichi Matsumoto Yuki Kozuki Yosuke Ashikari Seiji Suga Shigenori Kashimura Jun-ichi Yoshida 《Tetrahedron letters》2012,53(15):1916-1919
Arylbis(arylthio)sulfonium ions (ArS(ArSSAr)+), which were generated and accumulated by the low-temperature electrolysis of diaryl disulfide (ArSSAr), were found to serve as ArS+ equivalent in electrophilic substitution reactions of aromatic compounds, enolizable ketones, enol acetates, ketene silyl acetals and allylsilanes to give the corresponding arylthiolated products. 相似文献