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41.
The behavior of a polymer chain immersed in a binary solvent mixture is investigated via a single-polymer simulation using an effective Hamiltonian, where the solvent effects are taken into account through a density-functional theory for polymer-solvent admixtures. The liquid-liquid phase separation of the binary solvent mixture is modeled as that of a Lennard-Jones binary fluid mixture with weakly attractive interactions between the different components. Two types of energetic preferences of the polymer chain for the better solvent-(A) no preferential solvophilicity and (B) strong preferential solvophilicity-are employed as polymer-solvent interaction models. The radius of gyration and the polymer-solvent radial distribution functions are determined from the simulations of various molar fractions along an isotherm slightly above the critical temperature of the liquid-liquid phase separation. These quantities near the critical point conspicuously depend on the strength of the preferential solvophilicity. In the case where the polymer exhibits a strong preferential solvophilicity, a remarkable expansion of the polymer chain is observed near the critical point. On the other hand, in the case where the polymer has no preferential solvophilicity, no characteristic variation of the polymer conformation is observed even near the critical point. These results indicate that the expansion of a polymer chain enhances the local phase separation around it, acting as a nucleus of demixing in the vicinity of the critical point. This phenomenon in binary solvents near the liquid-liquid critical point is similar to the expansion of the polymer chain in one-component supercritical solvents near the liquid-vapor critical point, which we have reported [T. Sumi and H. Sekino J. Chem. Phys. 122, 194910 (2005)]. 相似文献
42.
Yasuhiro Kajihara Takashi Ebata Hisashi Kodama 《Angewandte Chemie (International ed. in English)》1998,37(22):3166-3169
A novel immobilization procedure for glycoproteins is based on the reacion of immobilized CMP-NeuAc (CMP-sialic acids) with sialyltransferase (see scheme). The transfer ability was tested under various conditions; a corresponding oligosaccharide or asialoglycoprotein acted as sialyl acceptor. The solid-phase synthesis of CMP-NeuAc is also described. 相似文献
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45.
Hideo Hosono Katsuro Hayashi Koichi Kajihara Peter V. Sushko Alexander L. Shluger 《Solid State Ionics》2009,180(6-8):550-555
12CaO·7Al2O3 (C12A7) with a unique nano-porous structure and free O2? ions entrapped in sub-nanometer-sized cages is a fast oxygen-ion-conducting material. These free O2– may be replaced by various oxygen-related species, OH?, O2? and O?, by tuning the atmosphere during the heat treatment. We examined the conduction mechanism for stoichiometric C12A7 (C12A7:O2?), in which O2? ions exist as counter anions in sub-nanometer-sized cages, by Raman measurement of C12A7:O2? annealed in a dry 18O2 atmosphere. It was revealed that the primary ion conducting species is an O2? ion which diffuses via exchange with O2? in the cage wall. An experimental result on the sample containing O? ions implied that O? is more mobile than O2? in C12A7. Ab initio calculations on the diffusion paths of O2? and O? ions in C12A7 supported the above experimental results. 相似文献
46.
A syringe-driven chelating column (SDCC) was applied to develop an on-line preconcentration/inductively coupled plasma mass spectrometry (ICP-MS) method for preconcentration and determination of rare earth elements (REEs) in seawater samples. The present on-line preconcentration system consists of only one pump, two valves, an SDCC, an ICP-MS, several connectors, and Teflon tubes. Optimizations of adsorption pH condition, sample loading flow rate, and integration range were carried out to achieve optimum measurement conditions for REEs in seawater sample. Six minutes was enough for a preconcentration and measurement cycle using 10 mL of seawater sample, where the detection limits for different REEs were in the range of 0.005 pg mL−1 to 0.09 pg mL−1. Analytical results of REEs in a seawater certified reference material (CRM), NASS-5, confirmed the usefulness of the present method. Furthermore, concentrations of REEs in Nikkawa Beach coastal seawater were determined and discussed with shale normalized REE distribution pattern. 相似文献
47.
We implemented an interaction site model integral equation for rigid molecules based on a density-functional theory where the molecular orientation is explicitly considered. In this implementation of the integral equation, multiple integral of the degree of freedom of the molecular orientation is performed using efficient quadrature methods, so that the site-site pair correlation functions are evaluated exactly in the limit of low density. We apply this method to Cl(2), HCl, and H(2)O molecular fluids that have been investigated by several integral equation studies using various models. The site-site pair correlation functions obtained from the integral equation are in good agreement with the one from a simulation of these molecules. Rotational invariant coefficients, which characterize the microscopic structure of molecular fluids, are determined from the integral equation and the simulation in order to investigate the accuracy of the integral equation. 相似文献
48.
Sakamoto I Tezuka K Fukae K Ishii K Taduru K Maeda M Ouchi M Yoshida K Nambu Y Igarashi J Hayashi N Tsuji T Kajihara Y 《Journal of the American Chemical Society》2012,134(12):5428-5431
Chemical synthesis of homogeneous human glycoproteins exhibiting bioactivity in vivo has been a challenging task. In an effort to overcome this long-standing problem, we selected interferon-β and examined its synthesis. The 166 residue polypeptide chain of interferon-β was prepared by covalent condensation of two synthetic peptide segments and a glycosylated synthetic peptide bearing a complex-type glycan of biological origin. The peptides were covalently condensed by native chemical ligation. Selective desulfurization followed by deprotection of the two Cys(Acm) residues gave the target full-length polypeptide chain of interferon-β bearing either a complex-type sialyl biantennary oligosaccharide or its asialo form. Subsequent folding with concomitant formation of the native disulfide bond afforded correctly folded homogeneous glycosyl-interferon-β. The chemically synthesized sialyl interferon-β exhibited potent antitumor activity in vivo. 相似文献
49.
Norimitsu Yoshida Sho Terazawa Kotaro Hayashi Tomonari Hamaguchi Hironori Natsuhara Shuichi Nonomura 《Journal of Non》2012,358(17):1987-1989
Effects of deposition conditions on the structure of microcrystalline silicon carbide (μc-SiC) films prepared by hot-wire chemical vapor deposition (hot-wire CVD) method have been investigated. It is found from X-ray diffraction patterns of the film that a diffraction peak from crystallites from hexagonal polytypes of SiC is observed in addition to those of 3 C-SiC crystallites. This result is obtained in the film under a narrow deposition conditions of SiH3CH3 gas pressure of 8 Pa, the H2 gas pressure of 80–300 Pa and the total gas pressure of 40–300 Pa under fixed substrate and filament temperatures employed in this study. Furthermore, the grain size of hexagonal crystallites (about 20 nm) on c-Si substrates becomes larger than that of 3 C-SiC crystallites (about 10 nm) for the films deposited under the total gas pressure of 36–88 Pa. The fact that microcrystalline hexagonal SiC can be deposited under limited deposition conditions could be interpreted in the context of a result for c-SiC polytypes prepared by thermal CVD method. 相似文献
50.
Maity P Wakabayashi T Ichikuni N Tsunoyama H Xie S Yamauchi M Tsukuda T 《Chemical communications (Cambridge, England)》2012,48(49):6085-6087
Organogold clusters Au(54)(C(2)Ph)(26) were selectively synthesized by reacting polymer-stabilized Au clusters (1.2 ± 0.2 nm) with excess phenylacetylene in chloroform. 相似文献