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61.
Koki Yoshizawa Dr. Keisuke Hirata Prof. Shun-ichi Ishiuchi Prof. Masaaki Fujii Dr. Anne Zehnacker 《Chemphyschem》2023,24(18):e202300172
Alkali metal complexes of cyclic dipeptide cyclo Tyr-Tyr have been studied under cryogenic ion trap conditions. Their structure was obtained by combining Infra-Red Photo-Dissociation (IRPD) and quantum chemical calculations. The structural motif strongly depends on the relative chirality of the tyrosine residues. For residues of identical chirality, the cation interacts with one amide oxygen and one of the aromatic rings only; the distance between the aromatic rings does not change with the nature of the metal. In contrast, for residues of opposite chirality, the metal cation is located in between the two aromatic rings and interacts with both of them. The distance between the two aromatic rings strongly depends on the metal. Electronic spectra obtained by Ultra Violet Photodissociation (UVPD) spectroscopy and analysis of the UV photo-fragments shed light on the excited state deactivation processes, which depend on both the chirality of the residue and that of the metal ion core. Na+ stands out by the presence of low-lying charge transfer states resulting in the broadening of the electronic spectrum. 相似文献
62.
An acidic polysaccharide having activity on the reticuloendothelial system from the root of Astragalus mongholicus. 总被引:3,自引:0,他引:3
An acidic polysaccharide, designated as AMon-S, was isolated from the roots of Astragalus mongholicus BUNGE. It was homogeneous on electrophoresis and gel chromatography, and its molecular mass was estimated to be 7.6 x 10(4). It showed significant reticuloendothelial system-potentiating activity in a carbon clearance test. It is composed of L-arabinose: D-galactose: D-galacturonic acid: D-glucuronic acid in the molar ratio of 18:18:1:1, in addition to small amounts of O-acetyl groups and peptide moiety. A part of the hexuronic acid residues exist as the methyl esters. Methylation analysis, carbon-13 nuclear magnetic resonance and periodate oxidation studies enabled elucidation of its structural features and revealed mainly alpha-arabino-beta-3,6-galactan type structural units. 相似文献
63.
Shun-ichi Tanaka Sanshiro Hattori Joon-Sung Chang Masana Minami 《Optics Communications》1973,9(1):54-57
A multiple object-beam holography is proposed, where a two-dimensional rectangular amplitude grating and a phase plate of matrix form placed at the frequency plane of the grating constitute the main parts of a speckle-free periodic illumination system of continuous tone transparencies. Demonstration experiments are made, where the number of diffracted orders of the grating, the ratio of the widths of transparent and opaque zones of the grating, the retardation of each matrix zone of the phase plate and the distance between planes of the image of the grating and a transparency are taken as variables. 相似文献
64.
65.
Ishiuchi S Asakawa T Mitsuda H Miyazaki M Chakraborty S Fujii M 《The journal of physical chemistry. A》2011,115(37):10363-10369
In our previous work, we found that synephrine has six conformers in the gas phase, while adrenaline, which is a catecholamine and has the same side chain as synephrine, has been reported to have only two conformers. To determine the conformational geometries of synephrine, we measured resonance enhanced multiphoton ionization, ultraviolet-ultraviolet hole burning, and infrared dip spectra by utilizing the laser desorption supersonic jet technique. By comparing the observed infrared spectra with theoretical ones, we assigned geometries except for the orientations of the phenolic OH group. Comparison between the determined structures of synephrine and those of 2-methylaminno-1-phenylethanol, which has the same side chain as synephrine but no phenol OH group, leads to the conclusion that the phenolic OH group in synephrine does not affect the conformational flexibility of the side chain. In the case of adrenaline, which is expected to have 12 conformers if there are no interactions between the catecholic OH groups and the side chain, some interactions possibly exist between them because only two conformations are observed. By estimation of the dipole-dipole interaction energy between partial dipole moments of the catecholic OH groups and the side chain, it was concluded that the dipole-dipole interaction stabilizes specific conformers which are actually observed. 相似文献
66.
Jozef Gonda Miroslava Martinková Monika Šoteková Patrik ?onka C. Oliver Kappe 《Tetrahedron letters》2007,48(39):6912-6915
The microwave-assisted thermal aza-Claisen rearrangement of allylic imidates and thiocyanates to the corresponding amides and isothiocyanates is investigated. Significant accelerations of the rearrangement of allylic imidates to amides and of allylic thiocyanates to isothiocyanates in comparison with standard thermal reactions is observed. 相似文献
67.
Miroslava Martinková Jozef Gonda Jana Raschmanová Margaréta Vojti?ková 《Tetrahedron》2007,63(43):10603-10607
An efficient stereoselective synthesis of unusual substituted serine synthons 7, 10, 12 is reported. It was shown that highly functionalized furanose 6 has the suitable structure for further synthetic manipulations toward the inhibitors of SPT. 相似文献
68.
R Gonda M Tomoda M Kanari N Shimizu H Yamada 《Chemical & pharmaceutical bulletin》1990,38(10):2771-2774
A novel acidic polysaccharide, designated as MVS-VI, was isolated from the seeds of Malva verticillata L. It was homogeneous on electrophoresis and gel chromatography, and its molecular mass was estimated to be 26000. It is composed of L-arabinose: D-xylose: D-galactose: D-glucose: L-rhamnose: D-galacturonic acid in the molar ratio of 30: 15: 20: 3: 2: 10, in addition to small amounts of peptide moiety. Methylation analysis, carbon-13 nuclear magnetic resonance and periodate oxidation studies indicated its structural features to have mainly acidic alpha-arabino-3,6-beta-galactan type structural units. MVS-VI showed significant reticuloendothelial system-potentiating activity in a carbon clearance test, and it possesses remarkable anti-complementary activity. 相似文献
69.
N Shimizu M Tomoda M Kanari R Gonda A Satoh N Satoh 《Chemical & pharmaceutical bulletin》1990,38(11):3069-3071
A neutral polysaccharide, named glycyrrhizan UC, was isolated from the root of Glycyrrhiza uralensis Fischer. It was homogeneous on electrophoresis and gel chromatography, and its molecular mass was estimated to be 69,000. Glycyrrhizan UC is composed of L-arabinose:D-galactose:D-glucose:L-rhamnose in the molar ratio of 10:30 27:1. Methylation analysis, carbon-13 nuclear magnetic resonance and periodate oxidation studies indicated its structural feature as an arabino-3,6-galacto-glucan type polysaccharide. 相似文献
70.
Tonan K Ikawa S 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2003,59(1):111-120
Proton NMR spectra of short peptides with a glycyl (Gly) or N-methylglycyl (sarcosyl, Sar) residue were measured in various mixed solvents with a wide range of dielectric constants: 78.3-2.3. From analyses of the octet and quartet signals of the geminal alpha-protons of Gly and Sar residues, respectively, we have estimated chemical shift differences between the two alpha-protons, Delta delta(alpha/alpha'). It is found that the Delta delta(alpha/alpha') values increase with decreasing solvent polarity and the increasing rates depend significantly on amino acid sequences. By referring to infrared spectra and chemical shift of the terminal NH protons, deltaNH, of the peptides, the Delta delta(alpha/alpha') values were found to be a good probe of beta-turn formation. From solvent-dependent change of Delta delta(alpha/alpha'), we estimated the free energies for the beta-turn formation and compared the results with those estimated from deltaNH. Using the resulting free energies, we have discussed effects of solvent on the beta-turn formation. 相似文献