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131.
An apparatus was designed and constructed for investigation of the tritium release rate from neutron-irradiated materials for fusion reactors. The design principles, as well as safe handling of tritium and complete trapping of tritium components released, are described and the tritium release rates obtained with this apparatus are discussed for sintered lithium fluoride pellets. 相似文献
132.
Arylboronic acids underwent the conjugate 1,4-addition to alpha, beta-unsaturated esters to give beta-aryl esters in high yields in the presence of a rhodium(I) catalyst. The addition of arylboronic acids to isopropyl crotonate resulted in high yields and high enantioselectivity exceeding 90% ee in the presence of 3 mol % of Rh(acac)(C(2)H(4))(2) and (S)-binap at 100 degrees C. The rhodium/(S)-binap complex provided (R)-3-phenylbutanoate in the addition of phenylboronic acid to benzyl crotonate. The effects on the enantioselectivity of chiral phosphine ligands, rhodium precursors, and substituents on alpha,beta-unsaturated esters are discussed, as well as the mechanistic aspect of the catalytic cycle. 相似文献
133.
Reactions of 4a,5-epoxy-5-deazaflavins with aqueous potassium carbonate, Vilsmeier reagent (dimethylformamide-phosphorus oxychloride), acetic anhydride-acetic acid, pyridine and triethanolamine gave the corresponding oxazolonoquinolines, 5-chloro-5-deazaflavins, 4a,5-diacetoxy-5-deazaflavins, 1,5-dihydro-5-deazaflavin-5-ones, and deoxygenated 5-deazaflavins, respectively. 相似文献
134.
Kunishima M Nakata D Sakuma T Kono K Sato S Tani S 《Chemical & pharmaceutical bulletin》2001,49(1):97-100
Transformation of acetals into ethers by partial reduction using a samarium diiodide-Lewis acids-acetonitrile system is described. The reaction with aromatic acetals occurred in good yields in the presence of aluminum chloride (2 eq) whereas the corresponding aliphatic, vinylic, and alkynyl derivatives did not afford ethers under the same conditions. Beta-elimination to give an enol ether becomes predominant when aliphatic acetals that possess a hydrogen at the 2-position are treated with iodotrimethylsilane in the presence of SmI2 or SmI3. 相似文献
135.
New convenient syntheses of 4,6-dimethyl[1,2,5]oxadiazolo[3,4-d]pyrimidine-5,7(4H,6H)-dione 1-oxide (I) from 1,3-dimethyl-6-hydroxylaminouracil by means of nitrosative and nitrative cyclizations are described. Compound I was converted into 4,6-dimethyl[1,2,5]oxadiazolo[3,4-d]pyrimidine-5,7(4H,6H)dione [4,6-dimethyl-5,7(4H,6H)furazano[3,4-d]pyrimidinedione] by refluxing in dimethylformamide. Transformation of I to 1,3,7,9-tetramethyl-2,4,6,8(1H,3H,7H,9H)pyrimido[5,4-g]pteridinetetrone and/or 1,3,6,8-tetramethyl-2,4,7,9(1H,3H,6H,8H)pyrimido[4,5-g]pteridinetetrone is described. 相似文献
136.
Yo Sakuma Yoshiaki Inaki Kiichi Takemoto 《Journal of polymer science. Part A, Polymer chemistry》1984,22(9):2061-2082
A series of polyethyleneimine derivatives and their oligomer models with pendant thymine or adenine bases separated by β-alanyl groups as spacers were prepared by an activated ester method. To elucidate the nature of intramolecular interaction of thymine and adenine bases ultraviolet (UV) spectrophotometric studies were undertaken for the series of compounds and the results were compared with those obtained for the corresponding oligomers without spacers. In the thymine derivatives, the nature of the intramolecular interaction resembled that of the corresponding compounds without β-alanyl units, although larger hypochromicities were found in the series with β-alanyl units. In the adenine derivatives, contrary to the corresponding thymine systems, UV hypochromicities of the compounds decreased by incorporation of the spacer group into side chains. It became evident that the intramolecular interaction of adenine bases was due to stacking neutral species, hydrogen bonding, and residual hypochromicity for the protonated species. 相似文献
137.
Hirosato Monobe Masaomi Kimoto Yo Shimizu 《Molecular Crystals and Liquid Crystals》2016,629(1):181-186
In this study, we used a LC semiconductor, C8BTBT, solution (e.g. 0.1 wt % in heptane) for forming an organic semiconductor layer by casting method, and fabricated bottom-gate/bottom-contact type FETs. The FETs mobility was determined 0.17 cm2 V?1 s?1 which was comparable to that determined by time-of-flight technique in a sandwich type cell at room temperature. We have investigated the surface morphology and the influence of temperature variation on FET properties. The LC FET mobility was kept below 60°C and drastically decreased after heat stress above 100°C irreversibly. 相似文献
138.
The chemical reaction between SiO2 and tetragonal zirconia polycrystal (TZP) was directly observed using a TEM in-situ heating technique in order to understand the behavior of SiO2 in TZP at high temperatures. Their dynamic interaction was recorded up to about 1400°C using a CCD camera-video system connected to the TEM. Most of SiO2 phase dissolved into the ZrO2 grains above 1300°C. On the other hand, during cooling from the high temperature to around 400°C, amorphous SiO2 reprecipitated from the surface of ZrO2 grains and formed a thin layer around the ZrO2 grains. This result agrees well with the fact that silicon segregates in the vicinity of grain boundaries in SiO2-doped TZP. In order to confirm the grain boundary segregation at high temperatures, we investigated grain boundaries in quenched specimens by high resolution electron microscopy (HREM), energy dispersive X-ray spectroscopy (EDS) and electron energy-loss spectroscopy (EELS). It was found that no amorphous phase was present between two adjacent grains in the quenched samples. EDS analysis revealed that silicon segregated at the grain boundaries and that the segregation layer was wider than that in as-sintered specimens. The electron energy loss near edge structure (ELNES) of O K-edge was measured from both grain boundary and grain interior in quenched specimen, and their spectra were interpreted by a first principles molecular-orbital (MO) calculation using the discrete-variational (DV)-X method. 相似文献
139.
Zachary O. Battaglia Jordan T. Kersten Elise M. Nicol Paloma Whitworth Kraig A. Wheeler Charlie L. Hall Jason Potticary Victoria Hamilton Simon R. Hall Gemma D. D'Ambruoso Masaomi Matsumoto Stephen D. Warren Matthew E. Cremeens 《Acta Crystallographica. Section C, Structural Chemistry》2023,79(6):217-226
Two crystal structures of chalcones, or 1,3-diarylprop-2-en-1-ones, are presented; both contain a p-methyl substitution on the 3-Ring, but differ with respect to the m-substitution on the 1-Ring. Their systematic names are (2E)-3-(4-methylphenyl)-1-(3-{[(4-methylphenyl)methylidene]amino}phenyl)prop-2-en-1-one (C24H21NO) and N-{3-[(2E)-3-(4-methylphenyl)prop-2-enoyl]phenyl}acetamide (C18H17NO2), which are abbreviated as 3′-(N=CHC6H4-p-CH3)-4-methylchalcone and 3′-(NHCOCH3)-4-methylchalcone, respectively. Both chalcones represent the first reported acetamide-substituted and imino-substituted chalcone crystal structures, adding to the robust library of chalcone structures within the Cambridge Structural Database. The crystal structure of 3′-(N=CHC6H4-p-CH3)-4-methylchalcone exhibits close contacts between the enone O atom and the substituent arene ring, in addition to C…C interactions between the substituent arene rings. The structure of 3′-(NHCOCH3)-4-methylchalcone exhibits a unique interaction between the enone O atom and the 1-Ring substituent, contributing to its antiparallel crystal packing. In addition, both structures exhibit π-stacking, which occurs between the 1-Ring and R-Ring for 3′-(N=CHC6H4-p-CH3)-4-methylchalcone, and between the 1-Ring and 3-Ring for 3′-(NHCOCH3)-4-methylchalcone. 相似文献
140.
Yoshihiro Natori Toshihiro Sakuma Haruka Watanabe Hideaki Wakamatsu Atsushi Kato Isao Adachi Hiroki Takahata Yuichi Yoshimura 《Tetrahedron》2019,75(20):2866-2876
We achieved synthesis of seven stereoisomers of 1-C-n-butyl-L-iminofuranose derivatives using catalytic asymmetric alkylation and Negishi coupling as key reactions. The synthetic strategy based on these key reactions was quite useful, since both α- and β-iminofuranoses could be obtained by switching the chirality of the ligand employed for the AAA reaction. The common intermediates for α- and β-isomers were subjected to further manipulations to install a diol unit at C2 and C3 to give the desired stereoisomers of L-iminofuranose derivatives. We achieved the preparation of all stereoisomers of 1-C-n-butyl-L-iminofuranose derivatives, with the exception of β-lyxo type iminofuranose. It is noteworthy that a synthetic route for many stereoisomers of iminofuranose derivatives was developed. Unfortunately, none of the L-iminofuranoses obtained showed inhibitory activity against the α-glycosidases examined—e.g., maltase, sucrase, and isomaltase. 相似文献