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201.
202.
203.
Wang X Adachi S Iwai H Takatsuki H Fujita K Kubo M Oku A Harada T 《The Journal of organic chemistry》2003,68(26):10046-10057
allo-Threonine-derived O-aroyl-B-phenyl-N-tosyl-1,3,2-oxazaborolidin-5-ones 1g,n catalyze the asymmetric Mukaiyama-Michael reaction of acyclic enones with a trimethylsilyl ketene S,O-acetal in high enantioselectivity. A range of alkenyl methyl ketones is successfully employed as Michael acceptors affording ee values of 85-90% by using 10 mol % of the catalyst. The use of 2,6-diisopropylphenol and tert-butyl methyl ether as additives is found to be essential to achieve high enantioselectivity in these reactions. The effects of the additives are discussed in terms of the retardation of an Si(+)-catalyzed racemic pathway, which seriously deteriorates the enantioselectivity of asymmetric Mukaiyama-Michael reactions. A working model for asymmetric induction is proposed based on correlation between catalyst structures and enantioselectivities. 相似文献
204.
Hiroyoshi Kamogawa Hideo Watanabe 《Journal of polymer science. Part A, Polymer chemistry》1973,11(7):1645-1651
The effects of the chemical structure of the functional portion as well as the comonomer composition on the photochromic behavior of vinyl polymers containing mercury thiocarbazonate functional groups in the side chains were investigated. It was found that, for p-acrylamidophenyl mercuric thiocarbazonate polymers, the uses of β-naphthyl and strongly electron-releasing p-methoxyphenyl groups for the thiocarbazone residue provide absorption maxima shifted somewhat to longer wavelengths as compared with the use of unsubstituted phenyl groups, whereas the electron-withdrawing o-trifluoromethylphenyl group brings about much larger shifts towards shorter wavelengths, the o-trifluoromethylphenyl group and those groups capable of exerting steric hindrances such as β-naphthyl and o-methylphenyl groups causing slower light and dark reactions too. The increase of free volumes in the polymers by regulating the comonomer composition, i.e., the lowering of Tg, was found to improve photochromic responses strikingly. 相似文献
205.
Hiroyoshi Kamogawa Yoko Takayanagi Masato Nanasawa 《Journal of polymer science. Part A, Polymer chemistry》1981,19(11):2947-2953
2,4-Dihydroxy-4′-vinylbenzophenone (I) and its 4-alkyl ethers (II), Me, Et, n-Bu, n-Oct, and n-dodecyl, were prepared in three steps by Hoesch synthesis, starting with p-(2-bromoethyl) benzonitrile and resorcinol and its monoalkyl ethers. I and its precursor 2,4-dihydroxy-4′-(2-bromoethyl) benzophenone were also converted into their 4-alkyl ethers with alkyl halides in dimethylformamide (DMF) in the presence of sodium hydrogen carbonate. Copolymerizations of I and II with styrene took place smoothly with satisfactory conversions to yield copolymers with ε-values around 104 L/mol cm?1 per benzophenone unit over the ultraviolet (UV) range of 235–340nm. 相似文献
206.
Kiyoshi Kawatsura Hiroyoshi Kageyama Ryohei Takahashi Dai Hamaguchi Shigeyoshi Arai Yasushi Aoki Shunya Yamamoto Hidefumi Takeshita Hiroshi Naramoto Tadashi Kambara Masaki Oura Yasuyuki Kanai Yohko Awaya 《Radiation Physics and Chemistry》1997,49(6):617-622
High resolution L X-ray emission spectra of Cu have been measured by 0.75 MeV/u H, He, and F, 0.73 MeV/u Ar, 0.64 MeV/u Si, and 0.073 MeV/u Si ion impacts with a crystal spectrometer. The X-ray transition energies in the Cu target for Lι, Lη, L1,2, Lβ1, and Lβ3,4 diagram lines induced by H ion impact are determined, which are in good agreement with those given in the reference by Bearden (Rev. Mod. Phys. 39, 78, 1967). The X-ray spectra produced by F, Si, and Ar ions have complicated structures due to multiple L and M shell vacancy production. The L1,2 and Lβ1 emission spectra for H and He ions are compared with the calculated ones based on the multiconfiguration Dirac-Fock method. The origin of the broadening of the L1,2 line to the lower energy for H ion impact is attributed to one 2p plus one 3d electron vacancy production. 相似文献
207.
Joo Yeon Ha Dr. Jin Young Koo Dr. Hiroyoshi Ohtsu Prof. Dr. Yumi Yakiyama Prof. Dr. Kimoon Kim Dr. Daisuke Hashizume Prof. Dr. Masaki Kawano 《Angewandte Chemie (International ed. in English)》2018,57(17):4717-4721
The multistate redox‐active/multi‐interactive ligand 5,5′,8,8′‐tetra(4‐pyridyl)‐2,2′‐(1,4‐phenylene)bis‐1H‐perimidine (H2TPP) was designed and synthesized. H2TPP undergoes four one‐electron oxidation steps, and was used for the preparation of a multistate redox‐active coordination network in a solid–liquid interface reaction using molten Cd2+ salts. The multiple redox states of H2TPP were confirmed spectroscopically by stepwise four‐electron oxidation. Spectroscopic analysis indicated that the mixed‐valence states of the ligand are class II on the UV/Vis/NIR timescale and borderline class II/class III on the ESR timescale. 相似文献
208.
The basic pseudotrisaccharide ( constituting the common and essential building block of several α-glucosidase inhibitors of microbial origin was synthesized by coupling two synthons: the chiral cyclohexyl halide () and the 4′-amino-4′-deoxy-disaccharide (). 相似文献
209.
Hiroyoshi Kamogawa Kazunori Maeda 《Journal of polymer science. Part A, Polymer chemistry》1984,22(6):1393-1407
p-Vinylphenylsulfonylmethyl isocyanide (1M) was synthesized starting with sodium p-styrenesulfinate via p-vinylphenylsulfonylmethylformamide (4M). Free-radical polymerization of 1M provided cross-linked insoluble polymers (1), whereas 4M provided soluble polymers, which could be converted to soluble polymer 1. Conversions of carbonyl compounds to nitriles and Schiff bases to 1,5-disubstituted imidazoles with both soluble and cross-linked polymers 1 as reagents proceeded almost as efficiently as with their low molecular weight analog. Reusability of polymer 1 was fairly good. 相似文献
210.
Leenawaty Limantara Shun Sakamoto Yasushi Koyama Hiroyoshi Nagae 《Photochemistry and photobiology》1997,65(2):330-337
The effects of nonpolar and polar solvents on the Qx and Qy energies of bacteriochlorophyll (BChl) a and bacteriopheophytin (BPhe) a were examined by electronic absorption spectroscopy. All of the four different energies exhibited a linear dependence on R(n) = (n2 - l)/(n2+ 2), where n is the refractive index of the solvent, in both nonpolar and polar solvents. The energy of each state of both pigments could be expressed as v = -dR(n) + e (in cm-1) where coefficient d was related to the dispersive interaction between the solute and the solvent molecules. A theory developed by Nagae showed that coefficient d originates from the quantum-mechanical fluctuation of the multipole moments of the solute, in terms of which the following characteristics of the observed d values were explained: (1) In all of the four cases of the Qx, and Qy energies of both BChl a and BPhe a, the d values for the polar solvents were smaller than those for the non-polar solvents. (2) In both nonpolar and polar solvents, the d value of BChl a was larger than that of BPhe a in the Qy energy, whereas the d value of BPhe a was larger than that of BChl a in the Qx energy. (3) The d value of the Qx energy was larger than that of the Qy, energy for either case of BChl a or BPhe a. 相似文献