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71.
72.
Anionic polymerization of acrolein (AL) by imidazole in the presence of several p-substituted phenols such as phenol, p-methyl-phenol, and p-nitrophenol were kinetically carried out in tetra-hydrofuran at 0°C. The initial polymerization rate Rp was estimated from the rate of monomer consumption by means of gas chromatography. A linear correlation was obtained from Hammett's equation, log RpX/Rp H = 0.22. Meanwhile, the polymerizabilities were found to be in the following order: p-methylphenol > phenol > p-nitrophenol. The additive effect of phenols was kinetically discussed on the basis of these results. 相似文献
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74.
Chotika Viriyarattanasak Motoo Shiro Shigeru Munekawa Felix Franks Satomi Ikeda Kazuhito Kajiwara 《Acta Crystallographica. Section C, Structural Chemistry》2015,71(11):954-958
Raffinose [or O‐α‐D‐galactopyranosyl‐(1→6)‐α‐D‐glucopyranosyl‐(1→2)‐β‐D‐fructofuranoside] pentahydrate, C18H32O16·5H2O, (I), and three lower hydrates, namely the 4.433‐, (II), 4.289‐, (III), and 4.127‐hydrated, (IV), forms, obtained in the course of the dehydration of (I), have been studied. The unit cells in the space group P212121 are of similar dimensions for all the crystals. The conformation of the raffinose molecules remains almost the same across the four crystal structures. The raffinose molecules are linked into a three‐dimensional hydrogen‐bonded network involving all the –OH groups, the ring and glycosidic O atoms, and the water molecules. Six water sites were identified in the structures of (II), (III) and (IV), of which W1, W4 and W6 (W = water) are partially occupied with their populations coupled. W1, W4 and one of the –OH groups of the galactose ring form an infinite hydrogen‐bonding chain around a 21 axis parallel to the a axis (denoted chain A), and W6 and the same –OH group form a similar chain (chain A′) disordered with chain A. The occupancy ratio of chain A to chain A′ for N‐hydrates (N is a hydration number between 4 and 5) is (N− 4):(5 −N). The transformation of chain A to chain A′ as part of the dehydration process has little effect on the rest of the structure. Thus, the dehydration proceeds without significant impact on the crystal structure. 相似文献
75.
Dr. Akihiro Ito Kazuhira Hata Kensuke Kawamoto Dr. Yasukazu Hirao Prof. Dr. Kazuyoshi Tanaka Dr. Motoo Shiro Dr. Ko Furukawa Prof. Dr. Tatsuhisa Kato 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(35):10866-10878
para‐Phenylene‐bridged spirobi(triarylamine) dimer 2 , in which π conjugation through four redox‐active triarylamine subunits is partially segregated by the unique perpendicular conformation, was prepared and characterized by structural, electrochemical, and spectroscopic methods. Quantum chemical calculations (DFT and CASSCF) predicted that the frontier molecular orbitals of 2 are virtually fourfold degenerate, so that the oxidized states of 2 can give intriguing electronic and magnetic properties. In fact, the continuous‐wave ESR spectroscopy of radical cation 2 .+ showed that the unpaired electron was trapped in the inner two redox‐active dianisylamine subunits, and moreover was fully delocalized over them. Magnetic susceptibility measurements and pulsed ESR spectroscopy of the isolated salts of 2 , which can be prepared by treatment with SbCl5, revealed that the generated tetracation 2 4+ decomposed mainly into a mixture of 1) a decomposed tetra(radical cation) consisting of a tri(radical cation) moiety and a trianisylamine radical cation moiety (≈75 %) and 2) a diamagnetic quinoid dication in a tetraanisyl‐p‐phenylendiamine moiety and two trianisylamine radical cation moieties (≈25 %). Furthermore, the spin‐quartet state of the tri(radical cation) moiety in the decomposed tetra(radical cation) was found to be in the ground state lying 30 cal mol?1 below the competing spin‐doublet state. 相似文献
76.
Hirata Y Nakamura S Watanabe N Kataoka O Kurosaki T Anada M Kitagaki S Shiro M Hashimoto S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(35):8898-8925
A carbonyl ylide cycloaddition approach to the squalene synthase inhibitors zaragozic acids A and C is described. The carbonyl ylide precursor 8 was synthesized starting from di-tert-butyl D-tartrate (47) via an eleven-step sequence involving the regioselective reduction of the mono-MPM (MPM=4-methoxybenzyl) ether 48 with LiBH4 and the diastereoselective addition of sodium tert-butyl diazoacetate to alpha-keto ester 10. The reaction of alpha-diazo ester 8 with 3-butyn-2-one (40) in the presence of a catalytic amount of [Rh2(OAc)4] gave the desired cycloadduct 59 as a single diastereomer. The dihydroxylation of enone 59 followed by sequential transformations permitted the construction of the fully functionalized 2,8-dioxabicyclo[3.2.1]octane core 5. Alkene 79 derived from 5 serves as a common precursor to zaragozic acids A (1) and C (2), since the elongation of the C1 alkyl side chain can be attained by olefin cross-metathesis, especially under the influence of Blechert's catalyst (85). 相似文献
77.
Sano S Shimizu H Kim K Lee WS Shiro M Nagao Y 《Chemical & pharmaceutical bulletin》2006,54(2):196-203
Diethyl alpha-alkynyl-alpha-methoxymalonates (2a--e) were smoothly hydrolyzed and then decarboxylated under alkaline conditions employing 1 N KOH in EtOH to give conjugated allenyl esters (6a--e) in high yields, and similar alkaline treatment of diethyl alpha-alkynyl-alpha-acetylaminomalonates (5a, b, d, e) furnished unexpectedly the oxazoles (7a, b, d, e) having three substituent groups in excellent yields. 相似文献
78.
Futaba DN Hata K Namai T Yamada T Mizuno K Hayamizu Y Yumura M Iijima S 《The journal of physical chemistry. B》2006,110(15):8035-8038
We propose a statistical and macroscopic analysis to estimate the catalyst activity of water-assisted growth (super-growth) of single-walled nanotubes (SWNT) and to characterize SWNT forests. The catalyst activity was estimated to be 84% (+/-6%), the highest ever reported. The SWNT forest was found to be a very sparse material where SWNTs represent only 3.6% of the total volume. This structural sparseness is believed to play a critical role in achieving highly efficient growth. 相似文献
79.
80.