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231.
Toyoji Kakuchi Shigeyuki Matsunami Hiroyuki Kamimura Fumiaki Ishii 《Journal of Polymer Science.Polymer Physics》1995,33(15):2151-2158
The chain structure of cis-poly(4′-ethynylbenzo-15-crown-5) (PEB15C5), prepared using the rhodium complex catalyst, was studied at ?175°C using the solid-state NMR technique. The second moment of PEB15C5 was 7.0 G2 for the main chain and 19.0 G2 for the side chain. These values agreed well with the respective theoretical ones for the cis form in the rigid state rather than the trans one. This agreement between experiment and theory suggested that the plane of the side chain (i.e., the benzo-15-crown-5 group) is orthogonal to the main chain plane of the cis-transoidal form. It was verified that the strong dipoledipole interaction between the side chains plays an important role as a clue to theoretically determine the cis-transoidal form. NMR results in solid state confirmed theoretically that multipeaks in the 1H and 13C NMR spectra in CDCl3 solution are attributed to cis-transoidal form in the chain. © 1995 John Wiley & Sons, Inc. 相似文献
232.
Copper‐Catalyzed Reaction of Trifluoromethylketones with Aldehydes via a Copper Difluoroenolate
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Ryohei Doi Prof. Dr. Masato Ohashi Prof. Dr. Sensuke Ogoshi 《Angewandte Chemie (International ed. in English)》2016,55(1):341-344
A copper‐catalyzed reaction of easily accessible α,α,α‐trifluoromethylketones with various aldehydes affords difluoro‐methylene compounds in the presence of diboron and NaOtBu. The key process of the reaction is the formation of a copper difluoroenolate by 1,2‐addition of a borylcopper intermediate to α,α,α‐trifluoromethylketones and subsequent β‐fluoride elimination. Mechanistic studies including the isolation and characterization of a possible anionic copper alkoxide intermediate are also described. 相似文献
233.
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
234.
Diazadibora[1.1.1.1]m,p,m,p‐cyclophanes: Ambipolar Conjugated Macrocycles with Different B–π–N Embedded Patterns
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Dr. Akihiro Ito Masashi Uebe Dr. Ryohei Kurata Soichiro Yano Dr. Hiroyuki Fueno Dr. Takashi Matsumoto 《化学:亚洲杂志》2018,13(7):754-760
Are different B(boron)–π–N(nitrogen) embedded patterns to bring about significant different (opto)electronic properties for the same macrocyclic molecular backbone? A series of B–π–N‐embedded alternate‐meta‐para‐linked cyclophanes 1 – 3 have been prepared and characterized as a new class of ambipolar π‐conjugated B–π–N macrocycles. The answer to the opening question is yes. These macrocycles revealed the intramolecular charge transfer in the oxidized states and the intriguing photophysical proprerties in accordance with the embedded patterns, suggesting the electronic structures are tunable by introducing multiple B–π–N moieties. 相似文献
235.
Toshifumi Satoh Tomoko Imai Norihiko Sugie Ryuji Nonokawa Kazuaki Yokota Toyoji Kakuchi 《Journal of polymer science. Part A, Polymer chemistry》2002,40(8):965-970
The bulk cyclopolymerization of diepisulfide, 1,2:5,6‐diepithio‐3,4‐di‐O‐methyl‐1,2:5,6‐tetradeoxy‐D ‐mannitol ( 1 ), was studied using R4N+Br? (R = ? CH3, C2H5, C3H7, C4H9, and C7H15) and (C4H9)4N+X? (X = Cl, I, NO3, and ClO4) as the initiators. All the bulk polymerizations of 1 using quaternary tetraalkylammonium salts at 90 °C proceeded without gelation even at high conversion to produce gel‐free polymers consisting of 2,5‐anhydro‐1,5‐dithio‐D ‐glucitol (I) as the major cyclic repeating unit along with 1,5‐anhydro‐2,5‐dithio‐D ‐mannitol (II) and the desulfurized acyclic unit (III) as the minor units. The polymerization rate and molar fraction of the I unit increased with the increasing alkyl chain length of the tetraalkylammonium cation and the increasing nucleophilicity of the counteranion. Tetrabutylammonium chloride exhibited the highest catalytic activity and the highest stereoselectivity, that is, the thiosugar polymer with I:II:III = 81:15:4 and a number‐average molecular weight of 31.9 × 103 was obtained in 85% yield for a polymerization time of 0.5 h. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 965–970, 2002 相似文献
236.
Regional distributions of manganese,iron, copper,and zinc in the brains of 6-hydroxydopamine-induced parkinsonian rats 总被引:1,自引:0,他引:1
Tarohda T Ishida Y Kawai K Yamamoto M Amano R 《Analytical and bioanalytical chemistry》2005,383(2):224-234
Time courses of changes in manganese, iron, copper, and zinc concentrations were examined in regions of the brain of a 6-hydroxydopamine
(6-OHDA)-induced rat model of Parkinson’s disease using inductively coupled plasma mass spectrometry (ICP-MS). The concentrations
were simultaneously determined in brain section at the level of the substantia nigra 1, 3, 7, 10, 14, and 21 days after the
6-OHDA treatment and compared with those of control rats. The distributions of these elements were obtained for 18 regions
of the sagittal section (1-mm thick). The ICP-MS results indicated that Mn, Fe, Cu, and Zn levels of the 6-OHDA-induced parkinsonian
brain were observed to increase in all regions that lay along the dopaminergic pathway. In the substantia nigra, the increase
in Mn level occurred rapidly from 3 to 7 days and preceded those in the other elements, reaching a plateau in the 6-OHDA brain.
Iron and Zn levels increased gradually until 7 days and then increased rapidly from 7 to 10 days. The increase in the copper
level was slightly delayed. In other regions, such as the globus pallidus, putamen, and amygdala, the levels of Mn, Fe, Cu,
and Zn increased with time after 6-OHDA treatment, although the time courses of their changes were region-specific. These
findings contribute to our understanding of the roles of Mn and Fe in the induction of neurological symptoms and progressive
loss of dopaminergic neurons in the development of Parkinson’s disease. Manganese may hold the key to disturbing cellular
Fe homeostasis and accelerating Fe levels, which play the most important role in the development of Parkinson’s disease. 相似文献
237.
To understand and characterize non-dimer DNA damage and cytotoxicity induced by ultraviolet-B light (UV-B, 290-320 nm), an alkaline elution technique for analysis of DNA damage was used on Chinese hamster V-79 cells. Ultraviolet-B exposure produced a dose-dependent induction of DNA single strand breaks and DNA-protein crosslinks; however, there was an absence of DNA-DNA interstrand crosslinks. Neither of these types of DNA damage were repaired within a a 24 h incubation of the cells following a single UV-B exposure; rather the damage increased. Using a colony forming assay, we found that UV-B exposure resulted in an increase of cytotoxicity in a dose-dependent fashion. In addition, UV-B exposure inhibited DNA and RNA synthesis. The role of non-dimer DNA damage in the cytotoxicity induced by UV-B is discussed. 相似文献
238.
Tsuda R Kodama K Ueki T Kokubo H Imabayashi S Watanabe M 《Chemical communications (Cambridge, England)》2008,(40):4939-4941
We present a new series of polymer-ionic liquid solutions exhibiting LCST-type liquid-liquid phase separation behaviour, and reveal their phase behaviour and intermolecular interactions based on phase diagrams and NMR analysis. 相似文献
239.
Nishii Y Nagano T Gotoh H Nagase R Motoyoshiya J Aoyama H Tanabe Y 《Organic letters》2007,9(4):563-566
A couple of radical carbonylations of gem-dihalocyclopropanes 1 using CO and Bu3SnH (formylation) or Bu3Sn(CH2CH=CH2) (allylacylation) successfully proceeded to give trans and cis adducts (2 and 3) with good to excellent stereoselectivity (trans/cis = >99/1-75/25 or 17/83-1/99). The formylation of 2,3-cis-disubstituted 1,1-dihalocyclopropanes enhanced trans selectivity (trans/cis = >99/1-95/5), whereas both 2,3-cis-disubstituted and 2-monosubstituted 1,1-dihalocyclopropanes underwent allylacylation with nearly complete trans selectivity (trans/cis = >99/1). Inherently less reactive gem-dichloro- and bromochlorocyclopropanes than gem-dibromocyclopropanes served as favorable substrates. [reaction: see text]. 相似文献
240.
The synthesis of novel hyperbranched carbohydrate polymers, prepared by the ring-opening multibranching polymerizations of anhydro and dianhydro sugars, is described. The hyperbranched carbohydrate polymers were formed by the cationic polymerization of 1,6-anhydro-beta-D-hexopyranose, 1,4-anhydrotetritol, 2,3-anhydrotetritol, and 1,2:5,6-dianhydro-D-mannitol. These polymerizations proceeded without gelation to produce water-soluble hyperbranched carbohydrate polymers with controlled molecular weights and narrow polydispersities. The values for the degree of branching of the polymers were in the range of 0.28-0.50. The polymerization method, which proceeds through a ring-opening reaction by a proton-transfer reaction mechanism, is a facile method leading to a spherical carbohydrate polymer with a high degree of branching. 相似文献