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51.
Shuji Hasegawa Xiao Tong Sakura Takeda Norio Sato Tadaaki Nagao 《Progress in Surface Science》1999,60(5-8):89-257
By utilizing a variety of surface superstructures formed on silicon surfaces and atomic layers grown on them, close correlations between the atomic-scale structures and electrical conduction phenomena at the surfaces have been revealed. State-of-art techniques for analyzing and controlling atomic/electronic structures of surfaces are leading to an understanding of the novel electronic transport properties at surfaces. For example, the electrical conduction through surface-state bands, which are inherent in the surface superstructure, has been confirmed in in-situ measurements. An important phenomenon has also been found, where adatoms donate carriers into the surface-state band, resulting in a remarkable enhancement in electrical conductance. The nucleation of the adatoms diminishes such a doping effect. Furthermore, electrical conduction through atomic layers grown on the surfaces, whose growth structures are sensitive to the substrate surface structures, will be also discussed. In this review, we emphasize that the surface electronic transport properties are closely related to the atomic structures and atomistic dynamics on surfaces. The ultimate two-dimensional electron systems, consisting of the surface-state bands and grown atomic layers, are expected to provide a new stage in surface physics, as well as a precursory stage leading to atomic-scale electronics devices. 相似文献
52.
Kobayashi J Ohki K Okimura K Hashimoto T Sakura N 《Chemical & pharmaceutical bulletin》2006,54(6):827-831
Application of aqueous methanesulfonic acid (MSA) for selective chemical removal of pyroglutamic acid (pGlu) residue from five biologically active pyroglutamyl-peptides (pGlu-X-peptides, X=amino acid residue at position 2) was examined. Gonadotropin releasing hormone (Gn-RH), dog neuromedin U-8 (d-NMU-8), physalaemin (PH), a bradykinin potentiating peptide (BPP-5a) and neurotensin (NT) as pGlu-X-peptides were incubated in either 70% or 90% aqueous MSA at 25 degrees C. HPLC analysis of the incubation solutions showed that the main decomposition product was H-X-peptide derived from each pGlu-X-peptide by the removal of pGlu. The results revealed that the pGlu-X peptide bond had higher susceptibility than various internal amide bonds in the five peptides examined, including the Trp-Ser bond in Gn-RH, the C-terminal Asn-NH(2) in d-NMU-8, and the Asp-Pro bond in PH, whose acid susceptibility is well known. Thus, mild hydrolysis with high concentrations of aqueous MSA may be applicable to chemically selective removal of pGlu from pGlu-X-peptides for structural examinations. 相似文献
53.
Max Wilke Karen Appel Laszlo Vincze Christian Schmidt Manuela Borchert Sakura Pascarelli 《Journal of synchrotron radiation》2010,17(5):669-675
A confocal set‐up is presented that improves micro‐XRF and XAFS experiments with high‐pressure diamond‐anvil cells (DACs). In this experiment a probing volume is defined by the focus of the incoming synchrotron radiation beam and that of a polycapillary X‐ray half‐lens with a very long working distance, which is placed in front of the fluorescence detector. This set‐up enhances the quality of the fluorescence and XAFS spectra, and thus the sensitivity for detecting elements at low concentrations. It efficiently suppresses signal from outside the sample chamber, which stems from elastic and inelastic scattering of the incoming beam by the diamond anvils as well as from excitation of fluorescence from the body of the DAC. 相似文献
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56.
Kazuhiro Kobayashi Hideo Tanaka Koujirou Tanaka Keiichi Yoneda Osamu Morikawa Hisatoshi Konishi 《合成通讯》2013,43(23):4277-4291
The reaction of 1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione with various alkenes or terminal alkynes in the presence of cerium(IV) ammonium nitrate (CAN) afforded the corresponding 5,6-dihydrofuro[2,3-d]pyrimidine-2,4(1H,3H)-diones or furo[2,3-d]pyrimidine-2,4(1H,3H)-diones in moderate to good yields. 相似文献
57.
Nami Choi Kumiko Asano Sakura Watanabe Wataru Ando 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1):379-380
1,3-Bis[tris(trimethylsilyl)methyl]-2,4,5-trichalcogena-1,3-disilabicyclo[1.1.1]pentanes display unusual short bridgehead Si---Si distances despite the absence of formal Si—Si bonds, and chalcogen---chalcogen interactions are observed by nmr, X-ray analysis and electronic spectroscopy. 相似文献
58.
Pierre Thuéry Martine Nierlich Zouhair Asfari Jacques Vicens Osamu Morikawa Hisatoshi Konishi 《Supramolecular chemistry》2013,25(4):521-527
Abstract The crystal structures of the all-cis epimer of C-(n-propyl)calix[4]resorcinarene (1) and its caffeine complex are reported. 1 · CH3CN · H2O (2) crystallizes in the tetragonal space group P4, a = 14.3645(9), c = 9.3344(8) Å, V = 1926(2) Å3. Refinement led to a final conventional R 1 value of 0.047 for 3406 reflections and 236 parameters. The caffeine complex 1 · C8H10N4O2 · CH3OH · H2O (3) crystallizes in the triclinic space group P1, a = 11.2892(4), b = 13.0367(8), c = 16.9700(11) Å, α = 82.902(2), β = 79.713(3), γ = 88.053(2)°, V = 2438(2) Å3. Refinement led to a final conventional R 1 value of 0.067 for 6393 reflections and 641 parameters. The resorcinarene displays the usual bowl shape in both compounds. The caffeine molecule in 3 is hydrogen bonded to two resorcinarene and one water molecules and one of its methyl groups is included in the cavity of a third macrocycle, suggesting CH3…π interactions. Extended hydrogen bonding patterns involving phenolic protons and solvent molecules are also present in both compounds. 相似文献
59.
Hisatoshi Kura Hidetaka Oka Masaki Ohwa Tadayoshi Matsumura Akira Kimura Yohei Iwasaki Teruhisa Ohno Michio Matsumura Hisao Murai 《Journal of Polymer Science.Polymer Physics》2005,43(13):1684-1695
Thiol‐substituted α‐aminoalkylphenone was newly developed as a radical photoinitiator. Introduction of the thiol group drastically improved photosensitivity in an alkaline developable resist formulation composed of a prepolymer and a multifunctional acrylate monomer. The improvement in the photocuring speed was explained by a mechanism based on chain transfer reaction of the thiol group. Time‐resolved electron spin resonance (ESR) spectroscopy indicated that the thiol group attached to the chromophore does not influence the photochemical process to generate primary radicals. The photoinitiation of α‐aminoalkylphenone can be spectrally sensitized by 2,4‐diethylthioxanthone (DETX). However, thiol‐substituted α‐aminoalkylphenone showed smaller spectral sensitization than the corresponding compound without a thiol group. Time resolved laser flash photolysis indicated that the rate constant of the quenching of the triplet state of DETX by thiol‐substituted α‐aminoalkylphenone is twice as large as that by the corresponding one without a thiol group. This suggests that, besides energy transfer from DETX in the excited triplet state to the α‐aminoalkylphenone, the thiol group quenches the excited triplet state of DETX via charge transfer and/or hydrogen transfer, as supported by the ESR analysis using a spin trapping technique, and lowers the efficiency of the spectral sensitization effect. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1684–1695, 2005 相似文献
60.
Kazuhiro Kobayashi Hiroo Hashimoto Teruhiko Suzuki Hisatoshi Konishi 《Helvetica chimica acta》2011,94(11):2002-2009
An efficient method for the synthesis of 2‐aryl‐2,3‐dihydro‐3‐sulfanyl‐1H‐isoindol‐1‐ones 1 via Pummerer‐type cyclization of N‐aryl‐2‐(sulfinylmethyl)benzamides 2 is described. Thus, treatment of these sulfinyl‐benzamides 2 , easily prepared from 2‐(bromomethyl)benzoates 3 in three steps, with Ac2O at ca. 100° resulted in the formation of the desired isoindolones 1 in generally good yields. 相似文献