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41.
EPR Spectroscopic Characterization (X‐, Q‐Band) of Monomeric AgII‐ and AuII‐Complexes of the Thiacrownethers [12]aneS4, [16]aneS4, [18]aneS6 and [27]aneS9 The reaction of the prepared AgI complexes of the thiacrownethers [12]aneS4, [16]aneS4, [18]aneS6 and [27]aneS9 with c. H2SO4 as well as the reaction of [AuIIICl4]‐ with [18]aneS6 and [27]aneS9 leads to labile AgII‐ (4d9, 107, 109Ag: I=1/2) and AuII‐ (5d9, 197Au: I=3/2) thiacrownether complexes, respectively, which were characterized by X‐ and Q‐band EPR. The EPR spectra of [AgII([12]anS4)]2+ and [AgII([18]anS6)]2+ were reinvestigated. According to an analysis of the spin‐density distribution only 20 ‐ 25 % is located on the Ag or Au atoms. Most of the spin‐density was found to be on the S donor atoms of the thiacrownethers. The high delocalization of the spin‐density leads certainly to a noticeable reduction of the AgI/AgII redox potential and is considered as being mainly responsible for the easy accessibility of the AgII compounds. 相似文献
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Polycrystalline copper and monocrystalline iron were tribomechanically loaded in a defined way. By fundamentals of a continuum mechanical analysis of the stress field and a transmission electron microscopical investigation of the dislocation arrangement conclusions were made regarding the crack nucleation, the crack propagation and the wear resistance. The proved development of a dislocation cell structure is an adaptation of the material to the friction loading to tolerate a high number of loading cycles without wear. 相似文献
44.
Michael Kampf Rainer Richter Lothar Hennig Andreas Eidner Jens Baldamus Reinhard Kirmse 《无机化学与普通化学杂志》2004,630(15):2677-2686
Synthesis, Structures, NMR and EPR Investigations on Transition Metal Complexes of monofluorosubstituted Acylselenourea Ligands The syntheses and the structures of the ligand N, N‐diethyl‐N′‐(2‐fluoro)benzoylselenourea HEt2mfbsu and the complexes [Ni(Et2mfbsu)2] and [Zn(Et2mfbsu)2] as well as of the ligand N, N‐diisobutyl‐N′‐(2‐fluoro)benzoylselenourea HBui2mfbsu and the complexes [NiII(Bui2mfbsu)2] and [PdII(Bui2mfbsu)2] are reported. The ligands coordinate bidendately forming bischelates. The PdII and NiII complexes are cis coordinated; in [ZnII(Et2mfbsu)2] the ligands are tetrahedrally arranged. The structure of the also obtained bis[diisobutylamino‐(2‐fluorobenzoylimino)methyl]diselenide is reported. The CuII complexes of both selenourea ligands could not be isolated. They were obtained as oils. Their EPR spectra, however, confirm the presence of CuII bischelates unambiguously. Detailed NMR investigations ‐ 1H‐, 13C‐ and 19F‐COSY, HMBC and HMQC ‐ on [MII(Et2mfbsu)2] (M = NiII, ZnII) allow an exact assignment of all signals to the magnetically active nuclei of the complexes. 相似文献
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We have measured directly the forces across water between hydrophilic surfaces covered with a random mosaic of positive and negative charged domains. We find a strong, long-ranged attraction between them at a surface separation comparable with the charge domain size (many tens of nanometers). This attraction persists at higher salt concentration, but its range then becomes comparable to the Debye screening length. We attribute the attraction to correlation between negative and positive regions on opposing surfaces, facilitated by the lateral mobility of the charge patches on the surfaces. 相似文献
48.
An improved synthesis of 3-(substituted)pyrimido[4,5-c]pyridazine-5,7(1H,6H)-diones, a known subclass of 4-deazatoxoflavins, is reported. The approach involves treatment of 3-methyl-6-(1-methylhydrazinyl)uracil with representative phenyl and alkyl glyoxal monohydrates, which in turn are obtained by selenium dioxide oxidation of the corresponding phenyl and alkyl methyl ketones. The first entry into 4-monosubstituted isomers is also reported. 相似文献
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Larissa Bessler Lea-Marie Vogt Marc Lander Dr. Christina Dal Magro Dr. Patrick Keller Dr. Jonas Kühlborn Dr. Christopher J. Kampf Prof. Dr. Till Opatz Prof. Dr. Mark Helm 《Angewandte Chemie (International ed. in English)》2023,62(11):e202217128
The fields of RNA modification and RNA damage both exhibit a plethora of non-canonical nucleoside structures. While RNA modifications have evolved to improve RNA function, the term RNA damage implies detrimental effects. Based on stable isotope labelling and mass spectrometry, we report the identification and characterisation of 2-methylthio-1,N6-ethenoadenosine (ms2ϵA), which is related to 1,N6-ethenoadenine, a lesion resulting from exposure of nucleic acids to alkylating chemicals in vivo. In contrast, a sophisticated isoprene labelling scheme revealed that ms2ϵA biogenesis involves cleavage of a prenyl moiety in the known transfer RNA (tRNA) modification 2-methylthio-N6-isopentenyladenosine (ms2i6A). The relative abundance of ms2ϵA in tRNAs from translating ribosomes suggests reduced function in comparison to its parent RNA modification, establishing the nature of the new structure in a newly perceived overlap of the two previously separate fields, namely an RNA modification damage. 相似文献
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