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131.
Alexandr G. Oshchepkov Antoine Bonnefont Elena R. Savinova 《Current Opinion in Electrochemistry》2021
Metal/metal (hydr)oxide heterostructures have been proposed as an efficient means to enhance the kinetics of hydrogen electrode reactions (the hydrogen evolution and the hydrogen oxidation reaction) on Pt, Ni, and other electrodes in the alkaline medium. However, the reasons for the faster electrode kinetics are still not fully understood. By considering two electrode materials, namely Pt and Ni, widely studied in hydrogen electrode reactions in alkaline media, this review brings to light differences in their pH-dependent behavior and likely different genesis of the enhancement in the presence of 3d transition metal oxides. 相似文献
132.
Olesya Y. Trofimova Arina V. Maleeva Irina V. Ershova Anton V. Cherkasov Georgy K. Fukin Rinat R. Aysin Konstantin A. Kovalenko Alexandr V. Piskunov 《Molecules (Basel, Switzerland)》2021,26(9)
Three new 3D metal–organic frameworks of lanthanum based on mixed anionic ligands, [(La2(pQ)2(BDC)4)·4DMF]n, [(La2(pQ)2(DHBDC)4)·4DMF]n, [(La2(CA)2(BDC)4)·4DMF]n (pQ—dianion of 2,5-dihydroxy-3,6-di-tert-butyl-para-quinone, CA—dianion of chloranilic acid, BDC-1,4-benzenedicarboxylate, DHBDC-2,5-dihydroxy-1,4-benzenedicarboxylate and DMF-N,N′-dimethylformamide), were synthesized using solvothermal methodology. Coordination polymers demonstrate the rare xah or 4,6T187 topology of a 3D framework. The homoleptic 2D-coordination polymer [(La2(pQ)3)·4DMF]n was obtained as a by-product in the course of synthetic procedure optimization. The thermal stability, spectral characteristics and porosity of coordination polymers were investigated. 相似文献
133.
We investigate questions related to the minimal degree of invariants of finitely generated diagonalizable groups. These questions were raised in connection to security of a public key cryptosystem based on invariants of diagonalizable groups. We derive results for minimal degrees of invariants of finite groups, abelian groups and algebraic groups. For algebraic groups we relate the minimal degree of the group to the minimal degrees of its tori. Finally, we investigate invariants of certain supergroups that are superanalogs of tori. It is interesting to note that a basis of these invariants is not given by monomials. 相似文献
134.
Aleksandr S. Oreshonkov Julia V. Gerasimova Alexandr A. Ershov Alexander S. Krylov Kirill A. Shaykhutdinov Aleksandr N. Vtyurin Maxim S. Molokeev Konstantin Y. Terent'ev Natalia V. Mihashenok 《Journal of Raman spectroscopy : JRS》2016,47(5):531-536
MnGeO3 single‐crystal samples have been synthesized by optical zonal melting and spontaneous crystallization. X‐ray crystal analysis showed the first sample to be a two‐phase one with phase ratio as follows: 17% – monoclinic C2/c, and 83% – orthorhombic Pbca; the phase ratio of the second sample was unknown. Raman spectra have been produced for these samples. Lattice dynamics has been simulated and polarization dependencies of lines' intensities have been analyzed to interpret experimental Raman spectra and to attribute lines to the spectra of monoclinic and orthorhombic phases. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
135.
Ohba has conjectured that if G is a k-chromatic graph with at most 2k+1 vertices, then the list chromatic number or choosability of G is equal to its chromatic number χ(G), which is k. It is known that this holds if G has independence number at most three. It is proved here that it holds if G has independence number at most five. In particular, and equivalently, it holds if G is a complete k-partite graph and each part has at most five vertices. 相似文献
136.
Piskunov AV Maleeva AV Fukin GK Baranov EV Bogomyakov AS Cherkasov VK Abakumov GA 《Dalton transactions (Cambridge, England : 2003)》2011,40(3):718-725
The interaction of 3,6-di-tert-butyl-o-benzoquinone (3,6-Q) with indium in toluene leads to the tris-o-semiquinolate derivative (3,6-SQ)(3)In (3,6-SQ - radical-anion of 3,6-Q). According to single-crystal X-ray diffraction analysis, this complex has a trigonal prismatic structure. Magnetic measurements revealed that the exchange interactions between odd electrons of the paramagnetic ligands in (3,6-SQ)(3)In are antiferromagnetic in character. The treatment of (3,6-SQ)(3)In with 2,2'-dipyridyl (Dipy) causes the displacement of one o-quinone ligand and the formation of the (3,6-SQ)In(Dipy)(3,6-Cat) (3,6-Cat - dianion of 3,6-Q) derivative containing mixed charged o-quinoid ligands. The reaction of InI with (3,6-SQ)K in THF solution is accompanied by a redox process and the potassium-indium(iii) catecholate derivative was obtained as a result. The oxidation of InI with 3,6-Q in THF produces the dimeric In(iii) iodo-catecholate complex [(3,6-Cat)(2)In·2THF]InI(2). The same derivative can be synthesized by the interaction of indium metal with a mixture of I(2) and 3,6-Q. 相似文献
137.
Shestivska V Nemec A Dřevínek P Sovová K Dryahina K Spaněl P 《Rapid communications in mass spectrometry : RCM》2011,25(17):2459-2467
Infection by Pseudomonas aeruginosa (PA) is a major cause of morbidity and mortality in patients with cystic fibrosis (CF). Breath analysis could potentially be a useful diagnostic of such infection, and analyses of volatile organic compounds (VOCs) emitted from PA cultures are an important part of the search for volatile breath markers of PA lung infection. Our pilot experiments using solid‐phase microextraction, SPME and gas chromatography/mass spectrometric (GC/MS) analyses of volatile compounds produced by PA strains indicated a clear presence of methyl thiocyanate. This provided a motivation to develop a method for real‐time online quantification of this compound by selected ion flow tube mass spectrometry, SIFT‐MS. The kinetics of reactions of H3O+, NO+ and O2+? with methyl thiocyanate at 300 K were characterized and the characteristic product ions determined (proton transfer for H3O+, rate constant 4.6 × 10–9 cm3 s–1; association for NO+, 1.7 × 10–9 cm3 s–1 and nondissociative charge transfer for O2+?, 4.3 × 10–9 cm3 s–1). The kinetics library was extended by a new entry for methyl thiocyanate accounting for overlaps with isotopologues of hydrated hydronium ions. Solubility of methyl thiocyanate in water (Henry's law constant) was determined using standard reference solutions and the linearity and limits of detection of both SIFT‐MS and SPME‐GC/MS methods were characterized. Thirty‐six strains of PA with distinct genotype were cultivated under identical conditions and 28 of them (all also producing HCN) were found to release methyl thiocyanate in headspace concentrations greater than 6 parts per billion by volume (ppbv). SIFT‐MS was also used to analyze the breath of 28 children with CF and the concentrations of methyl thiocyanate were found to be in the range 2–21 ppbv (median 7 ppbv). Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
138.
GA Senchyk VO Bukhan'ko AB Lysenko H Krautscheid EB Rusanov AN Chernega M Karbowiak KV Domasevitch 《Inorganic chemistry》2012,51(15):8025-8033
A series of new silver(I)-containing MOFs [Ag(2)(tr(2)ad)(2)](ClO(4))(2) (1), [Ag(2)(VO(2)F(2))(2)(tr(2)ad)(2)]·H(2)O (2), [Ag(2)(VO(2)F(2))(2)(tr(2)eth)(2)(H(2)O)(2)] (3), and [Ag(2)(VO(2)F(2))(2)(tr(2)cy)(2)]·4H(2)O (4) supported by 4-substituted bifunctional 1,2,4-triazole ligands (tr(2)ad = 1,3-bis(1,2,4-triazol-4-yl)adamantane, tr(2)eth = 1,2-bis(1,2,4-triazol-4-yl)ethane, tr(2)cy = trans-1,4-bis(1,2,4-triazol-4-yl)cyclohexane) were hydrothermally synthesized and structurally characterized. In these complexes, the triazole heterocycle as an N(1),N(2)-bridge links either two adjacent Ag-Ag or Ag-V centers at short distances forming polynuclear clusters. The crystal structure of compound 1 is based on cationic {Ag(2)(tr)(4)}(2+) fragments connected in a 2D rhombohedral grid network with (4,4) topology. The neighboring layers are tightly packed into a 3D array by means of argentophilic interactions (Ag···Ag 3.28 ?). Bridging between different metal atoms through the triazole groups assists formation of heterobimetallic Ag(I)/V(V) secondary building blocks in a linear V-Ag-Ag-V sequence that is observed in complexes 2-4. These unprecedented tetranuclear {Ag(2)(VO(2)F(2))(2)(tr)(4)} units (the intermetal Ag-Ag and Ag-V distances are 4.24-4.36 and 3.74-3.81 ?, respectively), in which vanadium(V) oxofluoride units possess distorted trigonal bipyramidal environment {VO(2)F(2)N}ˉ, are incorporated into 1D ribbon (2) or 2D square nets (3, 4) using bitopic μ(4)-triazole ligands. The valence bond calculation for vanadium atoms shows +V oxidation state in the corresponding compounds. Thermal stability and photoluminescence properties were studied for all reported coordination polymers. 相似文献
139.
Marina O. Shibinskaya Nina A. Kutuzova Alexandr V. Mazepa Sergey A. Lyakhov Sergey A. Andronati Mykhayl Ju. Zubritsky Valerij F. Galat Janusz Lipkowski Victor Ch. Kravtsov 《Journal of heterocyclic chemistry》2012,49(3):678-682
A series of 6‐(3‐aminopropyl)‐6H‐indolo[2,3‐b]quinoxalines were synthesized with high yields by the reaction of 6‐(3‐chloropropyl)‐6H‐indolo[2,3‐b]quinoxaline and corresponding amines in presence of tetrabutylammonium iodide in boiling toluene or dimethylformamide at room temperature. It was found that boiling of 6‐(3‐chloropropyl)‐6H‐indolo[2,3‐b]quinoxaline in acetone with sodium iodide or in acetic acid lead to intramolecular cyclization product. 相似文献
140.
Leonid P. Rokhinson Mason Overby Alexandr Chernyshov Yuli Lyanda-Geller Xinyu Liu Jacek K. Furdyna 《Journal of magnetism and magnetic materials》2012
We report experiments where magnetization in GaMnAs ferromagnetic semiconductor is manipulated via strain or electric current. In both cases, charge carrier holes become partially polarized due to the anisotropic modification of holes spectra caused by spin–orbit interactions, and this polarization exerts spin torque sufficient to rotate ferromagnetic domains. 相似文献