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41.
Calzolari A Alexandre SS Zamora F Di Felice R 《Journal of the American Chemical Society》2008,130(16):5552-5562
We present an ab initio study of the structural and electronic properties of the halogen-bridged MMX single polymer [Pt2(CH3CS2)4I]n and of various possible modifications of its sequence, in the framework of density functional theory. The computed band structure of the infinite regular polymer reveals a net metallic character; this evidence is compatible with the outcome of recent measurements done in the solid phase at room temperature. By taking the regular [Pt2(CH3CS2)4I]n polymer as our reference system, we analyzed the origin and the robustness of the metallic state along the chain with respect to a large set of geometrical and chemical perturbations of the subunits. In particular, we considered partial substitutions of the metal, halide, and dithiocarboxylate ligand subunits, as well as structural strain, defects, and magnetic effects. Our results demonstrate that the metallic character of single MMX chains is very resistant to a wide range of possible distortions that can occur in reality. 相似文献
42.
Delgado S Sanz Miguel PJ Priego JL Jiménez-Aparicio R Gómez-García CJ Zamora F 《Inorganic chemistry》2008,47(20):9128-9130
We report on a novel highly semiconducting 1D coordination polymer architecture obtained by the reaction of a Cu(II) salt with 2,2'-dipyridyldisulfide under microwave solvothermal conditions. This reaction proceeds with an unusual C-S and S-S bond cleavage of the 2,2'-dipyridyldisulfide ligand. The unprecedented architecture of this coordination polymer consists of a 1D chain formed by the assembling of Cu9 cluster cages. The electrical conductivity behavior of this novel material suggests new perspectives for the use of coordination polymers as electrical conducting materials. 相似文献
43.
Guijarro A Castillo O Calzolari A Sanz Miguel PJ Gómez-García CJ di Felice R Zamora F 《Inorganic chemistry》2008,47(21):9736-9738
Three new compounds of formula [Pt2(SSCR)4] (R = CH3, (CH2)4CH3, cyclohexyl) have been prepared and characterized by X-ray diffraction. Their crystal structures consist of one-dimensional linear chains formed by stacking of the dimetallic complexes in which the alkyl group on the dithioacetate modulates the intermetallic distances between dimetallic entities. Direct current electrical conductivity studies show that crystals of the three compounds behave as semiconductors and their conductivity values are directly connected to the intermolecular metal-to-metal distances. These experimental results are supported by density functional theory calculations. 相似文献
44.
A Branch and Contract Algorithm for Problems with Concave Univariate, Bilinear and Linear Fractional Terms 总被引:1,自引:0,他引:1
A new deterministic branch and bound algorithm is presented in this paper for the global optimization of continuous problems that involve concave univariate, bilinear and linear fractional terms. The proposed algorithm, the branch and contract algorithm, relies on the use of a bounds-contraction subproblem that aims at reducing the size of the search region by eliminating portions of the domain in which the objective function takes only values above a known upper bound. The solution of contraction subproblems at selected branch and bound nodes is performed within a finite contraction operation that helps reducing the total number of nodes in the branch and bound solution tree. The use of the proposed algorithm is illustrated with several numerical examples. 相似文献
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Flix Zamora Pilar Amo-Ochoa Birgit Fischer Arnd Schimanski Bernhard Lippert 《Angewandte Chemie (International ed. in English)》1999,38(15):2274-2275
Not only UV radiation can bring about the dimerization of the pyrimidine nucleobase uracil, a metal ion can as well! The reaction proceeds by a reductive elimination process of two cis-oriented uracil entities, each bonded to AuIII through C5 [Eq. (a)]. R/R′=H/CH3, CH3/CH3, H,C5H9O4 相似文献
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Maria A. Alvarez Edgardo J. Saavedra Mónica S. Olivella Fernando D. Suvire Miguel A. Zamora Ricardo D. Enriz 《Central European Journal of Chemistry》2012,10(1):248-255
The multidimensional Conformational Potential Energy Hypersurface (PEHS) of cyclotrisarcosyl was comprehensively investigated
at the DFT (B3LYP/6-31G(d), B3LYP/6-31G(d,p) and B3LYP/6-311++G(d,p)), levels of theory. The equilibrium structures, their
relative stability, and the Transition State (TS) structures involved in the conformational interconversion pathways were
analyzed. Aug-cc-pVTZ//B3LYP/6-311++G(d,p) and MP2/6-31G(d)//B3LYP/6-311++G(d,p) single point calculations predict a symmetric
cis-cis-cis crown conformation as the energetically preferred form for this compound, which is in agreement with the experimental data.
The conformational interconversion between the global minimum and the twist form requires 20.88 kcal mol-1 at the MP2/6-31G(d)//B3LYP/6-311++G(d,p)
level of theory. Our results allow us to form a concise idea about the internal intricacies of the PEHSs of this cyclic tripeptide,
describing the conformations as well as the conformational interconversion processes in this hypersurface. In addition, a
comparative analysis between the conformational behaviors of cyclotrisarcosyl with that previously reported for cyclotriglycine
was carried out 相似文献