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81.
Dr. George Dhimba Prof. Dr. Alfred Muller Prof. Dr. Koop Lammertsma 《欧洲无机化学杂志》2023,26(25):e202300256
Cis-MoO2(nacnac)2 (nacnac=β-diketiminate) can be a viable chiral-at-metal catalyst when its two β-diketiminate (nacnac) ligands are N-substituted to prevent Λ⇌Δ racemization. Even simple methyl groups raise the barriers for racemization significantly for the Bailar, Rây-Dutt, Conte-Hippler, and Dhimba-Muller-Lammertsma (DML) twists to a respectable 28.5, 37.8, 30.5, and 25.1 kcal/mol, respectively, at ωB97X-D/6-311+G(2d,p) (LANL2DZ for Mo) including acetonitrile solvation. The lowest energy DML barrier increases to ΔGo=27.4 kcal/mol with N-substituted t-butyl groups. The nacnac ligands’ electronic and steric components to the racemization barriers are discussed. 相似文献
82.
V. L. Ivanov R. R. Akhmetshin A. N. Amirkhanov A. V. Anisenkov V. M. Aulchenko V. S. Banzarov N. S. Bashtovoy D. E. Berkaev A. V. Bragin S. I. Eidelman D. A. Epifanov L. B. Epshteyn A. L. Erofeev G. V. Fedotovich S. E. Gayazov A. A. Grebenuk D. N. Grigoriev E. M. Gromov F. V. Ignatov S. V. Karpov V. F. Kazanin B. I. Khazin I. A. Koop O. A. Kovalenko A. N. Kozyrev E. A. Kozyrev P. P. Krokovny A. E. Kuzmenko A. S. Kuzmin I. B. Logashenko P. A. Lukin K. Yu. Mikhailov V. S. Okhapkin Yu. N. Pestov E. A. Perevedentsev A. S. Popov G. P. Razuvaev Yu. A. Rogovsky A. L. Romanov A. A. Ruban N. M. Ryskulov A. E. Ryzhenenkov V. E. Shebalin D. N. Shemyakin B. A. Shwartz D. B. Shwartz A. L. Sibidanov Yu. M. Shatunov P. Yu. Shatunov E. P. Solodov V. M. Titov A. A. Talyshev A. I. Vorobiov Yu. V. Yudin 《Physics of Atomic Nuclei》2016,79(2):251-259
We report preliminary results on the cross section of the process e+e? → φ(1020)η measured at 30 center-of-mass energy points in the range from 1.59 up to 2.0 GeV. Data analysis is based on the integrated luminosity of 22 pb?1 collected with the CMD-3 detector in 2011–2012. The obtained cross section agrees with the BaBar measurement and has better statistical accuracy. 相似文献
83.
Proton assisted O-O bond splitting of cytochromes' P450 hydroperoxo Compound 0 has been investigated by density functional theory, showing a barrier for the slightly endothermic formation of the iron-oxo Compound I. The barrier and the endothermicity increase with decreasing acidity of the distal proton source. Protonation of the proximal iron heme ligand favors the O-O bond scission and provides an important regulatory component in the catalytic cycle. The Compound 0 --> I conversion is slightly exothermic for the peroxidase and catalase models. Implications of the energetic relationship between the two reactive intermediates are discussed in terms of possible oxidative pathways. 相似文献
84.
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87.
Michael J. Bayer Hans Pritzkow Walter Siebert 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(5):o257-o258
In the title compound, 1,1,6a,7,9a,10‐hexachloro‐2,3,5,6,8,9,11,12‐octa‐p‐tolyl‐1,6a,9a,12a‐tetraborata‐3a,4a,7,10‐tetrabora‐4a1,6b,9b,12b‐tetraoxonia‐4‐oxatetracyclopenta[1,2‐a:2,1,5‐de:1,2‐g:1,2‐i]naphthalene dichloromethane pentasolvate, C64H56B8Cl6O5·5CH2Cl2, two condensed oxadiborole rings are attached to two further oxadiborole rings in a type of donor–acceptor bonding, thus forming a ten‐membered alternating (B—O)5 naphthalene‐like arrangement as the central building block. 相似文献
88.
Sebastian Burck Dr. Sander G. A. van Assema Dr. Bas Lastdrager Dr. J. Chris Slootweg Dr. Andreas W. Ehlers Dr. José M. Otero Dr. Bruno Dacunha‐Marinho Dr. Antonio L. Llamas‐Saiz Dr. Mark Overhand Dr. Mark J. van Raaij Dr. Koop Lammertsma Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(33):8134-8145
The natural product Gramicidin S is a promising scaffold for novel oligopeptide‐based bisphosphine ligands, combining the advantageous rigid chiral backbone with the close proximity of phosphine substituents. The required unnatural, phosphine‐containing, amino acid building blocks were synthesized by means of a novel protocol that involves the enantioselective alkylation of a chiral nickel Schiff base template. Three Ni complexes were prepared with different alkyl chains between the phosphine group and the α‐carbon atom of the incorporated glycine; the absolute stereochemistry of two of them was determined by single‐crystal X‐ray structure analysis. By detaching the template, enantiopure L ‐phosphine amino acids resulted enabling the solid‐phase, stepwise construction of a linear sequence of the phosphine‐modified oligopeptides. On cyclization three bisphosphine‐substituted Gramicidin S analogues resulted, differing only in the size and shape of the linkage between the phosphine groups and the oligopeptides backbone. Their crystal structures suggest these species to have potential as chelating ligands. 相似文献
89.
A. S. Romanov D. V. Muratov P. V. Petrovskii M. Yu. Antipin W. Siebert A. R. Kudinov 《Russian Chemical Bulletin》2009,58(3):594-599
The cationic triple-decker complexes [CpCo(1,3-C3B2Me5)M(C5R5)]+ (M = Rh (2), Ir (3), R = H (a), Me (b)) with the bridging diborolyl ligand were synthesized by the reaction of the sandwich anion [CpCo(1,3-C3B2Me5)]- (1) with the halide complexes [CpMI2]2 or [Cp*MCl2]2 (Cp* = C5Me5). The structures of [2b]PF6 and [3b]PF6 were established by X-ray diffraction. The nature of the metal—diborolyl bond in these complexes was analyzed using the energy
decomposition scheme. 相似文献
90.
Halil Aktas J. Chris Slootweg Dr. Andreas W. Ehlers Dr. Martin Lutz Dr. Anthony L. Spek Prof. Dr. Koop Lammertsma Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(17):3108-3111
Do the twist : The reaction of in situ generated phosphinidenes with phosphaalkynes is a facile route to the new metal‐coordinated η3‐diphosphavinylcarbene 1 , which shows facile ligand‐exchange reactions and undergoes an unprecedented rearrangement that involves phosphinidene complex 2 and η3‐phosphaalkenylphosphinidene complex 3 , the 1,3 isomer of 1 .