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41.
The first bidentate phosphanylborohydride: Synthesis, structure, and reactivity towards [CpFe(CO)2I]
Franz Dornhaus 《Journal of organometallic chemistry》2007,692(14):2949-2955
Deprotonation of the phosphane-borane adduct rac/meso-(HP(BH3)(Ph)CH2)2 (2) with KH provides facile access to the bidentate phosphanylborohydride rac/meso-K2[(P(BH3)(Ph)CH2)2] (3). Treatment of 3 with two equivalents of [CpFe(CO)2I] gives the dinuclear complex rac/meso-[(CpFe(CO)2)2-μ-(P(BH3)(Ph)CH2)2] (4). Single crystals of the pure diastereomers meso-2, meso-3(thf)4, and rac-4 have been grown from toluene/pentane, diethyl ether/thf, and benzene/pentane, respectively. The molecular structures of all three compounds have been determined by X-ray crystallography. 相似文献
42.
V. N. Khabashesku S. E. Boganov K. N. Kudin J. L. Margrave J. Michl O. M. Nefedov 《Russian Chemical Bulletin》1999,48(11):2003-2015
The recent advances in spectroscopic and quantum-chemical studies of carbene-to-olefin isomerization of carbene analogs of
Group 14 elements are discussed. Primary attention is devoted to the use of matrix isolation spectroscopy, whose successful
combination with modern calculation techniques has resulted in the first spectroscopic characterization of a number of novel
short-lived silylenes and germylenes and their structural isomers with unsaturated Si=C, Ge=C, and Si=O bonds.
Based on invited lecture given by Professor Dr. V. N. Khabashesku at the Sixth International Conference on Chemistry of Carbenes
and Related Intermediates (May 28–30, 1998, St. Petersburg, Russia).
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2027–2039, November, 1999. 相似文献
43.
44.
M. L. Lorenzini L. Bruno-Blanch G. L. Estiú 《International journal of quantum chemistry》1998,70(6):1195-1208
In order to determine the structural requirements that are important for GABAB binding affinity, a quantum-chemical-based conformational study has been performed, followed by a similarity analysis which includes 12 GABAB analogs. Due to the flexibility of the structures, a semigrid GABAB analog [2RS-(5,5-dimethyl) morpholinyl-acetic acid] has been used as a template for the amonium moiety in order to help to identify the active conformation. Both in vacuo, and solvent-simulated calculations, for the physiological media modeled as water molecules, have been compared, for this analog, at ab initio (G94, 6-31+G(d,p)) and semiempirical (PM3) levels, respectively. On the basis of this comparison, the results of in vacuo PM3 calculations have been chosen for the similarity analysis. We have included, in the calculations, a group of molecules heterogeneous enough to become representative of the different families that can bind to the GABAB receptor site. Following their comparison we report the leading characteristics that can be related to their binding capability and define a pharmacophoric pattern for GABAB analogs. The latter is compared with the one previously found for the binding affinity at the GABAA receptor site. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 70: 1195–1208, 1998 相似文献
45.
Two extra-hydroxylated analogs of 24-epibrassinolide (2), 17-hydroxy-24-epibrassinolide (4), 25-hydroxy-24-epibrassinolide (5), and two oxo-analogs of 24-epibrassinolide 22-oxo-23S-24-epibrassinolide (6), 22R-23-oxo-24-epibrassinolide (7) as impurities were isolated and identified from the initial material [purity: 2 and its 22S, 23S-isomer (3) >95%] by using various chromatographic methods and repeated crystallization. Among them, compound 4 and compound 6 were first reported. Their structures were established by spectrometric analysis and X-ray crystallography study. Formation of mixed crystals of 6 and 7 in the crystallization process was postulated and further confirmed. 相似文献
46.
Traditionally, groundwater flow models, as well as oil reservoir models, are based on the block-centered finite difference
method. Well-known models based on this approach are MODFLOW (groundwater) and ECLIPSE (oil and gas). Such models are well
proven and robust; their underlying principles are well understood by hydrologists and petroleum reservoir engineers. Nevertheless,
the desire to improve the block-centered finite difference paradigm has always been alive, for instance, to be able to apply
deformed grid blocks, or to model anisotropy that is not aligned along the coordinate axes. This article introduces the edge-based
stream function as a potential alternative to the paradigmatic model, not only to mitigate the above mentioned limitations,
but especially for its promise to inverse modeling. Computer programs have been developed for the discrete analog equations
of the stream function method and the conventional method. The two methods are tested by using synthetic forward modeling
problems of uniform and radial flow. The theoretical formulation and the numerical results show that the two methods are algebraically
equivalent and yield the same flux output. However, for rectangular grid blocks and anisotropy aligned along the coordinate
axes, the block-centered method is shown to be computationally more efficient than the edge-based stream function method.
The major advantage of the stream function method is that it is linear in the resistivities, proving it an ideal candidate
for direct inverse modeling. Moreover, any arbitrary specification of stream functions yields a solution that satisfies the
mass balance. 相似文献
47.
Alferov K. V. Zhukov Yu. N. Khurs E. N. Osipova T. I. Khomutov R. M. 《Russian Chemical Bulletin》2001,50(2):316-318
A convenient procedure for the synthesis of 1-amino-3-hydroxypropylphosphinic and -phosphonic acids (analogs of homoserine) was developed. The procedure involves the reaction of salts of phosphinic and phosphonic analogs of S-methylmethionine with AcONa/AcOH followed by hydrolysis. 相似文献
48.
综述了应用酶催化过渡态理论设计的几类正碳离子样的过渡态类似物作为酶的抑制剂的研究进展。其中包括类异戊二烯的正离子过渡态类似物,唾液酸转移酶的过渡态类似物,3-脱氧-D-甘露糖-2-辛酮糖酸酯-8-磷酸酯(KDO8P) 合成酶的过渡态类似物,尿苷二磷酸酯葡糖醛酸基转移酶(UGT) 的过渡态类似物。 相似文献
49.
50.
A synthetic route has been developed for incorporating pyrazoline derivatives as proline surrogates in constrained X-Pro peptidomimetics. The route allows for the synthesis of dipeptide building blocks having either a six or seven-membered-ring annulated onto the pyrazoline moiety, as well as for the asymmetric synthesis of analogs having substituents on N-terminal side of the building block. 相似文献