全文获取类型
收费全文 | 132篇 |
免费 | 7篇 |
专业分类
化学 | 124篇 |
力学 | 2篇 |
数学 | 7篇 |
物理学 | 6篇 |
出版年
2022年 | 1篇 |
2021年 | 4篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2015年 | 6篇 |
2014年 | 7篇 |
2013年 | 7篇 |
2012年 | 4篇 |
2011年 | 8篇 |
2010年 | 3篇 |
2009年 | 8篇 |
2008年 | 6篇 |
2007年 | 10篇 |
2006年 | 8篇 |
2005年 | 6篇 |
2004年 | 7篇 |
2003年 | 4篇 |
2002年 | 7篇 |
2001年 | 2篇 |
2000年 | 7篇 |
1998年 | 3篇 |
1996年 | 1篇 |
1994年 | 1篇 |
1993年 | 5篇 |
1991年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有139条查询结果,搜索用时 15 毫秒
41.
M. Vorona I. Potoročina G. Veinberg I. Shestakova I. Kanepe M. Petrova E. Liepinsh E. Lukevics 《Chemistry of Heterocyclic Compounds》2007,43(5):646-652
The reaction of tert-butyl 7α-chloro-and 7-β-chloro-7α-isopropoxy-3-methyl-1,1-dioxoceph-3-em-4-carboxylates with the Vilsmeier
reagent was carried out with introduction of N,N-dimethylaminomethylene group at position 2 in the E-and Z-isomeric forms.
Prolonged treatment of tert-butyl 7α-chloro-3-methyl-2-(N,N-dimethylaminomethylene)-1,1-dioxoceph-3-em-4-carboxylate with
hydroxylamine hydrochloride in acetonitrile at 40–50°C gave tert-butyl 10(S)-chloro-6-methyl-5-oxa-1,1,9-trioxo-1-thia-4,8-diazatricyclo[7,2,0,02,6]undecane-7(R)-carboxylate which isomerized into 1-tertbutoxycarbonylmethyl-3α-chloro-4-(5-methylisoxazole-4-sulfonyl)azetidin-2-one.
In the case of tertbutyl 7β-chloro-7α-isopropoxy-3-methyl-2-(N,N-dimethylaminomethylen)-1,1-dioxoceph-3-em-4-carboxylate the
analogous reaction gave tert-butyl 10β-chloro-(2S,6S,7S,10R,11R)-10α-isopropoxy-6-methyl-5-oxa-1,1,9-trioxo-1-thia-4,8-diazatricyclo[7,2,0,02,6]undecane-7(R)-carboxylate, the struc-ture of which was determined by 2D-NOESY two-dimensional spectroscopy. The compounds
synthesized showed weak or no cytotoxic activity with respect to monolayers of cancer cells in vitro. 相似文献
42.
E. Lukevics I. Shestakova I. Domracheva A. Nesterova D. Zaruma J. Ashaks 《Chemistry of Heterocyclic Compounds》2006,42(6):761-764
High cytotoxicity has been established for the 8-quinolinethiolates of copper, cadmium, indium, antimony, bismuth, ruthenium,
rhodium, palladium, osmium, iridium, and platinum on HT-1080 (human fibrosarcoma), MG-22A (mouse hepatoma), and B-16 (mouse
melanoma) tumor cells. The greatest activity against HT-1080 was possessed by the iridium complex, and against MG-22A by the
osmium complex. All the investigated metal 8-quinolinethiolates were highly toxic in relation to NIH 3T3 normal mouse embryo
fibroblasts.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 870–873, June, 2006. 相似文献
43.
Yana Nikolova Georgi M. Dobrikov Zhanina Petkova Pavletta Shestakova 《Molecules (Basel, Switzerland)》2021,26(22)
A series of squaric acid amides (synthesized in 66–99% isolated yields) and a set of chiral aminoalcohols were comparatively studied as ligands in a model reaction of reduction of α-chloroacetophenone with BH3•SMe2. In all cases, the aminoalcohols demonstrated better efficiency (up to 94% ee), while only poor asymmetric induction was achieved with the corresponding squaramides. A mechanistic insight on the in situ formation and stability at room temperature of intermediates generated from ligands and borane as possible precursors of the oxazaborolidine-based catalytic system has been obtained by 1H DOSY and multinuclear 1D and 2D (1H, 10/11B, 13C, 15N) NMR spectroscopy of equimolar mixtures of borane and selected ligands. These results contribute to better understanding the complexity of the processes occurring in the reaction mixture prior to the possible oxazaborolidine formation, which play a crucial role on the degree of enantioselectivity achieved in the borane reduction of α-chloroacetophenone. 相似文献
44.
Large-scale helical-vortex instability is simulated numerically for laminar convection regimes. The simulation is based on the nonlinear Boussinesq equations supplemented by an external force of special form, whose structure is identical to the tensor structure of the generative term in the equation for the hydrodynamic alpha-effect. Introducing the external force makes it possible to model the average effect produced by small-scale helical turbulence: generation of a positive feedback between the toroidal and poloidal components of the velocity vector field. The structure and energetics of helical-vortex flows developing in a convectively unstable medium are analyzed. The parameters of helical and non-helical convection regimes are compared. Certain novel effects related to spiral feedback are discussed: generation of a toroidal velocity field in structures with the poloidal circulation typical of ordinary convection; enlargement of the horizontal scale of supercritical motions as a result of the merging of vortex cells, accompanied by a significant increase in the circulation strength in the larger helical vortices formed; qualitative changes in the energetics. 相似文献
45.
46.
47.
The frequency conditions for absolute stability of a number of nonlinear automatic systems with double modulation (with double pulse modulation, and with pulse and continuous modulation) are established. These conditions are expressed directly in terms of the frequency responses of the linear part.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 15, No. 3, pp. 376–388, March, 1972. 相似文献
48.
Alla Zablotskaya Izolda Segal Anatoly Mishnev Mikhail Maiorov Elmars Blums Irina Shestakova Ilona Domracheva 《应用有机金属化学》2013,27(12):716-722
Superparamagnetic iron oxide/oleic acid nanoparticles bearing lipid‐like organosilicon N‐(2‐hydroxyethyl)‐1,2,3,4‐tetrahydroisoquinoline derivatives have been synthesized with the aim of their potential biomedical application. X‐ray diffraction analysis, Dynamic light‐scattering measurements, method of magnetogranulometry and some others have been employed to investigate the morphology and properties of the nanoparticles synthesized. The magnetic core diameter of mixed covered nanoparticles ranged between 4.8 and 9.6 nm. The magnetization analyses showed that the particles are superparamagnetic at room temperature. In vitro cell cytotoxicity and intracellular NO generation caused by the water magnetic solution of nanoparticles possessing cytotoxic organosilicon heterocyclic choline analogue, namely N‐(2‐dimethyl‐n‐hexadecylsiloxyethyl)‐N‐methyl‐1,2,3,4‐tetrahydroisoquinolinium iodide, was examined in relation to monolayer human fibrosarcoma (HT‐1080) and mouse hepatoma (MG‐22A) tumour cell lines and normal mouse fibroblasts (NIH 3T3). The biological studies have revealed its selective cytotoxicity in tumour cells and strong effect on MG‐22A cell morphology. Incorporation of the synthesized nanoparticles into cells was observed. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
49.
T. R. Prosochkina R. G. Shestakova E. A. Kantor K. G. Kichatov 《Russian Journal of General Chemistry》2011,81(11):2362-2368
Computational simulation of 3,6-bis(4-butylphenyl)[1,2,4,5]tetrazine was carried out. Based on the energy of intermolecular
interactions of dimers was determined the probability of each configuration (stacking, in-plane and terminal). It was revealed
that in the 3,6-bis(4-butylphenyl)[1,2,4,5]tetrazine dimers the sliding of the molecules relative to each other is energetically
allowed in the narrow range of distances that provides retaining orientation of the molecules in the mesophase. The relationship
between the translational rigidity of the molecules in the dimer and nematic properties was revealed. 相似文献
50.
Nonlinear regimes of roll structure development in the Ekman atmospheric boundary layer are considered. Within the framework of a turbulent boundary layer theory that takes the inherent helicity into account, the helicity effect on the stability and development of secondary vortices is studied. The stabilizing role of helicity in the Ekman layer dynamics is detected. With increasing nonlinearity the rolls become time-dependent self-oscillatory structures exchanging energy and helicity with the main flow. Multi-scale structure regimes are obtained, similar to those observable in the atmospheric boundary layer and the solitary vortex structures previously discovered in bench and numerical experiments for Ekman flows between disks rotating in opposite directions. 相似文献