全文获取类型
收费全文 | 143篇 |
免费 | 3篇 |
专业分类
化学 | 100篇 |
力学 | 1篇 |
数学 | 2篇 |
物理学 | 43篇 |
出版年
2021年 | 5篇 |
2019年 | 1篇 |
2017年 | 2篇 |
2015年 | 1篇 |
2014年 | 2篇 |
2013年 | 3篇 |
2012年 | 1篇 |
2011年 | 3篇 |
2009年 | 4篇 |
2008年 | 3篇 |
2007年 | 4篇 |
2006年 | 2篇 |
2005年 | 5篇 |
2004年 | 4篇 |
2003年 | 9篇 |
2002年 | 7篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 5篇 |
1998年 | 2篇 |
1996年 | 3篇 |
1994年 | 9篇 |
1993年 | 4篇 |
1992年 | 9篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1973年 | 3篇 |
1883年 | 2篇 |
排序方式: 共有146条查询结果,搜索用时 281 毫秒
41.
A series of beta-methanesulfonate phenethyl radicals bearing a range of electron donating and withdrawing aromatic substituents were generated and studied in a variety of solvent mixtures using nanosecond laser flash photolysis. Rate constants for the formation of the corresponding styrene radical cation via heterolytic loss of the beta-mesylate leaving group were measured using time-resolved absorption spectroscopy. The ionization reaction was investigated in a variety of solvents and solvent mixtures including 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,2-trifluoroethanol, acetonitrile, methanol and water. The influence of substituent electronic effect and solvent polarity on the kinetics of the beta-heterolysis reaction are discussed and assessed using the sigma+ Hammett parameter and Y(OMs) values, respectively. The small magnitude of m calculated for the formation of the 4-methoxystyrene radical cation by ionization of the mesylate group (m = 0.33) in aqueous methanol mixtures is compared to values obtained for the formation of the same radical cation via loss of chloride and bromide where m = 0.56 and m = 0.45, respectively. 相似文献
42.
43.
Lepailleur A Bureau R Paillet-Loilier M Fabis F Saettel N Lemaître S Dauphin F Lesnard A Lancelot JC Rault S 《Journal of chemical information and modeling》2005,45(4):1075-1081
The present study discusses the well-known 5-HT7/5-HT1A selectivity issue through a new series of phenylpyrrole derivatives. The first hits emerged from a virtual screening performed on a chemolibrary. Further study led to an optimization of a preliminary 5-HT7 pharmacophore model. The importance of each pharmacophoric feature is confirmed, but these characteristics have to be coupled to geometric constraints in order to achieve a 5-HT7 selectivity. Indeed, 5-HT1A affinity probably arises from extended conformations, whereas a bent one appears to be best suited for 5-HT7 selectivity. 相似文献
44.
45.
Nikul’shina M. S. Mozhaev A. V. Minaev P. P. Fournier M. Lancelot C. Blanchard P. Payen E. Lamonier C. Nikul’shin P. A. 《Kinetics and Catalysis》2017,58(6):825-832
Kinetics and Catalysis - The bimetallic MoWS2/Al2O3 catalyst was synthesized using the Keggin-type mixed heteropolyacid H4SiMo3W9O40. The monometallic catalysts SiMo12/Al2O3 and SiW12/Al2O3 based... 相似文献
46.
47.
Jason T Miller John H Bartley Hereward JC Wimborne Aisha L Walker David C Hess William D Hill James E Carroll 《BMC neuroscience》2005,6(1):63
Background
Stromal cell-derived factor 1 (SDF-1 or CXCL12) is chemotaxic for CXCR4 expressing bone marrow-derived cells. It functions in brain embryonic development and in response to ischemic injury in helping guide neuroblast migration and vasculogenesis. In experimental adult stroke models SDF-1 is expressed perivascularly in the injured region up to 30 days after the injury, suggesting it could be a therapeutic target for tissue repair strategies. We hypothesized that SDF-1 would be expressed in similar temporal and spatial patterns following hypoxic-ischemic (HI) injury in neonatal brain. 相似文献48.
About 103 neutrons are observed for two locations of the focus with respect to the surface of a D2 ice. A maximum 10% reflectivity is obtained for an intermediate position. 相似文献
49.
A feasibility and chemical study of the coupling conditions of L-ascorbic acid with ferulic acid derivatives are described on the basis of the known synergistic effects of mixtures of various antioxidants. Novel L-ascorbic ferulic hybrids linked at the C-3 hydroxyl group were prepared with the aim to protect the alcohol function and the enediol system. 相似文献
50.
Desbat B Lancelot E Krell T Nicolaï MC Vogel F Chevalier M Ronzon F 《Langmuir : the ACS journal of surfaces and colloids》2011,27(22):13675-13683
The production protocol of many whole cell/virion vaccines involves an inactivation step with β-propiolactone (BPL). Despite the widespread use of BPL, its mechanism of action is poorly understood. Earlier work demonstrated that BPL alkylates nucleotide bases, but its interaction with proteins has not been studied in depth. In the present study we use ellipsometry to analyze the influence of BPL treatment of two H1N1 influenza strains, A/Brisbane/59/2007 and A/New Caledonia/20/1999, which are used for vaccine production on an industrial scale. Analyses were conducted using a mixed lipid monolayer containing ganglioside GM3, which functions as the viral receptor. Our results show that BPL treatment of both strains reduces viral affinity for the mixed monolayer and also diminishes the capacity of viral domains to self-assemble. In another series of experiments, the pH of the subphase was reduced from 7.4 to 5 to provoke the pH-induced conformational change of hemagglutinin, which occurs following endocytosis into the endosome. In the presence of the native virus the pH decrease caused a reduction in domain size, whereas lipid layer thickness and surface pressure were increased. These observations are consistent with a fusion of the viral membrane with the lipid monolayer. Importantly, this fusion was not observed with adsorbed inactivated virus, which indicates that BPL treatment inhibits the first step of virus-membrane fusion. Our data also indicate that BPL chemically modifies hemagglutinin, which mediates the interaction with GM3. 相似文献