全文获取类型
收费全文 | 131篇 |
免费 | 15篇 |
专业分类
化学 | 114篇 |
晶体学 | 1篇 |
力学 | 1篇 |
数学 | 11篇 |
物理学 | 19篇 |
出版年
2023年 | 2篇 |
2021年 | 5篇 |
2020年 | 2篇 |
2019年 | 7篇 |
2018年 | 7篇 |
2017年 | 9篇 |
2016年 | 13篇 |
2015年 | 5篇 |
2014年 | 4篇 |
2013年 | 12篇 |
2012年 | 15篇 |
2011年 | 14篇 |
2010年 | 4篇 |
2009年 | 8篇 |
2008年 | 13篇 |
2007年 | 3篇 |
2006年 | 4篇 |
2005年 | 7篇 |
2004年 | 2篇 |
2003年 | 1篇 |
1999年 | 1篇 |
1996年 | 1篇 |
1993年 | 1篇 |
1991年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
排序方式: 共有146条查询结果,搜索用时 218 毫秒
31.
Chakraborty B Roy AS Dasgupta S Basu S 《The journal of physical chemistry. A》2010,114(51):13313-13325
Conventional spectroscopic tools such as absorption, fluorescence, and circular dichroism spectroscopy used in the study of photoinduced drug-protein interactions can yield useful information about ground-state and excited-state phenomena. However, photoinduced electron transfer (PET) may be a possible phenomenon in the drug-protein interaction, which may go unnoticed if only conventional spectroscopic observations are taken into account. Laser flash photolysis coupled with an external magnetic field can be utilized to confirm the occurrence of PET and authenticate the spin states of the radicals/radical ions formed. In the study of interaction of the model protein human serum albumin (HSA) with acridine derivatives, acridine yellow (AY) and proflavin (PF(+)), conventional spectroscopic tools along with docking study have been used to decipher the binding mechanism, and laser flash photolysis technique with an associated magnetic field (MF) has been used to explore PET. The results of fluorescence study indicate that fluorescence resonance energy transfer takes place from the protein to the acridine-based drugs. Docking study unveils the crucial role of Ser 232 residue of HSA in explaining the differential behavior of the two drugs towards the model protein. Laser flash photolysis experiments help to identify the radicals/radical ions formed in the due course of PET (PF(?), AY(?-), TrpH(?+), Trp(?)), and the application of an external MF has been used to characterize their initial spin-state. Owing to its distance dependence, MF effect gives an idea about the proximity of the radicals/radical ions during interaction in the system and also helps to elucidate the reaction mechanisms. A prominent MF effect is observed in homogeneous buffer medium owing to the pseudoconfinement of the radicals/radical ions provided by the complex structure of the protein. 相似文献
32.
The article deals with an optimal response-adaptive design for allocating patients among two competing treatments in a phase III clinical trial. An optimal response-adaptive target is developed for a general class of response distributions subject to two clinically relevant constraints. Various theoretical and numerical properties of the proposed procedure are investigated and compared with some existing competitors. A data study is also included for the assessment of the proposed procedure in real situation. 相似文献
33.
5'-norcarbocyclic nucleosides have been found to possess a variety of meaningful biological properties. Derivatives of these compounds possessing substituents at the hydroxyl and heterocyclic ring bearing carbon atoms have not been described. As entries into these compounds, the 4'- and 1'-methyl derivatives of 5'-noraristeromycin (2 and 3) have been prepared from a common cyclopentyl precursor 8. The synthetic methods developed are adaptable to 5'-norcarbanucleosides possessing a variety of heterocyclic bases and in the l-like configuration. In turn, the products from such syntheses will lend themselves to a number of structural and biochemical investigations relevant to carbanucleosides in general. Compounds 2 and 3 lack antiviral properties and were not cytotoxic. 相似文献
34.
Reaction of the in situ generated purine C-8 carbanion of a protected 5'-noraristeromycin derivative with N-fluorobenzenesulfonimide gave 8-phenylsulfonyl-5'-noraristeromycin rather than the expected 8-fluoro derivative. A single electron transfer (SET) mechanism is proposed for this occurrence. The phenylsulfonyl product offers a structural feature common to some anti-HIV agents. [reaction: see text] 相似文献
35.
36.
Porphyrin/Platinum(II) C^N^N Acetylide Complexes: Synthesis,Photophysical Properties,and Singlet Oxygen Generation 下载免费PDF全文
Dr. Atanu Jana Luke McKenzie Dr. Ashley B. Wragg Dr. Masatoshi Ishida Dr. Jonathan P. Hill Prof. Julia A. Weinstein Dr. Elizabeth Baggaley Prof. Dr. Michael D. Ward 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(12):4164-4174
A new class of substituted porphyrins has been developed in which a different number of cyclometalated PtII C^N^N acetylides and polyethylene glycol (PEG) chains are attached to the meso positions of the porphyrin core, which are meant for photophysical, electrochemical, and in vitro light‐induced singlet oxygen (1O2) generation studies. All of these ZnII porphyrin–PtII C^N^N acetylide conjugates show moderate to high (ΦΔ=0.55 to 0.63) singlet oxygen generation efficiency. The complexes are soluble in organic solvents but, despite the PEG substituents, slowly aggregate in aqueous solvent systems. These conjugates also exhibit interesting photophysical properties, including near‐complete photoinduced energy transfer (PEnT) through the rigid acetylenic bond(s) from the PtII C^N^N antenna units to the ZnII porphyrin core, which shows sensitized luminescence, as shown by quenching of PtII C^N^N‐based luminescence. Electrochemical measurements show a set of redox processes that are approximately the sum of what is observed for the PtII C^N^N acetylide and ZnII porphyrin units. UV/Vis spectroscopic properties are supported by DFT calculations. 相似文献
37.
A Sierpinski gasket fractal network model is studied in respect of its electronic spectrum and magneto-transport when each ‘arm’ of the gasket is replaced by a diamond shaped Aharonov–Bohm interferometer, threaded by a uniform magnetic flux. Within the framework of a tight binding model for non-interacting, spinless electrons and a real space renormalization group method we unravel a class of extended and localized electronic states. In particular, we demonstrate the existence of extreme localization of electronic states at a special finite set of energy eigenvalues, and an infinite set of energy eigenvalues where the localization gets ‘delayed’ in space (staggered localization). These eigenstates exhibit a multitude of localization areas. The two terminal transmission coefficient and its dependence on the magnetic flux threading each basic Aharonov–Bohm interferometer is studied in details. Sharp switch on–switch off effects that can be tuned by controlling the flux from outside, are discussed. Our results are analytically exact. 相似文献
38.
Kumaresh Ghosh Debasis Kar Atanu Panja Ioannis D. Petsalakis Giannoula Theodorakopoulos 《Supramolecular chemistry》2013,25(10-12):856-863
A series of pyridine-coupled benzimidazolium-based receptors 1, 2 and 3 have been designed and synthesised. In the series, only receptor 1 is structurally appealing in the selective recognition of H2PO4? in CHCl3 as well as in CH3CN over a series of other anions. The ratiometric change in emission with a triplet band at 420 nm is the distinctive feature of selective recognition of H2PO4? in CHCl3. In CH3CN, a ‘turn on’ response is selectively observed. Binding studies have been carried out using fluorescence, UV–vis, 1H NMR and 31P NMR spectroscopic techniques. Experimental results have been correlated with the theoretical findings. 相似文献
39.
A method for determining urine porphyrins by HPLC is described. In the preliminary step, porphyrins are purified in high yields and concentrated by low pressure reverse-phase chromatography on C18 (octadecylsilane bonded silica) cartridge. Porphyrins are stable for 10 days after adsorption on C18 cartridge. The separation of porphyrin esters is performed on an aminopropyl-bonded silica column with an eluting system containing n-heptane and ethyl acetate. The system enables rapid isocratic separation of porphyrin methyl esters with high selectivity. The simplicity and reproducibility of the whole procedure allows its application to the routine analysis of urinary porphyrins in the clinical laboratory. 相似文献
40.
Pavel Kotalík 《Czechoslovak Journal of Physics》1993,43(12):1165-1171
A one-dimensional Stefan problem for a thin plate which is heated by laser pulses is solved by approximating the enthalpy formulation of the problem byC
0 piecewise linear finite elements in space combined with a semi-implicit scheme in time.Dedicated to the memory of Professor Jozef Kvasnica. 相似文献