全文获取类型
收费全文 | 194篇 |
免费 | 17篇 |
专业分类
化学 | 149篇 |
晶体学 | 3篇 |
力学 | 9篇 |
数学 | 8篇 |
物理学 | 42篇 |
出版年
2023年 | 3篇 |
2022年 | 2篇 |
2021年 | 7篇 |
2020年 | 7篇 |
2019年 | 5篇 |
2018年 | 7篇 |
2017年 | 3篇 |
2016年 | 10篇 |
2015年 | 5篇 |
2014年 | 7篇 |
2013年 | 11篇 |
2012年 | 17篇 |
2011年 | 15篇 |
2010年 | 4篇 |
2009年 | 7篇 |
2008年 | 9篇 |
2007年 | 18篇 |
2006年 | 10篇 |
2005年 | 14篇 |
2004年 | 7篇 |
2003年 | 8篇 |
2002年 | 3篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1988年 | 1篇 |
1984年 | 5篇 |
1981年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 4篇 |
1972年 | 1篇 |
1971年 | 3篇 |
1970年 | 1篇 |
1969年 | 2篇 |
1968年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有211条查询结果,搜索用时 15 毫秒
61.
Strong Self-Similar Fluctuations of Target Fragments in Ring-like Events in Ultra-Relativistic Nuclear Collision 下载免费PDF全文
Dipak Ghosh Argha Deb Samabrata Sarkar Prabir Kumar Haldar 《中国物理快报》2006,23(11):2944-2947
The intermittent fluctuation of target evaporated particles is studied in both ring-like and jet-like events emitted in ^32 S-emulsion interactions at 200 A Ge V within the framework of multi-dimensional factorial moment methodology using the concept of the Hurst exponent. It is observed that the intermittent fluctuation in the ring-like event is self-similar, whereas in the jet-like event fluctuation is self-affine. However, study indicates that the strength of fluctuation in the ring-like events is much stronger than that in the jet-like events. 相似文献
62.
V. Selvamanickam T. Finkle K. Pfaffenbach P. Haldar E. J. Peterson K. V. Salazaar E. P. Roth J. E. Tkaczyk 《Physica C: Superconductivity and its Applications》1996,260(3-4):313-320
Optimum thermomechanical processing conditions have been developed to achieve a high current density in powder-in-tube (PIT) thallium-based (Tl,Pb)-1223 and (Tl,Bi)-1223 tapes. Critical currents in excess of 25 A corresponding to a current density of 20 000 A/cm2 have been achieved in these tapes at 77 K. Heat treatment and intermediate deformation sequences, heating rates, and starting precursor phase assemblages have been examined to optimize the current density. A combination of processing conditions that result in incremental densification, less microcracking and liquid formation in the early and final stages of thermomechanical treatment is found to result in the highest current densities. 相似文献
63.
64.
65.
Pranab Haldar 《Tetrahedron letters》2005,46(7):1071-1074
A simple methodology for the conversion of substituted N-aryl-γ-lactam 2/3-carboxylic acids to substituted N-aryl-2/3-formyl-pyrroles has been developed. Several N-aryl-γ-lactam 2/3-carboxylic acids were reduced to substituted (N-aryl-pyrrolidine-2/3-yl)-methanols in good yields at room temperature using sodium borohydride-iodine. Controlled oxidation and aromatisation of these alcohols using DDQ produced N-aryl-2/3-formyl-pyrroles. 相似文献
66.
P. K. Das Prasanta Haldar Arpita Chatterjee 《International Journal of Theoretical Physics》2016,55(11):4951-4962
We discuss nonclassicality of a superposition of coherent states in terms of sub-Poissonian photon statistics as well as the negativity of the Wigner function. We derive an analytic expression for the Wigner function from which we find that the function has some negative region in phase space. We obtain a compact form of the Wigner function when decoherence occurs and study the effect of decoherence on the state. We demonstrate the behaviour of the nonclassicality indicator. 相似文献
67.
Ritu Gupta Jhantu Pradhan Arabinda Haldar Chandrasekhar Murapaka Prakash Chandra Mondal 《Angewandte Chemie (International ed. in English)》2023,62(35):e202307458
The injection of pure spin current into the non-magnetic layer plays a crucial role in transmitting, processing, and storing data information in the realm of spintronics. To understand broadband molecular spintronics, pyrene oligomer film (≈20 nm thickness) was prepared using an electrochemical method forming indium tin oxide (ITO) electrode/pyrene covalent interfaces. Permalloy (Ni80Fe20) films with different nanoscale thicknesses were used as top contact over ITO/pyrene layers to estimate the spin pumping efficiency across the interfaces using broadband ferromagnetic resonance spectra. The spintronic devices are composed of permalloy/pyrene/ITO orthogonal configuration, showing remarkable spin pumping from permalloy to pyrene film. The large spin pumping is evident from the linewidth broadening of 5.4 mT at 9 GHz, which is direct proof of spin angular momentum transfer across the interface. A striking observation is made with the high spin-mixing conductance of ≈1.02×1018 m−2, a value comparable to the conventional heavy metals. Large spin angular moment transfer was observed at the permalloy-pyrene interfaces, especially at the lower thickness of permalloy, indicating a strong spinterface effect. Pure spin current injection from ferromagnetic into electrochemically grown pyrene films ensures efficient broadband spin transport, which opens a new area in molecular broadband spintronics. 相似文献
68.
The stability of thin electrically conducting viscoelastic fluid film flowing down on a non-conducting inclined plane in the presence of electromagnetic field is investigated under induction-free approximation. Surface evolution equation is derived by long-wave expansion method. The stabilizing role of Hartman number M (magnetic field) and the destabilizing role of the viscoelastic property \({\varGamma}\) and the electric parameter E on such fluid film are established through the linear stability analysis of the surface evolution equation. Investigation shows that at small values of Hartman number (M), the influence of electric parameter (E) on the viscoelastic parameter \({(\varGamma)}\) is insignificant, while for large values of M, E introduces more destabilizing effect at low values of \({\varGamma}\) than that at high values of \({\varGamma }\). An interesting result also perceived from our analysis is that the stabilizing effect of Hartman number (M) is decreasing with the increase of the values of \({\varGamma}\) and E, even it gives destabilizing effect after a certain high value of the electric field depending on the high value of \({\varGamma}\). The weakly nonlinear study reveals that the increase of \({\varGamma}\) decreases the explosive and subcritical unstable zones but increases the supercritical stable zone keeping the unconditional zone almost constant. 相似文献
69.
A series of heptameric oligoamides comprising 4-alkoxy-substituted 2,6-diaminopyridine and 2,6-pyridine-dicarbonyl units have been synthesized using convergent methods. The hybridization of these compounds into double helical dimers was studied in solution by 1H NMR spectroscopy in CDCl3 or DMSO-d6 at various concentrations, and in the solid state using X-ray crystallographic analysis. Both solid state and solution data suggest that these compounds follow identical hybridization schemes. In CDCl3, the oligomers possess dimerization constants considerably (up to 2000-fold) higher than related compounds having no alkoxy substituents on their 2,6-diaminopyridine units. The origin of this effect can be in part interpreted as a result of interactions between the 4-alkoxy side chains when they are present on all pyridine rings. For example, 4-benzyloxy-substituted oligomer 2 has a higher dimerization constant than 4-decyloxy and 4-methoxy-substituted analogues 1 and 3. The crystal structure of 2 reveals multiple aromatic-aromatic interactions between the benzyl side chains, both face-to-face and edge-to-face at various angles surrounding the duplex. In the solid state, these double helices are stacked on top of each other to form long channels filled with water molecules. The 4-methoxy and 4-decyloxy-substituted analogues 1 and 3 have similar dimerization constants, showing that interactions between side chains are not significant between purely aliphatic residues. Consequently, the high stability of the double helices formed by 1 and 3 compared to related compounds having alkoxy substituents on their 2,6-pyridine-dicarbonyl units only does not find its origin in interactions between side chains but in the direct effect of the alkoxy substituents upon main chain aryl-aryl interactions. 相似文献
70.
Dipolar relaxation within the protein matrix of the green fluorescent protein: a red edge excitation shift study 总被引:2,自引:0,他引:2
The fluorophore in green fluorescent protein (GFP) is localized in a highly constrained environment, protected from the bulk solvent by the barrel-shaped protein matrix. We have used the wavelength-selective fluorescence approach (red edge excitation shift, REES) to monitor solvent (environment) dynamics around the fluorophore in enhanced green fluorescent protein (EGFP) under various conditions. Our results show that EGFP displays REES in buffer and glycerol, i.e., the fluorescence emission maxima exhibit a progressive shift toward the red edge, as the excitation wavelength is shifted toward the red edge of the absorption spectrum. Interestingly, EGFP displays REES when incorporated in reverse micelles of sodium bis(2-ethylhexyl)sulfosuccinate (AOT), independent of the hydration state. We interpret the observed REES to the constrained environment experienced by the EGFP fluorophore in the rigid protein matrix, rather than to the dynamics of the bulk solvent. These results are supported by the temperature dependence of REES and characteristic wavelength-dependent changes in fluorescence anisotropy. 相似文献