全文获取类型
收费全文 | 398篇 |
免费 | 17篇 |
国内免费 | 4篇 |
专业分类
化学 | 234篇 |
晶体学 | 27篇 |
力学 | 7篇 |
数学 | 31篇 |
物理学 | 120篇 |
出版年
2024年 | 2篇 |
2023年 | 3篇 |
2022年 | 4篇 |
2021年 | 6篇 |
2020年 | 5篇 |
2019年 | 19篇 |
2018年 | 6篇 |
2017年 | 2篇 |
2016年 | 6篇 |
2015年 | 13篇 |
2014年 | 8篇 |
2013年 | 13篇 |
2012年 | 28篇 |
2011年 | 33篇 |
2010年 | 26篇 |
2009年 | 27篇 |
2008年 | 24篇 |
2007年 | 21篇 |
2006年 | 45篇 |
2005年 | 15篇 |
2004年 | 7篇 |
2003年 | 15篇 |
2002年 | 14篇 |
2001年 | 9篇 |
2000年 | 7篇 |
1999年 | 8篇 |
1998年 | 2篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 4篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1959年 | 1篇 |
1941年 | 1篇 |
排序方式: 共有419条查询结果,搜索用时 15 毫秒
381.
T. Varghese K. M. Balakrishna 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,57(1):9-11
The electron momentum distribution and Compton profiles of the rare earth
element Eu was measured using HPGe photon detector. The target atoms were
excited by means of 59.54 keV gamma rays from Am-241 radioactive source of
strength 300 mCi. Elemental foil of uniform aerial density, and purity
better than 99.9% was used as target. The data were recorded and analyzed
using a 4 K multichannel analyzer. These data duly corrected for instrumental
resolution effects, sample absorption, energy dependence of the differential
Compton cross-section and double scattering, and compared with theoretical
renormalized free atom (RFA) values. 相似文献
382.
Data reduction is an important issue in the field of data mining. The goal of data reduction techniques is to extract a subset of data from a massive dataset while maintaining the properties and characteristics of the original data in the reduced set. This allows an otherwise difficult or impossible data mining task to be carried out efficiently and effectively. This paper describes a new method for selecting a subset of data that closely represents the original data in terms of its joint and univariate distributions. A pair of distance criteria, motivated by the χ2-statistic, are used for measuring the goodness-of-fit between the distributions of the reduced and full datasets. Under these criteria, the data reduction problem can be formulated as a bi-objective quadratic program. A genetic algorithm technique is used in the search/optimization process. Experiments conducted on several real-world data sets demonstrate the effectiveness of the proposed method. 相似文献
383.
Bhavana Purushothaman Babu Varghese Puttaiah Bhyrappa 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(3):252-253
In the title complex, [Zn(C36H20N4S4)], the ZnII ion occupies a special position on an inversion centre with four-coordinate geometry. The porphyrin ring shows a wave-like conformation, with the closest interporphyrin plane separation being 3.60 (6) Å. The two disordered thienyl groups are inclined with respect to the porphyrin plane at angles of 70 (4) and 67 (2)°. 相似文献
384.
Vinayakrishnan Rajan Babu Varghese Ton G. van Leeuwen Wiendelt Steenbergen 《Optics Communications》2008,281(6):1755-1760
We report on the dependence of the decorrelation time on the spatial intensity correlation of speckles generated in the far-field by back-scattered photons from turbid media. The effects contribute to an explanation of an earlier observation that the average Doppler width of the power spectrum of detector current fluctuations depends on the size of the illuminating laser beam. The space-time correlation of the speckles generated by a particle suspension illuminated by a collimated laser beam is analyzed from serial images taken by a high speed camera. It was found that larger spatial correlation distances, associated with large speckles, exhibit a slower temporal decorrelation. 相似文献
385.
A molecular salt with formula [BmIm]3[PMo12O40]3? has been prepared using room temperature ionic liquid and phosphomolybdic acid. The material is characterized by single-crystal X-ray diffraction. The compound crystallizes in orthorhombic system with space group Pca21. It is also characterized by CHN analysis, 31P MAS NMR, UV–vis DRS and near-IR methods. Thermal stability of the compound is investigated by TGA, IR and PXRD methods. Near-IR shows the loss of water of crystallization by the Keggin ions of phosphomolybdic acid bonded with ionic liquid. 相似文献
386.
Hema Tresa Varghese C. Yohannan Panicker V.S. Madhavan Samuel Mathew Jarmila Vinsova Christian Van Alsenoy 《Journal of Raman spectroscopy : JRS》2009,40(9):1211-1223
FT‐IR and FT‐Raman spectra of 4‐chloro‐2‐(4‐bromophenylcarbamoyl)phenyl acetate were recorded and analyzed. The vibrational wavenumbers and corresponding vibrational assignments were examined theoretically using the Gaussian03 set of quantum chemistry codes. The red shift of the NH stretching wavenumber in the infrared (IR) spectrum from the computed wavenumber indicates the weakening of the NH bond resulting in proton transfer to the neighbouring oxygen atom. The simultaneous IR and Raman activations of the CO stretching mode give the charge transfer interaction through a π‐conjugated path. Optimized geometrical parameters of the title compound are in agreement with similar reported structures. From the optimized structure, it is clear that the hydrogen bonding decreases the double bond character of CO bond and increases the double bond character of the C N bonds. The first hyperpolarizability, predicted infrared intensities and Raman activities are reported. The calculated first hyperpolarizability is comparable with the reported values of similar derivatives and is an attractive object for future studies of non‐linear optics. The assignments of the normal modes are done by potential energy distribution (PED) calculations. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
387.
This paper uses techniques in noncommutative geometry as developed by Alain Connes [Co2], in order to study the twisted higher
index theory of elliptic operators on orbifold covering spaces of compact good orbifolds, which are invariant under a projective
action of the orbifold fundamental group, continuing our earlier work [MM]. We also compute the range of the higher cyclic
traces on K-theory for cocompact Fuchsian groups, which is then applied to determine the range of values of the Connes–Kubo Hall conductance
in the discrete model of the quantum Hall effect on the hyperbolic plane, generalizing earlier results in [Bel+E+S], [CHMM].
The new phenomenon that we observe in our case is that the Connes–Kubo Hall conductance has plateaux at integral multiples
of a fractional valued topological invariant, namely the orbifold Euler characteristic. Moreover the set of possible fractions has been determined, and
is compared with recently available experimental data. It is plausible that this might shed some light on the mathematical
mechanism responsible for fractional quantum numbers.
Received: 4 November 1999 / Accepted: 22 September 2000 相似文献
388.
Thermogravimetric Analysis and Thermal Ageing of Crosslinked Nitrile Rubber/Poly(ethylene-co-vinyl Acetate) Blends 总被引:1,自引:0,他引:1
Varghese H. Bhagawan S. S. Thomas S. 《Journal of Thermal Analysis and Calorimetry》2001,63(3):749-763
The thermal behaviour of nitrile rubber (NBR)/poly(ethylene-co-vinyl acetate) (EVA) blends was studied by thermogravimetry.
The effects of blend ratio, different crosslinking systems (sulphur, peroxide and mixed), various fillers (silica, clay and
carbon black) and filler loading on the thermal properties were evaluated. It was found that the initial decomposition temperature
increased with the addition of NBR to EVA. Among the various crosslinking systems studied, the peroxide cured system showed
the highest initial decomposition temperature. This is associated with the high bond dissociation energy of C–C linkages.
The addition of fillers improved the thermal stability of the blend. The mass loss at different temperatures and activation
energy of degradation were also studied. The thermal ageing of these blends was carried out at 50 and 100°C for 72 h. It was
seen that the properties are not affected by the mild ageing condition. Also, the peroxide cured system was found to exhibit
better retention in properties, than other crosslinking systems.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
389.
AbstractMetal cations observed with tetrachloroaluminate anion provide insights into the structure and stability of reactive cations. Addition of tris(3,5-dimethylpyrazolyl)borate anion (TpMe2) to [BiCl2][AlCl4] traps a bismuth(III) dication, [TpMe2Bi]2+, possessing a highly electrophilic bismuth center with short coordinate Bi―N bonds. [TpMe2Bi]2+ has weak interactions with the chlorides of [Bi3Cl13]∞. Strong affinity of [TpMe2Bi]2+ with the triflate (OTf) observed in [TpMe2Bi(OTf)3]- demonstrates the high electrophilicity at bismuth. 相似文献
390.
Effect of post thermal annealing on the structural and optical properties of ZnO thin films prepared from polymer precursor
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
ZnO thin films were synthesised by a new method which uses polyvinyl alcohol (PVA) as polymer precursor. The films are annealed at different temperatures and for different annealing times. The structural parameters, like grain size, lattice constants, optical band gap, and Urbach energy, depend on the annealing temperature and annealing time. All the films possess tensile strain which relaxes as the annealing temperature and the annealing time increases. The photoluminescence (PL) spectra contain only ultraviolet (UV) peaks at low temperature, but as the annealing temperature and time increase we observe peaks at blue and green regions with variation of the intensities of these peaks with annealing temperature and annealing time. 相似文献