全文获取类型
收费全文 | 115篇 |
免费 | 9篇 |
专业分类
化学 | 81篇 |
力学 | 1篇 |
数学 | 9篇 |
物理学 | 33篇 |
出版年
2024年 | 1篇 |
2021年 | 4篇 |
2020年 | 3篇 |
2019年 | 4篇 |
2018年 | 2篇 |
2017年 | 2篇 |
2016年 | 4篇 |
2015年 | 10篇 |
2014年 | 7篇 |
2013年 | 17篇 |
2012年 | 12篇 |
2011年 | 11篇 |
2010年 | 6篇 |
2009年 | 8篇 |
2008年 | 7篇 |
2007年 | 4篇 |
2006年 | 2篇 |
2005年 | 7篇 |
2004年 | 2篇 |
2003年 | 1篇 |
2002年 | 3篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1995年 | 1篇 |
1987年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
排序方式: 共有124条查询结果,搜索用时 343 毫秒
11.
J.S. Yadav B.V. Subba Reddy D.N. Chaya G.G.K.S. Narayana Kumar S. Aravind A.C. Kunwar C. Madavi 《Tetrahedron letters》2008,49(20):3330-3334
4-Iodopiperidines are prepared in good yields and with high selectivity by means of aza-Prins-cyclization using a catalytic amount of gallium(III) iodide and a stoichiometric amount of iodine under mild reaction conditions. This is the first report on the preparation of 4-iodopiperidines via aza-Prins-cyclization. 相似文献
12.
13.
It is shown how the 300 rays associated with the antipodal pairs of vertices of a 120-cell (a four-dimensional regular polytope) can be used to give numerous “parity proofs” of the Kochen–Specker theorem ruling out the existence of noncontextual hidden variables theories. The symmetries of the 120-cell are exploited to give a simple construction of its Kochen–Specker diagram, which is exhibited in the form of a “basis table” showing all the orthogonalities between its rays. The basis table consists of 675 bases (a basis being a set of four mutually orthogonal rays), but all the bases can be written down from the few listed in this paper using some simple rules. The basis table is shown to contain a wide variety of parity proofs, ranging from 19 bases (or contexts) at the low end to 41 bases at the high end. Some explicit examples of these proofs are given, and their implications are discussed. 相似文献
14.
Atiyah and Bott used equivariant Morse theory applied to theYang–Mills functional to calculate the Betti numbers ofmoduli spaces of vector bundles over a Riemann surface, rederivinginductive formulae obtained from an arithmetic approach whichinvolved the Tamagawa number of SLn. This article attempts tosurvey and extend our understanding of this link between Yang–Millstheory and Tamagawa numbers, and to explain how methods usedover the last three decades to study the singular cohomologyof moduli spaces of bundles on a smooth projective curve over can be adapted to the setting of 1-homotopy theory to studythe motivic cohomology of these moduli spaces over an algebraicallyclosed field. 相似文献
15.
The aim of this work was to establish optimal conditions for the maximum production of endo-β-1,4 mannanases using cheaper
sources. Eight thermotolerant fungal strains were isolated from garden soil and compost samples collected in and around the
Gulbarga University campus, India. Two strains were selected based on their ability to produce considerable endo-β-1,4 mannanases
activity while growing in liquid medium at 37 °C with locust bean gum (LBG) as the only carbon source. They were identified
as Aspergillus niger gr and Aspergillus flavus gr. The experiment to evaluate the effect of different carbon sources, nitrogen sources, temperatures and initial pH of the
medium on maximal enzyme production was studied. Enzyme productivity was influenced by the type of polysaccharide used as
the carbon source. Copra meal defatted with n-hexane showed to be a better substrate than LBG and guar gum for endo-β-1,4 mannanases production by A. niger gr (40.011 U/ml), but for A. flavus gr (33.532 U/ml), the difference was not significant. Endo-β-1,4 mannanases produced from A. niger gr and A. flavus gr have high optimum temperature (65 and 60 °C) and good thermostability in the absence of any stabilizers (maintaining 50%
of residual activity for 8 and 6 h, respectively, at 60 °C) and are stable over in a wide pH range. These new strains offer
an attractive alternative source of enzymes for the food and feed processing industries. 相似文献
16.
Rodrigues LM Sivasubramanian A Pinto EM Oliveira-Campos AM Seijas JA Vázquez-Tato MP 《Magnetic resonance in chemistry : MRC》2009,47(1):84-86
A series of 21 substituted pyrazolo[3,4-d]pyrimidines-4-amines were studied by (1)H and (13)C NMR. The application of two-dimensional techniques, HMQC and HMBC, allowed the complete assignment of the spectra for all the compounds. 相似文献
17.
Aravind Kumar Rengan Gopal Kundu Rinti Banerjee Rohit Srivastava 《Particle & Particle Systems Characterization》2014,31(3):398-405
Numerous gold nanostructures have the potential for photothermal therapy in cancers. Here, gold nanocages and gold nanoshells are synthesized, the sizes of which are fine‐tuned for a response at 750 nm wavelength. Their photothermal therapeutic efficiency is compared at gold concentration of 100 lg mL?1 using a near‐infrared laser (750 nm). The biocompatibility for varying concentrations of gold (1 to 100 lg mL?1) is performed in a normal cell line and laser‐mediated cell cytotoxicity for varying time intervals (7.5 and 10 min) is carried out in breast cancer cells. This study shows that when analyzed under similar conditions, the gold nanocages show better biocompatibility and are more efficient in near‐infrared absorption and photothermal conversion in comparison with conventional gold nanoshells. When subjected to photothermal laser ablation of breast cancer cell line for 7.5 min and 10 min, the nanocages are able to induce 62.92 ± 3.25% and 96.41 ± 3.04% reduction in cell viability, respectively, in comparison to nanoshells, in which a 43.35 ± 1.91% and 79.89 ± 4.74% reduction in cell viability is observed. The current study shows that the gold nanocages can outperform gold nanoshells and effectively kill cancer cells without any significant cytotoxic effect on normal cells. 相似文献
18.
Arun Aravind K. Hasna M. K. Jayaraj Mukesh Kumar Ramesh Chandra 《Applied Physics A: Materials Science & Processing》2014,115(3):843-849
Phase pure Zn1?x Co x O thin films grown by pulsed laser deposition have transmittance greater than 75 % in the visible region. Raman studies confirm the crystalline nature of Zn1?x Co x O thin films. Zn0.95Co0.05O thin films show room temperature ferromagnetism with saturation magnetization of 0.4μ B /Co atom. The possible origin of paramagnetism at higher Co doping concentrations can be attributed to the increased nearest-neighbor antiferromagnetic interactions between Co2+ ions in ZnO matrix. XPS confirms the substitution of Co2+ ions into the ZnO host lattice. 相似文献
19.
P. M. Aneesh M. R. Shijeesh Arun Aravind M. K. Jayaraj 《Applied Physics A: Materials Science & Processing》2014,116(3):1085-1089
In this paper we report the synthesis of highly luminescent ZnS and Mn-doped ZnS nanoparticles with uniform particle size distribution by liquid phase pulsed laser ablation. The formation of nanosized ZnS crystallites was confirmed by high-resolution transmission electron microscopy (HRTEM) images. The optical properties of these nanoparticles were studied by room temperature photoluminescence (PL) spectra. The PL emission from the ZnS nanoparticles shows a sharp peak in the UV region (334 nm) corresponding to the band edge and a broad peak in the visible region which can be attributed to the sulphur vacancies, cation vacancies and surface states in the nanocrystals. The yellow emission from the Mn-doped ZnS nanoparticles can be attributed to the radiative transition between 4T1 and 6A1 levels within the 3d5 orbital of Mn2+. 相似文献
20.
A stable high-order Spectral Difference method for hyperbolic conservation laws on triangular elements 总被引:1,自引:0,他引:1
Numerical schemes using piecewise polynomial approximation are very popular for high order discretization of conservation laws. While the most widely used numerical scheme under this paradigm appears to be the Discontinuous Galerkin method, the Spectral Difference scheme has often been found attractive as well, because of its simplicity of formulation and implementation. However, recently it has been shown that the scheme is not linearly stable on triangles. In this paper we present an alternate formulation of the scheme, featuring a new flux interpolation technique using Raviart–Thomas spaces, which proves stable under a similar linear analysis in which the standard scheme failed. We demonstrate viability of the concept by showing linear stability both in the semi-discrete sense and for time stepping schemes of the SSP Runge–Kutta type. Furthermore, we present convergence studies, as well as case studies in compressible flow simulation using the Euler equations. 相似文献