全文获取类型
收费全文 | 809篇 |
免费 | 26篇 |
国内免费 | 2篇 |
专业分类
化学 | 528篇 |
晶体学 | 19篇 |
力学 | 17篇 |
数学 | 42篇 |
物理学 | 231篇 |
出版年
2024年 | 2篇 |
2023年 | 10篇 |
2022年 | 30篇 |
2021年 | 30篇 |
2020年 | 33篇 |
2019年 | 29篇 |
2018年 | 31篇 |
2017年 | 41篇 |
2016年 | 37篇 |
2015年 | 21篇 |
2014年 | 46篇 |
2013年 | 67篇 |
2012年 | 51篇 |
2011年 | 64篇 |
2010年 | 20篇 |
2009年 | 31篇 |
2008年 | 41篇 |
2007年 | 38篇 |
2006年 | 27篇 |
2005年 | 26篇 |
2004年 | 19篇 |
2003年 | 6篇 |
2002年 | 13篇 |
2001年 | 10篇 |
2000年 | 7篇 |
1999年 | 6篇 |
1998年 | 8篇 |
1997年 | 6篇 |
1996年 | 2篇 |
1994年 | 4篇 |
1993年 | 6篇 |
1992年 | 2篇 |
1991年 | 4篇 |
1990年 | 7篇 |
1989年 | 2篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 7篇 |
1979年 | 2篇 |
1978年 | 7篇 |
1977年 | 3篇 |
1975年 | 2篇 |
1974年 | 4篇 |
1973年 | 2篇 |
1971年 | 2篇 |
排序方式: 共有837条查询结果,搜索用时 15 毫秒
71.
Water-soluble quantum dots (QDs) are fluorescent semiconductor nanoparticles with narrow, very specific, stable emission spectra.
Therefore, the bioconjugation of these QDs for biological fluorescent labeling may be of interest due to their unique physical
and optical properties as compared to organic fluorescent dyes. These intrinsic properties of QDs have been used for the sensitive
detection of target analytes. From the viewpoint of ensuring food safety, there is a need to develop rapid, sensitive and
specific detection techniques to monitor food toxicants in food and environmental samples. Even trace levels of these toxicants
can inadvertently enter the food chain, creating severe health hazards. The present review emphasizes the application of water-soluble
bioconjugated QDs for the detection of food contaminants such as pesticides, pathogenic bacterial toxins such as botulinum
toxin, enterotoxins produced by Staphylococcus aureus, Escherichia coli, and for the development of oligonucleotide-based microarrays. This review also emphasizes the application of a possible
resonance energy transfer phenomenon resulting from nanobiomolecular interactions obtained through the bioconjugation of QDs
with biomolecules. Furthermore, the utilization of significant changes in the spectral behavior of QDs (attributed to resonance
energy transfer in the bioconjugate) in future nanobiosensor development is also emphasized. 相似文献
72.
Recently a novel phase of ZnO has been synthesized which is analogous to α-boron nitride, although more three dimensional, and consists of planar hexagonal sheets of ZnO. Examining the dynamic stability of the structure, we find unstable phonon modes over a considerable part of the Brillouin zone. Local-density approximation (LDA) and generalized gradient approximation level calculations have usually been able to predict the structural stability of s-p bonded systems. The failure in the present case is a surprise and is traced to the self-interaction error which incorrectly locates the localized Zn d states in the valence band of ZnO. Correcting for this with a Hubbard-like U on the Zn d states, the optimized structure is predicted to be stable. This highlights the fact that the large bond length contraction that one finds in going from sp(3)- to sp(2)-type bonding results in an increased necessity to correct for self-interaction errors. 相似文献
73.
N.E. Rajeevan Ravi KumarD.K. Shukla R.J. ChoudharyP. Thakur A.K. SinghS. Patnaik S.K. AroraI.V. Shvets P.P. Pradyumnan 《Journal of magnetism and magnetic materials》2011,323(13):1760-1765
Thin films of BixCo2−xMnO4 (x=0, 0.1 and 0.3) were grown on quartz, LaAlO3 (LAO) and YBa2Cu3O7 (YBCO) buffer layer coated LAO substrates by pulsed laser deposition (PLD). X-ray diffraction (XRD) and Raman scattering measurements showed that the thin films exhibit single phase polycrystalline cubic spinel structure on all the substrates. Near edge X-ray absorption fine structure (NEXAFS) studies confirmed the octahedral occupancy of the substituted Bi3+ ions. Temperature dependent zero-field cooled (ZFC) magnetization measurements show the ferrimagnetic (FM) behavior (TC∼186 K) and magnetization undergoes a crossover from positive to negative, owing to the opposite contributions of magnetic moments from Co and Mn ions. A weak ferroelectric property exhibited by the films above room temperature was evidenced through the capacitance-voltage (C-V) and dielectric measurements. Magnetoelectric coupling was found to be maximum just below FM-TC. 相似文献
74.
In this paper our interest is in investigating properties and numerical solutions of Proximal Split feasibility Problems. First, we consider the problem of finding a point which minimizes a convex function \(f\) such that its image under a bounded linear operator \(A\) minimizes another convex function \(g\) . Based on an idea introduced in Lopez (Inverse Probl 28:085004, 2012), we propose a split proximal algorithm with a way of selecting the step-sizes such that its implementation does not need any prior information about the operator norm. Because the calculation or at least an estimate of the operator norm \(\Vert A\Vert \) is not an easy task. Secondly, we investigate the case where one of the two involved functions is prox-regular, the novelty of this approach is that the associated proximal mapping is not nonexpansive any longer. Such situation is encountered, for instance, in numerical solution to phase retrieval problem in crystallography, astronomy and inverse scattering Luke (SIAM Rev 44:169–224, 2002) and is therefore of great practical interest. 相似文献
75.
Some integral bounds are obtained which provide refinements and extensions of the Grüss type inequalities. We also get an
alternative formulation of the Grüss inequality. 相似文献
76.
N. Thilagavathi A. Manimaran N. Padma Priya N. Sathya C. Jayabalakrishnan 《应用有机金属化学》2010,24(4):301-307
Four tridentate O, N, O donor Schiff base ligands were prepared by the reaction of substituted benzhydrazide and appropriate salicylaldehyde. The complexes of these ligands were synthesized by refluxing the ligands with ruthenium(II) starting complexes of the formula [RuHCl(CO)(EPh3)2B] in benzene, where E = P or As; B = PPh3 or AsPh3 or pyridine. The newly synthesized complexes were characterized by elemental, spectral (FT‐IR, UV and NMR) and electrochemical data. On the basis of the above studies, an octahedral structure has been proposed for all the complexes. The catalytic efficiency of the complexes in aryl–aryl couplings and oxidation of alcohols was examined and their inhibition activity against the growth of the micro‐organisms was also examined. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
77.
Chandreshwar Thakur Ram Babu Mishra 《International Journal of Theoretical Physics》1990,29(9):1029-1037
Steady flow of an inviscid, incompressible two-phase magnetofluid with infinite electrical conductivity is treated. With one ignorable coordinate in a general orthogonal curvilinear system, general solutions of the equations, considering number densityN constant throughout the motion, are obtained. 相似文献
78.
Various state-equations, derived by expanding energy as a function of volume in Taylor series and using different order Pade’s
approximants, have been combined with quasi-harmonic approximation for free energy to reproduce the pressure dependence of
thermodynamic properties of NaBr, NaI and AgCl crystals. We have used these state-equations to compute the reduced volume,
the isothermal bulk modulus and the pressure derivative of isothermal bulk modulus for the three crystals at various pressures
(up to 80 kbar) and at room temperature (T=298 K). The results obtained are reasonably good lending support to the state-equations and the technique used to extend
their applicability. The significant results obtained in the present study include the unified reduced equation of state for
the three crystals which generates almost a single curve for theP – V behaviour at room temperature. 相似文献
79.
Ralph E. Schlief Wlodzimierz Jarzeba Khalid A. M. Thakur Joseph C. Alfano Alan E. Johnson Paul F. Barbara 《Journal of Molecular Liquids》1994,60(1-3):201-220
Ultrafast pump - probe measurements have been made on the benzene - bromine atom charge transfer (CT) complex in CCl4 and cyclohexane solutions. Ultrafast optical excitation of the CT band of the complex yields an ion pair, which is comprised of a benzene cation and a bromide anion. The rate of charge recombination between the bromide and the benzene cation in the ion pair has been observed to be much faster than the rate of diffusion apart. The charge recombination rate is accelerated at high benzene concentrations as a result of the formation of a benzene dimer cation - bromide ion pair which undergoes much faster charge recombination than the benzene cation - bromide ion pair. 相似文献
80.