全文获取类型
收费全文 | 282篇 |
免费 | 3篇 |
国内免费 | 3篇 |
专业分类
化学 | 143篇 |
力学 | 4篇 |
数学 | 94篇 |
物理学 | 47篇 |
出版年
2018年 | 2篇 |
2016年 | 3篇 |
2015年 | 4篇 |
2014年 | 7篇 |
2013年 | 9篇 |
2012年 | 14篇 |
2011年 | 21篇 |
2010年 | 9篇 |
2009年 | 3篇 |
2008年 | 16篇 |
2007年 | 14篇 |
2006年 | 12篇 |
2005年 | 11篇 |
2004年 | 8篇 |
2003年 | 11篇 |
2002年 | 13篇 |
2001年 | 6篇 |
2000年 | 4篇 |
1999年 | 8篇 |
1998年 | 2篇 |
1997年 | 4篇 |
1996年 | 5篇 |
1995年 | 5篇 |
1994年 | 2篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 6篇 |
1987年 | 3篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1982年 | 3篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 8篇 |
1972年 | 5篇 |
1971年 | 2篇 |
1969年 | 2篇 |
1964年 | 1篇 |
1963年 | 1篇 |
1961年 | 1篇 |
1959年 | 2篇 |
1954年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有288条查询结果,搜索用时 15 毫秒
81.
Shimrit Gendler Stanislav Groysman Zeev Goldschmidt Michael Shuster Moshe Kol 《Journal of polymer science. Part A, Polymer chemistry》2006,44(3):1136-1146
The polymerization of the substituted olefins 4‐methylpentene and vinylcyclohexane by dibenzyl titanium and zirconium complexes of three amine bis(phenolate) ligands is reported. The ligands featured a dimethylamino side‐arm donor and either electron‐withdrawing (Cl and Br) or methyl phenolate substituents. After activation with B(C6F5)3, the zirconium catalysts exhibited a higher activity than the titanium catalysts toward these bulky olefins. Very high weight‐average molecular weight poly(4‐methylpentene) was obtained with the zirconium catalysts. The zirconium catalysts were employed in 1‐hexene polymerization, and their activity was found to be the highest ever reported for catalysts of the amine bis(phenolate) family. The catalysts featuring methyl phenolate substituents showed a higher activity toward these substituted olefins than the electron‐poor catalysts; this trend was opposite to their activity toward 1‐hexene. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1136–1146, 2006 相似文献
82.
David Elbaz Sophia Buhbut Benjamin Zeev Kupfer Arie Zaban Zeev Zalevsky 《Optics Communications》2012,285(10-11):2746-2749
In this paper we present a new type of optical fiber aiming to radially polarize the electrical field. This special device is composed of a tapered fiber having a classical core while on top of its external surface, radially oriented nanorods are disposed. The tails of the propagated wave are interacting with those radially oriented nanorods. This interaction performs the polarization of the propagated mode into a radial polarization. 相似文献
83.
Iron complexes of porphyrins (and corroles to a lesser extent) are the first catalysts to utilize ammonia for the synthesis of N-free amino acid esters. 相似文献
84.
Shi L De Paoli V Rosenzweig N Rosenzweig Z 《Journal of the American Chemical Society》2006,128(32):10378-10379
Preparation of FRET-based quantum dots as protease sensors-RGDC peptide molecules are bound to the surface of CdSe/ZnS quantum dots. The peptide molecules are then labeled with rhodamine dye molecules. The emission color of the quantum dots change from green to orange due to fluorescence resonance energy transfer (FRET) between the quantum dots and the bound rhodamine molecules. Cleavage of the peptide by selective proteases releases the rhodamine molecules from the quantum dots surface, which results in decreasing FRET efficiency between the quantum dots and the rhodamine molecules. The emission color of the quantum dots changes back to green. 相似文献
85.
We present a superresolving approach that allows one to exceed the diffraction limit and recover highly resolved contours of moving targets from a sequence of low-resolution images. The presented approach is suitable for remote sensing applications. The resolution decoding algorithm that is used to recover the high-resolution features of the target can be run partially via optical means and that way can be used to reduce the required computational complexity. 相似文献
86.
87.
New electronic and magnetic properties are induced by the adsorption of closed packed monolayers on solid substrates. For many thiolated molecules self-assembled on gold, a surprisingly large paramagnetism is observed. In the case where the layers are made from chiral molecules, in addition an unexpectedly large electronic dichroism is observed, which manifests itself as spin specific electron transmission. This dichroism was observed for monolayers made from polyalanine and from DNA. Self-assembled monolayers of double-stranded DNA oligomers on gold interact with polarized electrons similarly to a strong and oriented magnetic field. The direction of the field for right-handed DNA is away from the substrate. Moreover, the layer shows very high paramagnetic susceptibility. Interestingly, thiolated single-stranded DNA oligomers on gold do not show this effect. All the observations can be rationalized by assuming organization induced charge transfer between the substrate and the organic layer. The charge transfer results in spin alignment of the transferred electrons/holes. While for achiral molecules the spin alignment varies among the domains, in the case of monolayer made from chiral molecules the alignment is the same across the entire sample. When magnetic field is applied, large magnetic moment is observed that results from orbital magnetism. 相似文献
88.
We study the problem of existence and nonexistence of positive solutions of the semilinear elliptic inequalities in divergence form with measurable coefficients in exterior domains in . For W(x)?|x|−σ at infinity we compute the critical line on the plane (p,σ), which separates the domains of existence and nonexistence, and reveal the class of potentials V that preserves the critical line. Example are provided showing that the class of potentials is maximal possible, in certain sense. The case of (p,σ) on the critical line has also been studied. 相似文献
89.
For f L
n
(T
d
) and
, the modulus of smoothness
is shown to be equivalent to
where T
n is the best trigonometric polynomial approximant of degree n to f in L
p and is the Laplacian. The above result is shown to be incorrect for 0 < p
. 相似文献
90.
Fractional Derivatives and Best Approximation 总被引:8,自引:0,他引:8
Z. Ditzian 《Acta Mathematica Hungarica》1998,81(4):323-348
We relate fractional derivatives of some operators to the rate of best approximation from a space of eigenfunctions of those operators. This is done via the introduction of "fractional" K-functionals and appropriate Riesz means. Continuous simultaneous approximations and fractional Kolmogorov-type inequalities are also achieved. 相似文献