全文获取类型
收费全文 | 124篇 |
免费 | 2篇 |
国内免费 | 2篇 |
专业分类
化学 | 73篇 |
晶体学 | 1篇 |
力学 | 1篇 |
数学 | 25篇 |
物理学 | 28篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 4篇 |
2020年 | 2篇 |
2019年 | 1篇 |
2018年 | 7篇 |
2017年 | 4篇 |
2016年 | 4篇 |
2015年 | 1篇 |
2014年 | 3篇 |
2013年 | 7篇 |
2012年 | 8篇 |
2011年 | 5篇 |
2010年 | 3篇 |
2009年 | 5篇 |
2008年 | 14篇 |
2007年 | 7篇 |
2006年 | 5篇 |
2005年 | 6篇 |
2004年 | 5篇 |
2003年 | 2篇 |
2002年 | 4篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1998年 | 1篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1991年 | 1篇 |
1988年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1971年 | 3篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1966年 | 1篇 |
1964年 | 1篇 |
1958年 | 2篇 |
1957年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有128条查询结果,搜索用时 31 毫秒
91.
Radoslaw Bonikowski Jozef Kula Anna Bujacz Anna Wajs Wieslaw Majzner 《Tetrahedron: Asymmetry》2009,20(22):2583-2588
3-Isopropyl-7a-methyl-1,2,3,6,7,7a-hexahydro-inden-5-one is a building block used in the reconstruction of the cyathane skeleton. In this article, a new and efficient method of the synthesis for (3R,7aR)-3-isopropyl-7a-methyl-1,2,3,6,7,7a-hexahydro-inden-5-one has been described. 相似文献
92.
Michal Chudy Ilona Grabowska Patrycja Ciosek Alicja Filipowicz-Szymanska Dorota Stadnik Iwona Wyzkiewicz Elzbieta Jedrych Marcin Juchniewicz Maciej Skolimowski Karina Ziolkowska Radoslaw Kwapiszewski 《Analytical and bioanalytical chemistry》2009,395(3):647-668
This article presents an overview of various miniaturized devices and technologies developed by our group. Innovative, fast and cheap procedures for the fabrication of laboratory microsystems based on commercially available materials are reported and compared with well-established microfabrication techniques. The modules fabricated and tested in our laboratory can be used independently or they can be set up in different configurations to form functional measurement systems. We also report further applications of the presented modules e.g. disposable poly(dimethylsiloxane) (PDMS) microcuvettes, fibre optic detectors, potentiometric sensors platforms, microreactors and capillary electrophoresis (CE) microchips as well as integrated microsystems e.g. double detection microanalytical systems, devices for studying enzymatic reactions and a microsystem for cell culture and lysis. 相似文献
93.
Wojciech Czaja Gitta Kutyniok Darrin Speegle 《Journal of Fourier Analysis and Applications》2008,14(4):514-537
Pseudoframes for subspaces have been recently introduced by Li and Ogawa as a tool to analyze lower dimensional data with
arbitrary flexibility of both the analyzing and the dual sequence.
In this paper we study Gabor pseudoframes for affine subspaces by focusing on geometrical properties of their associated sets
of parameters. We first introduce a new notion of Beurling dimension for discrete subsets of ℝ
d
by employing a certain generalized Beurling density. We present several properties of Beurling dimension including a comparison
with other notions of dimension showing, for instance, that our notion includes the mass dimension as a special case. Then
we prove that Gabor pseudoframes for affine subspaces satisfy a certain Homogeneous Approximation Property, which implies
invariance under time–frequency shifts of an approximation by elements from the pseudoframe.
The main result of this paper is a classification of Gabor pseudoframes for affine subspaces by means of the Beurling dimension
of their sets of parameters. This provides us, in particular, with a Nyquist dimension which separates sets of parameters
of pseudoframes from those of non-pseudoframes and which links a fixed value to sets of parameters of pseudo-Riesz sequences.
These results are even new for the special case of Gabor frames for an affine subspace.
相似文献
94.
95.
W. Czaja 《Zeitschrift für Physik B Condensed Matter》1971,12(3):226-236
An approximate calculation of the ground state energy of direct and indirect free excitons for group IV and group III–V semiconductors is presented. The basic assumption in this treatment is that the anisotropy of the effective masses can be neglected, however, the degeneracy of the valence band cannot. The resulting exciton ground state energy has the usual form but with a reduced mass \(\overline \mu \) given by ( \(\overline \mu \) )?1=(m e)?1+(m lh)?1+(m hh)?1. The agreement with experiments is considerably improved as compared to the conventional ground state energy comprising the reduced mass defined as (μ)?1=(m e)?1+(m hh)?1. Anisotropy corrections are shown to be of minor importance in many cases. However, for the heavier III–V-compounds the neglect of linear terms inE(k) for the valence band results in more serious errors, which invalidate the present theoretical approach. 相似文献
96.
We report the observation of a sharp photoluminescence line in AgBr at 2.6754 eV below 3 K. Spectral position, width and temperature dependence of the intensity can only be explained by us consistently with the assumption that this line is due to the recombination of Bose-Einstein condensed indirect excitons. 相似文献
97.
Radoslaw Czaja Messoud Efendiev 《Journal of Mathematical Analysis and Applications》2011,381(2):766-765
The existence of a pullback exponential attractor being a family of compact and positively invariant sets with a uniform bound on their fractal dimension which at a uniform exponential rate pullback attract bounded subsets of the phase space under the evolution process is proved for the nonautonomous logistic equation and a system of reaction-diffusion equations with time-dependent external forces including the case of the FitzHugh-Nagumo system. 相似文献
98.
99.
Radoslaw Sobczynski Hubert Lange Stanislaw Kurowski 《Plasma Chemistry and Plasma Processing》1988,8(1):101-110
The dynamics of the formation and decay of excited hydrogen during a pulse discharge in methane at a pressure of 200 Pa and energy density of 0.05 J/cm3 has been studied. The population of hydrogen in the n=2 state was monitored by the laser absorption method. The time constant of the decay of the excited hydrogen was measured to be 95±15 ns. The concentration of free electrons reached a maximum value of 7×1014 cm–3, and the time constant of their recombination was 220±50 ns. The formation of appreciable amounts of atomic hydrogen in the ground state during the discharge, H(n=1)>1016 cm–3, was estimated on the basis of a kinetic model.Notation
absorption coefficient
-
wave number, cm–1
-
c
velocity of light
-
e
electron charge
-
m
e
mass of electron
-
A
mn
Einstein coefficient
-
F
mn
collisional deexcitation rate constant
-
S
m
ionization rate constant
-
f
24
oscillator strength
-
n
e
electron concentration
-
n
H(n=2,3,4)
excited-state hydrogen concentration
-
v
e
electron velocity
-
q
mn
excitation cross-section
- (q
mnve)
excitation rate constants
-
T
e
electron temperature
-
E (t)
electrical field strength
-
j
current density
-
t
ei
–1
electron-ion collision frequency
- 2,m
two-body recombination rate constant
- 3,m
three-body recombination rate constant 相似文献
100.