全文获取类型
收费全文 | 313篇 |
免费 | 2篇 |
国内免费 | 4篇 |
专业分类
化学 | 149篇 |
晶体学 | 2篇 |
力学 | 8篇 |
数学 | 81篇 |
物理学 | 79篇 |
出版年
2020年 | 3篇 |
2019年 | 4篇 |
2018年 | 3篇 |
2015年 | 3篇 |
2013年 | 13篇 |
2012年 | 15篇 |
2011年 | 11篇 |
2010年 | 9篇 |
2009年 | 7篇 |
2008年 | 8篇 |
2007年 | 23篇 |
2006年 | 13篇 |
2005年 | 19篇 |
2004年 | 13篇 |
2003年 | 12篇 |
2002年 | 7篇 |
2001年 | 3篇 |
2000年 | 3篇 |
1999年 | 7篇 |
1997年 | 3篇 |
1996年 | 5篇 |
1994年 | 4篇 |
1993年 | 5篇 |
1992年 | 2篇 |
1991年 | 4篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 6篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 6篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1973年 | 4篇 |
1972年 | 3篇 |
1971年 | 4篇 |
1967年 | 6篇 |
1958年 | 2篇 |
1956年 | 3篇 |
1948年 | 2篇 |
1940年 | 3篇 |
1939年 | 3篇 |
1937年 | 2篇 |
1932年 | 2篇 |
1931年 | 2篇 |
排序方式: 共有319条查询结果,搜索用时 31 毫秒
1.
M. Kroon E. Andreasson E. Persson Jutemar V. Petersson L. Persson M. Dorn P.A.T. Olsson 《Experimental Mechanics》2018,58(1):75-86
Injection-moulding is one of the most common manufacturing processes used for polymers. In many applications, the mechanical properties of the product is of great importance. Injection-moulding of thin-walled polymer products tends to leave the polymer structure in a state where the mechanical properties are anisotropic, due to alignment of polymer chains along the melt flow direction. The anisotropic elastic-viscoplastic properties of low-density polyethylene, that has undergone an injection-moulding process, are therefore examined in the present work. Test specimens were punched out from injection-moulded plates and tested in uniaxial tension. Three in-plane material directions were investigated. Because of the small thickness of the plates, only the in-plane properties could be determined. Tensile tests with both monotonic and cyclic loading were performed, and the local strains on the surface of the test specimens were measured using image analysis. True stress vs. true strain diagrams were constructed, and the material response was evaluated using an elastic-viscoplasticity law. The components of the anisotropic compliance matrix were determined together with the direction-specific plastic hardening parameters. 相似文献
2.
3.
H. Petersson 《Acta Mathematica Hungarica》2003,100(1-2):69-81
The PDE-preserving operators O on the space of nuclearly entire functions of bounded type HNb(E) on a Banach space E are characterized. An operator is PDE-preserving when it preserves homogenous solutions to homogeneous convolution equations.
We establish a one to one correspondence between O and a set Σ of sequences of entire functionals, i.e. exponential type functions. In this way, algebraic structures on Σ,
such as ring structures, can be carried over to O and vice versa. In particular, it follows that O is a non-commutative ring (algebra) with unity with respect to composition and the convolution operators form a commutative
subring (subalgebra). We discuss range and kernel properties, for the operators in O, and characterize the projectors (onto polynomial spaces) in O by determining the corresponding elements in Σ.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
4.
R. Lacaze A. Morel B. Petersson J. Schröper 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(4):509-523
We present an investigation of the 2D attractive Hubbard model, considered as an effective model relevant to superconductivity
in strongly interacting electron systems. We use both hybrid Monte-Carlo simulations and existing hopping parameter expansions
to explore the low temperature domain. The increase of the static S-wave pair correlation with decreasing temperature, which depends weakly on the band filling in the explored temperature range,
is analyzed in terms of an expected Kosterlitz-Thouless superconducting transition. Using both our data and previously published
results, we show that the evidence for this transition is weak: If it exists, its temperature is very low. The number of unpaired
electrons remains nearly constant with temperature at fixed attractive potential strength. In contrast, the static magnetic
susceptibility decreases fast with temperature, and cannot be related only to pair formation. We introduce a method by which
the Padé approximants of the existing series for the susceptibility give sensible results down to rather low temperature region,
as shown by comparison with our numerical data.
Received: 30 October 1996 / Revised: 23 October 1997 / Accepted: 29 January 1998 相似文献
5.
The strain energies and through-space distances between the two bridgehead E atoms of a selection of 1,3-dimethyl-1,3-ditetrelbicyclo[1.1.1]pentanes
(tetrel E = Si, Ge or Sn) were examined by quantum chemical calculations at MP2 and B3LYP levels. The aim is to identify which
bridges lead to short through-space E,E distances, and simultaneously, to as low strain as possible. A short E,E distance
should improve through-space interaction, and a low strain should promote the thermal stability and possibly also facilitate
their synthesis. The bridges examined included CH2, CMe2, CtBu2, C(CH2)n (n = 2–4), O, NMe, S, PMe, SiMe2, GeMe2, and SnMe2. The calculations indicate that the phospha bridge is a good compromise providing reasonably low strain as well as E,E through-space
distances which are only longer than normal E–E single bonds by factors of 1.06–1.10.
This paper is dedicated to Professor Mitsuo Kira in recognition of his stimulating Si chemistry and his 2005 Wacker Award. 相似文献
6.
Veronica?StigssonEmail author G?ran?Kloow Ulf?Germg?rd Niclas?Andersson 《Cellulose (London, England)》2005,12(4):395-401
Controlling the reduction in molecular weight of the cellulose chains is essential in the production of carboxymethyl cellulose
(CMC). Such a reduction can be achieved by the addition of cobalt during the process of cobalt(II) ions, which act as a catalyst
for oxidative cleavage, and the influence thereof has been studied under a variety of conditions. This study has resulted
in a model that summarises the effects of the added amount of cobalt, the time for the cobalt reaction, the temperature in
the mercerisation stage of the CMC-manufacturing process and finally the effect of the temperature in the etherification stage.
It is shown that it is important for cobalt to be present during the mercerisation stage in order to achieve the desired viscosity. 相似文献
7.
Ferrocene attached to the surface of a platinum electrode catalyses the electrochemical oxidation of ascorbic acid in acidic buffer solutions. The overpotential for ascorbic acid oxidation is decreased by 150 mV at pH 2.2 compared with reaction at bare platinum; and an increase in anodic current and decrease in cathodic current for the redox reaction of ferrocene occurs on addition of ascorbic acid to the solution. The ferrocene-modified electrode is useful for the voltammetric determination of ascorbic acid in natural fruit juices. The advantages result from the electrocatalytic effect and from the prevention of adsorption of inhibitory substances from solution. 相似文献
8.
The frequency distribution of the87Rb NMR 1/2–1/2 central transition is measured in a detailed manner as a function of the temperature and the crystal orientation in the normal (N), incommensurate (IC), and commensurate (C) phases of high quality single crystals of Rb2ZnCl4 (RZC). Special emphasis is laid upon the region around the lock-in transition atT
c
. While in the N and C phases discrete lines are observed, in the IC phase a continuous distribution of frequencies is detected. In a temperature interval not exceeding 15 K aboveT
c
some centers of intensity termed C lines can be observed in the frequency distribution. They reflect the fact that in the IC phase close toT
c
several nuclei feel a local surrounding very similar to that of the low temperature C phase. For the first time in the region aroundT
c
the influence could be studied which an electric field favouring the ferroelectric C phase has on the NMR spectra. The experimental results are related to the temperature and electric field dependence of the soliton density near the lock-in transition. A general definition of the soliton density is developed whose validity is not limited to the very narrow soliton limit. The meaning of this definition is also discussed in terms of well known phenomenological theories of the three phases of RZC. The experimental NMR data can be well described by this general definition.Dedicated to Prof. Dr. H.E. Müser on the occasion of his 60th birthday 相似文献
9.
I. Blomqvist B. Bülow A. Fredrikson B. Johnsson G. G. Jonsson K. Lindgren M. Nilsson R. Petersson O. Glomset N. Freed W. Rhodes 《Zeitschrift für Physik A Hadrons and Nuclei》1978,284(3):313-317
The lifetime of the 331.3 keV 0 2 + state in100Zr has been measured at the gas-filled recoil separator for fission products JOSEF. By observing the delayed coincidences between theβ-particles populating the level and theE0 conversion electrons from its decay into the ground state, a half-life of 3.37±0.30 ns has been obtained. From the measured lifetime and the relative intensities of the 0 2 + →0 1 + and 0 2 + →2 1 + transitions, values of 0.493±0.015 for theE0 strength parameterρ, and of 16 single particle units forB(E2,2 1 + → 0 2 + ) have been deduced. The enhanced nature of theE0 transitions suggests mixing of the 0 1 + and 0 2 + states which may be estimated by comparing the experimentalB(E2) values for the 2 1 + →0 1 + and 2 1 + →0 2 + transitions with the predictions of the asymmetric VMI model. 相似文献
10.
The convergence of ab initio calculations of the beryllium dimer potential is examined with several basis sets orders of perturbation theory. When the atomic pair natural orbital basis set calculations are extrapolated to the complete basis set and full CI limits, the calculated parameters: Re=2.447 Å, De=827 cm−1, ν01=212.7 cm−1, ν12=167.2 cm−1, ν23=121.5 cm−1 and ν34=77.7 cm−1 are in good agreement with the experimental parameters: Re=2.45 Å, De=839±10 cm−1, ν01=223.2 cm−1, ν12=169.7 cm−1, ν23=122.5 cm−1, and ν34=79 cm−1. 相似文献