全文获取类型
收费全文 | 141篇 |
免费 | 0篇 |
专业分类
化学 | 43篇 |
力学 | 4篇 |
数学 | 11篇 |
物理学 | 83篇 |
出版年
2022年 | 1篇 |
2014年 | 2篇 |
2013年 | 3篇 |
2012年 | 22篇 |
2011年 | 17篇 |
2010年 | 15篇 |
2009年 | 21篇 |
2008年 | 8篇 |
2007年 | 9篇 |
2006年 | 8篇 |
2005年 | 5篇 |
2004年 | 6篇 |
2003年 | 1篇 |
2002年 | 2篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1995年 | 1篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有141条查询结果,搜索用时 328 毫秒
31.
H. Figiel Ł. Gondek B. Dubiel F. Ciura J. Chmist A. Czyrska-Filemonowicz 《Journal of magnetism and magnetic materials》2008
The results of transmission electron microscopy (TEM), magnetic and magneto-resistivity investigations of the Cu–10Co (wt%) giant magneto-resistance (GMR) melt-spun ribbons are reported and discussed. To obtain different distributions of ferromagnetic Co particles in a non-magnetic Cu matrix, the alloy was aged at 550 °C for 0.5, 1, 2, 16, and 32 h. Particle size measurements were performed using quantitative TEM metallography methods. Two size classes of Co particles are identified: primary particles (P) precipitated during the melt-spinning process and the secondary particles (S) precipitated during the ageing process. The results of magnetization and coercitivity are correlated with the results of calculations based on the real Co particle distributions determined from TEM micrographs. The behavior of magnetization and coercive force in function of ageing time is explained as related with changes of a mean particle size. It is shown that the GMR effect is not influenced by Co particles distribution for the S particles with the mean size less than 10 nm, whereas for Co distributions with larger mean diameters, the GMR effect is strongly reduced. 相似文献
32.
Koścień E Gondek E Kityk AV 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,70(5):1097-1103
Paper presents the quantum chemical modeling of the optical absorption spectra of 6-fluoro, 6-bromo, 7-trifluoromethyl, 6-cyano and 6-carboethoxy derivatives of 1,3-Dimethyl-1H-Pyrazolo[3,4-b]quinoline. The calculations are performed by means of the semiempirical quantum chemical methods (AM1 or PM3) in combination with molecular dynamics (MD) simulations at T=300 K. It is shown that a particular rotational dynamics of the methyl, trifluoromethyl or ethyl groups practically does not influence the optical absorption in the spectral range 200-500 nm whereas broadening of absorption bands may be well reproduced within MD simulations including all types of nuclei vibrations. The results of calculations are compared with the measured spectra of optical absorption. The quantum chemical method AM1 in combination with MD simulations gives for all dyes the best agreement between the calculated and measured spectral positions of the first absorption band (absorption threshold). 相似文献
33.
N. S. ?eng?r Y. ?ak?r C. Güzeli? F. Pekergin ?. Morgül 《ARI - An International Journal for Physical and Engineering Sciences》1999,51(4):268-276
Several formulations and methods used in solving an NP-hard discrete optimization problem, maximum clique, are considered in a dynamical system perspective proposing continuous methods to the problem. A compact form for a saturated linear dynamical network, recently developed for obtaining approximations to maximum clique, is given so its relation to the classical gradient projection method of constrained optimization becomes more visible. Using this form, gradient-like dynamical systems as continuous methods for finding the maximum clique are discussed. To show the one to one correspondence between the stable equilibria of the saturated linear dynamical network and the minima of objective function related to the optimization problem, La Salle's invariance principle has been extended to the systems with a discontinuous right-hand side. In order to show the efficiency of the continuous methods simulation results are given comparing saturated the linear dynamical network, the continuous Hopfield network, the cellular neural networks and relaxation labelling networks. It is concluded that the quadratic programming formulation of the maximum clique problem provides a framework suitable to be incorporated with the continuous relaxation of binary optimization variables and hence allowing the use of gradient-like continuous systems which have been observed to be quite efficient for minimizing quadratic costs. 相似文献
34.
?. Ayta? S. Akyil M. A. A. Aslani U. Aytekin 《Journal of Radioanalytical and Nuclear Chemistry》1999,240(3):973-976
In this study, the removal of uranium from aqueous solutions by diatomite earth (Kieselguhr) fine particules has been investigated.
Diatomite earth is an important adsorbent material in chromatographic studies. Uranium adsorption capacity of four different
types of diatomite was determined. The adsorption of uranium on the chosen diatomite sample was examined as a function of
uranium concentration, solution pH, contact time and temperature. The adsorption of uranium on diatomite followed a Langmuir-type
isotherm. 相似文献
35.
?. Ate? G. Tekeli G. ?elik E. Ak?n M. Ta?er 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(1):21-24
The electric dipole oscillator strengths for multiplet and
individual lines between some doublet and quartet levels have been
calculated using the weakest bound electron potential model theory (WBEPMT)
in singly ionized oxygen. We employed both numerical Coulomb approximation
(NCA) wave functions and numerical non-relativistic Hartree-Fock (NRHF) wave
functions for expectation values of radii in determination of parameters.
The calculated oscillator strengths have been compared with available
theoretical and experimental results. A good agreement with results in
literature has been obtained. Moreover, oscillator strengths not existing in
the literature for some highly excited levels have been obtained using this
method.
Electronic supplementary material Supplementary Online Material 相似文献
36.
. Gondek J. Czub A. Szytua Z. Izaola E. Kemner 《Solid State Communications》2009,149(39-40):1596-1599
The RPdIn compounds (R = rare earth) crystallise in the hexagonal ZrNiAl-type crystal structure. The compounds from this family exhibit a great variety of interesting magnetic properties including heavy fermion behaviour. In order to get a deeper insight into nature of magnetism of RPdIn with light rare earths elements (La–Nd) an inelastic neutron scattering experiment was performed. For compounds with Pr and Nd excitations due to crystal field were clearly distinguished. On the other hand, interesting behaviour for the CePdIn sample was observed. The sample exhibits no signs of crystal field excitations, likely due to highly delocalised Ce 4f states leading to its heavy fermion behaviour. 相似文献
37.
?. Kuru 《Annals of Physics》2009,324(12):2548-264
The dynamical algebras of the trigonometric and hyperbolic symmetric Pöschl-Teller Hamiltonian hierarchies are obtained. A kind of discrete-differential realizations of these algebras are found which are isomorphic to so(3, 2) Lie algebras. In order to get them, first the relation between ladder and factor operators is investigated. In particular, the action of the ladder operators on normalized eigenfunctions is found explicitly. Then, the whole dynamical algebras are generated in a straightforward way. 相似文献
38.
?. N. Radenovi? M. G. Jeremi? G. V. Maximov M. V. Beljanski A. R. Radoj?i? 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2009,83(9):1582-1591
Standard induction processes of delayed fluorescence (DF) of chlorophyll (induction signals) occur when an intact leaf segment
of maize inbreds and hybrids is initially kept in the phosphoroscope darkroom for more than 15 min (τ > 15 min), and then
the leaf is illuminated with the intermittent white light and measured. Resolved induction processes of DF chlorophyll into
transients: A, B, C, D, and E occur when the intact leaf segment of maize inbreds and hybrids is kept in the phosphoroscope
darkroom for a significantly shorter period (30 s ≤ τ ≤ 240 s), with the time rate τ of 30 s, prior to its illumination with
the intermittent white light. Induction transients: A, B, C, D, and E are characterised with their temporal parameters: t
A, t
B, t
C, t
D, and t
E, dynamics of changes in transients intensities and mechanisms of their generation. The induction processes of chlorophyll
DF of the intact leaf of maize inbreds and hybrids resolved into transients: A, B, C, D, and E are accompanied by the occurrence
and different levels of activation energy (E
a, kJ mol−1) that correspond to different critical temperatures. The generation mechanisms of induction transients: A, B, C, D, and E
are classified into two groups. Transients A and B are of a physical character, while the transients: C, D, and E are of a
chemical character. It is shown that the generation of the induction transients: B, C, D, and E simultaneously follows establishing
of the oscillations of induction processes of the DF chlorophyll. Oscillating of induction processes of DF chlorophyll is
explained by the ion (K+, Na+, H+, Cl−) transport mechanism across the thylakoid membrane of the intact leaf of maize inbreds and hybrids grown under conditions
of air drought, increased temperatures and water deficiency in the medium.
The article is published in the original. 相似文献
39.
Weiqi Fu Manuela Magnúsdóttir Sigureur Brynjólfson Bernhard ?. Palsson Giuseppe Paglia 《Analytical and bioanalytical chemistry》2012,404(10):3145-3154
A fast method for quantification and identification of carotenoid and chlorophyll species utilizing liquid chromatography coupled with UV detection and mass spectrometry has been demonstrated and validated for the analysis of algae samples. This method allows quantification of targeted pigments and identification of unexpected compounds, providing isomers separation, UV detection, accurate mass measurements, and study of fragment ions for structural elucidation in a single run. This is possible using parallel alternating low- and high-energy collision spectral acquisition modes, which provide accurate mass full scan chromatograms and accurate mass high-energy chromatograms. Here, it is shown how this approach can be used to confirm carotenoid and chlorophyll species by identification of key diagnostic fragmentations during high-energy mode. The developed method was successfully applied for the analysis of Dunaliella salina samples during defined red LED lighting growth conditions, identifying 37 pigments including 19 carotenoid species and 18 chlorophyll species, and providing quantification of 7 targeted compounds. Limit of detections for targeted pigments ranged from 0.01?ng/mL for lutein to 0.24?ng/mL for chlorophyll a. Inter-run precision ranged for of 3 to 24 (RSD%) while inter-run inaccuracy ranged from ?17 to 11. Figure
Identification of carotenoids and chlorophylls combining UPLC separation, UV detection, accurate mass measurements and study of fragment ions in a single run 相似文献
40.
Two types of Schottky Barrier Diodes (SBDs) with and without PVA (Bi2O3-doped) polymeric interfacial layer, were fabricated and measured at room temperature in order to investigate the effects of the PVA (Bi2O3-doped) interfacial layer on the main electrical parameters such as the ideality factor (n), zero-bias barrier height (ΦB0), series resistance (Rs) and interface-state density (Nss). Electrical parameters of these two diodes were calculated from the current-voltage (I-V) characteristics and compared with each other. The values of ΦB0, n and Rs for SBDs without polymeric interfacial layer are 0.71 eV, 1.44 and 4775 Ω, respectively. The values of ΦB0, n and Rs for SBDs with PVA (Bi2O3-doped) polymeric interfacial layer are 0.74 eV, 3.49 and 10,030 Ω, respectively. For two SBDs, the energy density distribution profiles of interface states (Nss) were obtained from forward-bias I-V measurements by taking the bias dependence of Rs of these devices into account. The values of Nss obtained for the SBD with PVA (Bi2O3-doped) polymeric interfacial layer are smaller than those of the SBD without polymeric interfacial layer. 相似文献