全文获取类型
收费全文 | 222篇 |
免费 | 3篇 |
国内免费 | 1篇 |
专业分类
化学 | 32篇 |
晶体学 | 10篇 |
力学 | 14篇 |
数学 | 95篇 |
物理学 | 75篇 |
出版年
2022年 | 2篇 |
2021年 | 4篇 |
2020年 | 6篇 |
2019年 | 5篇 |
2018年 | 7篇 |
2017年 | 3篇 |
2016年 | 7篇 |
2015年 | 4篇 |
2014年 | 6篇 |
2013年 | 17篇 |
2012年 | 17篇 |
2011年 | 21篇 |
2010年 | 23篇 |
2009年 | 20篇 |
2008年 | 17篇 |
2007年 | 16篇 |
2006年 | 15篇 |
2005年 | 4篇 |
2004年 | 3篇 |
2003年 | 5篇 |
2002年 | 5篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1998年 | 1篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1981年 | 2篇 |
1980年 | 2篇 |
排序方式: 共有226条查询结果,搜索用时 15 毫秒
1.
2.
B. Gorski Nguyen Za Hung N. Ya Ljubman 《Isotopes in environmental and health studies》2013,49(3):275-282
Abstract Possibilities of using a new generation of sorbents have been investigated. Polymers of spatial-globular (spherulitic) structure (RGS polymers) have been tested to separate Cs, Sr and rare earth elements – which can also be radioactive contaminants – from different waters. RGS polymers are both, solids and highly-disperse systems being extremely permeable to fluids and gases with low pressure decline. They were currently used to clean industrial waste-water. It is shown that these polymers can be used successfully to separate radionuclides. Polymers RGS-81 and RGS-112 have high distribution coefficients for CS, Sr, Sc, the lanthanide series and Hf in weakly acid solutions. In HF solutions, Sc and Hf can be separated from Cs, Sr and the lanthanides. 相似文献
3.
Stock indexes for some European emerging markets are analyzed using an investment-horizon approach. Austrian ATX index and Dow Jones have been studied and compared with several emerging European markets. The optimal investment horizons are plotted as a function of an absolute return value. Gain–loss asymmetry, originally found for American DJIA index, is observed for all analyzed data. It is shown, that this asymmetry has different character for emerging and for established markets. For established markets, gain curve lies typically above loss curve, whereas in the case of emerging markets the situation is just the opposite. We propose a measure quantifying the gain–loss asymmetry that clearly exhibits a difference between emerging and established markets. 相似文献
4.
Toufik Hadjersi 《Applied Surface Science》2007,253(9):4156-4160
The mechanism of metal-assisted electroless etching of silicon in HF-oxidizing agent-H2O etching system as a function of oxidizing agent concentration was studied. Three types of oxidizing agent were experimented namely Na2S2O8, K2Cr2O7 and KMnO4. Their concentrations were varied from 0.05 M to 0.3 M. The layers formed on silicon were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy-dispersive X-ray (EDX). It is shown that an insoluble solid-phase film (K2SiF6) form on silicon surface when concentration of K2Cr2O7 or KMnO4 increases in chemical solutions. On other hand, when Na2S2O8 concentration increases, the surface roughness decreases without any chemical complex formation. 相似文献
5.
Jeļena Leičūnaite Igors KļimenkovsJorens Kviesis Dzintars ZačsJuris Pauls Kreišmanis 《Comptes Rendus Chimie》2010,13(10):1335-1340
A new series [CnOmmim]Cl of imidazolium cation-based ionic liquids (ILs), with an ether functional group on the alkyl side-chain, has been prepared. The possibility of analyzing the ionic liquids by high performance liquid chromatography (HPLC) was investigated on mixed-mode reversed/cation exchange stationary phase with the aqueous-acetonitrile mobile phase. Elution parameters, such as retention factor, selectivity and column efficiency, were studied as functions of mobile phase composition and pH. The ILs were characterized by elemental analysis, and infrared, UV and 1H, 13C NMR spectroscopy. 相似文献
6.
O. V. Kovalchukova A. I. Stash S. B. Strashnova E. P. Romashkina B. E. Za?tsev 《Crystallography Reports》2010,55(3):428-431
The complex compounds (H3
L · Cl)[CoCl4] (I) and H2
L[CuBr4] (II), where L is 2,4,6-tri(N,N-dimethylamino)methylphenol, were isolated in the crystalline state and studied by X-ray diffraction. The organic cations
were found to be outer-sphere ligands. All three nitrogen atoms of the tertiary amino groups are protonated. In compound I, the H3
L
3+ cation exists as the cis tautomer. In compound II, the H2
L
2+ dication exists as the trans isomer. In the crystal structure, the dications are arranged in layers via hydrogen bonds. 相似文献
7.
I. G. Pervova A. V. Zaĭdman I. N. Lipunov P. A. Slepukhin 《Crystallography Reports》2010,55(2):237-239
1,5-Bis(2-Formylphenoxy)pentane was studied by X-ray diffraction. There are two crystallographically independent molecules
with similar geometric parameters in the asymmetric unit of the crystal structure. The molecules occupy special positions
on a rotation axis. 相似文献
8.
Johannes Hatzl Toufik Mansour Mark Shattuck 《Journal of Mathematical Modelling and Algorithms》2011,10(2):193-203
Consider the set S of points in the plane consisting of the ordered pairs (i, j ), where
1 \leqslant i \leqslant m1 \leqslant i \leqslant m and
1 \leqslant j \leqslant n1 \leqslant j \leqslant n. A problem related to the study of segmentation evaluation of visual images concerns finding a permutation σ of the points of S for which the sum
?s ? Sd(s, s(s)) \sum\limits_{s \in S}d(s, \sigma(s)) 相似文献
9.
Zañartu M Mehta DD Ho JC Wodicka GR Hillman RE 《The Journal of the Acoustical Society of America》2011,129(1):326-339
Different source-related factors can lead to vocal fold instabilities and bifurcations referred to as voice breaks. Nonlinear coupling in phonation suggests that changes in acoustic loading can also be responsible for this unstable behavior. However, no in vivo visualization of tissue motion during these acoustically induced instabilities has been reported. Simultaneous recordings of laryngeal high-speed videoendoscopy, acoustics, aerodynamics, electroglottography, and neck skin acceleration are obtained from a participant consistently exhibiting voice breaks during pitch glide maneuvers. Results suggest that acoustically induced and source-induced instabilities can be distinguished at the tissue level. Differences in vibratory patterns are described through kymography and phonovibrography; measures of glottal area, open/speed quotient, and amplitude/phase asymmetry; and empirical orthogonal function decomposition. Acoustically induced tissue instabilities appear abruptly and exhibit irregular vocal fold motion after the bifurcation point, whereas source-induced ones show a smoother transition. These observations are also reflected in the acoustic and acceleration signals. Added aperiodicity is observed after the acoustically induced break, and harmonic changes appear prior to the bifurcation for the source-induced break. Both types of breaks appear to be subcritical bifurcations due to the presence of hysteresis and amplitude changes after the frequency jumps. These results are consistent with previous studies and the nonlinear source-filter coupling theory. 相似文献
10.
In this paper, the approximate controllability of neutral stochastic fractional differential equations involving nonlocal initial conditions is studied. By using Sadovskii’s fixed point theorem with stochastic analysis theory, we derive a new set of sufficient conditions for the approximate controllability of semilinear fractional stochastic differential equations with nonlocal conditions under the assumption that the corresponding linear system is approximately controllable. Finally, an application to a fractional partial stochastic differential equation with nonlocal initial condition is provided to illustrate the obtained theory. 相似文献
|