全文获取类型
收费全文 | 491篇 |
免费 | 26篇 |
国内免费 | 5篇 |
专业分类
化学 | 355篇 |
晶体学 | 10篇 |
力学 | 23篇 |
数学 | 30篇 |
物理学 | 104篇 |
出版年
2024年 | 2篇 |
2023年 | 4篇 |
2022年 | 16篇 |
2021年 | 12篇 |
2020年 | 14篇 |
2019年 | 12篇 |
2018年 | 16篇 |
2017年 | 20篇 |
2016年 | 32篇 |
2015年 | 32篇 |
2014年 | 33篇 |
2013年 | 57篇 |
2012年 | 33篇 |
2011年 | 51篇 |
2010年 | 30篇 |
2009年 | 29篇 |
2008年 | 23篇 |
2007年 | 22篇 |
2006年 | 12篇 |
2005年 | 15篇 |
2004年 | 10篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1998年 | 1篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1995年 | 7篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1990年 | 1篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1973年 | 1篇 |
排序方式: 共有522条查询结果,搜索用时 0 毫秒
61.
62.
Extended X-ray absorption fine structure (EXAFS) of the iron K edges in copper, cobalt, zinc and manganese ferrites is studied and the EXAFS parameter α of the Lytle, Sayers and Stern's theory is shown to be a measure of fractional covalency. The linear relationship between metal to oxygen (iron to oxygen) distance and the parameter α leads us to conclude that the copper ferrite is the most covalent among the four ferrites studied in the present investigation. 相似文献
63.
The theory of the transverse static magnetoconductivity (σxx) in a two-dimensional system under the simultaneous influence of electron-phonon and electron-impurity interactions is presented. The memory function technique is employed to obtain explicit expression for σxx under conditions appropriate for typical Shubnikov-deHaas measurements. It is shown that σxx involves two different effective masses and scattering times, of which one is the scattering time in the absence of the magnetic field. In addition, the Landau level width appears in σxx, thus providing an experimental means for extracting the same from a study of the background conductivity. 相似文献
64.
65.
66.
A. Madhukar 《Solid State Communications》1975,16(4):461-465
A smooth correlation between the determined chemisorption bond lengths, for O, S, Se and Te on Ni (001) and for sulphur on Ni (110) and Ni (111) as well, and Pauling's resonating bond ionicity is demonstrated, when the latter are calculated with due regard for the coordination and valency saturation effects. Pauling's bond length-bond number relation is used to provide (i) an independent estimate of the Ni-O bond length on Ni (001), which is found capable of discriminating among the reported values, and (ii) estimates of the bond lengths for O, S, Se and Te on Ni (111) and Ni (110) by using the determined bond lengths on Ni (001). Agreement with the determined values for sulphur is surprisingly good. 相似文献
67.
We consider an n-player non-cooperative game with random payoffs and continuous strategy set for each player. The random payoffs of each player are defined using a finite dimensional random vector. We formulate this problem as a chance-constrained game by defining the payoff function of each player using a chance constraint. We first consider the case where the continuous strategy set of each player does not depend on the strategies of other players. If a random vector defining the payoffs of each player follows a multivariate elliptically symmetric distribution, we show that there exists a Nash equilibrium. We characterize the set of Nash equilibria using the solution set of a variational inequality (VI) problem. Next, we consider the case where the continuous strategy set of each player is defined by a shared constraint set. In this case, we show that there exists a generalized Nash equilibrium for elliptically symmetric distributed payoffs. Under certain conditions, we characterize the set of a generalized Nash equilibria using the solution set of a VI problem. As an application, the random payoff games arising from electricity market are studied under chance-constrained game framework. 相似文献
68.
This paper presents an ant colony optimization algorithm to address the constrained redundancy allocation problem in order to maximize system reliability for complex binary systems. The constraints involved, though separable, are both linear and non-linear. We couple an adaptive penalty function with the basic ant colony approach to handle highly constrained problems and embed a local search technique to find still better locally optimal solutions. The proposed algorithm has been tested on a large number of problems, containing even up to 500 subsystems, with both fixed and randomly generated parameters. Experimental results demonstrate the advantage of the proposed algorithm to solve similar types of problems. 相似文献
69.
Vinod D. Gupta Abhinav B. Tathe Vikas S. Padalkar Vikas S. Patil Kiran R. Phatangare Prashant G. Umape Ponnadurai Ramasami Nagaiyan Sekar 《Journal of fluorescence》2013,23(6):1121-1138
Push-pull chromophores attached to carbazole based π-conjugating spacers bearing N-alkylamino donors, cyanovinyl and carbethoxy acceptors have been studied by the means of UV-Visible measurements. The intramolecular charge transfer (ICT) of these π-conjugated systems has also been tested by investigating the ability of the solute molecules to undergo shifts in their fluorescence emission maxima with increasing solvent polarity. Density Functional Theory [B3LYP/6-31G(d)] and Time Dependent Density Functional Theory [TD-B3LYP/6-31G(d)] computations have been used to have more understanding of the structural, molecular, electronic and photophysical parameters of push-pull dyes. The largest wavelength difference between the experimental and computed electronic absorption maxima was 45 nm. For emission, a largest difference of 61 nm was observed. The ground state and excited state dipole moments in different solvents were determined using experimental solvatochromic data and computed Onsager radii. The dipole moments of the molecules in the excited state were observed to be higher than in the ground state. 相似文献
70.
Vikas S. Patil Vikas S. Padalkar Abhinav B. Tathe Vinod D. Gupta N. Sekar 《Journal of fluorescence》2013,23(5):1019-1029
Novel ESIPT inspired benzimidazole, benzoxazole and benzothiazole were synthesized from 2,4-dihydroxy benzoic acid and 1,2-phenelenediamine, 2-aminophenol, and 2-aminothiophenol respectively. The synthesized 2-(2′,4′-dihydroxyphenyl) benzimidazole, benzoxazole and benzothiazole are fluorescent and the emission characteristic are very sensitive to the micro-environment. They show a single absorption and dual emission with large Stokes shift originating from excited state intramolecular proton transfer. The absorption-emission characteristics of all these compounds are studied as a function of pH. The change in the electronic transition, energy levels, and orbital diagrams of synthesized compounds were investigated by the molecular orbital calculation and were correlated with the experimental spectral emission. Experimental absorption and emission wavelengths are in good agreement with those predicted using the Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT) [B3LYP/6-31G(d)]. Figure
Novel ESIPT inspired benzimidazole, benzoxazole and benzothiazole were synthesized from 2,4-dihydroxy benzoic acid and o- amino aromatics. Single absorption and dual emission are the interesting properties of the synthesized compounds. 相似文献