全文获取类型
收费全文 | 191篇 |
免费 | 5篇 |
国内免费 | 2篇 |
专业分类
化学 | 93篇 |
力学 | 1篇 |
数学 | 44篇 |
物理学 | 60篇 |
出版年
2023年 | 2篇 |
2022年 | 1篇 |
2021年 | 1篇 |
2019年 | 3篇 |
2018年 | 1篇 |
2017年 | 3篇 |
2016年 | 4篇 |
2015年 | 7篇 |
2014年 | 6篇 |
2013年 | 8篇 |
2012年 | 10篇 |
2011年 | 11篇 |
2010年 | 9篇 |
2009年 | 6篇 |
2008年 | 14篇 |
2007年 | 7篇 |
2006年 | 17篇 |
2005年 | 8篇 |
2004年 | 12篇 |
2003年 | 5篇 |
2002年 | 6篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 4篇 |
1993年 | 1篇 |
1991年 | 6篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1973年 | 4篇 |
1970年 | 2篇 |
1966年 | 1篇 |
排序方式: 共有198条查询结果,搜索用时 15 毫秒
31.
Aharon Razon 《manuscripta mathematica》1997,94(1):531-542
We construct an abundance of Hilbertian domains: LetK be an abelian extension of ? such that {ord(a)|a εG(K/?)} is unbounded, let ? K be its ring of integers, and lete ≥ 2 be an integer. Then, for almost all σ εG (?) e , each ring between ? K andK · (σ) is Hilbertian. 相似文献
32.
A random variable (RV) X is given aminimum selling price (S) $$S_U \left( X \right): = \mathop {\sup }\limits_x \left\{ {x + EU\left( {X - x} \right)} \right\}$$ and amaximum buying price (B) $$B_p \left( X \right): = \mathop {\inf }\limits_x \left\{ {x + EP\left( {X - x} \right)} \right\}$$ whereU(·) andP(·) are appropriate functions. These prices are derived from considerations ofstochastic optimization with recourse, and are calledrecourse certainty equivalents (RCE's) of X. Both RCE's compute the “value” of a RV as an optimization problem, and both problems (S) and (B) have meaningful dual problems, stated in terms of theCsiszár φ-divergence $$I_\phi \left( {p,q} \right): = \sum\limits_{i = 1}^n {q_i \phi \left( {\frac{{p_i }}{{q_i }}} \right)} $$ a generalized entropy function, measuring the distance between RV's with probability vectors p and q. The RCES U was studied elsewhere, and applied to production, investment and insurance problems. Here we study the RCEB P, and apply it to problems ofinventory control (where the attitude towards risk determines the stock levels and order sizes) andoptimal insurance coverage, a problem stated as a game between the insurance company (setting the premiums) and the buyer of insurance, maximizing the RCE of his coverage. 相似文献
33.
We study cyclicity of operators on a separable Banach space which admit a bicyclic vector such that the norms of its images
under the iterates of the operator satisfy certain growth conditions. A simple consequence of our main result is that a bicyclic
unitary operator on a Banach space with separable dual is cyclic. Our results also imply that if is the shift operator acting on the weighted space of sequences , if the weight ω satisfies some regularity conditions and ω(n) = 1 for nonnegative n, then S is cyclic if . On the other hand one can see that S is not cyclic if the series diverges. We show that the question of Herrero whether either S or S* is cyclic on admits a positive answer when the series is convergent. We also prove completeness results for translates in certain Banach spaces of functions on . 相似文献
34.
35.
Shiran Aharon Dr. Shanti Gopal Patra Prof. Dr. Dan Meyerstein Dr. Eyal Tzur Dr. Dror Shamir Dr. Yael Albo Prof. Dr. Ariela Burg 《Chemphyschem》2023,24(22):e202300517
The Na3[Ru2(μ-CO3)4] complex is acting as a water oxidation catalyst in a homogeneous system. Due to the significance of heterogeneous systems and the effect of bicarbonate on the kinetic, we studied the bicarbonate effect on the heterogeneous electrocatalyst by entrapping the Na3[Ru2(μ-CO3)4] complex in a sol-gel matrix. We have developed two types of sol-gel electrodes, which differ by the precursor, and are demonstrating their stability over a minimum of 200 electrochemical cycles. The pH increases affected the currents and kcat for both types of electrodes, and their hydrophobicity, which was obtained from the precursor type, influenced the electrocatalytic process rate. The results indicate that NaHCO3 has an important role in the catalytic activity of the presented heterogeneous systems; without NaHCO3, the diffusing species is probably OH−, which undergoes diffusion via the Grotthuss mechanism. To the best of our knowledge, this is the first study to present a simple and fast one-step entrapment process for the Na3[Ru2(μ-CO3)4] complex by the sol-gel method under standard laboratory conditions. The results contribute to optimizing the WSP, ultimately helping expand the usage of hydrogen as a green and more readily available energy source. 相似文献
36.
Amorphous iron(III) oxide--a review 总被引:1,自引:0,他引:1
37.
38.
39.
Josiah Sinclair David Spierings Aharon Brodutch Aephraim M. Steinberg 《Physics letters. A》2019,383(24):2839-2845
Constructing an ontology for quantum theory is challenging, in part due to measurement back-action. The Aharonov-Albert-Vaidman weak measurement formalism provides a method to predict measurement results (weak values) when back-action is negligible. The weak value appears analogous to a classical conditional mean, yet can be complex and unbounded. We study weak values in the context of a recent quantum optical experiment involving two-photon interactions. The results of the experiment are reinterpreted within a realist ‘stochastic optics’ model of light. We show that the conditional means of the intensities in the model correspond to the experimentally observed weak values and study the breakdown of the model outside the experimentally probed regime in the limit where the weak value predicts ‘anomalous’ results. 相似文献
40.
Witold Lojkowski Aharon Gedanken Ewa Grzanka Agnieszka Opalinska Tomasz Strachowski Roman Pielaszek Anita Tomaszewska-Grzeda Sergyi Yatsunenko Marek Godlewski Hubert Matysiak Krzysztof J. Kurzyd?owski 《Journal of nanoparticle research》2009,11(8):1991-2002
ZnO nanopowders doped with Mn2+, Ni2+, Co2+ and Cr3+ ions have been synthesised for the first time using a solvothermal reaction with microwave heating. The nanopowders were produced from a solution of zinc acetate and manganese (II), chromium (III), nickel (II) and cobalt (II) acetates, using ethylene glycol as a solvent. The content of Ni2+, Co2+ and Cr3+ ions in the solution and in the solid phase were close to each other up to 5 mol%. The doping level of Mn2+ ions in the solid is about 50% of that in the solution. No phases or compounds other than ZnO were detected by X-ray diffraction with Mn2+, Co2+ and Ni2+ doping. With Cr3+ ions a small amount of chromium oxide was found. None of the powders displayed any luminescence after doping. The Mn2+-doped powder displayed a paramagnetic behaviour. ESR and magnetisation investigations have revealed that no clustering of Mn2+ ions occurred up to a doping level of 3.9 mol%. The average grain size of powders doped with Ni2+, Cr3+, Co2+ and Mn2+ for a 10 mol% ion content in the solution was about 20 nm and the grain size dispersion 30%. With increasing dopant content the grain size decreased. It appears that the solvothermal process employed allows relatively high doping levels of the transition metal ions to be achieved without any dopant clustering or oxide precipitation. 相似文献