全文获取类型
收费全文 | 107篇 |
免费 | 11篇 |
国内免费 | 28篇 |
专业分类
化学 | 35篇 |
综合类 | 1篇 |
数学 | 106篇 |
物理学 | 4篇 |
出版年
2023年 | 2篇 |
2022年 | 1篇 |
2021年 | 1篇 |
2020年 | 6篇 |
2019年 | 3篇 |
2018年 | 7篇 |
2017年 | 3篇 |
2016年 | 2篇 |
2014年 | 3篇 |
2013年 | 7篇 |
2012年 | 7篇 |
2011年 | 7篇 |
2010年 | 8篇 |
2009年 | 7篇 |
2008年 | 8篇 |
2007年 | 6篇 |
2006年 | 10篇 |
2005年 | 5篇 |
2004年 | 5篇 |
2003年 | 8篇 |
2002年 | 3篇 |
2001年 | 8篇 |
2000年 | 4篇 |
1999年 | 5篇 |
1998年 | 5篇 |
1997年 | 5篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1992年 | 1篇 |
1984年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有146条查询结果,搜索用时 203 毫秒
1.
Dang Lanh Hoang Thi Thuy Hanh Dang Jana Engeldinger Matthias Schneider Jörg Radnik Manfred Richter Andreas Martin 《Journal of solid state chemistry》2011,184(8):1915-1923
Reducibility of Cu supported on Al2O3, zeolite Y and silicoaluminophosphate SAPO-5 has been investigated in dependence on the Cu content using a method combining conventional temperature programmed reduction (TPR) by hydrogen with reoxidation in N2O followed by a second the so-called surface-TPR (s-TPR). The method enables discrimination and a quantitative estimation of the Cu oxidation states +2, +1 and 0. The quantitative results show that the initial oxidation state of Cu after calcination in air at 400 °C, independent on the nature of the support, is predominantly +2. Cu2+ supported on Al2O3 is quantitatively reduced by hydrogen to metallic Cu0. Comparing the TPR of the samples calcined in air and that of samples additionally pre-treated in argon reveals that in zeolite Y and SAPO-5 Cu2+ cations are stabilized as weakly and strongly forms. In both systems, strongly stabilized Cu2+ ions are not auto-reduced by pre-treatment in argon at 650 °C, but are reduced in hydrogen to form Cu+. The weakly stabilized Cu2+ ions, in contrast, may be auto-reduced by pre-treatment in argon at 650 °C forming Cu+ but are reduced in hydrogen to metallic Cu0. 相似文献
2.
3.
Roman Sasyk 《Journal of Functional Analysis》2009,256(8):2710-2724
We prove that it is not possible to classify separable von Neumann factors of types II1, II∞ or IIIλ, 0?λ?1, up to isomorphism by a Borel measurable assignment of “countable structures” as invariants. In particular the isomorphism relation of type II1 factors is not smooth. We also prove that the isomorphism relation for von Neumann II1 factors is analytic, but is not Borel. 相似文献
4.
贵金属助剂促进的费-托合成用钴基催化剂具有高活性和长链烃(C5+)选择性优越等特点,被广泛应用于由合成气制清洁燃料的合成反应中。 本文重点讨论了贵金属助剂对活性钴物种的结构(还原度、分散度、双金属颗粒或合金的构成), 钴基催化剂稳定性以及其对费-托合成的反应速率和产物选择性的影响规律。 相似文献
5.
Arno Pauly 《Mathematical Logic Quarterly》2010,56(5):488-502
Continuous reducibilities are a proven tool in Computable Analysis, and have applications in other fields such as Constructive Mathematics or Reverse Mathematics. We study the order‐theoretic properties of several variants of the two most important definitions, and especially introduce suprema for them. The suprema are shown to commutate with several characteristic numbers (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
6.
Valeriy K. Bulitko 《Mathematical Logic Quarterly》1999,45(4):561-571
We apply complexity concepts to define a new sort of sub-Turing reducibilities ≤ ?? make the degree hierarchy thinner and to obtain some new specifications of the well known jump inversion theorem of Friedberg. We show that this theorem doesn't hold when ≤ T is replaced with ≤ ??, where ?? is any countable subset of the class ?? of all total increasing functions f : ? → ?. 相似文献
7.
Let A?(??) denote the set of functions belonging to the disc algebra having real Fourier coefficients. We show that A?(??) has Bass and topological stable ranks equal to 2, which settles the conjecture made by Brett Wick in [18]. We also give a necessary and sufficient condition for reducibility in some real algebras of functions on symmetric domains with holes, which is a generalization of the main theorem in [18]. A sufficient topological condition on the symmetric open set ?? is given for the corresponding real algebra A?(??) to have Bass stable rank equal to 1 (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
8.
I.N. Soskov 《Archive for Mathematical Logic》2000,39(6):417-437
Abstract. We prove a jump inversion theorem for the enumeration jump and a minimal pair type theorem for the enumeration reducibilty.
As an application some results of Selman, Case and Ash are obtained.
Received: 15 May 1998 相似文献
9.
Ta‐Tsien Li Yue‐Jun Peng Yong‐Fu Yang Yi Zhou 《Mathematical Methods in the Applied Sciences》2008,31(2):193-227
One often believes that there is no shock formation for the Cauchy problem of quasilinear hyperbolic systems (of conservation laws) with linearly degenerate characteristic fields. It has been a conjecture for a long time (see Arch. Rational Mech. Anal. 2004; 172 :65–91; Compressible Fluid Flow and Systems of Conservation Laws in Several Space Variables. Springer: New York, 1984) and it is still an open problem in the general situation up to now. In this paper, a framework to justify this conjecture is proposed, and, by means of the concept such as the strict block hyperbolicity, the part richness and the successively block‐closed system, some general kinds of quasilinear hyperbolic systems, which verify the conjecture, are given. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
10.