全文获取类型
收费全文 | 721篇 |
免费 | 11篇 |
国内免费 | 1篇 |
专业分类
化学 | 395篇 |
晶体学 | 3篇 |
力学 | 48篇 |
数学 | 156篇 |
物理学 | 131篇 |
出版年
2023年 | 3篇 |
2022年 | 27篇 |
2021年 | 30篇 |
2020年 | 8篇 |
2019年 | 19篇 |
2018年 | 12篇 |
2017年 | 6篇 |
2016年 | 37篇 |
2015年 | 21篇 |
2014年 | 26篇 |
2013年 | 46篇 |
2012年 | 36篇 |
2011年 | 38篇 |
2010年 | 27篇 |
2009年 | 17篇 |
2008年 | 25篇 |
2007年 | 39篇 |
2006年 | 35篇 |
2005年 | 39篇 |
2004年 | 32篇 |
2003年 | 16篇 |
2002年 | 18篇 |
2001年 | 13篇 |
2000年 | 6篇 |
1999年 | 11篇 |
1998年 | 3篇 |
1997年 | 8篇 |
1996年 | 9篇 |
1995年 | 4篇 |
1994年 | 10篇 |
1993年 | 5篇 |
1992年 | 9篇 |
1991年 | 5篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 7篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 6篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1980年 | 7篇 |
1977年 | 6篇 |
1975年 | 3篇 |
1968年 | 2篇 |
1928年 | 2篇 |
1915年 | 2篇 |
1905年 | 2篇 |
排序方式: 共有733条查询结果,搜索用时 9 毫秒
61.
62.
Ryuichi Ashino Carlos A. Berenstein Akira Morimoto Mitsuo Morimoto Domenico Napoletani 《Applicable analysis》2013,92(5):577-609
The blind source separation problem is discussed in this article. Focusing on the assumption of independency of the sources in the time-frequency domain, we present a mathematical formulation for the estimation problem of the number of sources. The proposed method uses the quotient of complex valued time-frequency information of only two observed signals to detect the number of sources. No fewer number of observed signals than the detected number of sources is needed to separate sources. The assumption on sources is quite general independence in the time-frequency plane, which is different from that of independent component analysis. We propose algorithms with feedback and give numerical simulations to show the method works well even for noisy case. 相似文献
63.
We analyze the spectral behavior of higher-order elliptic operators when the domain is perturbed. We provide general spectral stability results for Dirichlet and Neumann boundary conditions. Moreover, we study the bi-harmonic operator with the so-called intermediate boundary conditions. We give special attention to this last case and analyze its behavior when the boundary of the domain has some oscillatory behavior. We will show that there is a critical oscillatory behavior and that the limit problem depends on whether we are above, below or just sitting on this critical value. 相似文献
64.
We generalize the classical definition of hypergroups of type U on the right to semihypergroups, and we prove some properties of their subsemihypergroups and subhypergroups. In particular, we obtain that a finite proper semihypergroup of type U on the right can exist only if its order is at least 6. We prove that one such semihypergroup of order 6 actually exists. Moreover, we show that there exists a hypergroup of type U on the right of cardinality 9 containing a proper non-trivial subsemihypergroup. In this way, we solve a problem left open in [D. Freni, Sur les hypergroupes de type U et sous-hypergroupes engendrés par un sous-ensemble, Riv. Mat. Univ. Parma 13 (1987) 29-41]. 相似文献
65.
The Gauge/Bethe correspondence of Nekrasov and Shatashvili relates the spectrum of integrable spin chains to the ground states of supersymmetric gauge theories. Up to now, this correspondence has been an observation; the underlying reason for its existence remaining elusive. We argue here that geometrical representation theory is a mathematical foundation of the Gauge/Bethe correspondence, and it provides a framework to study families of gauge theories in a unified way. 相似文献
66.
67.
Francesco Mallamace Carmelo Corsaro Enza Fazio Sow-Hsin Chen Domenico Mallamace 《中国科学:物理学 力学 天文学(英文版)》2019,(10)
We study the hydrogen bonds effect on the water density as a function of temperature and pressure from the supercritical region to the metastable supercooled and amorphous phases. We identify two important thermodynamic thresholds, that is P~*2■kbar and T~*■315 K, that separate two different water behaviors in terms of hydrogen bonding capability. For T T~* and P P~* the formation and stability of hydrogen bonded local structures are enhanced. The additional analyses of the proton NMR chemical shift and of the relaxation time confirm this evidence and highlight the structure breaking effects of the pressure. The investigation of both structural and dynamical quantities allow us to draw a complete picture of the water properties in terms of the temperaturepressure dependence of hydrogen bonding. 相似文献
68.
Domenico Catalano Filip Defever Ryszard Deszcz Marian Hotloś Zbigniew Olszak 《Abhandlungen aus dem Mathematischen Seminar der Universit?t Hamburg》1999,69(1):59-65
For anyn ≥ 2, we give examples of almost Kähler conformally flat manifoldsM 2n which are not Kähler. We discuss the meaning of these examples in the context of the Goldberg conjecture on almost Kahler manifolds. 相似文献
69.
Domenico Spinelli Anlonino Corrao Vincenzo Frenna Nicol
Vivona Michele Ruccia Giuseppe Cusmano 《Journal of heterocyclic chemistry》1976,13(2):357-360
The rates of the mononuclear heterocyclic rearrangement of the phenylhydrazone of 3-benzoyl-5-phenyl-1,2,4-oxadiazole (1) into 2,5-diphenyl-4-benzoylamino-1,2,3-triazole (II) have heen measured in dioxane/water (50:50, v:v) in the range of pS+ 3.8–12.2 at various temperatures and the activation parameters determined. On the basis of the results obtained, we present evidence for the occurrence of two different types of reaction: the first, base-catalyzed; the second, pS+ -independent. In the base-catalyzed range the catalysis is of the general type. 相似文献
70.
Condensation of ruthenium vapour with a mixture of pentane and buta-1,3-diene vapours at ?196°C, followed by warming to ?40°C, yields an unstable brown solution which reacts above ?40°C with PF3, CO or (CH3)3 CNC to give the corresponding complex [RuL(η4-C4H6)2] in > 40% yield. The ease of isolation and purification of these air sensitive complexes decreases in the order PF3 > (CH3)3CNC > CO. 相似文献