全文获取类型
收费全文 | 491篇 |
免费 | 10篇 |
国内免费 | 2篇 |
专业分类
化学 | 219篇 |
力学 | 29篇 |
数学 | 193篇 |
物理学 | 62篇 |
出版年
2022年 | 7篇 |
2021年 | 9篇 |
2020年 | 4篇 |
2019年 | 10篇 |
2018年 | 3篇 |
2017年 | 6篇 |
2016年 | 10篇 |
2015年 | 15篇 |
2014年 | 10篇 |
2013年 | 19篇 |
2012年 | 21篇 |
2011年 | 24篇 |
2010年 | 20篇 |
2009年 | 15篇 |
2008年 | 20篇 |
2007年 | 23篇 |
2006年 | 16篇 |
2005年 | 26篇 |
2004年 | 16篇 |
2003年 | 18篇 |
2002年 | 9篇 |
2001年 | 11篇 |
2000年 | 5篇 |
1999年 | 7篇 |
1998年 | 11篇 |
1997年 | 8篇 |
1996年 | 8篇 |
1995年 | 6篇 |
1993年 | 9篇 |
1992年 | 10篇 |
1991年 | 12篇 |
1990年 | 5篇 |
1989年 | 14篇 |
1988年 | 6篇 |
1987年 | 8篇 |
1986年 | 3篇 |
1985年 | 10篇 |
1984年 | 9篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 8篇 |
1980年 | 8篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1975年 | 2篇 |
1971年 | 2篇 |
1965年 | 2篇 |
1959年 | 2篇 |
1958年 | 2篇 |
排序方式: 共有503条查询结果,搜索用时 593 毫秒
31.
Edoardo Magnone Myung Jae Seo Hak Joo Kim Jung Hoon Park 《Journal of Thermal Analysis and Calorimetry》2014,116(1):215-218
The chemical compatibility of perovskite-type Ba0.5Sr0.5Co0.8Fe0.2O3?δ (BSCF) oxides with Cr2O3 has been examined between room temperature and 1,100 °C. Differential thermal analysis and thermogravimetric analysis were used to analyze the thermal behavior of BSCF–Cr2O3 binary mixtures in all composition ranges (0–100 mass% BSCF). The reaction products were identified by X-ray analysis after heating at 700–1,100 °C. As we expected, it was found that perovskite-type BSCF oxide had a poor chemical compatibility with the Cr2O3 oxide. In particular, the decomposition process of the BSCF–Cr2O3 binary mixture is quite complex and it starts at about 700–750 °C. The mixtures of BSCF and Cr2O3 oxides reacted forming mixed complex oxides based on (Ba/Sr)FeO3, (Co/Fe)CrO4, and (Ba/Sr)CrO4 mixtures. 相似文献
32.
H. E. Stanley P. Kumar G. Franzese L. Xu Z. Yan M. G. Mazza S. V. Buldyrev S.-H. Chen F. Mallamace 《The European physical journal. Special topics》2008,161(1):1-17
We present evidence from experiments and computer
simulations supporting the hypothesis that water displays
polyamorphism, i.e., water separates into two distinct liquid
phases. This concept of a new liquid-liquid phase transition is
finding application to other liquids as well as water, such as
silicon and silica. Specifically, we investigate, the relation
between changes in dynamic and thermodynamic anomalies arising from
the presence of the liquid-liquid critical point in (i) Two models
of water, TIP5P and ST2, which display a first order liquid-liquid
phase transition at low temperatures; (ii) the Jagla model, a
spherically symmetric two-scale potential known to possess a
liquid-liquid critical point, in which the competition between two
liquid structures is generated by repulsive and attractive ramp
interactions; and (iii) A Hamiltonian model of water where the idea
of two length/energy scales is built in. This model also displays a
first order liquid-liquid phase transition at low temperatures
besides the first order liquid-gas phase transition at high
temperatures. We find a correlation between the dynamic fragility
crossover and the locus of specific heat maxima CPmax
(“Widom line”) emanating from the critical point. Our findings are
consistent with a possible relation between the previously
hypothesised liquid-liquid phase transition and the transition in
the dynamics recently observed in neutron scattering experiments on
confined water. More generally, we argue that this connection
between CPmax and the dynamic crossover is not limited to
the case of water, a hydrogen bonded network liquid, but is a more
general feature of crossing the Widom line, an extension of the
first-order coexistence line in the supercritical region.
Dedicated to Armin Bunde on the occasion of his 60th birthday. 相似文献
33.
Christian Mazza 《Probability Theory and Related Fields》1999,113(2):171-190
We consider the ±J spin glass on a finite graph G=(V,E), with i.i.d. couplings. Our approach considers the Z
2 local gauge invariance of the system. We see the gauge group as a graph theoretic linear code ? over GF(2). The gauge is fixed by choosing a convenient linear supplement of ?. Assuming some relation between the disorder parameter
p and the inverse temperature of the thermal bath β
pb
, we study percolation in the random interaction random cluster model, and extend the results to dilute spin glasses.
Received: 5 May 1997 / Revised version: 9 April 1998 相似文献
34.
Edoardo Benvenuto 《Meccanica》1985,20(2):99-109
Summary A brief historical outline and some epistemological suggestions are presented on the scientific debate about the parallelogram
of forces.
Sommario Si espone brevemente lo sviluppo storico del dibattito sulla regola del parallelogrammo delle forze e sui diversi tentativi di una sua dimostrazione razionale, alla luce di alcune considerazioni epistemologiche.相似文献
35.
Dario Del Mazza Manfred G. Reinecke William B. Smith 《Magnetic resonance in chemistry : MRC》1980,14(6):540-542
Diphenyliodonium-2-carboxylate, phenyl 4-methylphenyliodonium-2-carboxylate and phenyl 5-methyl-phenyliodonium-2-carboxylate have been examined by 1H and 13C NMR spectroscopy. Each compound showed one proton considerably upfield from the others. From the two substituted compounds this was deduced to be H-6 on the ring containing the carboxylate group. Shift reagents and relaxation measurements were used to make the 13C chemical shift assignments. These data are most consistent with a cyclic, neutral structure for these iodonium carboxylates. The iodine is in the center of a trigonal bipyramid with the unsubstituted phenyl and carboxylate group apical, which places the C-6 proton in the shielding region of the adjacent phenyl group. 相似文献
36.
37.
38.
Edoardo Ballico Claudio Fontanari Cristiano Bocci Enrico Carlini 《Rendiconti del Circolo Matematico di Palermo》2004,53(3):429-436
We generalize the classical Terracini’s Lemma to higher order osculating spaces to secant varieties. As an application, we
address with the so-called Horace method the case of thed-Veronese embedding of the projective 3-space.
This research is part of the T.A.S.C.A. project of I.N.d.A.M., supported by P.A.T. (Trento) and M.I.U.R. (Italy). 相似文献
39.
Edoardo Ballico Changho Keem Seungsuk Park 《Proceedings of the American Mathematical Society》2004,132(11):3153-3158
Let be a smooth projective algebraic curve of genus and an integer with . For all integers we prove the existence of a double covering with a smooth curve of genus and the existence of a degree morphism that does not factor through . By the Castelnuovo-Severi inequality, the result is sharp (except perhaps the bound ).
40.