全文获取类型
收费全文 | 1043篇 |
免费 | 26篇 |
国内免费 | 10篇 |
专业分类
化学 | 750篇 |
晶体学 | 5篇 |
力学 | 24篇 |
数学 | 103篇 |
物理学 | 197篇 |
出版年
2024年 | 4篇 |
2023年 | 6篇 |
2022年 | 29篇 |
2021年 | 42篇 |
2020年 | 19篇 |
2019年 | 23篇 |
2018年 | 33篇 |
2017年 | 25篇 |
2016年 | 30篇 |
2015年 | 26篇 |
2014年 | 34篇 |
2013年 | 83篇 |
2012年 | 54篇 |
2011年 | 54篇 |
2010年 | 51篇 |
2009年 | 50篇 |
2008年 | 54篇 |
2007年 | 64篇 |
2006年 | 48篇 |
2005年 | 48篇 |
2004年 | 60篇 |
2003年 | 33篇 |
2002年 | 41篇 |
2001年 | 11篇 |
2000年 | 9篇 |
1999年 | 14篇 |
1997年 | 10篇 |
1996年 | 13篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 7篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 6篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 10篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1980年 | 8篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 4篇 |
1962年 | 2篇 |
排序方式: 共有1079条查询结果,搜索用时 0 毫秒
991.
Abdel-Shafi Ayman A. Khalil Mostafa M. H. Abdalla Hossam H. Ramadan Ramadan M. 《Transition Metal Chemistry》2002,27(1):69-74
Ru3(CO)12 reacts with 2,3-bis (2-pyridyl)quinoxaline (dpq) in benzene in the presence of either 2,2(dipyridine (dpy) or pyridine (py) to give the mononuclear complexes Ru(CO)3(dpq) (1) and Ru(CO)2(dpq)(py) (2), respectively. On the other hand, reactions of Os3(CO)12 with dpq alone, or in the presence of dipyridine, yield only Os(CO)3(dpq) (3). Spectroscopic studies of the three complexes were consistent with the proposed structures. Reactions of RuCl3 with dpq, under reduced pressure in PhH/EtOH gave bis-[Ru(dpq)2Cl2]Cl (4). Magnetic measurements showed RuIII, d5, to be in a low-spin electronic configuration. Three complexes, Rh2(dpq)2Cl6
(5), [Rh(dpq)2Cl2]Cl (6) and Rh(dpq)(py)Cl3
(7), were isolated from reactions of RhCl3 with dpq. The type of product was dependent on the reactants and conditions. The complexes exhibit either irreversible or quasi-reversible ligand-based reductions. In addition, the zerovalent complexes (1)–(3) displayed one metal(based oxidation in their cyclic voltammograms, due to the formation of M+ species. 相似文献
992.
The kinetic current-convective instability excited in a hot electron plasma, i.e. for Te ? Ti, is investigated in the linear stage. Density and temperature of plasma components have gradients along the x-direction. In the absence of longitudinal current (u = 0) and homogeneous temperature the instability is also excited with maximum growth rate much exceeding that obtained in the case of u ≠ 0. Gradual increasing of the ion temperature over that of the electrons and a large density gradient leads to reduce the instability in the linear stage. 相似文献
993.
The development of Buneman kinetic instability in plasma with hot electrons and cold ions is investigated in the quasilinear approximation at current velocites close to the instability threshold values. It is shown that the contribution of electron's dielectric permeability in the dispersion equation is negligible and that quasilinear theory has in general stabilizing effect. 相似文献
994.
We present a possible supersymmetric solution to the discrepancy between the observed mixing CP asymmetries in B-->phiK(S) and B-->eta(')K(S). We show that, due to the different parity in the final states of these processes, their supersymmetric contributions from the R sector have opposite signs, which naturally leads to S(phiK(S)) not equal Seta(')(K(S)). We also consider the proposed mechanisms to solve the puzzle of the observed large branching ratio of B-->eta'K and their impact on Seta(')(K(S)). 相似文献
995.
The mode of formation of keto-hexahydro-s-triazines has been studied by conducting the reaction in two stages. The experiments revealed that the condensation with aromatic aldehydes is more complex, and the mechanism is not clear, although in the case of aliphatic aldehydes the step-wise formation of hexahydro-s-triazines has been reported. 相似文献
996.
Gulmamed Z. Suleimanov Yuri S. Bogatchev Leila T. Abdullaeva Irina L. Zhuravleva Khalil S. Khalilov Lyudmila F. Rybakova Irina P. Beletskaya 《Polyhedron》1985,4(1):29-31
It has been established that the reaction of metallocyclopentadienyl mercurials with an excess of elemental lanthanides Ln(Ln = Sm, Eu, Yb) in tetrahydrofuran yields substituted cyclopentadienyl derivatives of the metals. 相似文献
997.
Two-dimensional infrared photon echo spectroscopy has been used to describe the anharmonic nuclear potential of two coupled molecular vibrations. The two-dimensional spectrum shows diagonal and off-diagonal features, each composed of two peaks. The splitting between these peaks is directly related to the anharmonicity, while the relative amplitude of the diagonal and off-diagonal features describes the projection angle between interacting dipoles. 相似文献
998.
999.
1000.
Khalil F. Matta 《随机分析与应用》2013,31(4):417-430
A single-item inventory model with probabilistic demand is considered in this paper. The replenishment of items is cyclical and occurs every n-periods. The order for replenishment can be p laced at the end of any period during the cycle . The uni ts ordered fluctuate based on actual and expected demand during the cycle. The general expression of this inventory system is formulated by developing the stationary distribution of the inventory position, units ordered and the probability of placing an order during any period. The expression is stated in terms of the reorder point (s) and the order level (S). 相似文献