全文获取类型
收费全文 | 480篇 |
免费 | 11篇 |
国内免费 | 1篇 |
专业分类
化学 | 323篇 |
晶体学 | 3篇 |
力学 | 13篇 |
数学 | 43篇 |
物理学 | 110篇 |
出版年
2023年 | 5篇 |
2022年 | 6篇 |
2021年 | 16篇 |
2020年 | 6篇 |
2019年 | 3篇 |
2018年 | 10篇 |
2017年 | 4篇 |
2016年 | 6篇 |
2015年 | 7篇 |
2014年 | 14篇 |
2013年 | 24篇 |
2012年 | 26篇 |
2011年 | 25篇 |
2010年 | 17篇 |
2009年 | 10篇 |
2008年 | 28篇 |
2007年 | 24篇 |
2006年 | 20篇 |
2005年 | 27篇 |
2004年 | 21篇 |
2003年 | 10篇 |
2002年 | 18篇 |
2001年 | 7篇 |
2000年 | 3篇 |
1999年 | 14篇 |
1998年 | 5篇 |
1996年 | 6篇 |
1995年 | 8篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 5篇 |
1989年 | 3篇 |
1988年 | 8篇 |
1987年 | 9篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1973年 | 4篇 |
1968年 | 4篇 |
1966年 | 3篇 |
1955年 | 2篇 |
1954年 | 2篇 |
排序方式: 共有492条查询结果,搜索用时 390 毫秒
31.
Electron-rich alkoxy- and chloro-substituted azaspirocyclic cyclohexadienyl Ru(II) complexes have been converted to either azaspiro[4.5]decane derivatives or functionalized tetrahydroisoquinolines by treatment with suitable oxidizing agents. Copper(II) chloride was found to provide demetalated products in high yield relative to the other oxidants examined (FeCl(3), DDQ, CAN, [Cp(2)Fe][PF(6)], phenyliodine diacetate, IBX). In certain instances, the efficiency of oxidative demetalation was enhanced by the inclusion of chloride ion additives in the reaction. Pyridinium dichromate (PDC) was also found to effect the demetalation of a wide range of cyclohexadienyl Ru complexes; however, isolated yields of metal-free products were exceedingly low. The cyclohexadienyl ruthenium complexes used in this study were prepared from (arene)Ru(II) precursors; thus, the isolation of alicyclic cyclohexadienone derivatives upon demetalation constitutes completion of a Ru-mediated dearomatization process. 相似文献
32.
We show that the exact energy eigenvalues and eigenfunctions of the Schrödinger equation for charged particles moving in certain class of non-central potentials can be easily calculated analytically in a simple and elegant manner by using Nikiforov and Uvarov (NU) method. We discuss the generalized Coulomb and harmonic oscillator systems. We study the Hartmann Coulomb and the ring-shaped and compound Coulomb plus Aharanov–Bohm potentials as special cases. The results are in exact agreement with other methods. 相似文献
33.
34.
Neha Sharma Bipin K. Srivastava Anjali Krishnamurthy A.K. Nigam 《Solid State Sciences》2010,12(8):1464-1468
Magnetic behaviour of the perovskite La0.5Gd0.5CrO3 has been studied. The orthochromite orders canted antiferromagnetically below Neel temperature TN of ~225 K. Reversal of magnetization is observed in temperature dependence of magnetization measured in field cooled mode under external fields upto 500 Oe. In the field dependence of magnetization below TN, a small hysteresis is observed with the magnetic anisotropy continuously increasing with lowering of temperature. Estimated values of Cr3+ moments, internal field due to sub-lattice of canted ordered Cr3+ and the paramagnetic Curie temperature of Gd3+ sub-lattice are found to be smaller than reported for GdCrO3. Compared with Pr substituted analogue La0.5Pr0.5CrO3, Cr3+ moment is about the same but the internal field at the Gd3+ sub-lattice is much smaller. 相似文献
35.
We report an extensive first-principles study of the structure and electronic properties of Ag(n) (n = 1-8) clusters isolated in gas phase and deposited on the α-Al(2)O(3) surface. We have used the plane wave based pseudopotential method within the framework of density functional theory. The electron ion interaction has been described using projector augmented wave (PAW), and the spin-polarized GGA scheme was used for the exchange correlation energy. The results reveal that, albeit interacting with support alumina, the Ag atoms prefers to remain bonded together suggesting an island growth motif is preferred over wetting the surface. When compared the equilibrium structures of Ag clusters between free and on alumina substrate, a significant difference was observed starting from n = 7 onward. While Ag(7) forms a three-dimensional (3D) pentagonal bipyramid in the isolated gas phase, on alumina support it forms a planar hexagonal structure parallel to the surface plane. Moreover, the spin moment of the Ag(7) cluster was found to be fully quenched. This has been attributed to higher delocalization of electron density as the size of the cluster increases. Furthermore, a comparison of chemical bonding analysis through electronic density of state (EDOS) shows that the EDOS of the deposited Ag(n) cluster is significantly broader, which has been ascribed to the enhanced spd hybridization. On the basis of the energetics, it is found that the adsorption energy of Ag clusters on the α-Al(2)O(3) surface decreases with cluster size. 相似文献
36.
37.
38.
Using a recently disclosed modification to the dimethyldioxirane method we have synthesized four arene monooxides and one trioxide in good to excellent yield. The X-ray crystal structures have been determined for all of these compounds. In the case of the chrysene trioxide the X-ray determination reveals that the structure is bent out of the plane. 相似文献
39.
40.
Summary Films of cobalt and nickel were electroplated in the presence of an external magnetic-induction field. This resulted in the
deposition of magnetic films which show, in addition to a magnetic anisotropy, also thermo-e.m.f. anisotropy. The latter is
a new effect, not deriving from the anisotropy in electrical conduction deduced earlier by Kornevet al. on the basis of measurements of transmission coefficients of polarized RF field. 相似文献