全文获取类型
收费全文 | 543篇 |
免费 | 17篇 |
国内免费 | 1篇 |
专业分类
化学 | 358篇 |
晶体学 | 8篇 |
力学 | 25篇 |
数学 | 57篇 |
物理学 | 113篇 |
出版年
2024年 | 2篇 |
2023年 | 6篇 |
2022年 | 15篇 |
2021年 | 16篇 |
2020年 | 23篇 |
2019年 | 19篇 |
2018年 | 16篇 |
2017年 | 24篇 |
2016年 | 31篇 |
2015年 | 15篇 |
2014年 | 27篇 |
2013年 | 48篇 |
2012年 | 40篇 |
2011年 | 53篇 |
2010年 | 17篇 |
2009年 | 20篇 |
2008年 | 28篇 |
2007年 | 26篇 |
2006年 | 31篇 |
2005年 | 21篇 |
2004年 | 24篇 |
2003年 | 13篇 |
2002年 | 9篇 |
2001年 | 2篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1981年 | 3篇 |
排序方式: 共有561条查询结果,搜索用时 46 毫秒
131.
Recent progress in asymmetric organocatalysis has led to the development of several asymmetric transformations that employ various substrates. Among these substrates, maleimides have emerged as excellent Michael acceptors, dienophiles, and dipolarophiles. In this Focus Review we highlight the advances in the asymmetric synthesis of succinimide derivatives through asymmetric organocatalytic addition reactions of maleimides. 相似文献
132.
133.
A new air‐stable Pd(II) complex containing a sulfonamide–Schiff base ligand has been synthesized, characterized and investigated as a catalyst for the Suzuki–Miyaura reactions of aryl halides with arylboronic acids. Theoretical calculations (B3LYP) and spectroscopic evidence suggest that the sulfonamide–Schiff base coordinates to the Pd centre through sulfonamide nitrogen (? SO2NH2) rather than imine (? CH?N). The complex shows excellent cross‐coupling activity with aryl bromides in water at room temperature and aryl chlorides in isopropanol at 60°C. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
134.
135.
Nonlinear Dynamics - Dynamics of discontinuous nonlinear systems subjected to random excitation is studied. Such systems occur in many mechanical and aerospace applications involving impact,... 相似文献
136.
137.
138.
The reaction of [Fe3(CO)12] with bis[2‐(diphenylphosphino)phenyl]ether (DPEphos) in refluxing THF afforded a mononuclear complex, [Fe(CO)4(η1‐P‐DPEphos)] (1), as major product and a binuclear complex, [Fe2(CO)6(μ‐CO)(μ‐P,P‐DPEphos)] (2), as minor product respectively. The DPEphos ligand acts as a terminal P‐donor in complex 1 and a bridging P,P‐donor in complex 2. Complexes 1 and 2 were characterized by elemental analysis, fast atom bombardment mass spectrometry, FT‐IR, 1H and 31P{1H} NMR spectroscopy. The structure of complex 1 has been tentatively assigned by density functional theory calculations and its analogy with reported complexes. Combination of complex 1 and PdCl2 furnished an active catalyst for the Suzuki–Miyaura cross‐coupling reactions of various aryl halides with arylboronic acids. Interestingly, under the same experimental condition, complex 1/PdCl2 as catalyst showed superior activity over the DPEphos/PdCl2 system. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
139.
We have investigated the stability and electronic properties of Co-doped zigzag graphene nanoribbons (ZGNR) by employing first principles calculations based on density functional theory. The results show that Co impurities settled in antiferromagnetic ground state which is ~2 meV favourable than ferromagnetic state. The formation energy indicates spontaneous formation of one-edge and centre doped structures, however, one-edge doping is found to be the most energetically favourable configuration. A charge transfer takes place from C to Co atoms which shows the formation of chemical bonding between C and Co. Binding energy also confirms the strong bonding of dopant Co impurity with C. The calculations show that band structures of all the ZGNR is substantially modified due to CoC charge transfer and the characteristic edge states of ZGNR are completely lost. Co-doping induces site independent enhanced metallicity irrespective of the ribbon widths. The broken degeneracy of electronic states in one-edge and centre doped ZGNR is important for spintronic applications. 相似文献
140.
Nonlinear Dynamics - We obtain analytical approximations for period-1 rotations of both vertically and horizontally excited pendulum using Galerkin projections with elliptic functions (GP),... 相似文献