全文获取类型
收费全文 | 471篇 |
免费 | 14篇 |
国内免费 | 4篇 |
专业分类
化学 | 295篇 |
晶体学 | 3篇 |
力学 | 17篇 |
数学 | 27篇 |
物理学 | 147篇 |
出版年
2023年 | 3篇 |
2022年 | 3篇 |
2021年 | 12篇 |
2020年 | 8篇 |
2019年 | 6篇 |
2018年 | 9篇 |
2017年 | 6篇 |
2016年 | 8篇 |
2015年 | 5篇 |
2014年 | 13篇 |
2013年 | 10篇 |
2012年 | 32篇 |
2011年 | 32篇 |
2010年 | 13篇 |
2009年 | 27篇 |
2008年 | 33篇 |
2007年 | 32篇 |
2006年 | 24篇 |
2005年 | 24篇 |
2004年 | 16篇 |
2003年 | 20篇 |
2002年 | 28篇 |
2001年 | 12篇 |
2000年 | 12篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 9篇 |
1993年 | 10篇 |
1992年 | 9篇 |
1991年 | 5篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1973年 | 4篇 |
1969年 | 2篇 |
1934年 | 2篇 |
1911年 | 2篇 |
1907年 | 2篇 |
1888年 | 2篇 |
排序方式: 共有489条查询结果,搜索用时 15 毫秒
101.
102.
103.
104.
105.
106.
107.
A general, full-dimensional computational method for the accurate calculation of rotationally and vibrationally excited states of tetra-atomic molecules is further developed. The resulting computer program may be run in serial and parallel modes and is particularly appropriate for molecules executing wide-amplitude motions and isomerizations. An application to the isomerizing acetylene/vinylidene system is presented. Large-scale calculations using a coordinate system based on orthogonal satellite vectors have been performed in six dimensions and vibrational term values and wave functions for acetylene and vinylidene states up to approximately 23 000 cm(-1) above the potential minimum have been determined. This has permitted the characterization of acetylene and vinylidene states at and above the isomerization barrier. These calculations employ more extensive vibrational basis sets and hence consider a much higher density of states than in any variational calculations reported hitherto for this system. Comparison of the calculated density of states with that determined empirically suggests that our calculations are the most realistic achieved for this system to date. Indeed more states have been converged than in any previous study of this system. Calculations on lower lying excited states of acetylene based on HC-CH diatom-diatom coordinates give nearly identical results to those based on orthogonal satellite vectors. Comparisons are also made with calculations based on HH-CC diatom-diatom coordinates. 相似文献
108.
Ogier L Turpin F Baldwin RM Riché F Law H Innis RB Tamagnan G 《The Journal of organic chemistry》2002,67(11):3637-3642
Nucleophilic substitution of 2beta-mesyloxymethyl-N-methyl-3beta-p-tolyl-tropane intermediate with alkoxides, metal imides, or amines was found to lead not only to the expected bicyclo[3.2.1]octane (tropane) ether, imide, and amine derivatives but also to unexpected bicyclo[3.2.2]nonane derivatives. When alkoxides were used as nucleophile, only the rearranged bicyclo[3.2.2]nonane structure was obtained, whereas the use of amines or imides as nucleophile afforded a mixture of the two structures. The bicyclo[3.2.2]nonane structure was assigned by NMR analysis. 相似文献
109.
The Lewis acid-catalyzed atom transfer radical cyclization reactions of olefinic -bromo β-keto amides were investigated. It was found Lewis acid Yb(OTf)3 or Mg(ClO4)2 not only promoted the cyclization reactions, but also resulted in excellent trans stereocontrol in the cyclization products. With the catalysis of Lewis acid Yb(OTf)3 or Mg(ClO4)2 at −78°C in the presence of Et3B/O2, the cyclization reactions of C-olefinic β-keto amides provided cyclic ketones, while the cyclization reactions of N-olefinic β-keto amides led to the formation of γ-lactams, which could be converted to 3-aza-bicyclo[3,1,0]hexan-2-ones. 相似文献
110.
Eng‐Chi Wang Keng‐Shiang Huang Hsing‐Ming Chen Chung‐Chin Wu Gwo‐Jiun Lin 《中国化学会会志》2004,51(3):619-627
A new and highly efficient method for the conversion of aldoximes to nitriles was established. By fusing with phthalic anhydride, aldoximes were efficiently and smoothly converted into nitriles, in high yields (over 85%) and in a short time (within 5 minutes). The mixture of phthalic anhydride, a cyclic anhydride, and aldoximes in fusing state set up an ideal transition state for a selective [3.3]‐sigmatropic rearrangement of the acylated aldoximes to nitriles. 相似文献