全文获取类型
收费全文 | 250篇 |
免费 | 17篇 |
国内免费 | 56篇 |
专业分类
化学 | 292篇 |
晶体学 | 20篇 |
物理学 | 11篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 13篇 |
2021年 | 13篇 |
2020年 | 17篇 |
2019年 | 7篇 |
2018年 | 4篇 |
2017年 | 5篇 |
2016年 | 9篇 |
2015年 | 9篇 |
2014年 | 12篇 |
2013年 | 25篇 |
2012年 | 26篇 |
2011年 | 11篇 |
2010年 | 8篇 |
2009年 | 7篇 |
2008年 | 13篇 |
2007年 | 12篇 |
2006年 | 12篇 |
2005年 | 8篇 |
2004年 | 15篇 |
2003年 | 17篇 |
2002年 | 12篇 |
2001年 | 12篇 |
2000年 | 6篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 8篇 |
1996年 | 6篇 |
1995年 | 6篇 |
1994年 | 3篇 |
1993年 | 7篇 |
1992年 | 1篇 |
1991年 | 4篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1982年 | 2篇 |
1979年 | 1篇 |
排序方式: 共有323条查询结果,搜索用时 905 毫秒
11.
本文以2.6─二乙酰吡啶和1,3一二氨基一2一丙醇通过模板合成西佛碱大环配体H_2L(图1),并合成了它的Co(Ⅱ)、Ni(Ⅱ)及Fe(Ⅱ)的双核配合物,重点讨论了Co_2(HL)(ClO_4)_2(NO_3)·4H_2O配合物的光谱与磁性。变温磁化率数据(4─300K)通过用最小二乘法与理论方程拟合,得到磁参数为J=-1.24cm ̄(-1),θ=-0.24K,表明配合物中co(Ⅱ)-Co(Ⅱ)间存在弱的反铁磁相互作用,分子间也存在反铁磁相互作用。 相似文献
12.
Hideko Koshima Teruo Matsuura 《Journal of photochemistry and photobiology. A, Chemistry》1996,100(1-3):85-91
This paper deals with the solid state bimolecular photoreactions occurring at the interface between crystallites of two different organic compounds prepared as a polycrystalline mixture by melting-resolidification. The photoreactions include the photoaddition of NH compounds to aromatic and olefinic double bonds, hydrogen abstraction, condensation reaction via photoelectron transfer and [2+2] photoaddition. Particular attention is focused on the characterization of the polycrystalline mixture, the selectivity of the photoreactions in the solid state compared with those in the solution phase and the factors controlling the photoreactions. 相似文献
13.
万古霉素和替考拉宁都属于糖肽类的大环抗生素,具有立体的环状结构和多个手性中心,是两种常见的手性识别材料,广泛应用于对映体的色谱手性分离分析。该文以万古霉素和替考拉宁为手性选择剂,哌嗪为单体,4,4'-二苯基甲烷二异氰酸酯(MDI)、1,6-己二异氰酸酯(HDI)和2,4-甲苯二异氰酸酯(TDI)为交联剂,通过界面聚合反应形成网状层包裹硅胶载体的方法制得6种高效液相色谱手性固定相,用于分离外消旋化合物,并与MDI直接交联万古霉素和替考拉宁在硅胶表面所得固定相进行了比较。结果表明,利用"网包法"和直接交联法制备的手性柱与商品万古霉素和替考拉宁柱之间具有互补性,均对不同的外消旋体有不同程度的拆分。 相似文献
14.
Yasar Gok 《无机化学与普通化学杂志》1995,621(7):1243-1246
The new dinuclear, octahedral cobalt(III) complexes have been synthesized and then their ability to interact with 4,4′-trimethylene dipyridine investigated. The 1H and 13C-NMR, IR and elemental analysis data indicated that the cobalt(III) complexes are dinuclear. 相似文献
15.
Silvia Stumpf Gudrun Goretzki Kerstin Gloe Karsten Gloe Wilhelm Seichte Edwin Weber Jan W. Bats 《Journal of inclusion phenomena and macrocyclic chemistry》2003,45(3-4):225-233
The di- and tetra-allyl ethers of tert-butylcalix[4]arene 1 and 2 have been prepared by alkylation of tert-butylcalix[4]arene with allyl bromide and K2CO3 using different reaction times. Solution 1H NMR measurement of the di-allyl ether 1 and X-ray crystal structures of the complexes of 1 with chloroform (1a) or methanol (1b) indicate the cone conformation of 1 in which intramolecular hydrogen bonding can be maximized. The crystalline state conformers 1a and 1b are distorted in different grades depending on the solvent. While methanol is incorporated in the macrocycle, chloroform molecules do not occupy the cage. The solution 1H NMR spectra of tetra-allyl ether 2 show the co-existence of the cone and partial cone conformation. The partial cone conformer of 2 was investigated by X-ray crystallography. In this compound hydrogen bonding is not existent. The conformer distribution is likely affected by steric and template effects. 相似文献
16.
17.
18.
环状芴基张力半导体由于其特殊的分子结构,发射状排布的p轨道和纳米级空腔等诸多特点,引起了科学家广泛的关注.相对于直链型芴基半导体,环状芴基张力半导体展现出独特的光电性质.然而,迄今为止其振动性质没有被报道.对四元环芴的晶体与直链四聚芴粉末样品进行拉曼光谱表征和归一化处理,并结合理论计算.结果表明,与直链寡聚芴相比,环芴类似于碳纳米管的G峰发生了偏移,并且低频区域拉曼频移峰的峰强增加.其原因是由于张力的引入,改变了芴基主链的骨架和电子结构,加强芴骨架上π电子离域,同时使环芴中每个芴单元都参与到振动中.该研究结果为芴基张力半导体材料拉曼光谱的研究提供了一定的工作基础. 相似文献
19.
Ludovic Jullien Jean-Marie Lehn 《Journal of inclusion phenomena and macrocyclic chemistry》1992,12(1-4):55-74
An approach to a transmembrane cation channel is described. It is based on the grafting of oxygen bearing side-chains on a macrocyclic polyether unit that constitutes the organizing core. The resulting species has a structure of overall bouquet shape. The synthesis of such a molecule .
M
0
,14a is described, together with that of its analogue bearing polymethylene side-chains
M
C
,14b. The physicochemical properties of these molecules indicate that they possess the features expected on the basis of their structure.This paper is dedicated to the memory of the late Dr C. J. Pedersen. 相似文献
20.
Sergey?P.?BabailovEmail author Lubov?D.?Nikulina 《Journal of inclusion phenomena and macrocyclic chemistry》2005,51(1-2):103-109
1H and 13C NMR measurements are reported for the CDCl3 and CD2Cl2 solutions of [La(NO3)3(18-crown-6)] (I), [Pr(NO3)3(18-crown-6)] (II) and [Ce(NO3)3(18-crown-6)] (III) complexes. Temperature dependencies of the 1H NMR spectra of II have been analyzed using the dynamic NMR methods for multi-site exchange. Two types of conformational dynamic processes in II were identified (the first one with activation enthalpy ΔH
‡=26 ± 4 kJ/mol is conditioned by interconversion of complex enantiomeric form and pseudorotation of macrocycle molecule upon the C
2 symmetry axis, the second one with ΔH
‡=46 ± 5 kJ/mol is conditioned by macrocycle molecule inversion). Studies of the values of the lanthanide-induced shifts revealed that the structure of complexes in solution is similar to that reported for the complex I in the crystal state.This revised version was published online in July 2005 with a corrected issue number. 相似文献