全文获取类型
收费全文 | 199篇 |
免费 | 9篇 |
国内免费 | 54篇 |
专业分类
化学 | 257篇 |
晶体学 | 3篇 |
物理学 | 2篇 |
出版年
2023年 | 6篇 |
2022年 | 6篇 |
2021年 | 11篇 |
2020年 | 14篇 |
2019年 | 9篇 |
2018年 | 9篇 |
2017年 | 8篇 |
2016年 | 15篇 |
2015年 | 7篇 |
2014年 | 7篇 |
2013年 | 36篇 |
2012年 | 8篇 |
2011年 | 8篇 |
2010年 | 12篇 |
2009年 | 5篇 |
2008年 | 13篇 |
2007年 | 14篇 |
2006年 | 16篇 |
2005年 | 7篇 |
2004年 | 11篇 |
2003年 | 10篇 |
2002年 | 6篇 |
2001年 | 5篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 2篇 |
排序方式: 共有262条查询结果,搜索用时 15 毫秒
1.
Xin‐Gui Li Run‐Feng Chen Mei‐Rong Huang Mei‐Fang Zhu Qun Chen 《Journal of polymer science. Part A, Polymer chemistry》2004,42(9):2073-2092
A new series of copolymers was synthesized through the oxidative polymerization of pyrrole (PY) and o‐phenetidine (PHT) with inorganic oxidants in acidic media. The polymerization parameters including the mixing method of the oxidant with the comonomer, the comonomer ratio, the time, the temperature, the oxidant, the organic medium, and the acid were systematically optimized for the synthesis of copolymers with high yields, intrinsic viscosities, and solubility. The resultant copolymers were characterized by elemental analysis, infrared, ultraviolet–visible, solution high‐resolution 1H NMR and solid‐state high‐resolution 13C NMR, circular dichroism spectroscopy, and cyclic voltammetry. The results showed that the PY observed content in the copolymers was much higher than the PY feed content. The regular variation of the polymerization yield, intrinsic viscosity, solubility, macromolecular structure, and electroactivity of the resulting polymers with the comonomer ratio, together with the complete solubility of a PY/PHT (10/90) polymer in highly polar solvents, indicated the formation of real random copolymers containing both PY and PHT units rather than a mixture of two homopolymers. However, the polymers containing more than 59 mol % PY were not homogeneous copolymers consisting of soluble and insoluble parts. A semiquantitative relationship between the polymerization yield or solubility of the copolymers and the polarity index of the organic solvents was examined. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2073–2092, 2004 相似文献
2.
1-苯基-3-甲基-4-(6-氢-4-甲基氨基-5-硫杂-2,3-吡嗪)-吡唑啉酮的合成与晶体结构 总被引:1,自引:0,他引:1
通过1-苯基-3-甲基-4-氯乙酰基-吡唑啉酮-5 (PMCP) 和4-甲基氨基硫脲 (MTSC) 缩合, 形成了一种新的双杂环化合物 (PMCP-MTSC)。利用元素分析与单晶X-射线衍射进行了表征。 该化合物(C14H15N5OS)属单斜晶系, P21 空间群, 晶体学参数为 a = 7.634(1), b = 11.639(2), c = 8.150(2) ? ?= 98.13(1), V = 716.9(2) ?, Z = 2, Dc = 1.396 g/cm3, (MoKa) = 0.232 mm-1, F(000) = 316, Mr = 301.37。结构由直接法解出,共收集3114个衍射点,其中I > 2(I)的独立衍射点有2453个,用全矩阵最小二乘法修正,最终偏离因子:R = 0.0294, wR = 0.0738。结构分析表明: 该化合物以酮式存在,分子间通过氢键作用(N(5)H…O)连接起来并形成一维链状结构。 相似文献
3.
Timothy S. Keizer Lauren J. De Pue Sean Parkin David A. Atwood 《Journal of Cluster Science》2002,13(4):609-620
Various Salen ligands (Salen(
t
Bu)H2=N, N-ethylenebis(3,5-di-tertbutyl(2-hydroxy)benzylidenimine) were used to prepare borosilyl and -O bridged borosilyl compounds having the formula, L{B(OSiMe3)2}2 (L=Salen(
t
Bu) (1), Salpen(
t
Bu) (2), Salben(
t
Bu) (3), Salhen(
t
Bu) (4) and L(BOSiMe3)2(-O) (L=Salen(
t
Bu) (5) and Salben(
t
Bu) (6)). In the case of 5 and 6 the formation of the B–O–B linkage takes precedence over the formation of a B–O–Si linkage. All of the compounds were characterized by Mp, elemental analysis, 1H and 11B NMR, IR, MS and in the case of 1, 2, and6 by X-ray crystallography. 相似文献
4.
I. Goba B. Turovska J. Stradins I. Turovskis E. Liepinsh S. Belyakov 《Chemistry of Heterocyclic Compounds》2007,43(2):175-186
It has been shown that chemical oxidation of the methyl ester of 3,4,5-trimethoxycarbonyl-1,2,6-trimethyl-1,4-dihydropyridine
to the pyridinium salt, requiring forcing experimental conditions, may be replaced by electrochemical oxidation. On electrochemical
reduction of 3,4,5-trimethoxycarbonyl-1,2,6-trimethylpyridinium perchlorate in the presence of alkylating agents 1,2,3,4,4,5,6-substituted
1,4-dihydropyridines are obtained.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 226–237, February, 2007. 相似文献
5.
6.
常规加热或微波照射下, 含氮杂环1与多聚甲醛反应以良好的产率生成含氮杂环基甲醇3, 反应物物质的量的比、反应温度等对反应产率有影响, 微波条件下的反应时间比常规加热下大大缩短. 化合物3和异氰酸酯4在常规加热或微波照射下生成相应的氨基甲酸含氮杂环甲基酯5a~5m. 反应温度、反应物物质的量的比、反应时间、微波辐射功率等对反应产率都有一定的影响, 与常规加热相比微波条件下的反应时间大大缩短. 化合物5的结构经过IR, 1H NMR, MS, 元素分析测定, 部分化合物经过13C NMR测定. 测定了化合物5的杀虫和除草活性, 结果表明其杀虫活性较低, 除草活性高于杀虫活性, 5a, 5d, 5e和5m对苋菜和黄瓜的防除率高达100%. 相似文献
7.
A new method for the synthesis of eight-membered heterocyclic 1,4,5-oxadiazocines has been described from β-diketone and β,β,β-triketone with an acidic α-hydrogen. The method entails the reaction of a di- or triketone with 2-hydroxyethylhydrazine and an aldehyde in the presence of acetic acid providing respectable yield. 相似文献
8.
M. S. Shvartsberg I. D. Ivanchikova S. F. Vasilevsky 《Russian Chemical Bulletin》1998,47(10):1971-1974
I-Acetylenyl-9,10-anthraquinones react with an excess of NH2NH2 at 80–115°C to give a mixture of substituted 7H-dibenzo[de,h]quinolin-7-ones and anthra[9,1-cd]-1,2-diazepin-8-ones. The latter compounds undergo reductive contraction of the sevenmembered ring to give the corresponding
7H-dibenzo[de,h]quinolin-7-ones. Bulky substituents in position 2 of the initial acetylenylanthraquinones prevent the formation of the sevenmembered
heterocycle. A scheme of the cyclocondensation was proposed.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2027–2030, October, 1998. 相似文献
9.
Hiroto Yoshida 《Tetrahedron》2007,63(22):4793-4805
A variety of aldehydes, ketones, benzoquinones, or sulfonylimines were found to couple with arynes and isocyanides, giving iminodihydroisobenzofuran or iminoisoindoline derivatives of structural diversity in a straightforward manner. Nucleophilic addition of isocyanides to arynes, a first step of the three-component coupling, was proved to be reversible by the reaction of an unsymmetrical aryne. 相似文献
10.