全文获取类型
收费全文 | 404篇 |
免费 | 12篇 |
国内免费 | 73篇 |
专业分类
化学 | 458篇 |
晶体学 | 8篇 |
综合类 | 5篇 |
物理学 | 18篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 19篇 |
2021年 | 13篇 |
2020年 | 18篇 |
2019年 | 16篇 |
2018年 | 14篇 |
2017年 | 10篇 |
2016年 | 20篇 |
2015年 | 11篇 |
2014年 | 14篇 |
2013年 | 62篇 |
2012年 | 21篇 |
2011年 | 21篇 |
2010年 | 17篇 |
2009年 | 20篇 |
2008年 | 16篇 |
2007年 | 20篇 |
2006年 | 12篇 |
2005年 | 15篇 |
2004年 | 18篇 |
2003年 | 13篇 |
2002年 | 60篇 |
2001年 | 9篇 |
2000年 | 7篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 7篇 |
1996年 | 3篇 |
1995年 | 7篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1981年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有489条查询结果,搜索用时 15 毫秒
231.
Rubina Munir Noman Javid Muhammad Zia-ur-Rehman Muhammad Zaheer Rahila Huma Ayesha Roohi Muhammad Makshoof Athar 《Molecules (Basel, Switzerland)》2021,26(16)
In this article, a synthesis of N’-(benzylidene)-2-(6-methyl-1H-pyrazolo[3,4-b]quinolin-1-yl)acetohydrazides and their structural interpretation by NMR experiments is described in an attempt to explain the duplication of some peaks in their 1H- and 13C-NMR spectra. Twenty new 6-methyl-1H-pyrazolo[3,4-b]quinoline substituted N-acylhydrazones 6(a–t) were synthesized from 2-chloro-6-methylquinoline-3-carbaldehyde (1) in four steps. 2-Chloro-6-methylquinoline-3-carbaldehyde (1) afforded 6-methyl-1H-pyrazolo[3,4-b]quinoline (2), which upon N-alkylation yielded 2-(6-methyl-1H-pyrazolo[3,4-b]quinolin-1-yl)acetate (3). The hydrazinolysis of 3 followed by the condensation of resulting 2-(6-methyl-1H-pyrazolo[3,4-b]quinolin-1-yl)acetohydrazide (4) with aromatic aldehydes gave N-acylhydrazones 6(a–t). Structures of the synthesized compounds were established by readily available techniques such as FT-IR, NMR and mass spectral studies. The stereochemical behavior of 6(a–t) was studied in dimethyl sulfoxide-d6 solvent by means of 1H NMR and 13C NMR techniques at room temperature. NMR spectra revealed the presence of N’-(benzylidene)-2-(6-methyl-1H-pyrazolo[3,4-b]quinolin-1-yl)acetohydrazides as a mixture of two conformers, i.e., E(C=N)(N-N) synperiplanar and E(C=N)(N-N) antiperiplanar at room temperature in DMSO-d6. The ratio of both conformers was also calculated and E(C=N) (N-N) syn-periplanar conformer was established to be in higher percentage in equilibrium with the E(C=N) (N-N) anti-periplanar form. 相似文献
232.
Priyankar Paira Krishnendu B. Sahu Nirup B. Mondal Niranjan P. Sahu Peter Luger 《Tetrahedron》2008,64(18):4026-4036
Phase transfer catalyzed one-pot syntheses of fused oxazepino, oxazocino, and oxazonino quinolinium cations and quinolones were achieved from 8-hydroxy quinoline derivatives with 1,ω-dihaloalkanes. Structures of all the products were elucidated by spectroscopic analysis. Single crystal X-ray crystallographic analysis of three compounds and graphical superposition of the structures indicate that products having seven-membered ring are less planar compared to the product having eight-membered ring. 相似文献
233.
《Journal of Coordination Chemistry》2012,65(1-2):45-56
Abstract Infrared assignments (4000 - 50 cm?1) are presented for the complexes [M(quinO)n](ClO4)2(quinO = quinoline N-oxide; n = 6 for Mn, Co, Ni; n = 5 for Zn, and n = 4 for Cu) and their perdeuterated analogues. The spectra are consistent with octahedral structures for the 6-coordinate complexes, a trigonal bipyramidal structure for the Zn(II) complex and a square planar structure for the Cu(II) complex, with some distortion from idealised symmetry evident for each complex. In the Mn(II) complex, strong coupling occurs between the vM-O of lowest frequency and the ligand vibration, xN-O (mode 45). In the Cu(II) complex, the single vCu-O is strongly coupled with the ring torsion (mode 28). 相似文献
234.
235.
236.
The required chalcones 1a–h were prepared by reaction of aryl acetophenone with different aryl aldehydes, which in turn treated with guanidine nitrate, yielded 4-(substituted phenyl)-6-(substituted phenyl)-2-pyrimidinamines 2a–h. Novel pyrimidine–quinoline clubbed molecules 3a–h have been prepared by reaction of 2a–h with 4-chloro-2,6-dimethylquinoline. All the compounds were characterized by elemental analysis and spectral studies. The newly synthesized compounds were evaluated for their antibacterial and antifungal activities. 相似文献
237.
Swadhin Chetia Samprity Sarmah Dr. Apurba Dutta Prof. Diganta Sarma 《European journal of organic chemistry》2023,26(26):e202300390
A copper acetate monohydrate catalyzed simple, effective and economic protocol has been developed for the construction of quinazoline derivatives via acceptorless dehydrogenative coupling of easily available 2-aminoaryl methanols and nitriles. The methodology was also highly effective for the synthesis of medicinally important quinolines analogues. The reactions proceeded in presence of KOtBu in toluene at 110 °C for 5 h without the requirement of inert condition, external additives and ligands. 相似文献
238.
A new protocol based on a palladium-catalyzed Heck reaction of an amino acid–derived vinyl unit with 3-bromoquinoline has been developed to access the title compounds in good yield and optical purity. 相似文献
239.
A short and simple synthesis of chromeno[4,3‐b]benzo[f]quinolin‐6‐one derivatives was accomplished in good to high yields via the reaction of N‐arylidenenaphthalen‐2‐amine with 4‐hydroxycoumarin in aqueous media catalyzed by TEBAC. The structures were established by spectroscopic data and further confirmed by X‐ray analysis. In addition, water was chosen as a green solvent. 相似文献
240.
A. B.A. El-Gazzar H. N. Hafez A. A. Abu-Hashem A. S. Aly 《Phosphorus, sulfur, and silicon and the related elements》2013,188(2):379-405
The behavior of the 2-methylthio-pyrimido[4,5-b]quinolin-4-one towards differently substituted amines is reported. Also, the reactivity of 3-aminothiazolo[3′,2′ :1,2]-pyrimido[4,5-b]quinoline-2-carbonitrile towards formic acid, urea, thiourea, formamide, and carbon disulfide is discussed. Some of the synthesized derivatives possess biological activities as anti-inflammatory and analgesic agents. Some of these selective biologically active compounds were screened for antioxidant properties. 相似文献