全文获取类型
收费全文 | 392篇 |
免费 | 20篇 |
国内免费 | 73篇 |
专业分类
化学 | 454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 | 15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485条查询结果,搜索用时 890 毫秒
181.
合成了新试剂1-(2-噻唑)-3-(8-(5-对磺酸基苯基偶氮)喹啉-三氮烯(TCPQT),并研究了其与Cu2+的显色反应。结果表明:在pH 7.5的磷酸盐缓冲溶液中,TCPQT与Cu2+形成摩尔比为1:1的紫红色络合物,该络合物在606.5nm处有一最大吸收峰,其表观摩尔吸光系数为3.36×105L.mol-1.cm-1,Cu2+的质量浓度在0~0.4μg/mL范围内符合比尔定律,相关系数r=0.9993。方法已用于测定食品中的微量铜。 相似文献
182.
183.
184.
Ameen A. Abu-Hashem Mahmoud N. M. Yousif Abdel-Rhman Barakat Ahmed El-Gazzar Hend N. Hafez 《中国化学会会志》2023,70(12):2187-2205
The pyrido[2,3-d]pyrimidine moieties are one of the most biologically widespread heterocyclic compounds as antimicrobial, antioxidant, antitubercular, antiviral and anti-inflammatory. Hence, we synthesized an efficient new series of 2-thioxo-pyrido[2,3-d]pyrimidinone, 2-hydrazinyl-(quinolin-2-yl)pyrido[2,3-d]pyrimidinone,N′-(quinolin-2-yl)-pyrido[2,3-d]pyrimidine-(formo/aceto)-hydrazide and substituted-(quinolin-2-yl)pyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidinone derivatives. The characterization of new compounds was corresponded by using spectroscopic techniques, IR, NMR and Mass spectra. In vitro, all compounds were evaluated as antimicrobial activity compared with cefotaxime sodium and nystatin as the standard drug. This work deals with the exploration of the new heterocyclic compounds and medicinal diversity of quinoline-pyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidine derivatives that might pave the way for long in the discovery of therapeutic medicine for future drug design. 相似文献
185.
186.
In an attempt to search for more potent positive inotropic agents,a series of 1-(benzylamino)-3-(4,5-dihydro[1,2,4]trizaolo[4,3- a]quinolin-7-yloxy)propan-2-ol derivatives was synthesized in four steps using 6-hydroxy-3,4-dihydro-2(1H)-quinolinone as a starting material,and their positive inotropic activities were evaluated by measuring the coronary blood flow(CBF)and the left ventricular pressure(LVP)followed by calculating the rate of pressure development(dp/dt_(max)values)in the preparation of rat Lan... 相似文献
187.
Vijay Singh Shigeyoshi Sakaki Milind M. Deshmukh 《Journal of computational chemistry》2019,40(24):2119-2130
Catalytic synthesis of dihydropyridine by transition-metal complex is one of the important research targets, recently. Density functional theory calculations here demonstrate that nickel(I) hydride complex (bpy)NiIH (bpy = 2,2′-bipyridine) 1 is a good catalyst for hydrosilylation of both quinoline and pyridine. Two pathways are possible; in path 1, substrate reacts with 1 to form stable intermediate Int1 . After that, N3─C1 bond of substrate inserts into Ni─H bond of 1 via TS1 to afford N-coordinated 1,2-dihydroquinoline Int2 with the Gibbs activation energy (ΔG°‡) of 21.8 kcal mol−1. Then, Int2 reacts with hydrosilane to form hydrosilane σ-complex Int3 ; this is named path 1A. In the other route (path 1B), Int1 reacts with phenylsilane in a concerted manner via hydride-shuttle transition state TS2 to afford Int3 . In TS2 , Si atom takes hypervalent trigonal bipyramidal structure. Formation of hypervalent structure is crucial for stabilization of TS2 (ΔG°‡ = 17.3 kcal mol−1). The final step of path 1 is metathesis between Ni─N3 bond of Int3 and Si─H bond of PhSiH3 to afford N-silylated 1,2-dihydroproduct and regenerate 1 (ΔG°‡ = 4.5 kcal mol−1). In path 2, 1 reacts with hydrosilane to form Int5 , which then forms adduct Int6 with substrate through Si–N interaction between substrate and PhSiH3. Then, N-silylated 1,2-dihydroproduct is produced via hydride-shuttle transition state TS5 (ΔG°‡ = 18.8 kcal mol−1). The absence of N-coordination of substrate to NiI in TS5 is the reason why path 2 is less favorable than path 1B. Quinoline hydrosilylation occurs more easily than pyridine because quinoline has the lowest unoccupied molecular orbital at lower energy than that of pyridine. © 2019 Wiley Periodicals, Inc. 相似文献
188.
The first heterogeneous intermolecular cycloaddition of 2-aminoaryl carbonyls and internal alkynes was realized in DMF at 100?°C by using a triphenylphosphine-functionalized MCM-41-supported gold(I) complex [MCM-41-PPh3-AuCl] and AgOTf as catalysts, yielding a variety of polyfunctionalized quinolines in good to excellent yields. This heterogeneous gold(I) complex could easily be prepared via a simple two-step procedure from commercially available reagents and recovered by filtration of the reaction mixture. The recovered catalyst could be reused at least seven times with almost consistent activity without addition of AgOTf as a cocatalyst. 相似文献
189.
Sumera Zaib Rubina Munir Muhammad Tayyab Younas Naghmana Kausar Aliya Ibrar Sehar Aqsa Noorma Shahid Tahira Tasneem Asif Hashem O. Alsaab Imtiaz Khan 《Molecules (Basel, Switzerland)》2021,26(21)
Alzheimer’s disease (AD) is a progressive neurodegenerative disorder and the leading cause of dementia worldwide. The limited pharmacological approaches based on cholinesterase inhibitors only provide symptomatic relief to AD patients. Moreover, the adverse side effects such as nausea, vomiting, loss of appetite, muscle cramps, and headaches associated with these drugs and numerous clinical trial failures present substantial limitations on the use of medications and call for a detailed insight of disease heterogeneity and development of preventive and multifactorial therapeutic strategies on urgent basis. In this context, we herein report a series of quinoline-thiosemicarbazone hybrid therapeutics as selective and potent inhibitors of cholinesterases. A facile multistep synthetic approach was utilized to generate target structures bearing multiple sites for chemical modifications and establishing drug-receptor interactions. The structures of all the synthesized compounds were fully established using readily available spectroscopic techniques (FTIR, 1H- and 13C-NMR). In vitro inhibitory results revealed compound 5b as a promising and lead inhibitor with an IC50 value of 0.12 ± 0.02 μM, a 5-fold higher potency than standard drug (galantamine; IC50 = 0.62 ± 0.01 μM). The synergistic effect of electron-rich (methoxy) group and ethylmorpholine moiety in quinoline-thiosemicarbazone conjugates contributes significantly in improving the inhibition level. Molecular docking analysis revealed various vital interactions of potent compounds with amino acid residues and reinforced the in vitro results. Kinetics experiments revealed the competitive mode of inhibition while ADME properties favored the translation of identified inhibitors into safe and promising drug candidates for pre-clinical testing. Collectively, inhibitory activity data and results from key physicochemical properties merit further research to ensure the design and development of safe and high-quality drug candidates for Alzheimer’s disease. 相似文献
190.
偶氮喹啉双重光谱响应识别氟离子 总被引:1,自引:1,他引:0
8-羟基喹啉-5-偶氮-4'-对二甲氨基苯(1)在乙腈中发射双重荧光,其波长分别为512 nm和370 nm,加入F-后,长波处的荧光猝灭,短波处的荧光增强.同时1的吸收光谱和溶液颜色均发生明显变化.结果表明1通过氢键作用与F-形成了1:1型配合物,结合常数为5.0×104 mol-1·L,其它阴离子的存在均不影响1的吸收光谱和荧光光谱,表明1对F-有很高的选择性.据此建立了荧光比值法与裸眼比色法检测F-的方法. 相似文献