全文获取类型
收费全文 | 202篇 |
免费 | 8篇 |
国内免费 | 54篇 |
专业分类
化学 | 259篇 |
晶体学 | 3篇 |
物理学 | 2篇 |
出版年
2023年 | 6篇 |
2022年 | 8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264条查询结果,搜索用时 15 毫秒
181.
An eco-friendly and practical approach was developed for the synthesis of pyrimidine derivatives via a one-pot, three-component coupling reaction of commercially available aldehydes, alkynes, and indazole3/triazole catalyzed by ferric chloride with good to excellent yields. The advantages of this method include environmentally friendly catalyst, easily available materials, and ease of product isolation. 相似文献
182.
Wei-Feng Wang Dr. Jin-Bao Peng Dr. Xinxin Qi Dr. Jun Ying Prof. Dr. Xiao-Feng Wu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(14):3521-3524
A convenient palladium-catalyzed carbonylation reaction for the efficient synthesis of (E)-3-benzylidenechroman-4-ones has been developed. Using TFBen as a solid CO source, a range of substituted (E)-3-benzylidenechroman-4-ones were prepared in moderate to good yields with 2-iodophenols and allyl chlorides as the substrates. Additionally, substituted quinolin-4(1H)-ones can also be obtained with 2-iodoaniline as the starting material. 相似文献
183.
Guan-Yeow Yeap Wan-Sinn Yam Daisuke Takeuchi Kohtaro Osakada Ewa Gorecka Wan Ahmad Kamil Mahmood Peng-Lim Boey Shafida Abd Hamid 《Liquid crystals》2008,35(3):315-323
A series of new isoflavonic esters 7-decanoyloxy-3-(4'-substitutedphenyl)-4H-1-benzopyran-4-ones containing a heterocycle in their central core with one flexible alkyl chain and various substituents, R (where R = F, Cl, Br, CH3, OCH3, or H) at 4'-position at one end, have successfully been synthesised, isolated, and characterised. The physical properties of title compounds were studied using spectroscopic techniques (Fourier transform infrared, 1H and 13C nuclear magnetic resonance). The liquid crystalline properties and the textures of these compounds along with their thermal stabilities were investigated via polarising optical microscopy and differential scanning calorimetry. All the compounds except the member without the substituent were enantiotropic mesogens exhibiting smectic A and/or nematic phases. The layer periodicities in relation to different phases were substantiated by X-ray diffraction wherein the molecules within the SmA phase were found to be intercalated. The structural changes that resulted in a variation of transition temperature as well as the electronic polarisability of the respective compounds are also discussed. 相似文献
184.
The interaction of 3,5-carbonyl-substituted derivatives of 1,4-dihydropyridine and some analogs of it with hydrazine hydrate occurs with fission of the heterocycle. In the case of alkoxycarbonyl-substituted compounds a reverse Michael reaction predominates leading to fragmentation of the molecules. 相似文献
185.
186.
A mesoionic acyclic C-nucleoside (4), serves as the starting chiron to construct highly functionalized 2-aza-7-thiabicyclo[2.2.1]heptanes and heptenes by means of a [3+2] cycloaddition with acetylenic and olefinic dipolarophiles. Further elimination of either sulfur or hydrogen sulfide leads to acyclic C-nucleosides bearing a heterocyclic moiety of 2-pyridone. 相似文献
187.
《应用有机金属化学》2017,31(10)
Eight heteroleptic palladium complexes containing both N‐heterocyclic carbenes and NH‐heterocycle azoles (pyrazole and indazole) were synthesized and characterized, and their structures were unambiguously confirmed using single‐crystal X‐ray diffraction. Further investigation of the complexes as catalysts in the Suzuki–Miyaura reaction and Buchwald–Hartwig amination revealed good reactivities for aryl chlorides. 相似文献
188.
Shashikant U. Dighe Surya K. Samanta Shivalinga Kolle Sanjay Batra 《Tetrahedron》2017,73(17):2455-2467
An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y1 and Y2. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones. 相似文献
189.
Sandra Fusco Domenica Capasso Roberto Centore Sonia Di Gaetano Emmanuele Parisi 《Acta Crystallographica. Section C, Structural Chemistry》2019,75(10):1398-1404
A study of three isomeric compounds containing a phenolic moiety attached to the nitrogen‐rich triazolo–triazole bicycle is presented. In the three isomers, the phenolic OH group is in the ortho, meta and para positions. The crystal structure analysis of the meta isomer (C10H9N5O) shows that the 2H‐tautomer is present in the crystal and that the molecule adopts a substantially planar geometry. However, the conformation found in the crystal is different compared to the monoprotonated cation of the same compound previously investigated in several salts. The packing of the meta isomer is driven by the formation of strong hydrogen bonds and shows the formation of infinite planar ribbons, parallel to a, formed around 21 crystallographic axes. The three isomers were tested against some cancer cell lines and also against normal cell lines. The ortho isomer shows a weak antiproliferative activity, the meta isomer shows significant antiproliferative activity against some cancer lines and no activity against healthy cell lines, and the para isomer is active against all the tested cell lines. 相似文献
190.
为了寻找具有生物活性的新化合物,以氟乙酸甲酯、氰乙酰胺和甲酸乙酯为起始原料,经环合、氯化、水解、酰氯化等反应合成了含氟吡啶酰氯中间体,再与醇类和酚类反应合成了一系列含氟吡啶羧酸酯类化合物,总收率约38%。其结构经1HNMR、13CNMR、IR、MS及元素分析测试技术确证。初步杀虫抑菌活性测试表明,部分化合物1e、1i、1j和1k在500mg/L浓度下,对淡色库蚊的杀死率在61.9%~100%之间,但对几种受试植物病菌的抑制活性很差。化合物1k活性最好,在500mg/L时对粘虫(armyworm)和淡色库蚊(culex mosquito)的杀死率均为100%。初步构效关系分析表明,芳杂环酚的该类化合物有较好的活性,而脂肪醇的该类化合物无活性。 相似文献