全文获取类型
收费全文 | 617篇 |
免费 | 12篇 |
国内免费 | 63篇 |
专业分类
化学 | 650篇 |
晶体学 | 16篇 |
综合类 | 2篇 |
物理学 | 24篇 |
出版年
2023年 | 4篇 |
2022年 | 1篇 |
2021年 | 11篇 |
2020年 | 7篇 |
2019年 | 13篇 |
2018年 | 17篇 |
2017年 | 18篇 |
2016年 | 11篇 |
2015年 | 11篇 |
2014年 | 26篇 |
2013年 | 74篇 |
2012年 | 50篇 |
2011年 | 29篇 |
2010年 | 21篇 |
2009年 | 30篇 |
2008年 | 54篇 |
2007年 | 53篇 |
2006年 | 39篇 |
2005年 | 54篇 |
2004年 | 27篇 |
2003年 | 26篇 |
2002年 | 11篇 |
2001年 | 8篇 |
2000年 | 13篇 |
1999年 | 7篇 |
1998年 | 3篇 |
1997年 | 7篇 |
1996年 | 9篇 |
1995年 | 8篇 |
1994年 | 10篇 |
1993年 | 13篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有692条查询结果,搜索用时 109 毫秒
21.
水溶液中2,4,6-三溴苯酚在银阴极上的选择性脱卤 总被引:2,自引:0,他引:2
采用循环伏安法比较了玻碳、光亮银和粗糙化银电极对2,4,6-三溴苯酚还原脱卤反应的电催化活性, 初步研究了碱性水溶液中2,4,6-三溴苯酚在粗糙化银电极上的还原脱卤历程; 在此基础上, 利用恒电位电解法进一步探索了2,4,6-三溴苯酚在粗糙化银电极上的电还原脱卤历程. 结果表明, 粗糙化银电极对2,4,6-三溴苯酚的选择性还原脱卤反应具有优良的电催化活性, 且其活性优于光亮银和玻碳电极; 2,4,6-三溴苯酚在粗糙化银电极上的还原反应是个逐步脱卤过程, 推测得出其邻位和对位C—Br键的还原断裂所需的活化能非常接近, 而反应中间产物2,4-二溴苯酚的对位C—Br键的还原断裂所需的活化能比邻位要低; 2,4,6-三溴苯酚能实现完全脱卤生成苯酚, 主要路径为2,4,6-三溴苯酚→2,4-二溴苯酚→2-溴苯酚→苯酚. 相似文献
22.
<正>Certain phenols and naphthols were nitrated regioselectively with Zn(NO_3)_2·6H_2O/TCT in acetonitrile as solvent at room temperature and short reaction time in good yields.The reaction condition was mild.TCT is a cheap and commercially available reagent.It performed as an acid catalyst in this transformation. 相似文献
23.
《Journal of Coordination Chemistry》2012,65(10):1803-1811
Self-assembly of the flexible ligand 1,3,5-tri(1,2,4-triazol-1-ylmethyl)-2,4,6-trimethylbenzene (ttmb) with Cd(II) salts gave three coordination polymers {[Cd(ttmb)2](SO4)(H2O)16} n (1), {[Cd(ttmb)2(H2O)2](NO3)2(H2O)6} n (2), and {[Cd(ttmb)2(H2O)2](ClO4)2(H2O)7} n (3). Complex 1 has a (3,6)-connected CdCl2-type 2-D network. However, 2 and 3 show the 2-D (4,4) network and 1-D double chain, respectively. Complexes 1, 2, and 3 exhibit luminescent emission maxima at 306, 339, and 298?nm, respectively, in the solid state at room temperature. 相似文献
24.
《Green Chemistry Letters and Reviews》2013,6(2):185-193
Abstract A variety of 1,3,5-trisubstituted benzenes could be obtained upon heating enaminones in absence of solvent over montmorillonite-K-10. Heating mixtures of two different enaminones 2a–d have also afforded 1,3,5-trisubstituted benzenes 7b–d and 8b–d resulting from self-condensation of one enaminone with two molecules of the other enaminone. Heating enaminone 2b with ethyl propiolate afforded a mixture of triaroylbenzene 3b in addition to diaroylbenzoic acid esters 11 and 1,3,5-aroylbenzene dicarboxylate 12. On the other hand, reaction of enaminone derivative 2b with dimethyl acetylenedicarboxylate has afforded 2-oxopyran-4-carboxylic acid derivative 15. 2-Aminoprop-1-ene-1,1,3-tricarbonitrile 16 was reacted with enaminones to yield polysubstituted benzenes 19a–c. Likewise the reaction of 2-aminoprop-1-ene-1,1,3-tricarbonitrile 16 with benzylidenemalononitrile has afforded polysubstituted benzenes 24. 相似文献
25.
Hasmukh S. Patel Ketan B. Patel 《Phosphorus, sulfur, and silicon and the related elements》2013,188(9):2443-2452
4-Amino-1,2,4-triazole (1) undergoes facile condensation with aromatic aldehydes to afford the corresponding 4-(arylidene-amino)-4H-[1,2,4]-triazole (2a–h) in good yield. Rearrangement of compounds (2a–h) with benzoyl isothiocyanate/4-chloro-benzoyl isothiocyanate/2,4-dichloro-benzoyl isothiocyanate yields corresponding 1,3,5-oxadiazine derivatives (3). Structural elucidation of these compounds was based on elementary analysis and spectral data studies. The newly synthesized compounds were evaluated for their antibacterial activities. 相似文献
26.
Raoudha Abderrahim Khaled Boujlel 《Phosphorus, sulfur, and silicon and the related elements》2013,188(5):995-999
The imidates derived from 3-aminotriazole 1 react with isocyanates and isothiocyanates to give corresponding 1,2,4-triazolo-1,3,5-triazin-4-ones and 1,2,4-triazolo-1,3,5-triazin-4-thiones in a 60–75% overall yield. If the condensation is realized at r.t., then the intermediate 2 can be isolated. 相似文献
27.
Amit C. Patel Dharmesh H. Mahajan Kishor H. Chikhalia 《Phosphorus, sulfur, and silicon and the related elements》2013,188(2):368-376
A new series of 2-(coumarin-3-yl)-5-mercapto-1,3,4-oxadiazoles based on various aryl thiourea/ureas incorporating a 1,3,5-s-triazine moiety is reported. The components of this series have been obtained by the reaction of cyanuric chloride (1) with 2-(coumarin-3-yl)-5-mercapto-1,3,4-oxadiazole (2). The prepared 2-{(coumarin-3-yl-1,3,4-oxadiazolyl)-5-thio}-4,6-dichloro-s-triazine (3) was subsequently treated with morpholine (4) to form 2-{(coumarin-3-yl-1,3,4-oxadiazolyl)-5-thio}-4-(morpholino)-6-chloro-s-triazine (5). This was further treated with various substituted aryl urea/thioureas (6a–k/7a–k) to afford the title compounds 8a–k and 9a–k, which were and tested for their antibacterial activity (MIC) against different microorganisms. The structures of the novel synthesized compound have been established on the basis of 1H NMR and FT-IR data together with elemental analysis. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. 相似文献
28.
Raoudha Abderrahim 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3):581-585
The reaction of ethyl chloroformate with iminoesters derived from 3-aminotriazole, followed by amine or phenyl hydrazine condensation, leads to a variety of 1,2,4-triazolo-1,3,5-triazin-4-ones in a 60–85% overall yield. 相似文献
29.
30.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(30):8960-8964
A new fused N‐heterocyclic framework, dipyrazolo‐1,3,5‐triazinane, was synthesized and the physiochemical properties of its derivatives were investigated to evaluate the integrated energetic performance. In contrast to 1,3,5‐trinitro‐1,3,5‐triazinane (RDX) featuring a distorted chair confirmation, polynitro‐functionalized dipyrazolo‐1,3,5‐triazinanes have nearly planar backbones, thereby enhancing the density and thermal stability. Among these new energetic tricyclic compounds, 5 a and 12 show favorable crystal densities of 1.937 g cm−3 and 1.990 g cm−3 at 150 K, respectively, which rank highest in triazinane‐based energetic compounds. Additionally, this synthetic approach was carried out to form seven‐membered and eight‐membered rings, giving rise to tetranitro dipyrazolo‐1,3,5‐triazepane ( 5 b ) and tetranitro dipyrazolo‐1,3,5‐triazocane ( 5 c ), respectively. 相似文献