全文获取类型
收费全文 | 211篇 |
免费 | 5篇 |
国内免费 | 42篇 |
专业分类
化学 | 241篇 |
晶体学 | 7篇 |
综合类 | 2篇 |
物理学 | 8篇 |
出版年
2023年 | 2篇 |
2022年 | 2篇 |
2021年 | 3篇 |
2020年 | 3篇 |
2019年 | 1篇 |
2017年 | 5篇 |
2016年 | 8篇 |
2015年 | 3篇 |
2014年 | 7篇 |
2013年 | 72篇 |
2012年 | 9篇 |
2011年 | 8篇 |
2010年 | 3篇 |
2009年 | 2篇 |
2008年 | 1篇 |
2007年 | 10篇 |
2006年 | 9篇 |
2005年 | 13篇 |
2004年 | 11篇 |
2003年 | 13篇 |
2002年 | 3篇 |
2001年 | 7篇 |
2000年 | 11篇 |
1999年 | 7篇 |
1998年 | 6篇 |
1997年 | 3篇 |
1996年 | 8篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 4篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1980年 | 2篇 |
排序方式: 共有258条查询结果,搜索用时 250 毫秒
81.
Liza Salehitabar 《Phosphorus, sulfur, and silicon and the related elements》2013,188(11):731-739
AbstractStable substituted dialkyl phosphorylsuccinates were synthesized, as a mixture of two diastereoisomers, in high yields using one-pot reaction of dialkyl acetylenedicarboxylates, trialkyl phosphites, and thioamides in CH2Cl2 at room temperature. Using triphenylphosphine instead of phosphites, afforded stabilized triphenylphosphanylidenesuccinates. DFT calculations at B3LYP/6-31?+?G(d) level indicated that among four possible conformational diastereoisomers of dimethyl 2-(dimethoxyphosphoryl)-3-ethanethioamidosuccinate, the (2R,3S) and (2S,3S) diastereomers are the most stable forms. 相似文献
82.
Tadeusz Gajda 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4):327-331
Abstract Diethyl 1-bromoalkylphosphonates 1 have been obtained in good to moderate yields by the reaction of diethyl I-hydroxyalkylphosphonates 2 with the triphenylphosphine-carbon tetrabromide system or dibromotriphenylphosphorane. 相似文献
83.
Abdolali Alizadeh Mohamad Acedi 《Phosphorus, sulfur, and silicon and the related elements》2013,188(11):2601-2606
4,5-dialkyl 1-isopropyl 3-isopropoxy-1H-pyrazole-1,4,5-tricarboxylate was obtained in an excellent yield from the reaction of dialkyl acetylenedicarboxylates and diisopropyl azodicarboxylate in the presence of triphenylphosphine in dry dichloromethane. This reaction provides a useful synthetic route to highly functionalized pyrazoles. 相似文献
84.
Issa Yavari Mohammad M. Ghanbari Ashraf S. Shahvelayati Maryam Ghazvini 《Phosphorus, sulfur, and silicon and the related elements》2013,188(12):2551-2557
Stable crystalline phosphorus ylides are obtained in excellent yields from the 1:1:1 addition reaction between 5,5-diarylthiohydantoins and dialkyl acetylenedicarboxylates in the presence of triphenylphosphine. These phosphoranes undergo a smooth intramolecular Wittig reaction followed by an electrocyclic ring opening to produce dialkyl 2-(2,5-dihydro-5,5-diaryl-2-thioxo-1H-imidazol-4-yl)but-2-enedioates in good yields. 相似文献
85.
Demetrios N. Nicolaides Konstantinos E. Litinas Ioannis Psaroulis Aristea Makri Spyros Adamopoulos 《Phosphorus, sulfur, and silicon and the related elements》2013,188(10):2104-2111
Abstract Dimethyl (chromen-3-yl)-(dialkoxyphosphoryl)succinates are prepared from the reaction of 4-hydroxycoumarin with DMAD and P(OR)3. 4-Hydroxy-1-methylquinolinone reacts with DMAD and P(OEt)3 to give dimethyl (quinoline-3-yl)-(diethoxyphosphoryl)-succinate. GRAPHICAL ABSTRACT 相似文献
86.
合成了2个含有杂环硫酮的银(Ⅰ)配合物,[AgBr(PPh3)2(BTZT)]2 (1),[Ag2Cl2(PPh3)2(BTZT)2]CH3OH (2)(PPh3=三苯基膦;BTZT=苯并噻唑-2-硫酮),并通过红外光谱、X射线单晶衍射、荧光光谱和核磁氢谱进行表征.2个配合物是在含有2-巯基苯并噻唑(MBT)的甲醇与二氯甲烷混合溶液中,AgX(X=Cl,Br)与三苯基膦反应得到的.MBT配体由于存在化学活性基团(-N(H)-C(=S)-),所以可以转化为BTZT配体.结构分析显示有2个相同的分子结构存在于配合物1中,但是它们具有不同的键长和键角.配合物2是一个含有菱形的[Ag2Cl2]单元在中心的反转对称二聚体,2个相邻[AgCl(PPh3)(BTZT)]单元由2个氯原子桥连. 相似文献
87.
合成了2个含有杂环硫酮的银(Ⅰ)配合物, [AgCl(PPh3)2(BTZT)]2 (1), [Ag(PPh3)2(BTZT)2](NO3)CH3OH (2)(PPh3=三苯基膦; BTZT=苯并噻唑-2-硫酮), 并通过红外光谱、X射线单晶衍射、荧光光谱和核磁共振氢谱进行分析和表征。杂环硫酮存在化学活性基团-N(H)-C(=S)-在平衡中, 与其硫醇形式可以相互转化。2个配合物是在含有2-巯基苯并噻唑(MBT)的甲醇与二氯甲烷混合溶液中, AgCl或AgNO3与三苯基膦反应得到的。配合物1的每个不对称单元中包含2个相同的分子结构, 但是它们具有不同的键长和键角。配合物2是一个简单的单核杂配配合物, 它的主体结构通过氢键作用连接游离的CH3OH和NO3-离子。配合物1和2发射峰的红移源于配体中的π-π*跃迁。 相似文献
88.
Ali Souldozi Ali Ramazani Nader Noshiranzadeh 《Phosphorus, sulfur, and silicon and the related elements》2013,188(6):1271-1275
Protonation of the highly reactive 1:1 intermediates, produced in the reaction between triphenylphosphine and dialkyl acetylenedicarboxylates, by 1-(2-hydroxy-1-naphtyl)-1-ethanone leads to vinyltriphenylphosphonium salts, which undergo a Michael addition reaction with a conjugate base to produce corresponding stabilized phosphorus ylides. Dipotassium hydrogen phosphate powder was found to catalyze the conversion of stabilized phosphorus ylides to dialkyl (E, Z)-2-(1-acetyl-2-naphthyl)-2-butenedioates under thermal and microwave conditions in a solventless system. 相似文献
89.
Shyam Babu Singh Pankaj Kumar Verma Kamleshwar Tiwari Mandavi Singh Preyas Ankit Shahin Fatma 《合成通讯》2014,44(12):1795-1802
An efficient triphenylphosphine-catalyzed synthesis of β-acetamido carbonyls via multicomponent reaction of aromatic aldehydes, enolizable ketones or β-keto esters, acid chlorides and acetonitrile at room temperature is described. The process is remarkably simple, environmentally benign, and uses Lewis base for the first time in such type of reaction. 相似文献
90.
《Tetrahedron letters》2014,55(50):6868-6872
A new series of 2-amino, 4-azepanone, 5-aryl substituted derivatives of pyrimidine compounds were synthesized for the first time from the commercially available 2-amino-4-hydroxypyrimidine. The key step in the reaction is a conceptually new single step palladium catalyzed cross coupling along with the deprotection of N,N-diisopropylformimidamide using bis(triphenylphosphine)palladium(II) dichloride (PdCl2(PPh3)2). 相似文献