首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   49篇
  免费   2篇
化学   39篇
晶体学   1篇
数学   6篇
物理学   5篇
  2023年   1篇
  2022年   2篇
  2021年   1篇
  2020年   2篇
  2019年   2篇
  2016年   1篇
  2015年   2篇
  2014年   1篇
  2013年   5篇
  2012年   6篇
  2011年   3篇
  2010年   3篇
  2009年   2篇
  2008年   7篇
  2007年   4篇
  2006年   3篇
  2005年   3篇
  2001年   1篇
  2000年   1篇
  1999年   1篇
排序方式: 共有51条查询结果,搜索用时 15 毫秒
31.
In the title compound, C11H12BrN5O2, the rings in the pterin moiety are planar. The carbonyl O atom is in a synperiplanar conformation, while the C—N—C(=O)—C linkage is antiperiplanar. N—H?N and N—H?O intermolecular hydrogen bonds transform the mol­ecules into infinite chains.  相似文献   
32.
Abstract

Wavelets have motivated development of a host of new ideas in nonparametric regression smoothing. Here we apply the too] of exact risk analysis, to understand the small sample behavior of wavelet estimators, and thus to check directly the conclusions suggested by asymptotics. Comparisons between some wavelet bases, and also between hard and soft thresholding, are given from several viewpoints. Our results provide insight as to why the viewpoints and conclusions of Donoho and Johnstone differ from those of Hall and Patil.  相似文献   
33.
In this paper, the concept of lattice over generalized intuitionistic fuzzy matrices (GIFMs) are introduced and have shown that the set of GIFMs forms a distributive lattice. Some algebraic properties of generalized intuitionistic fuzzy matrices (GIFMs) are presented over distributive lattice. Also, some characteristics of generalized intuitionistic fuzzy nilpotent matrices (GIFNMs) are discussed over distributive lattice. Finally, the reduction of GIFNMs over distributive lattice are given with some properties.  相似文献   
34.
35.
Field equations of the Chern–Simons modified gravity in four dimensions are obtained by a truncation of the field equations of the low energy effective string models with first order corrections in the string constant included.  相似文献   
36.
A simple and facile approach for the synthesis of various structurally different tricyclic bent oxepine frameworks from a readily accessible precursor has been introduced. The synthesis of substituted oxepine derivative involved Pd(0)-catalyzed Heck reaction. This methodology enriches the literature for the large ring formation.  相似文献   
37.
Allylindium reagents undergo facile and highly regioselective cross-coupling with benzylic and cinnamyl bromides in THF at room temperature without any catalyst producing terminal alkenes in high yields. The addition is highly regioselective and is found to provide γ-adducts in all reactions.  相似文献   
38.
Palladium(0) nanoparticle has been used as an efficient catalyst for the allylation of active methylene compounds. Very efficient bisallylation is achieved for a variety of active methylene compounds by allyl acetate and its derivatives in one stroke in THF solvent. The reaction in water provides monoallylated product selectively by allyl acetate only. The recovered Pd(0) nanoparticle is recycled. A probable mechanism is suggested.  相似文献   
39.
Reactions of various heterocycles 1–6 with N‐bromosuccinimide in the presence or absence of water have been studied for side chain versus ring bromination to afford some new and important heterocyclic synthons. Interestingly, the N‐bromosuccinimide reaction in the presence of perchloric acid, a new condition, affords exclusively the new dibromo aminopicoline 1f , which is not obtained by other presently studied methods.  相似文献   
40.
We report here an iron–bisphosphine complex-catalyzed annulation reaction of an arylindium reagent and two alkyne molecules that affords a substituted naphthalene derivative in moderate to good yield. The reaction represents a new example of iron-catalyzed C–C bond forming reactions via C–H bond functionalization.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号