全文获取类型
收费全文 | 329篇 |
免费 | 18篇 |
国内免费 | 38篇 |
专业分类
化学 | 378篇 |
晶体学 | 1篇 |
综合类 | 1篇 |
物理学 | 5篇 |
出版年
2023年 | 1篇 |
2022年 | 4篇 |
2021年 | 5篇 |
2020年 | 3篇 |
2019年 | 14篇 |
2018年 | 11篇 |
2017年 | 8篇 |
2016年 | 6篇 |
2015年 | 5篇 |
2014年 | 16篇 |
2013年 | 27篇 |
2012年 | 10篇 |
2011年 | 15篇 |
2010年 | 13篇 |
2009年 | 11篇 |
2008年 | 12篇 |
2007年 | 11篇 |
2006年 | 13篇 |
2005年 | 14篇 |
2004年 | 5篇 |
2003年 | 15篇 |
2002年 | 119篇 |
2001年 | 19篇 |
2000年 | 5篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1997年 | 4篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1986年 | 1篇 |
排序方式: 共有385条查询结果,搜索用时 15 毫秒
31.
3‐Bromoallyl alcohols are carbonylatively cyclized under carbon monoxide pressure in toluene in the presence of a catalytic amount of Pd(OAc)2 and PPh3 along with Na2CO3 to give furan‐2(5H)‐ones in good yields. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
32.
33.
Harshadas Mitaram Meshram Palakuri RameshBandi Chennakesava Reddy Balasubramanian SridharJhillu Singh Yadav 《Tetrahedron》2011,67(17):3150-3155
An efficient vinylogous Mukaiyama aldol reaction (VMAR) of 2-(trimethylsilyloxy)furan with various (N-alkyl)isatins is described in the presence of lanthanum(III) triflates (5 mol %). The reaction proceeds rapidly and affords the corresponding 3-hydroxy-(5-oxo-2,5-dihydrofuran-2-yl)indolin-2-one in high yields with good diastereoselectivities (threo:erythro ratio up to ≤95:5). 相似文献
34.
Mark York 《Tetrahedron letters》2011,52(47):6267-6270
A synthesis of di-, tri- and tetra-substituted furans from reaction of the corresponding ketones and α-haloketones with LiHMDS is reported. Reaction under continuous-flow conditions gave increased yields and removed the need for external cooling when compared to the unoptimised batch conditions. 相似文献
35.
Unsaturated acyloxy sulfones 3 undergo intramolecular cyclization upon deprotonation with LHMDS in THF. Dehydration and double bond isomerization of the products upon exposure to acid, gave the fused ring furans, 4, in good yields. This strategy could be readily adapted to prepare substituted benzofurans 12 from the cyclization reactions of acyloxy sulfones 11 prepared from phenols. Finally, this approach could be successfully modified to access dihydropyrans and benzopyrans. 相似文献
36.
37.
Curtis R. Fincher Jr 《Molecular Crystals and Liquid Crystals》2013,570(1):559-570
In most liquid crystal polymers when a thin sample is sheared the polymer exhibits a periodic pattern or texture. While this phenomena has been widely noted, a complete and satisfactory explanation is not yet in hand. We present the results of a study of the dynamics of the formation of the banded texture in liquid crystalline polymers after shear. The data were collected by the diffraction of light from the texture. This approach directly provides the key parameters to characterize the texture without the ambiguity that is often involved with microscopy. It was found that the overall nature of the modulation that gives rise to the texture appears to not vary with time except in magnitude. Both thewavelength and the coherence length of the modulation remain fixed. While both shear rate and thickness of the sample have little effect upon the texture, concentration of the polymer has a very large effect. 相似文献
38.
39.
40.