全文获取类型
收费全文 | 258篇 |
免费 | 5篇 |
国内免费 | 128篇 |
专业分类
化学 | 261篇 |
力学 | 23篇 |
综合类 | 1篇 |
数学 | 19篇 |
物理学 | 87篇 |
出版年
2018年 | 1篇 |
2013年 | 2篇 |
2011年 | 48篇 |
2010年 | 20篇 |
2009年 | 26篇 |
2008年 | 2篇 |
2007年 | 2篇 |
2006年 | 5篇 |
2005年 | 23篇 |
2004年 | 76篇 |
2003年 | 28篇 |
2002年 | 15篇 |
2001年 | 25篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1997年 | 6篇 |
1996年 | 5篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 12篇 |
1992年 | 23篇 |
1991年 | 11篇 |
1990年 | 13篇 |
1989年 | 13篇 |
1988年 | 4篇 |
1987年 | 1篇 |
1986年 | 5篇 |
1985年 | 1篇 |
1984年 | 4篇 |
1983年 | 3篇 |
排序方式: 共有391条查询结果,搜索用时 15 毫秒
91.
92.
预柱吸附-毛细管气相色谱-质谱法是分析鲜花头香化学成分的快速和简便方法。本文讨论了该法的一些实验条件对分析结果的影响,为选择最佳的实验条件提供了科学依据。 相似文献
93.
LiMingWEI QingYuOU JuBaiLI 《中国化学快报》2004,15(9):1127-1130
The sol-gel technology is applied for the preparation of solid-phase microextraction (SPME) fiber. The fiber demonstrates high thermal stability, efficient extraction rate and the selectivity for non-polar or low-polar analytes. Efficient SPME-GC-FID analyses of benzenetoluene-ethylbenzene-xylenes (BTEXs) and low-polar halocarbon were achieved by the sol-gel coated DSDA-DDBT-TiO2 fiber. Some parameters of the SPME fiber for the determination of halocarbon in aqueous sample were investigated. 相似文献
94.
XiCunWANG JunKeWANG ZhengLI 《中国化学快报》2004,15(6):635-638
An efficient poly(ethylene glycol) (PEG)-supported liquid-phase parallel approach to di(aryloxyacetyl)thiosemicarbazides is described. PEG-bound phenol reacted with chloroacetic acid to afford PEG-bound phenyloxyacetic acid, which was readily converted into corresponding phenyloxyacetyl chloride. Subsequent nucleophilic substitution with ammonium thiocyanate followed by addition of aryloxyacetic acid hydrazides gave PEG-bound di(aryloxyacetyl)thiosemicarbazides, which were easily cleaved to give the resulting library of 1-aryloxyacetyl-4-(4‘-methoxylcarbonylphenyloxyacetyl)thiosemicarbazides in good to high yield and high purity. 相似文献
95.
ErWeiLI KunGAO ZhongJianJIA 《中国化学快报》2004,15(2):194-196
A new stigmasterol 3β, 7α, 22-trihydoxystigmast-5-ene (1) and a new eremophilenolide 8α-methoxy-6β-angeloyloxyeremophil-7(1 l)-en-8β, 12-olide-14-oic acid (2) were isolated from Ligularia dolichobotrys Diels. Their structures were deduced on the basis of spectral data. 相似文献
96.
A New Triterpenoid from Doellingeria scaber 总被引:1,自引:0,他引:1
SuPingBAI LiDONG ZhiAnHE LiYANG 《中国化学快报》2004,15(11):1303-1305
A new oleanane-type triterpene was isolated from the roots ofDoellingeria scaber. Itsstructure was identified as 3-oxo-16ct-hydroxy-olean-12-en-28-oic acid based on 1D and 2D NMRspectroscopy and X-ray analysis. 相似文献
97.
Chen ZHANG Guo Jun ZHEN Jin Chun CHEN Li Jing FANG Yu Lin LI 《中国化学快报》2006,17(10):1290-1292
Eudesmane and agarofuran are naturally occurring sesquiterpenoids with characteristic decalin skeletons. These natural products frequently contain multiple hydroxyl groups and contiguous stereocenters. Members from these families show cytotoxic, immuno- s… 相似文献
98.
ChuanZhiXU LinCHEN ZhenLI WeiSUN ChunGuXIA 《中国化学快报》2004,15(10):1149-1152
A mild and efficient oxidation of alcohols to the corresponding carbonyl compounds using the PhI(OAc)2 (1.1 eq.) with n-Bu4NBr (8 mol %) in water at room temperature is described.This new procedure is very simple and affords the desired carbonyl compounds in high yields. 相似文献
99.
100.
ZHANG Fang-Jie LI Yu-LinState Key Laboratory of Applied Organic Chemistry Institute of Organic Chemistry Lanzhou University Lanzhou Gansu China 《中国化学》1994,12(1):73-78
The reaction of 2'-hydroxychalcones with I_2-H_2SO_4-DMSO system has been studied. The results obtained by us are entirely different from those reported in the literature. The mechanism of this reaction has also been investigated. 相似文献