全文获取类型
收费全文 | 511篇 |
免费 | 64篇 |
国内免费 | 102篇 |
专业分类
化学 | 563篇 |
力学 | 7篇 |
综合类 | 10篇 |
数学 | 20篇 |
物理学 | 77篇 |
出版年
2019年 | 1篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2015年 | 2篇 |
2014年 | 30篇 |
2013年 | 47篇 |
2012年 | 44篇 |
2011年 | 11篇 |
2010年 | 5篇 |
2009年 | 7篇 |
2008年 | 27篇 |
2007年 | 22篇 |
2006年 | 16篇 |
2005年 | 21篇 |
2004年 | 31篇 |
2003年 | 41篇 |
2002年 | 89篇 |
2001年 | 196篇 |
2000年 | 33篇 |
1999年 | 25篇 |
1998年 | 10篇 |
1997年 | 8篇 |
1996年 | 1篇 |
1995年 | 4篇 |
1993年 | 1篇 |
1992年 | 1篇 |
排序方式: 共有677条查询结果,搜索用时 46 毫秒
141.
LIU Zhongdong* LIU Huihua LUO Peng LIU Peng Xiao Fugang .Grain food college Henan University of Technology Zhengzhou China .Southern Yangtze University Wuxi China 《Chinese Journal of Reactive Polymers》2006,(1)
1. INTRODUCTIONSucrose polyester (SPE) is neither metabolized nor absorbed, it makes no caloric contribution to the diet. Excessive dietary fat intake is associated with increasing risk of obesity, high blood cholesterol, hypertension, coronary heart disease and some types of cancer. At present, fat substitutes are fashionable all over the world. SPE is a new functional fat substitute, which is similar to ordinary oils in physical and chemical properties. In a word, the research and dev… 相似文献
142.
Zhi Hui HE Wen Rui JIN* School of Chemistry Chemical Engineering Shandong University Jinan 《中国化学快报》2002,13(11)
CA15-3 is a circulating antigen that is relatively specific for human breast tissue. CA15-3 is significantly more sensitive than carcinoembryonic antigen in the evaluation of patients with both primary and metastatic breast cancer. CA15-3 levels are often measured by using radioimmunoassay and enzyme immunoassay (EIA) in clinic. These methods are carried out manually. Tedious processes, slow reaction, poor reproducibility are their major problems. Capillary electrophoretic immunoassay … 相似文献
143.
Ye Min LIU Gui Yun XU* Center for Molecular Science Institute of Chemistry Chinese Academy of Sciences Beijing 《中国化学快报》2002,13(11)
Hydroxyethyl starches (HES) have been used medically as plasma volume expanders. They are composed of a starch backbone and substituted hydroxyethyl groups. The backbone is ?(1,4)-glycosidic-linked anhydroglucose units, which has branches formed by ?(1,6)-glycosidic bonds. Hydroxyethylation can take place at the C-2, C-3 and C-6 sites of the glucose rings, as well as at the hydroxyl groups of the substituted hydroxyethyl groups. Variation of the position and quantity of the substituted … 相似文献
144.
采用剪除增加Rosenbluth方法(Pruned-enriched-Rosenbluth method,PERM)算法计算了嫁接于平行板的受限紧密高分子链的末端距分布函数.由于受限紧密高分子链具有各向异性,重点研究了平行板方向x轴上的分布函数P(x),发现P(x)可以表示为ln[P(x)/Pm(x)]/ND-5/3=a0+a1u+a2u2+a3u3(其中u=x/ND-2/3).这里N为链长,Pm(x)为分布函数P(x)的最大值,两平行板的间距为D+1.通过计算P(x)的Shannon熵发现末端距分布函数P(x)的Shannon熵可以用来描述高分子链受限的程度,Shannon熵对平行板间距的变化非常敏感,对于同一链长N,P(x)的Shannon熵会随着D的增大而迅速减小,超过临界值Dc会趋向一个定值,即当D≥Dc时Shannon熵将趋于稳定,也说明了此时受限条件对紧密高分子链影响非常小.同时临界值Dc与链长N有关,Dc~Nλ,其中λ=0.543,并进行了一定的理论分析. 相似文献
145.
Jian GONG Ji Hua YANG Xiu Jun CUI Zhong Min SU Lun Yu QU* Faculty of Chemistry Northeast Normal University Changchun 《中国化学快报》2002,(3)
Polyaniline, especially its acid-dopping composite material, is a kind of important photoelectric material due to its potential application in many fields1~3. However, it seems to be a problem that the polymers exhibit several deficiencies, including chemical and structural imperfections as a result of mislinkage, saturated sites, molecular weight distribution, the presence of the end groups and conformation defects. All of these defects affect the device efficiency and make it difficult to … 相似文献
146.
FANG Xue-dong REN Hui ZHANG Yan * WANG Guan-jun . No. Affiliated Hospital Jilin University Changchun P. R. China . China-Japan Union Hospital Jilin University Changchun P. R. China . No. Affiliated Hospital Jilin University Changchun P. R. China 《高等学校化学研究》2006,22(2):193-196
Introduction Gastriccancerisoneofthemostcommonlyen counteredmalignantdiseasesworldwide,especiallyin AsiaandAfrica[1].Thecombinationofoperation,chemotherapyandradiotherapyisusedfortreatinggas triccarcinoma.However,the5yearsurvivalrateof patientsofgastricca… 相似文献
147.
WEI Xiaolan* & SHEN Peikang State Key Laboratory of Optoelectromic Materials Technologies School of Physics Engineering Sun Yat-Sen University Guangzhou China Department of Applied Chemistry South China University of Technology Guangzhou China. 《中国科学B辑(英文版)》2005,48(6):511-515
Approaches for preparation of porous oxides with different length scales are currently available[1?3]. Materials with hierarchical pore systems at two or three different length scales have also been prepared[4?7]. Such materials are important both for the… 相似文献
148.
Qian Feng WENG Wen Rui JIN* School of Chemistry Chemical Engineering Shandong University Jinan 《中国化学快报》2002,13(10)
Capillary electrophoresis (CE) has become a useful and powerful separation technique and has many applications. Electrochemical detection (ED) has been shown to be one of the most sensitive detection techniques available for use in CE. Dual-electrode detection can expand the applicability of CE-ED1-5, the materials such as gold/mercury1,3, carbon fiber2, Pt4 and Au3,5 have been used for the two electrodes in dual-electrodes. As is well known, the electrochemical response of different c… 相似文献
149.
采用弹性竿模型 (Elasticrodmodel) ,用MonteCarlo方法对DNA分子的构象进行研究 .通过计算发现 ,DNA分子的能量是由弯曲势能EB 和扭转势能ET 两部分组成 ,通常EB 比ET 大一至两个数量级 .同时给出了均方回转半径与链长之间的关系为〈R2g〉 =1 1 69 5 -3 5×n +0 0 2 5×n2 ,它体现了DNA分子结构的特点 .验证了公式Lk=Wr+Tw ,得出Lk与Wr比较接近的结论 ,考虑DNA分子的构型 ,意味着DNA分子容易被弯曲而不易被扭转 ,但随着连接系数的增加 ,DNA被扭转的几率也在增加 .这为分析DNA分子的结构特征提供了一种新方法 相似文献
150.
Man LU Jian Guo FANG Zhong Li LIU Long Min WU* National Laboratory of Applied Organic Chemistry Lanzhou University Lanzhou 《中国化学快报》2002,13(10)
Nitroxides have been found to be the intermediate in the in vivo metabolism of hydroxamic acid, a well-known biological molecule1. Structural modification of some antitumor drugs by introducing nitroxides can lower toxicity remarkably with retention or even increase of the antitumor activity2. Furthermore, the use of nitroxides as spin probes makes it possible to get information regarding the microenvironment of the reaction. 4-Substituted Hantzsch 1,4-dihydropyridines (DHP) are analogs … 相似文献