全文获取类型
收费全文 | 121篇 |
免费 | 18篇 |
国内免费 | 20篇 |
专业分类
化学 | 78篇 |
晶体学 | 1篇 |
力学 | 1篇 |
数学 | 22篇 |
物理学 | 57篇 |
出版年
2018年 | 1篇 |
2017年 | 1篇 |
2016年 | 3篇 |
2015年 | 3篇 |
2013年 | 6篇 |
2012年 | 10篇 |
2011年 | 4篇 |
2010年 | 4篇 |
2009年 | 7篇 |
2008年 | 6篇 |
2007年 | 1篇 |
2006年 | 4篇 |
2005年 | 3篇 |
2004年 | 7篇 |
2003年 | 13篇 |
2002年 | 13篇 |
2001年 | 9篇 |
2000年 | 10篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 6篇 |
1996年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1967年 | 1篇 |
1938年 | 1篇 |
1932年 | 1篇 |
1930年 | 2篇 |
1926年 | 1篇 |
1907年 | 1篇 |
排序方式: 共有159条查询结果,搜索用时 921 毫秒
1.
2.
Detlef Gabel Claudia Bauer Mohamed E. El-Zaria Afaf R. Genady Udo Drfler 《Journal of organometallic chemistry》2003,680(1-2):23-26
The preparation and properties of the R1R2NH---B8H11NHR cluster are described. The cluster is stable to aqueous solutions and can be made water-soluble by the introduction of a few hydrophilic groups. This makes the cluster a good candidate as the boron moiety in compounds for boron neutron capture therapy. The chemistry of the cluster preparation, the stability of the cluster, and conditions for reactions of the organic moieties are reviewed. Pyridine derivatives of the cluster show electronic interaction between the cluster and the pyridine. 相似文献
3.
S. G. Yunusova S. D. Gusakova A. I. Glushenkova U. K. Nadzhimov Sh. Turabekov SA. Musaev 《Chemistry of Natural Compounds》1991,27(2):147-150
A comparative analysis has been made of the amounts of lipids and their fatty-acid compositions in the seeds of the lines of agenetic collection of cotton plants of the speciesGossypium hirsutum and their hybrids and the variety Tashkent-1. The results obtained on the fatty-acid compositions of some hybrids make it possible to recommend the use of individual lines of cotton plants as donors for improving the food-value indices of cottonseed oil.Institute of Chemsitry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. V. I. Lenin Tashkent State University. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 173–176, March–April, 1991. 相似文献
4.
The syntheses, solid state structures, and spectral properties of O-alkyl and O-acyl derivatives of hydroxoundecahydro-closo-dodecaborate(2-), 1, are described. Alkylation of 1 with ethyl iodide was achieved in dimethyl sulfoxide using potassium hydroxide as a base, leading to [N(n-C(4)H(9))(4)](2)[CH(3)CH(2)O-B(12)H(11)(2-)], 2, bis(tetrabutylammonium) ethoxyundecahydro-closo-dodecaborate(2-) [monoclinic P2(1)/n, a = 1192.4(9) pm, b = 1253.9(4) pm, c = 3049.1(10) pm, beta = 92.69(4) degrees, Z = 4, R1 = 0.0693, wR(2) = 0.1517]. Alkylation with 1,5-dibromopentane afforded the cyclic oxonium salt [PPN][C(5)H(10)O-B(12)H(11)(1-)], 3, (&mgr;-nitrido)bis(triphenylphosphorus)(1+) tetrahydropyrane-undecahydro-closo-dodecaborate(1-) [monoclinic P2(1)/c, a = 1938.1(2) pm, b = 1329.7(10) pm, c = 1944.0(2) pm, beta = 108.82(10) degrees, Z = 4, R1 = 0.0484, wR(2) = 0.0833]. Acylation of 1 in acetonitrile with acyl chlorides in the presence of pyridine yielded [N(n-C(4)H(9))(4)](2)[C(6)H(5)CO(2)-B(12)H(11)(2-)], 4, bis(tetrabutylammonium) undecahydrobenzoyl-closo-dodecaborate(2-) [monoclinic P2(1)/c, a = 1812.0(4) pm, b = 1711.9(3) pm, c = 1685.0(3) pm, beta = 114.03(3) degrees, Z = 4, R1 = 0.0915, wR(2) = 0.2093], and [N(n-C(4)H(9))(4)](2)[CH(3)CO(2)-B(12)H(11)(2-)], 5, bis(tetrabutylammonium) acetoxyundecahydro-closo-dodecaborate(2-) [monoclinic P2(1)/n, a = 1190.5(2) pm, b = 1243.0(10) pm, c = 3078.4(4) pm, beta = 92.76(10) degrees, Z = 4, R1 = 0.0642, wR(2) = 0.1462]. All crystal structures showed distortion of the pseudoicosahedral geometry of the boron cluster. The boron-oxygen distances varied from 144.2(5) pm for 2, 148.5(3) pm for 5, 149.4(12) pm for 4, to 152.8(4) pm for 3. The 3-fold coordinated oxygen of oxonium salt 3 is nearly planar. 相似文献
5.
Ohne Zusammenfassung 相似文献
6.
Xiangli Liu Ping Fan Ming Chen Hossam Hefesha GerhardK.E. Scriba Detlef Gabel Alfred Fahr 《Helvetica chimica acta》2010,93(2):203-211
The objective of this study was to investigate drug–membrane interaction by immobilized liposome chromatography (ILC; expressed as lipophilicity index log Ks) and the comparison with lipophilicity indices obtained by liposome/H2O, octan‐1‐ol/H2O, and immobilized artificial membrane (IAM) systems. A set of structurally diverse monofunctional compounds and drugs (nonsteroidal anti‐inflammatory drugs and β‐blockers) were selected in this study. This set of solutes consists of basic or acidic functionalities which are positively or negatively charged at physiological pH 7.4. No correlation was found between log Ks from ILC and lipophilicity indices from any of the other membrane model systems for the whole set of compounds. For structurally related compounds, significant correlations could be established between log Ks from ILC and lipophilicity indices from IAM chromatography and octan‐1‐ol/H2O. However, ILC and liposome/H2O systems only yield parallel partitioning information for structurally related large molecules. For hydrophilic compounds, the balance between electrostatic and hydrophobic interactions dominating drug partitioning is different in these two systems. 相似文献
7.
利用溶液聚合和成酰胺反应合成了多功能梳状两亲性共聚物,聚(甲基丙烯酸-co-甲基丙烯酸十八酯)-(乙醇胺-乙二胺叶酸)(PSM-EE-FA).用红外光谱(FTIR),核磁共振(1H-NMR)及凝胶渗透色谱(GPC)表征了该聚合物的结构及分子量分布.实验结果证明合成了该聚合物,其数均分子量(Mn)为28600,多分散性为1.375.用该两亲梳状聚合物包覆油溶性CdSe/ZnS量子点,通过相转移作用,得到水溶性靶向量子点(PSM-EE-FA-QDs).该水溶性量子点溶液具有较好的稳定性.通过紫外-可见(UV-Vis)及荧光发射光谱分析对该量子点的光学性质进行研究.结果表明,PSM-EE-FA-QDs的紫外-可见光谱及荧光发射光谱峰形与原量子点基本一致.由于量子点表面聚合物层的形成,峰位发生少量红移.该量子点水溶液的荧光强度是原量子点氯仿溶液的98%,荧光产率是原量子点氯仿溶液的95%.动态光散射(DLS)及透射电镜(TEM)测试结果表明水溶性量子点分布均匀.合成的水溶性量子点不但光学性能稳定,而且聚合物及水溶性量子点的合成方法较为简便. 相似文献
8.
9.
10.
以LCD为目标的自动定焦判据选择 总被引:2,自引:0,他引:2
在光学综合自动测量中 ,使用液晶显示屏作为分划板可以大大简化结构 ,提高效率 ,真正地实现自动测量。由于液晶显示具有对比度低、噪声大等特点 ,所以根据液晶的这些特点以及图像处理和CCD信号接收的特点选择两种适用的判据进行了分析和试验比较 ,并给出了结果。结果表明 ,这两种判别函数都适用于以液晶显示屏为目标和用图像处理方法进行光学参数测量的系统 ,其中锐度判别函数更优于信息熵判别函数 ,前者具有更好的抗干扰性和稳定性 ,而且其判定结果更接近目视清晰度判别 相似文献