全文获取类型
收费全文 | 241篇 |
免费 | 10篇 |
专业分类
化学 | 181篇 |
晶体学 | 21篇 |
力学 | 1篇 |
数学 | 10篇 |
物理学 | 38篇 |
出版年
2022年 | 1篇 |
2017年 | 1篇 |
2016年 | 2篇 |
2015年 | 10篇 |
2014年 | 8篇 |
2013年 | 10篇 |
2012年 | 6篇 |
2011年 | 6篇 |
2010年 | 6篇 |
2009年 | 2篇 |
2008年 | 8篇 |
2007年 | 8篇 |
2006年 | 13篇 |
2005年 | 11篇 |
2004年 | 15篇 |
2003年 | 11篇 |
2002年 | 9篇 |
2001年 | 5篇 |
2000年 | 13篇 |
1999年 | 7篇 |
1998年 | 11篇 |
1997年 | 5篇 |
1996年 | 11篇 |
1995年 | 8篇 |
1994年 | 8篇 |
1993年 | 7篇 |
1992年 | 6篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 7篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1976年 | 2篇 |
1974年 | 1篇 |
1973年 | 2篇 |
排序方式: 共有251条查询结果,搜索用时 812 毫秒
161.
162.
Antonius T. M. Marcelis Arie Koudijs Enno A. Klop Ernst J. R. Sudhölter 《Liquid crystals》2013,40(6):881-887
The smectic properties of four series of dimer liquid crystals containing cholesteryl and biphenylyl groups were investigated by polarization microscopy, DSC and X-ray diffraction. Compounds that contain the strongly dipolar cyanobiphenylyl group exhibit a smectic layer spacing that is about 1.7 times the length of the molecule. Three series of alkoxybiphenylylcontaining dimers exhibit two other smectic modifications. For short spacers, a smectic layer spacing is observed that is about the same length as the molecule and for long spacers the smectic layer spacing is about half the length of the molecule. In the latter cases the entropy change at the SmA-N* transition is clearly larger than for the compounds with the other smectic modifications. One or two compounds in each alkoxybiphenylyl-containing series, that have similar spacer length and terminal group length and have an odd number of flexible units in the spacer, exhibit only a chiral nematic phase, and no smectic phase. 相似文献
163.
Willemen HM Marcelis AT Sudhölter EJ Bouwman WG Demé B Terech P 《Langmuir : the ACS journal of surfaces and colloids》2004,20(6):2075-2080
Small-angle neutron scattering measurements were performed on some cholic acid-based gel systems in order to gain detailed information about the network structure. The presence of thin fibers with a radius of about 10-20 A was found for various gelators. Two types of interaction between different sorts of fibers were demonstrated, depending on the molecular structure of the gelator. The first type involves the presence of microcrystalline knots with a dimension of about 100-200 A between the fibers. Upon heating, this network gradually disintegrates. The second type involves loose entanglements between flattened fibers. The occurrence of these types of interaction is related to the length of the alkyl tail attached to cholic acid. 相似文献
164.
Rainbow techniques permit measurement of refractive indices, and hence the temperatures of liquid droplets through determination of the absolute angular position of a rainbow interference image in space. The Airy theory, which is commonly used to explain the rainbow effect, permits the determination of a unique refractive-index value, even in the presence of nonuniformities in the droplet. An extension of this theory to spheres that exhibit internal refractive-index gradients is proposed. The case of burning droplets is considered as an example of such spheres, and the results obtained are successfully compared with those presented in the literature. 相似文献
165.
Background
Although octopamine has long been known to have major roles as both transmitter and modulator in arthropods, it has only recently been shown to be functionally important in molluscs, playing a role as a neurotransmitter in the feeding network of the snail Lymnaea stagnalis. The synaptic potentials cannot explain all the effects of octopamine-containing neurons on the feeding network, and here we test the hypothesis that octopamine is also a neuromodulator. 相似文献166.
167.
168.
Background
Intermolecular autophosphorylation at Tyr416 is a conserved mechanism of activation among the members of the Src family of nonreceptor tyrosine kinases. Like several other tyrosine kinases, Src can catalyze the thiophosphorylation of peptide and protein substrates using ATPγS as a thiophosphodonor, although the efficiency of the reaction is low.Results
Here, we have characterized the ability of Src to auto-thiophosphorylate. Auto-thiophosphorylation of Src at Tyr416 in the activation loop proceeds efficiently in the presence of Ni2+, resulting in kinase activation. Other tyrosine kinases (Ack1, Hck, and IGF1 receptor) also auto-thiophosphorylate in the presence of Ni2+. Tyr416-thiophosphorylated Src is resistant to dephosphorylation by PTP1B phosphatase.Conclusions
Src and other tyrosine kinases catalyze auto-thiophosphorylation in the presence of Ni2+. Thiophosphorylation of Src occurs at Tyr416 in the activation loop, and results in enhanced kinase activity. Tyr416-thiophosphorylated Src could serve as a stable, persistently-activated mimic of Src.169.
Prof. Dr. Antonius Kettrup Manfred Grote Jürgen Hartmann 《Monatshefte für Chemie / Chemical Monthly》1976,107(6):1391-1411
The mass, IR- and NMR-spectra of 18 compounds were interpreted; one of these compounds has been15N-labelled.Fragmentation processes give evidence that azo- and hydrazone-tautomeres are present in the gaseous state. IR-and NMR-spectroscopic investigations show, that the phenyl-hydrazones as solids and in solution exist as bis chelated (Z)-isomers only. An approximately linear relationship is given between the chemical shifts of NH-Protons and pK
B-and Hammett -values resp.
Mit 5 Abbildungen
M. Grote, Dissertation, Ruhr-Universität Bochum, 1975. 相似文献
Mit 5 Abbildungen
M. Grote, Dissertation, Ruhr-Universität Bochum, 1975. 相似文献
170.
Ping G Zhang L Zhang L Zhang W Schmitt-Kopplin P Kettrup A Zhang Y 《Journal of chromatography. A》2004,1035(2):265-270
Methacrylate-based monolithic columns with electroosmotic flow (EOF) or very weak EOF are prepared by in situ copolymerization in the presence of a porogen in fused-silica capillaries pretreated with a bifunctional reagent. Satisfactory separations of acidic and basic compounds on the column with EOF at either low or high pH are achieved, respectively. With sulfonic groups as dissociation functionalities, sufficient EOF mobility still remains as high as 1.74 x 10(-4) cm2 s(-1) V(-1) at low pH. Under this condition, seven acidic compounds are readily separated within 5.7 min. Moreover, at high pH, the peak shape of basic compounds is satisfactory without addition of any masking amines into running mobile phase since the secondary interaction between the basic compounds and the monolithic stationary phase are minimized at high pH. Reversed-phase mechanism for both acidic and basic compounds is observed under investigated separation conditions. In addition, possibilities of acidic and basic compound separations on a monolithic column with extremely low EOF are discussed. 相似文献