全文获取类型
收费全文 | 104篇 |
免费 | 4篇 |
国内免费 | 6篇 |
专业分类
化学 | 80篇 |
晶体学 | 2篇 |
力学 | 5篇 |
数学 | 8篇 |
物理学 | 19篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 2篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2016年 | 1篇 |
2015年 | 2篇 |
2014年 | 2篇 |
2013年 | 10篇 |
2012年 | 4篇 |
2011年 | 4篇 |
2010年 | 2篇 |
2009年 | 7篇 |
2008年 | 8篇 |
2007年 | 4篇 |
2006年 | 5篇 |
2005年 | 4篇 |
2004年 | 4篇 |
2003年 | 1篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1988年 | 2篇 |
1986年 | 3篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1979年 | 2篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1969年 | 1篇 |
1967年 | 1篇 |
1948年 | 3篇 |
1944年 | 1篇 |
1941年 | 1篇 |
1935年 | 1篇 |
1934年 | 1篇 |
1932年 | 1篇 |
排序方式: 共有114条查询结果,搜索用时 171 毫秒
91.
92.
Frank Schaper Hans‐Herbert Brintzinger 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(3):e78-e78
Bis(tetrahydroborato)[1,1,2,2‐tetramethyl‐1,2‐ethylenebis(η5‐cyclopentadienyl)]zirconium, (I), was synthesized by the reaction of the zirconocene dichloride with lithium tetrahydroborate. Crystals suitable for X‐ray structure analysis were obtained by recrystallization from toluene. The molecule adopts an appproximate C2v symmetry. Both tetrahydroborate ligands are η2‐coordinated and tilted by 18–19° out of the equatorial plane; the angle B1—Zr1—B2 is 104.7°. The cyclopentadienyl rings show a normal η5‐coordinaton, with a centroid–Zr–centroid angle of 124.3°. 相似文献
93.
Y. Alarie M. Schaper G. D. Nielsen M. H. Abraham 《SAR and QSAR in environmental research》2013,24(3):151-165
Abstract This article describes the possibility of estimating whether or not a mixture of nonreactive volatile organic chemicals (NRVOC) is likely to elicit complaints of sensory irritation in humans. For this estimation we rely on: a) the sensory irritating potency of individual NRVOC can be estimated from a variety of physicochemical properties of these chemicals, b) at low exposure concentrations, the additivity rule can be applied using the potency of each chemical in a mixture and c) a threshold concentration exists below which no sensory irritation will occur. We used this estimating approach and we compared the results obtained with those obtained experimentally in humans exposed to a well defined mixture. The approach presented can be used to arrive at a decision as to whether or not exposure to a mixture of NRVOC is likely to result in sensory irritation complaints by humans, either in the general indoor air situation or for industrial workers. 相似文献
94.
German L. Perlovich Alex M. Ryzhakov Nadezda N. Strakhova Vladimir P. Kazachenko Klaus-Jürgen Schaper Oleg A. Raevsky 《The Journal of chemical thermodynamics》2011,43(5):683-689
The thermodynamic aspects of sublimation processes of three sulfonamides with the general structures C6H5–SO2NH–C6H4–R (R = 4-NO2) and 4-NH2–C6H4–SO2NH–C6H4–R (R = 4-NO2; 4-CN) were studied by investigating the temperature dependence of vapor pressure using the transpiration method. These data together with those obtained earlier for C6H5–SO2NH–C6H4–R (R = 4-Cl) and 4-NH2–C6H4–SO2NH–C6H4–R (R = 4-Cl; 4-OMe; 4-C2H5) were analyzed and compared. A correlation was derived between sublimation Gibbs free energies and the sum of H-bond acceptor factors of the molecules. Solubility processes of the compounds in water, phosphate buffer with pH 7.4 and n-octanol (as phases modeling various drug delivery pathways) were investigated and corresponding thermodynamic functions were calculated as well. Thermodynamic characteristics of the sulfonamides solvation were evaluated. Also in this case a correlation between solubility/solvation Gibbs free energy values and the sum of H-bond acceptor factors was observed. For the sulfonamides with various substituents at para-position the processes of transfer from one solvent (water or buffer) to n-octanol were studied by a diagram method combined with analysis of enthalpic and entropic terms. Distinguishing between enthalpy and entropy, as is possible through the present approach, leads to the insight that the contribution of these terms is different for different molecules (entropy- or enthalpy-determined). Thus, in contrast to the interpretation of only the Gibbs free energy of transfer (extensively used for pharmaceuticals in the form of the partition coefficient, log P), the analysis of thermodynamic functions of the transfer process provides additional mechanistic information. This may be important for further evaluation of the physiological distribution of drug molecules and may provide a better understanding of biopharmaceutical properties of drugs. 相似文献
95.
Agullo J Canesi S Schaper F Morin M Bélanger D 《Langmuir : the ACS journal of surfaces and colloids》2012,28(10):4889-4895
The in situ generation of 3-diazonium cations from 3-aminopyridine and their subsequent stability under experimental conditions used for electrografting of pyridine groups were investigated by spectroscopy and electrochemistry. UV spectroscopy revealed the rapid kinetics for the reaction of 3-aminopyridine with sodium nitrite in HCl to form the 3-diazopyridinium cation with a second-order rate constant of 550 ± 20 L mol(-1) s(-1) at 22 °C. UV spectroscopy showed that the 3-diazopyridinium ion was relatively unstable and its transformation into 3-hydroxypyridine was proven by (1)H NMR. Its hydrolytic decomposition was investigated by NMR and followed first-order kinetics with a rate constant of (53 ± 5) × 10(-3) s(-1) at 22 °C. These results enable us to establish the appropriate conditions for the electrografting of pyridine from the corresponding diazonium cations generated in situ. The electrochemical modification of glassy carbon electrodes with pyridine was characterized by cyclic voltammetry and the resulting grafted layer by electrochemical impedance spectroscopy in the presence of Fe(CN)(6)(3-/4-) as redox probes. The effect of diazotization time before electrochemical reduction on the blocking effect of the grafted layer was investigated and showed that an increase of the diazotization time led to less efficient grafting. The presence of immobilized pyridine on the electrode surface was demonstrated by X-ray photoelectron spectroscopy measurements, and a surface coverage of 8.8 × 10(-10) mol cm(-2) was estimated for the grafted pyridine groups. The significance of these results for researchers using the in situ generation approach for electrochemical and chemical grafting is discussed. 相似文献
96.
97.
98.
Wu A Jia Z Schaper A Noll F Hampp NA 《Langmuir : the ACS journal of surfaces and colloids》2006,22(12):5213-5216
Self-organization of membrane-embedded peptides and proteins causes the formation of lipid mesostructures in the membranes. One example is purple membranes (PM), which consist of lipids and bacteriorhodopsin (BR) as the only protein component. The BRs form a hexagonal crystalline lattice. A complementary structure is formed by the lipids. Employing BR and PM as an example, we report a method where major parts of the mesoscopic self-assembled protein structures can be extracted from the lipid bilayer membrane. A complementary lipid nanostructure remains on the substrate. To remove such a large number of thiolated proteins simultaneously by applying a mechanical force, they are first reacted at physiological conditions with gold nanoparticles, and then a thin gold film is sputtered onto them that fuses with the gold nanoparticles forming a uniform layer, which finally can be lifted off. In this step, all of the previously gold-labeled proteins are pulled out of the membrane simultaneously. A stable lipid nanostructure is obtained on the mica substrate. Its stability is due to either binding of the lipids to the substrate through ionic bonds or to enough residual proteins to stabilize the lipid nanostructure against reorganization. This method may be applied easily and efficiently wherever thiolated proteins or peptides are employed as self-assembling and structure-inducing units in lipid membranes. 相似文献
99.
With an improved Maier-Leibnitz collision chamber absolute values of the total excitation cross sections of the rare gases were measured. The half width of energy distribution in the beam of exciting electrons was approximately 0.7 eV. The results for He and Ne are in reasonable agreement with the excitation functions given by Maier-Leibnitz, if some necessary corrections (especially with regard to contact potentials) are made. Only the cross sections obtained by us are a little smaller. Furthermore the better fine structure yielded more favourable possibilities of comparison with other measurements published so far. The error should not be greater than 30%. 相似文献
100.