全文获取类型
收费全文 | 116篇 |
免费 | 2篇 |
专业分类
化学 | 61篇 |
力学 | 14篇 |
数学 | 12篇 |
物理学 | 31篇 |
出版年
2022年 | 2篇 |
2021年 | 2篇 |
2020年 | 7篇 |
2019年 | 2篇 |
2018年 | 2篇 |
2017年 | 4篇 |
2016年 | 3篇 |
2015年 | 3篇 |
2014年 | 2篇 |
2013年 | 4篇 |
2012年 | 3篇 |
2011年 | 3篇 |
2010年 | 6篇 |
2009年 | 4篇 |
2008年 | 9篇 |
2007年 | 5篇 |
2006年 | 7篇 |
2005年 | 6篇 |
2004年 | 4篇 |
2003年 | 4篇 |
2002年 | 4篇 |
2001年 | 5篇 |
2000年 | 4篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1984年 | 1篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1933年 | 1篇 |
1927年 | 2篇 |
1925年 | 1篇 |
1912年 | 1篇 |
排序方式: 共有118条查询结果,搜索用时 265 毫秒
61.
Amaury De Cattelle Arne Billen Ward Brullot Thierry Verbiest Guy Koeckelberghs 《应用有机金属化学》2020,34(7):e5648
Palladium functionalized gold nanoparticles were used in the past as a catalyst system in light induced cross-coupling reactions, but with a main limitation of the recuperation. To overcome this problem, a palladium functionalized Fe3O4/Au core-shell nanoparticle was successfully synthesized with a peak wavelength of 680 nm from the plasmon resonance of the gold shell. By the presence of the magnetite core, the nanoparticle catalyst can easily be removed using magnetic precipitation. This is accompanied with the advantage of having less valuable gold present in the system. The gold shell makes it possible to induce local heating using plasmon resonance. By this combination, it is possible to recuperate the catalyst system using magnetic precipitation and increase the control and safety of the reaction due to the presence of the light-induced plasmonic heating. It was possible to perform light-induced Suzuki cross-coupling reactions using this catalyst system, but with a dependency of the substrate. It was found that an anionic substrate is repulsed from the negatively charged core-shell nanoparticle. The catalyst was examined on its recuperation abilities and could be reused up to 5 cycles. At the catalytic site a temperature was reached between 40 °C and 45 °C. Despite the promising results of the Suzuki reaction, it was not possible to perform light-induced Sonogashira reactions due to the insufficient heat generation at the catalytic site. Nevertheless, these results are promising in the development of an easily recyclable catalyst together with an alternative heating source, resulting in an increase of control and safety. 相似文献
62.
Marvin Mendel Indrek Kalvet Daniel Hupperich Guillaume Magnin Franziska Schoenebeck 《Angewandte Chemie (International ed. in English)》2020,59(5):2115-2119
Since 2014, the interest in aryl fluorosulfates (ArOSO2F) as well as their implementation in powerful applications has continuously grown. In this context, the enabling capability of ArOSO2F will strongly depend on the substitution pattern of the arene, which ultimately dictates its overall function as drug candidate, material, or bio‐linker. This report showcases the modular, substrate‐independent, and fully predictable, selective functionalization of polysubstituted arenes bearing C?OSO2F, C?Br, and C?Cl sites, which makes it possible to diversify the arene in the presence of OSO2F or utilize OSO2F as a triflate surrogate. Sequential and triply selective arylations and alkylations were realized within minutes at room temperature, using a single and air‐stable PdI dimer. 相似文献
63.
L. Magnin 《Algebras and Representation Theory》2010,13(6):723-753
For any complex 6-dimensional nilpotent Lie algebra
\mathfrakg,\mathfrak{g}, we compute the strain of all indecomposable 7-dimensional nilpotent Lie algebras which contain
\mathfrakg\mathfrak{g} by the adjoining a derivation method. We get a new determination of all 7-dimensional complex nilpotent Lie algebras, allowing
to check earlier results (some contain errors), along with a cross table intertwining nilpotent 6- and 7-dimensional Lie algebras. 相似文献
64.
Palladium-catalyzed microwave-assisted amination of 1-bromonaphthalenes and 5- and 8-bromoquinolines
[reaction: see text] 1-Aminonaphthalenes and 5- and 8-aminoquinolines were rapidly prepared from the respective aryl bromides in good yields by Pd-catalyzed aryl amination under microwave conditions. Consistent improvements in yields over those obtained under standard conditions were seen with quinoline substrates. In the cases where 5-bromo-8-cyanoquinoline was used as a substrate, no desired products were obtained under standard conditions with a number of different primary and secondary amines. However, microwave conditions provided the desired products in good to excellent yields. 相似文献
65.
This article considers the rheometric properties of mixtures containing a micron-sized mineral filler of calcium carbonate (CaCO3) in a polymer matrix gelled by adding colloidal silica (CS). These mixtures, consisting of a polymer matrix (polyols, catalysts, surfactant) are used to produce polyurethane foams. The suspending phase (polymer matrix/CS) has a yield stress that has been linked to fractal aggregation of the colloidal filler. Suspensions without any colloidal silica (polymer matrix/CaCO3), show aggregation of CaCO3 which is most probably due to the adsorption of catalysts present in the polymer matrix. Beyond a critical CaCO3 volume fraction, a yield stress is detected indicating a 3D connected structure. In the case of suspensions containing colloidal silica (polymer matrix/CaCO3/SC), the yield stress is due to a combination of the fractal network formed by the colloidal silica and aggregation of the micron-sized particles of CaCO3. 相似文献
66.
67.
Indrek Kalvet Guillaume Magnin Prof. Dr. Franziska Schoenebeck 《Angewandte Chemie (International ed. in English)》2017,56(6):1581-1585
While chemoselectivities in Pd0‐catalyzed coupling reactions are frequently non‐intuitive and a result of a complex interplay of ligand/catalyst, substrate, and reaction conditions, we herein report a general method based on PdI that allows for an a priori predictable chemoselective C −C coupling at C−Br in preference to C−OTf and C−Cl bonds, regardless of the electronic or steric bias of the substrate. The C−C bond formations are extremely rapid (<5 min at RT) and are catalyzed by an air‐ and moisture‐stable PdI dimer under open‐flask conditions. 相似文献
68.
69.
Romulo D. A. Andrade Elaine A. Faria Amaury M. Silva Wandallas C. Araujo Gustavo C. Jaime Kenia P. Costa Alexandre G. S. Prado 《Journal of Thermal Analysis and Calorimetry》2011,106(2):469-474
The Brazilian government has presented a biofuel program, which aims the addition of 2% of biofuel in fossil diesel in 2008
and 5% up to 2013. Thus, the knowledge of heat of combustion of biofuel/diesel blends is necessary. The biodiesel was produced
by transesterification of soybean oil with a yield of 87%. The diesel-like was obtained by pyrolysis of soybean oil. This
biofuel presented all parameters according to ANP. The obtained heats of combustion were 41.36 ± 0.17; 38.70 ± 0.16; and 36.71 ± 0.17 MJ/kg
for diesel, diesel-like and biodiesel, respectively. The results show that the heats of combustion of biofuels are approximately
17% smaller than fossil diesel. The obtained data also show that the heats of combustion depend on the methodology used for
the biofuel production. Addition of biofuels to traditional diesel fuel results in a linear decreasing of the heat of combustion
with the amount of the alternative fuel added to the diesel. 相似文献
70.
Elia Liitiäinen Amaury Lendasse Francesco Corona 《Random Structures and Algorithms》2010,37(2):223-247
In this article, the moments of nearest neighbor distance distributions are examined. While the asymptotic form of such moments is well‐known, the boundary effect has this far resisted a rigorous analysis. Our goal is to develop a new technique that allows a closed‐form high order expansion, where the boundaries are taken into account up to the first order. The resulting theoretical predictions are tested via simulations and found to be much more accurate than the first order approximation obtained by neglecting the boundaries. While our results are of theoretical interest, they definitely also have important applications in statistics and physics. As a concrete example, we mention estimating Rényi entropies of probability distributions. Moreover, the algebraic technique developed may turn out to be useful in other, related problems including estimation of the Shannon differential entropy.© 2010 Wiley Periodicals, Inc. Random Struct. Alg., 2010 相似文献