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251.
Mateusz Barczewski Danuta Matykiewicz Kamila Sałasińska Damian Kozicki Adam Piasecki Katarzyna Skórczewska 《International Journal of Polymer Analysis and Characterization》2019,24(5):447-456
For the purpose of the study, epoxy (EP) composites modified with 5–40?wt% of poly(vinyl chloride) (PVC) powder were manufactured. The influence of PVC powder on the fire behavior of EP-based composites was determined with a UL-94 HB test and cone calorimetry, supplemented by a thermogravimetric analysis. The fire behavior study showed that PVC powder may effectively decrease the flammability of EP in case of at least 20?wt% filler content while composites containing lower amounts of PVC powder (5 and 10?wt%) were characterized with significant improvement in tensile strength without reduction in flammability in reference to the unmodified EP. 相似文献
252.
Christina Schubert Dr. Mateusz Wielopolski Lars‐Hendrik Mewes Dr. Gustavo de Miguel Rojas Dr. Cornelia van der Pol Dr. Kathryn C. Moss Prof. Martin R. Bryce Prof. Jacques E. Moser Prof. Timothy Clark Prof. Dirk M. Guldi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(23):7575-7586
A new series of donor–bridge–acceptor (D–B–A) compounds consisting of π‐conjugated oligofluorene (oFL) bridges between a ferrocene (Fc) electron‐donor and a fullerene (C60) electron‐acceptor have been synthesized. In addition to varying the length of the bridge (i.e., mono‐ and bi‐fluorene derivatives), four different ways of linking ferrocene to the bridge have been examined. The Fc moiety is linked to oFL: 1) directly without any spacer, 2) by an ethynyl linkage, 3) by a vinylene linkage, and 4) by a p‐phenylene unit. The electronic interactions between the electroactive species have been characterized by cyclic voltammetry, absorption, fluorescence, and transient absorption spectroscopy in combination with quantum chemical calculations. The calculations reveal exceptionally close energy‐matching between the Fc and the oFL units, which results in strong electronic‐coupling. Hence, intramolecular charge‐transfer may easily occur upon exciting either the oFLs or Fcs. Photoexcitation of Fc–oFL–C60 conjugates results in transient radical‐ion‐pair states. The mode of linkage of the Fc and FL bridge has a profound effect on the photophysical properties. Whereas intramolecular charge‐separation is found to occur rather independently of the distance, the linker between Fc and oFL acts (at least in oFL) as a bottleneck and significantly impacts the intramolecular charge‐separation rates, resulting in beta values between βCS 0.08 and 0.19 Å?1. In contrast, charge recombination depends strongly on the electron‐donor–acceptor distance, but not at all on the linker. A value of βCR (0.35±0.01 Å?1) was found for all the systems studied. Oligofluorenes prove, therefore, to be excellent bridges for probing how small structural variations affect charge transport in D–B–A systems. 相似文献
253.
Mateusz Marianski Eike Mucha Kim Greis Sooyeon Moon Alonso Pardo Carla Kirschbaum Daniel A. Thomas Gerard Meijer Gert von Helden Kerry Gilmore Peter H. Seeberger Kevin Pagel 《Angewandte Chemie (International ed. in English)》2020,59(15):6166-6171
The stereoselective formation of 1,2‐cis‐glycosidic bonds is challenging. However, 1,2‐cis‐selectivity can be induced by remote participation of C4 or C6 ester groups. Reactions involving remote participation are believed to proceed via a key ionic intermediate, the glycosyl cation. Although mechanistic pathways were postulated many years ago, the structure of the reaction intermediates remained elusive owing to their short‐lived nature. Herein, we unravel the structure of glycosyl cations involved in remote participation reactions via cryogenic vibrational spectroscopy and first principles theory. Acetyl groups at C4 ensure α‐selective galactosylations by forming a covalent bond to the anomeric carbon in dioxolenium‐type ions. Unexpectedly, also benzyl ether protecting groups can engage in remote participation and promote the stereoselective formation of 1,2‐cis‐glycosidic bonds. 相似文献
254.
We apply lattice point counting methods to compute the multiplicities in the plethysm of \(\textit{GL}(n)\). Our approach gives insight into the asymptotic growth of the plethysm and makes the problem amenable to computer algebra. We prove an old conjecture of Howe on the leading term of plethysm. For any partition \(\mu \) of 3, 4, or 5, we obtain an explicit formula in \(\lambda \) and k for the multiplicity of \(S^\lambda \) in \(S^\mu (S^k)\). 相似文献
255.
Jiaxin Li Dr. Janina Kossmann Prof. Ke Zeng Kun Zhang Prof. Bingjie Wang Dr. Christian Weinberger Prof. Markus Antonietti Dr. Mateusz Odziomek Dr. Nieves López-Salas 《Angewandte Chemie (International ed. in English)》2023,62(26):e202217808
Self-templating is a facile strategy for synthesizing porous carbons by direct pyrolysis of organic metal salts. However, the method typically suffers from low yields (<4%) and limited specific surface areas (SSA<2000 m2 g−1) originating from low activity of metal cations (e.g., K+ or Na+) in promoting construction and activation of carbon frameworks. Here we use cesium acetate as the only precursor of oxo-carbons with large SSA of the order of 3000 m2 g−1, pore volume approaching 2 cm3 g−1, tunable oxygen contents, and yields of up to 15 %. We unravel the role of Cs+ as an efficient promoter of framework formation, templating and etching agent, while acetates act as carbon/oxygen sources of carbonaceous frameworks. The oxo-carbons show record-high CO2 uptake of 8.71 mmol g−1 and an ultimate specific capacitance of 313 F g−1 in the supercapacitor. This study helps to understand and rationally tailor the materials design by a still rare organic solid-state chemistry. 相似文献
256.
Mateusz Drach Anna Andrzejewska Jolanta Ciesla Jolanta Narkiewicz-Michałek 《Adsorption》2008,14(4-5):629-638
A theory of cationic dimeric (gemini) surfactant adsorption onto negatively charged surface is presented. In the proposed model it is assumed that the adsorbed phase is a mixture of singly dispersed molecules of surfactant and spherical, globular and cylindrical aggregates of different dimensions. Only the “excluded area” interactions between the adsorbed species are considered and the effects of surface heterogeneity on monomer adsorption are taken into account. The aggregation behavior of gemini surfactants is based on the additive free energy model proposed by Camesano and Nagarajan (2000). The calculated surfactant adsorption isotherms and the differential molar enthalpies of micellisation and adsorption are compared with the experimental results obtained for a series of gemini surfactants depending on the length of a spacer, temperature or the presence of electrolyte. On the basis of theoretical results the evolution of adsorbed phase of gemini surfactants with the increasing adsorption is discussed. It is shown that the evaluated cmc values and the dimensions of surfactant aggregates are in a good agreement with experiment. Unfortunately, the theoretical model does not describe properly the temperature dependence of micellisation process. 相似文献
257.
We present an experimentally realizable stabilized charge pumping scheme in a linear array of Cooper-pair boxes. The system design intrinsically protects the pumping mechanism from severe errors, especially current reversal and spontaneous charge excitation. The quantum Zeno effect is implemented to further diminish pumping errors. The characteristics of this scheme are considered from the perspective of improving the current standard. Such an improvement bears relevance to the closure of the so-called measurement triangle (see [D. Averin, Nature (London) 434, 285 (2005)). 相似文献
258.
A Bifunctional Electrocatalyst for Oxygen Evolution and Oxygen Reduction Reactions in Water 下载免费PDF全文
Prof. Dr. Wolfgang Schöfberger Dipl.‐Ing. Felix Faschinger Samir Chattopadhyay Snehadri Bhakta Biswajit Mondal Prof. Dr. Johannes A. A. W. Elemans Prof. Dr. Stefan Müllegger M. Sc. Stefano Tebi Prof. Dr. Reinhold Koch Priv.‐Doz. Dr. Florian Klappenberger Dipl.‐Chem. Mateusz Paszkiewicz Prof. Dr. Johannes V. Barth Dr. Eva Rauls Hazem Aldahhak Prof. Dr. Wolf Gero Schmidt Prof. Dr. Abhishek Dey 《Angewandte Chemie (International ed. in English)》2016,55(7):2350-2355
Oxygen reduction and water oxidation are two key processes in fuel cell applications. The oxidation of water to dioxygen is a 4 H+/4 e? process, while oxygen can be fully reduced to water by a 4 e?/4 H+ process or partially reduced by fewer electrons to reactive oxygen species such as H2O2 and O2?. We demonstrate that a novel manganese corrole complex behaves as a bifunctional catalyst for both the electrocatalytic generation of dioxygen as well as the reduction of dioxygen in aqueous media. Furthermore, our combined kinetic, spectroscopic, and electrochemical study of manganese corroles adsorbed on different electrode materials (down to a submolecular level) reveals mechanistic details of the oxygen evolution and reduction processes. 相似文献
259.
Dr. Amanda J Welford Dr. John J. Caldwell Dr. Manjuan Liu Meirion Richards Dr. Nathan Brown Dr. Cara Lomas Dr. Graham J. Tizzard Dr. Mateusz B. Pitak Dr. Simon J. Coles Prof. Suzanne A. Eccles Dr. Florence I. Raynaud Prof. Ian Collins 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(16):5657-5664
The 2,11‐cembranoid family of natural products has been used as inspiration for the synthesis of a structurally simplified, functionally diverse library of octahydroisobenzofuran‐based compounds designed to augment a typical medicinal chemistry library screen. Ring‐closing metathesis, lactonisation and SmI2‐mediated methods were exemplified and applied to the installation of a third ring to mimic the nine‐membered ring of the 2,11‐cembranoids. The library was assessed for aqueous solubility and permeability, with a chemical‐space analysis performed for comparison to the family of cembranoid natural products and a sample set of a screening library. Preliminary investigations in cancer cells showed that the simpler scaffolds could recapitulate the reported anti‐migratory activity of the natural products. 相似文献
260.
Dr. Maria A. Palacios Dr. Eufemio Moreno Pineda Dr. Sergio Sanz Dr. Ross Inglis Dr. Mateusz B. Pitak Dr. Simon J. Coles Dr. Marco Evangelisti Prof. Hiroyuki Nojiri Christian Heesing Prof. Euan K. Brechin Prof. Jürgen Schnack Prof. Richard E. P. Winpenny 《Chemphyschem》2016,17(1):55-60
Keplerates are molecules that contain metal polyhedra that describe both Platonic and Archimedean solids; new copper keplerates are reported, with physical studies indicating that even where very high molecular symmetry is found, the low‐temperature physics does not necessarily reflect this symmetry. 相似文献