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排序方式: 共有313条查询结果,搜索用时 22 毫秒
1.
Dr. Josh Abbenseth Dr. Florian Wätjen Dr. Markus Finger Prof. Dr. Sven Schneider 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(52):23780-23784
The utilization of monomeric, lower phosphorous oxides and oxoanions, such as metaphosphite (PO2−), which is the heavier homologue of the common nitrite anion but previously only observed in the gas phase and by matrix isolation, requires new synthetic strategies. Herein, a series of rhenium(I–III) complexes with PO2− as ligand is reported. Synthetic access was enabled by selective oxygenation of a terminal phosphide complex. Spectroscopic and computational examination revealed slightly stronger σ-donor and comparable π-acceptor properties of PO2− compared to homologous NO2−, which is one of the archetypal ligands in coordination chemistry. 相似文献
2.
Dr. Youai Qiu Alexej Scheremetjew Dr. Lars H. Finger Prof. Dr. Lutz Ackermann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(15):3241-3246
Electrophotochemistry has enabled arene C−H trifluoromethylation with the Langlois reagent CF3SO2Na under mild reaction conditions. The merger of electrosynthesis and photoredox catalysis provided a chemical oxidant-free approach for the generation of the CF3 radical. The electrophotochemistry was carried out in an operationally simple manner, setting the stage for challenging C−H trifluoromethylations of unactivated arenes and heteroarenes. The robust nature of the electrophotochemical manifold was reflected by a wide scope, including electron-rich and electron-deficient benzenes, as well as naturally occurring heteroarenes. Electrophotochemical C−H trifluoromethylation was further achieved in flow with a modular electro-flow-cell equipped with an in-operando monitoring unit for on-line flow-NMR spectroscopy, providing support for the single electron transfer processes. 相似文献
3.
4.
Martin Schels Stefan Scherer Michael Glodek Hans A. Kestler Günther Palm Friedhelm Schwenker 《Computational Statistics》2013,28(1):5-18
One way to tackle brain computer interfaces is to consider event related potentials in electroencephalography, like the well established P300 phenomenon. In this paper a multiple classifier approach to discover these events in the bioelectrical signal and with them whether or not a subject has recognized a particular pattern, is employed. Dealing with noisy data as well as heavily imbalanced target class distributions are among the difficulties encountered. Our approach utilizes partitions of electrodes to create robust and meaningful individual classifiers, which are then subsequently combined using decision fusion. Furthermore, a classifier selection approach using genetic algorithms is evaluated and used for optimization. The proposed approach utilizing information fusion shows promising results (over 0.8 area under the ROC curve). 相似文献
5.
Cover Picture: Nanoimprint texturing of transparent flexible substrates for improved light management in thin‐film solar cells (Phys. Status Solidi RRL 4/2015) 下载免费PDF全文
6.
Elisabeth Siebert Marius Horch Yvonne Rippers Johannes Fritsch Stefan Frielingsdorf Oliver Lenz Francisco VelazquezEscobar Friedrich Siebert Lars Paasche Uwe Kuhlmann Friedhelm Lendzian Maria‐Andrea Mroginski Ingo Zebger Peter Hildebrandt 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2013,125(19):5267-5270
7.
Long Yang Ralf Steinbock Alexej Scheremetjew Rositha Kuniyil Lars H. Finger Antonis M. Messinis Lutz Ackermann 《Angewandte Chemie (International ed. in English)》2020,59(27):11130-11135
A ruthenium‐catalyzed electrochemical dehydrogenative annulation reaction of imidazoles with alkynes has been established, enabling the preparation of various bridgehead N‐fused [5,6]‐bicyclic heteroarenes through regioselective electrochemical C?H/N?H annulation without chemical metal oxidants. Novel azaruthenabicyclo[3.2.0]heptadienes were fully characterized and identified as key intermediates. Mechanistic studies are suggestive of an oxidatively induced reductive elimination pathway within a ruthenium(II/III) regime. 相似文献
8.
This paper presents a postprocessing technique for estimating the local regularity of numerical solutions in high-resolution finite element schemes. A derivative of degree p ≥ 0 is considered to be smooth if a discontinuous linear reconstruction does not create new maxima or minima. The intended use of this criterion is the identification of smooth cells in the context of p-adaptation or selective flux limiting. As a model problem, we consider a 2D convection equation discretized with bilinear finite elements. The discrete maximum principle is enforced using a linearized flux-corrected transport algorithm. The deactivation of the flux limiter in regions of high regularity makes it possible to avoid the peak clipping effect at smooth extrema without generating spurious undershoots or overshoots elsewhere. 相似文献
9.
Measurements of microwave attenuation at room temperature and 4.2 K have been performed on some conductors commonly used in
receiver input circuits. The reduction in loss on cooling is substantial, particularly for copper and plated gold, both of
which showed a factor of 3 loss reduction. Copper passivated with benzotriazole shows the same loss as without passivation.
The residual resistivity ratio between room temperature and 4.2 K, deduced from the measurements using the classical skin
effect formula, was smaller than the measured DC value to a degree consistent with conduction in the extreme anomalous skin
effect regime at cryogenic temperatures. The measurements were made in the 5–10 GHz range. The materials tested were: aluminum
alloys 1100-T6 and 6061-O, C101 copper, benzotriazole treated C101 copper, and brass plated with electroformed copper, Pur-A-Gold
125-Au soft gold, and BDT200 bright gold. 相似文献
10.
Nathanaëlle Schneider Dr. Markus Finger Dr. Christian Haferkemper Stéphane Bellemin‐Laponnaz Dr. Peter Hofmann Prof. Dr. Lutz H. Gade Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(43):11515-11529
A detailed density functional theory (DFT) computational study (using the BP86/SV(P) and B3LYP/TZVP//BP86/SV(P) level of theory) of the rhodium‐catalyzed hydrosilylation of ketones has shown three mechanistic pathways to be viable. They all involve the generation of a cationic complex [LnRhI]+ stabilized by the coordination of two ketone molecules and the subsequent oxidative addition of the silane, which results in the Rh–silyl intermediates [LnRhIII(H)SiHMe2]+. However, they differ in the following reaction steps: in two of them, insertion of the ketone into the Rh? Si bond occurs, as previously proposed by Ojima et al., or into the Si? H bond, as proposed by Chan et al. for dihydrosilanes. The latter in particular is characterized by a very high activation barrier associated with the insertion of the ketone into the Si? H bond, thereby making a new, third mechanistic pathway that involves the formation of a silylene intermediate more likely. This “silylene mechanism” was found to have the lowest activation barrier for the rate‐determining step, the migration of a rhodium‐bonded hydride to the ketone that is coordinated to the silylene ligand. This explains the previously reported rate enhancement for R2SiH2 compared to R3SiH as well as the inverse kinetic isotope effect (KIE) observed experimentally for the overall catalytic cycle because deuterium prefers to be located in the stronger bond, that is, C? D versus M? D. 相似文献