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排序方式: 共有517条查询结果,搜索用时 15 毫秒
511.
Wilm Pickhardt Eleonora Siegfried Dr. Sven Fabig Marisol Fabienne Rappen Dr. Martin Etter Maximilian Wohlgemuth Dr. Sven Grätz Prof. Dr. Lars Borchardt 《Angewandte Chemie (International ed. in English)》2023,62(27):e202301490
Utilizing direct mechanocatalytical conditions, the Sonogashira coupling was successfully performed on the surface of milling tools by using pure Pd and Pd coated steel balls. The optimization of co-catalyst forming additives led to a protocol, which generates quantitative yields under aerobic conditions for various substrates within as little as 90 minutes. Using state-of-the-art spectroscopic, diffractive, as well as in situ methods lead to the identification of a previously unknown and highly reactive complex of the co-catalyst copper. This new complex differs substantially from the known complexes in liquid phase Sonogashira couplings, proving that reaction pathways in mechanochemistry may differ from those in established synthetic procedures. 相似文献
512.
513.
Tiago F. T. Cerqueira Sun Lin Maximilian Amsler Stefan Goedecker Silvana Botti Miguel A. L. Marques 《ChemInform》2015,46(38):no-no
Ab initio global structural prediction and specifically, the minima hopping method combined with high‐throughput calculations are used to explore the periodic table in search of novel oxide phases. 相似文献
514.
Maximilian Franta Johannes Gramüller Philipp Dullinger Simon Kaltenberger Prof. Dr. Dominik Horinek Prof. Dr. Ruth M. Gschwind 《Angewandte Chemie (International ed. in English)》2023,62(27):e202301183
Chiral phosphoric acids (CPA) have become a privileged catalyst type in organocatalysis, but the selection of the optimum catalyst is still challenging. So far hidden competing reaction pathways may limit the maximum stereoselectivities and the potential of prediction models. In CPA-catalyzed transfer hydrogenation of imines, we identified for many systems two reaction pathways with inverse stereoselectivity, featuring as active catalyst either one CPA or a hydrogen bond bridged dimer. NMR measurements and DFT calculations revealed the dimeric intermediate and a stronger substrate activation via cooperativity. Both pathways are separable: Low temperatures and high catalysts loadings favor the dimeric pathway (ee up to −98 %), while low temperatures with reduced catalyst loading favor the monomeric pathway and give significantly enhanced ee (92–99 % ee; prior 68–86 % at higher temperatures). Thus, a broad impact is expected on CPA catalysis regarding reaction optimization and prediction. 相似文献
515.
Dr. Mowpriya Das Dr. Conor Hogan Robert Zielinski Milan Kubicki Dr. Maximilian Koy Canan Kosbab Simone Brozzesi Ankita Das Mike Thomas Nehring Viktoria Balfanz Juls Brühne Prof. Dr. Mario Dähne Dr. Martin Franz Prof. Dr. Norbert Esser Prof. Dr. Frank Glorius 《Angewandte Chemie (International ed. in English)》2023,62(50):e202314663
The adsorption of N-heterocyclic olefins (NHOs) on silicon is investigated in a combined scanning tunneling microscopy, X-ray photoelectron spectroscopy, and density functional theory study. We find that both of the studied NHOs bind covalently, with ylidic character, to the silicon adatoms of the substrate and exhibit good thermal stability. The adsorption geometry strongly depends on the N-substituents: for large N-substituents, an upright adsorption geometry is favored, while a flat-lying geometry is found for the NHO with smaller wingtips. These different geometries strongly influence the quality and properties of the obtained monolayers. The upright geometry leads to the formation of ordered monolayers, whereas the flat-lying NHOs yield a mostly disordered, but denser, monolayer. The obtained monolayers both show large work function reductions, as the higher density of the flat-lying monolayer is found to compensate for the smaller vertical dipole moments. Our findings offer new prospects in the design of tailor-made ligand structures in organic electronics and optoelectronics, catalysis, and material science. 相似文献
516.
Maximilian Baur Nina K. Mast Jan P. Brahm Rosa Habé Tobias O. Morgen Stefan Mecking 《Angewandte Chemie (International ed. in English)》2023,62(45):e202310990
Polyethylenes endowed with low densities of in-chain hydrolyzable and photocleavable groups can improve their circularity and potentially reduce their environmental persistency. We show with model polymers derived from acyclic diene metathesis polymerization that the simultaneous presence of both groups has no adverse effect on the polyethylene crystal structure and thermal properties. Post-polymerization Baeyer–Villiger oxidation of keto-polyethylenes from non-alternating catalytic ethylene-CO chain growth copolymerization yield high molecular weight in-chain keto-ester polyethylenes (Mn≈50.000 g mol−1). Oxidation can proceed without chain scission and consequently the desirable materials properties of HDPE are retained. At the same time we demonstrate the suitability of the in-chain ester groups for chemical recycling by methanolysis, and show that photolytic degradation by extended exposure to simulated sunlight occurs via the keto groups. 相似文献
517.
Dr. Bernhard von Vacano Dr. Hannah Mangold Dr. Guido W. M. Vandermeulen Dr. Glauco Battagliarin Dr. Maximilian Hofmann Dr. Jessica Bean Dr. Andreas Künkel 《Angewandte Chemie (International ed. in English)》2023,62(12):e202210823
To achieve a sustainable circular economy, polymer production must start transitioning to recycled and biobased feedstock and accomplish CO2 emission neutrality. This is not only true for structural polymers, such as in packaging or engineering applications, but also for functional polymers in liquid formulations, such as adhesives, lubricants, thickeners or dispersants. At their end of life, polymers must be either collected and recycled via a technical pathway, or be biodegradable if they are not collectable. Advances in polymer chemistry and applications, aided by computational material science, open the way to addressing these issues comprehensively by designing for recyclability and biodegradability. This Review explores how scientific progress, together with emerging regulatory frameworks, societal expectations and economic boundary conditions, paint pathways for the transformation towards a circular economy of polymers. 相似文献