全文获取类型
收费全文 | 1652篇 |
免费 | 66篇 |
国内免费 | 5篇 |
专业分类
化学 | 1072篇 |
晶体学 | 9篇 |
力学 | 18篇 |
数学 | 207篇 |
物理学 | 417篇 |
出版年
2022年 | 10篇 |
2021年 | 29篇 |
2020年 | 31篇 |
2019年 | 26篇 |
2018年 | 11篇 |
2017年 | 17篇 |
2016年 | 50篇 |
2015年 | 34篇 |
2014年 | 43篇 |
2013年 | 71篇 |
2012年 | 88篇 |
2011年 | 109篇 |
2010年 | 64篇 |
2009年 | 57篇 |
2008年 | 80篇 |
2007年 | 96篇 |
2006年 | 112篇 |
2005年 | 62篇 |
2004年 | 78篇 |
2003年 | 35篇 |
2002年 | 38篇 |
2001年 | 26篇 |
1999年 | 20篇 |
1998年 | 17篇 |
1997年 | 16篇 |
1996年 | 18篇 |
1995年 | 20篇 |
1994年 | 18篇 |
1993年 | 15篇 |
1992年 | 13篇 |
1990年 | 11篇 |
1989年 | 17篇 |
1988年 | 21篇 |
1987年 | 15篇 |
1986年 | 12篇 |
1985年 | 31篇 |
1984年 | 25篇 |
1983年 | 12篇 |
1982年 | 24篇 |
1981年 | 16篇 |
1980年 | 19篇 |
1979年 | 12篇 |
1978年 | 15篇 |
1977年 | 17篇 |
1976年 | 10篇 |
1974年 | 13篇 |
1973年 | 11篇 |
1972年 | 13篇 |
1971年 | 9篇 |
1970年 | 12篇 |
排序方式: 共有1723条查询结果,搜索用时 15 毫秒
1.
Positivity - We prove new characterisations of exponential stability for positive linear discrete-time systems in ordered Banach spaces, in terms of small-gain conditions. Such conditions have... 相似文献
2.
Russian Physics Journal - Using spectral-kinetic data obtained for nanoassemblies based on CdSe/ZnS semiconductor quantum dots and tetrapyridylporphyrin molecules in methylcyclohexane-toluene... 相似文献
3.
4.
Dennis Jansen Johannes Gramüller Felix Niemeyer Torsten Schaller Matthias C. Letzel Stefan Grimme Hui Zhu Ruth M. Gschwind Jochen Niemeyer 《Chemical science》2020,11(17):4381
Organocatalysis has revolutionized asymmetric synthesis. However, the supramolecular interactions of organocatalysts in solution are often neglected, although the formation of catalyst aggregates can have a strong impact on the catalytic reaction. For phosphoric acid based organocatalysts, we have now established that catalyst–catalyst interactions can be suppressed by using macrocyclic catalysts, which react predominantly in a monomeric fashion, while they can be favored by integration into a bifunctional catenane, which reacts mainly as phosphoric acid dimers. For acyclic phosphoric acids, we found a strongly concentration dependent behavior, involving both monomeric and dimeric catalytic pathways. Based on a detailed experimental analysis, DFT-calculations and direct NMR-based observation of the catalyst aggregates, we could demonstrate that intermolecular acid–acid interactions have a drastic influence on the reaction rate and stereoselectivity of asymmetric transfer-hydrogenation catalyzed by chiral phosphoric acids.Supramolecular acid–acid interactions lead to competing monomeric and dimeric pathways in phosphoric acid catalysis – so that stereoselectivities depend on catalyst concentration. 相似文献
5.
6.
7.
Myriam Drouin Dr. Parvesh Wadhwani Dr. Stephan L. Grage Dr. Jochen Bürck Dr. Johannes Reichert Sébastien Tremblay Marie Sabine Mayer Christian Diel Alexander Staub Prof. Jean-François Paquin Prof. Dr. Anne S. Ulrich 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(7):1511-1517
Solid-state 19F NMR is a powerful method to study the interactions of biologically active peptides with membranes. So far, in labelled peptides, the 19F-reporter group has always been installed on the side chain of an amino acid. Given the fact that monofluoroalkenes are non-hydrolyzable peptide bond mimics, we have synthesized a monofluoroalkene-based dipeptide isostere, Val-Ψ[(Z)-CF=CH]-Gly, and inserted it in the sequence of two well-studied antimicrobial peptides: PGLa and (KIGAKI)3 are representatives of an α-helix and a β-sheet. The conformations and biological activities of these labeled peptides were studied to assess the suitability of monofluoroalkenes for 19F NMR structure analysis. 相似文献
8.
Ceren Kütahya Nicolai Meckbach Prof. Dr. Veronika Strehmel Prof. Dr. Jochen S. Gutmann Prof. Dr. Bernd Strehmel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(46):10444-10451
NIR exposure at 790 nm activated photopolymerization of monomers comprising UV-absorbing moieties by using [CuII/(TPMA)]Br2 (TPMA=tris(2-pyridylmethyl)amine) in the ppm range and an alkyl bromide as initiator. Some of them comprised structural elements selected either from those showing proton transfer or photocycloaddition upon UV excitation. Polymers obtained comprise living end groups serving as macroinitiator for controlled synthesis of block copolymers with relatively narrow molecular weight distributions. Chromatographic results indicated formation of block copolymers produced by this synthetic approach. Free-radical polymerization of monomers pursued for comparison exhibited the expected broader dispersity of molecular weight compared to photo-ATRP. Polymerization of these monomers by UV photo-ATRP failed on the contrary to NIR photo-ATRP demonstrating the UV-filter function of the monomers. This work conclusively provides a new approach for the polymerization of monomers comprising UV-absorbing moieties through photo-ATRP in the NIR region. This occurred in a simple and efficient pathway. However, studies also showed that not all monomers chosen successfully proceeded in the NIR photo-ATRP protocol. 相似文献
9.
Dr. Ritesh Haldar Kamal Batra Stefan Michael Marschner Dr. Agnieszka B. Kuc Dr. Stefan Zahn Prof. Dr. Roland A. Fischer Prof. Dr. Stefan Bräse Prof. Dr. Thomas Heine Prof. Dr. Christof Wöll 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(33):7847-7851
In organic photovoltaics, porphyrins (PPs) are among the most promising compounds owing to their large absorption cross-section, wide spectral range, and stability. Nevertheless, a precise adjustment of absorption band positions to reach a full coverage of the so-called green gap has not been achieved yet. We demonstrate that a tuning of the PP Q- and Soret bands can be carried out by using a computational approach for which substitution patterns are optimized in silico. The most promising candidate structures were then synthesized. The experimental UV/Vis data for the solvated compounds were in excellent agreement with the theoretical predictions. By attaching further functionalities, which allow the use of PP chromophores as linkers for the assembly of metal-organic frameworks (MOFs), we were able to exploit packing effects resulting in pronounced redshifts, which allowed further optimization of the photophysical properties of PP assemblies. Finally, we use a layer-by-layer method to assemble the PP linkers into surface-mounted MOFs (SURMOFs), thus obtaining high optical quality, homogeneous and crystalline multilayer films. Experimental results are in full accord with the calculations, demonstrating the huge potential of computational screening methods in tailoring MOF and SURMOF photophysical properties. 相似文献
10.
The European Physical Journal H - This is a tutorial for the many-worlds theory by Everett, which includes some of my personal views. It has two main parts. The first main part shows the emergence... 相似文献