全文获取类型
收费全文 | 4225篇 |
免费 | 190篇 |
国内免费 | 34篇 |
专业分类
化学 | 3001篇 |
晶体学 | 70篇 |
力学 | 96篇 |
数学 | 705篇 |
物理学 | 577篇 |
出版年
2023年 | 39篇 |
2022年 | 31篇 |
2021年 | 77篇 |
2020年 | 77篇 |
2019年 | 95篇 |
2018年 | 57篇 |
2017年 | 56篇 |
2016年 | 130篇 |
2015年 | 108篇 |
2014年 | 154篇 |
2013年 | 248篇 |
2012年 | 293篇 |
2011年 | 332篇 |
2010年 | 182篇 |
2009年 | 165篇 |
2008年 | 277篇 |
2007年 | 241篇 |
2006年 | 248篇 |
2005年 | 248篇 |
2004年 | 207篇 |
2003年 | 162篇 |
2002年 | 163篇 |
2001年 | 67篇 |
2000年 | 49篇 |
1999年 | 37篇 |
1998年 | 38篇 |
1997年 | 45篇 |
1996年 | 51篇 |
1995年 | 35篇 |
1994年 | 34篇 |
1993年 | 27篇 |
1992年 | 28篇 |
1991年 | 21篇 |
1990年 | 23篇 |
1989年 | 23篇 |
1988年 | 19篇 |
1987年 | 21篇 |
1986年 | 17篇 |
1985年 | 35篇 |
1984年 | 34篇 |
1983年 | 18篇 |
1982年 | 25篇 |
1981年 | 15篇 |
1980年 | 24篇 |
1979年 | 24篇 |
1978年 | 21篇 |
1977年 | 23篇 |
1976年 | 16篇 |
1975年 | 17篇 |
1974年 | 17篇 |
排序方式: 共有4449条查询结果,搜索用时 46 毫秒
1.
2.
Dr. Samuel Oger Damien Schapman Dr. Romain Mougeot Dr. Stéphane Leleu Dr. Noëlle Lascoux Dr. Patrice Baldeck Dr. Magalie Bénard Dr. Thibault Gallavardin Dr. Ludovic Galas Dr. Xavier Franck 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(46):10954-10964
Epicocconone 1 is a natural chromophore isolated from the fungus Epicoccum nigrum that has shown applications in proteomics and fluorescent microscopy thanks to its unique pro-fluorescence properties. The modification of the skeleton of the natural product by replacing the triene side chain by a fluorenyl scaffold can noticeably increase the fluorophore's absorption coefficient. The synthesis of the analogues of the natural product has been made possible by the use of a palladium-catalyzed carbonylation reaction, allowing the construction of the β-keto-dioxinone key intermediate. Two-photon absorption cross-section measurements of the fluorenyl epicocconone analogues show a structure dependency with values ranging from 60 to 280 GM and live cell imaging show intense staining of intracellular vesicle-like structures around the nucleus. 相似文献
3.
Robin van der Veer 《Discrete Mathematics》2019,342(9):2680-2693
4.
5.
Supramolecular Recognition Influences Magnetism in [X@HVIV8VV14O54]6− Self‐Assemblies with Symmetry‐Breaking Guest Anions 下载免费PDF全文
Dr. Kirill Yu. Monakhov Oliver Linnenberg Dr. Piotr Kozłowski Dr. Jan van Leusen Dr. Claire Besson Tim Secker Dr. Arkady Ellern Dr. Xavier López Prof. Dr. Josep M. Poblet Prof. Dr. Paul Kögerler 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(6):2387-2397
Mixed‐valence polyoxovanadates(IV/V) have emerged as one of the most intricate class of supramolecular all‐inorganic host species, able to encapsulate a wide variety of smaller guest templates during their self‐assembly formation process. As showcased herein, the incorporation of guests, though governed solely by ultra‐weak electrostatic and van der Waals interactions, can cause drastic effects on the electronic and magnetic characteristics of the shell complex of the polyoxovanadate. We address the question of methodology for the magnetochemical analysis of virtually isostructural {VIV/V22O54}‐type polyoxoanions of D2d symmetry enclosing diamagnetic VO2F2? (C2v), SCN? (C∞v), or ClO4? (Td) template anions. These induce different polarization effects related to differences in their geometric structures, symmetry, ion radii, and valence shells, eventually resulting in a supramolecular modulation of magnetic exchange between the V(3d) electrons that are partly delocalized over the {V22O54} shells. We also include the synthesis and characterization of the novel [VVO2F2@HVIV8VV14O54]6? system that comprises the rarely encountered discrete difluorovanadate anion as a quasi‐isolated guest species. 相似文献
6.
A Promiscuous De Novo Retro‐Aldolase Catalyzes Asymmetric Michael Additions via Schiff Base Intermediates 下载免费PDF全文
Dr. Xavier Garrabou Dr. Tobias Beck Prof. Dr. Donald Hilvert 《Angewandte Chemie (International ed. in English)》2015,54(19):5609-5612
Recent advances in computational design have enabled the development of primitive enzymes for a range of mechanistically distinct reactions. Here we show that the rudimentary active sites of these catalysts can give rise to useful chemical promiscuity. Specifically, RA95.5‐8, designed and evolved as a retro‐aldolase, also promotes asymmetric Michael additions of carbanions to unsaturated ketones with high rates and selectivities. The reactions proceed by amine catalysis, as indicated by mutagenesis and X‐ray data. The inherent flexibility and tunability of this catalyst should make it a versatile platform for further optimization and/or mechanistic diversification by directed evolution. 相似文献
7.
8.
9.
Synthesis of poly(ω‐pentadecalactone)‐b‐poly(acrylate) diblock copolymers via a combination of enzymatic ring‐opening and RAFT polymerization techniques 下载免费PDF全文
Robin L. Pflughaupt Sally A. Hopkins Peter M. Wright Andrew P. Dove 《Journal of polymer science. Part A, Polymer chemistry》2016,54(20):3326-3335
Herein the first reported preparation of diblock copolymers of the polyethylene‐like polyester poly(ω‐pentadecalactone) (PPDL) via a combination of enzymatic ring‐opening polymerization (eROP) and reversible addition‐fragmentation chain‐transfer (RAFT) polymerization techniques is described. PPDL was synthesized via eROP using Novozyme 435 as a catalyst and a bifunctional initiator/chain transfer agent (CTA) appropriate for the eROP of ω‐pentadecalactone (PDL) and RAFT polymerization of acrylic and styrenic monomers. Chain growth of the PPDL macro‐CTA was performed to prepare acrylic and styrenic diblock copolymers of PPDL, and demonstrates a facile, metal‐free, and “greener” alternative to preparing acrylic diblock copolymers of polyethylene (PE). Diblock copolymer architecture was substantiated via analysis of 1H NMR spectroscopic, UV‐GPC chromatographic, DSC onset crystallization (Tc), and MALDI‐ToF mass spectrometric data. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3326–3335 相似文献
10.