全文获取类型
收费全文 | 1466453篇 |
免费 | 40438篇 |
国内免费 | 14763篇 |
专业分类
化学 | 749593篇 |
晶体学 | 15172篇 |
力学 | 80523篇 |
综合类 | 417篇 |
数学 | 255642篇 |
物理学 | 420307篇 |
出版年
2021年 | 14885篇 |
2020年 | 18249篇 |
2019年 | 18553篇 |
2018年 | 17969篇 |
2017年 | 16535篇 |
2016年 | 32212篇 |
2015年 | 23828篇 |
2014年 | 33973篇 |
2013年 | 79137篇 |
2012年 | 49107篇 |
2011年 | 50828篇 |
2010年 | 44422篇 |
2009年 | 45765篇 |
2008年 | 46318篇 |
2007年 | 42966篇 |
2006年 | 44663篇 |
2005年 | 38205篇 |
2004年 | 37331篇 |
2003年 | 33822篇 |
2002年 | 33875篇 |
2001年 | 32656篇 |
2000年 | 26472篇 |
1999年 | 22770篇 |
1998年 | 20393篇 |
1997年 | 20891篇 |
1996年 | 20595篇 |
1995年 | 19696篇 |
1994年 | 19169篇 |
1993年 | 18510篇 |
1992年 | 19019篇 |
1991年 | 19101篇 |
1990年 | 18264篇 |
1989年 | 18148篇 |
1988年 | 17705篇 |
1987年 | 17605篇 |
1986年 | 16561篇 |
1985年 | 22932篇 |
1984年 | 23963篇 |
1983年 | 19914篇 |
1982年 | 21514篇 |
1981年 | 20710篇 |
1980年 | 20012篇 |
1979年 | 20552篇 |
1978年 | 21660篇 |
1977年 | 21387篇 |
1976年 | 21149篇 |
1975年 | 19850篇 |
1974年 | 19498篇 |
1973年 | 19954篇 |
1972年 | 14428篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
992.
Dmytro Strilets Dr. Shixin Fa Arthur Hardiagon Dr. Marc Baaden Prof. Tomoki Ogoshi Dr. Mihail Barboiu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(51):23413-23419
Artificial water channels mimicking natural aquaporins (AQPs) can be used for selective and fast transport of water. Here, we quantify the transport performances of peralkyl-carboxylate-pillar[5]arenes dimers in bilayer membranes. They can transport ≈107 water molecules/channel/second, within one order of magnitude of the transport rates of AQPs, rejecting Na+ and K+ cations. The dimers have a tubular structure, superposing pillar[5]arene pores of 5 Å diameter with twisted carboxy-phenyl pores of 2.8 Å diameter. This biomimetic platform, with variable pore dimensions within the same structure, offers size restriction reminiscent of natural proteins. It allows water molecules to selectively transit and prevents bigger hydrated cations from passing through the 2.8 Å pore. Molecular simulations prove that dimeric or multimeric honeycomb aggregates are stable in the membrane and form water pathways through the bilayer. Over time, a significant shift of the upper vs. lower layer occurs initiating new unexpected water permeation events through toroidal pores. 相似文献
993.
Haruka Takeuchi Prof. Dr. Shinsuke Inuki Kohei Nakagawa Takaaki Kawabe Dr. Atsuhiko Ichimura Prof. Dr. Shinya Oishi Prof. Dr. Hiroaki Ohno 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(47):21396-21401
We report herein a nonbiomimetic strategy for the total synthesis of the plicamine-type alkaloids zephycarinatines C and D. The key feature of the synthesis is a stereoselective reductive radical ipso-cyclization using visible-light-mediated photoredox catalysis. This cyclization enabled the construction of a 6,6-spirocyclic core structure through the addition of a carbon-centered radical onto the aromatic ring. Biological evaluation of zephycarinatines and their derivatives revealed that the synthetic derivative with a keto group displays moderate inhibitory activity against LPS-induced NO production. This approach could offer future opportunities to expand the chemical diversity of plicamine-type alkaloids as well as providing useful intermediates for their syntheses. 相似文献
994.
995.
Shuzhen Li Bo Lu Xiaoyu Fang Prof. Dongpeng Yan 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(50):22812-22819
Smart molecular crystals with light-driven mechanical responses have received interest owing to their potential uses in molecular machines, artificial muscles, and biomimetics. However, challenges remain in control over both the dynamic photo-mechanical behaviors and static photonic properties of molecular crystals based on the same molecule. Herein, we show the construction of isostructural co-crystals allows their light-induced cracking and jumping behaviors (photosalient effect) to be controlled. Hydrogen-bonded co-crystals from 4-(1-naphthylvinyl)pyridine ( NVP ) with co-formers (tetrafluoro-4-hydroxybenzoic acid ( THA ) and tetrafluorobenzoic acid ( TA )) crystallize as isostructural crystals, but have different static and dynamic photo-mechanical behaviors. These differences are due to alternations in the orientation of NVP and hydrogen-bonding modes of the co-formers. After light activation, the 1D NVP-TA crystal splits and shears off within 1 s. For NVP-THA , its photostability and high quantum yield give novel photonic properties, including low optical waveguide loss, highly polarized anisotropy, and efficient up-conversion fluorescence. 相似文献
996.
Ruirui Xu Kun Wang Haoying Liu Prof. Dr. Weijun Tang Dr. Huaming Sun Prof. Dr. Dong Xue Prof. Dr. Jianliang Xiao Prof. Dr. Chao Wang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(49):22143-22148
A ruthenium-catalyzed formal anti-Markovnikov hydroamination of allylic alcohols for the synthesis of chiral γ-amino alcohols is presented. Proceeding via an asymmetric hydrogen-borrowing process, the catalysis allows racemic secondary allylic alcohols to react with various amines, affording enantiomerically enriched chiral γ-amino alcohols with broad substrate scope and excellent enantioselectivities (68 examples, up to >99 % ee). 相似文献
997.
Tongtong Feng Dr. Yingxiang Ye Xiao Liu Hui Cui Dr. Zhiqiang Li Dr. Ying Zhang Dr. Bin Liang Prof. Huanrong Li Prof. Banglin Chen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(48):21936-21941
Temperature sensors play a significant role in biology, chemistry, and engineering, especially those that can work accurately in a noninvasive manner. We adopted a photoinduced post-synthetic copolymerization strategy to realize a membranous ratiometric luminescent thermometer based on the emissions of two lanthanide ions. This novel mixed-lanthanide polyMOF membrane exhibits not only the integrity and temperature sensing behaviour of the Ln-MOF powder but also excellent mechanical properties, such as flexibility, elasticity, and processability. Moreover, the polyMOF membrane shows remarkable stability under harsh conditions, including high humidity, strong acid and alkali (pH 0–14), which allowed the mapping of temperature distributions in extreme circumstances. This work highlights a simple strategy for polyMOF membrane formation and pushes forward the further practical application of Ln-MOF-based luminescent thermometers in various fields and conditions. 相似文献
998.
Philipp Dabringhaus Marcel Schorpp Dr. Harald Scherer Prof. Dr. Ingo Krossing 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(49):22207-22211
The potential of a dicationic strontium ansa-arene complex for Lewis acid catalysis has been explored. The key to its synthesis was a simple salt metathesis from SrI2 and 2 Ag[Al(ORF)4], giving the base-free strontium-perfluoroalkoxyaluminate Sr[Al(ORF)4]2 (ORF=OC(CF3)3). Addition of an ansa-arene yielded the highly Lewis acidic, dicationic strontium ansa-arene complex. In preliminary experiments, the complex was successfully applied as a catalyst in CO2-reduction to CH4 and a surprisingly controlled isobutylene polymerization reaction. 相似文献
999.
Dr. Yaru Gong Chao Qin Yuteng Zhang Prof. Chunyi Sun Prof. Qinhe Pan Xinlong Wang Zhongmin Su 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(49):22218-22222
Systematic design and self-assembly of metal–organic polyhedra with predictable configurations has been a long-standing challenge in crystal engineering. Herein a concave polyoxovanadate cluster, [V6O6(OCH3)9(SO4)4]5−, which can be generated in situ under specific reaction conditions, is reported. Based on this cluster, a potential trivalent molecular building block, [V6O6(OCH3)9(SO4)(CO2)3]2−, can be obtained by the bridging-ligand-substitution strategy and it possesses appropriate angle information for the design of molecular cubes. Utilizing the face-directed assembly of the trivalent molecular building block and a diverse set of tetratopic carboxylate linkers, a series of metal–organic cubes ( VMOC-1 – VMOC-5 ) with the same topology but different functionalities and dimensions were designed and constructed. An inclusion study using VMOC-3 shows that they are potential molecular receptors for selective capture of size-matching polycyclic aromatic hydrocarbon guest molecules. 相似文献
1000.