全文获取类型
收费全文 | 840篇 |
免费 | 6篇 |
国内免费 | 12篇 |
专业分类
化学 | 851篇 |
晶体学 | 4篇 |
物理学 | 3篇 |
出版年
2024年 | 1篇 |
2023年 | 40篇 |
2022年 | 1篇 |
2021年 | 8篇 |
2020年 | 31篇 |
2019年 | 68篇 |
2018年 | 21篇 |
2017年 | 61篇 |
2016年 | 10篇 |
2015年 | 33篇 |
2014年 | 33篇 |
2013年 | 36篇 |
2012年 | 45篇 |
2011年 | 63篇 |
2010年 | 30篇 |
2009年 | 26篇 |
2008年 | 46篇 |
2007年 | 64篇 |
2006年 | 35篇 |
2005年 | 52篇 |
2004年 | 35篇 |
2003年 | 13篇 |
2002年 | 11篇 |
2001年 | 9篇 |
2000年 | 14篇 |
1999年 | 17篇 |
1998年 | 11篇 |
1997年 | 10篇 |
1996年 | 8篇 |
1995年 | 11篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1984年 | 3篇 |
1966年 | 1篇 |
排序方式: 共有858条查询结果,搜索用时 343 毫秒
121.
Victor Martínez‐Agramunt Tobias Eder Heidar Darmandeh Gregorio Guisado‐Barrios Eduardo Peris 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(17):5738-5742
A palladium‐cornered molecular square with four pyrene‐bis(imidazolylidene) bridging ligands is reported. This metallo‐polygon can encapsulate C60 and C70. The X‐ray diffraction structures of the empty cage as well as the cages complexed with both fullerenes are described. The fullerene encapsulation produces perturbations in the structural parameters of the metallo‐square, showing that it can adjust the shape of its cavity to the size of each fullerene. 相似文献
122.
Jian‐Qiang Huang Chun‐Yu Ho 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(17):5758-5762
A cross‐hydroalkenylation/rearrangement cascade (HARC), using a cyclopropene and alkyne as substrate pairs, was achieved for the first time by using new [(NHC)Ni(allyl)]BArF catalysts (NHC=N‐heterocyclic carbenes). By controlling the (NHC)NiIIH relative insertion reactivity with cyclopropene and alkyne, a broad scope of cyclopentadienes was obtained with highly selectively. The structural features of the new (NHC)NiII catalyst were important for the success of the reaction. The mild reaction conditions employed may serve as an entry for exploring (NHC)NiII‐assisted vinylcyclopropane rearrangement reactivity. 相似文献
123.
Markus R. Anneser Gaya R. Elpitiya Jacob Townsend Elizabeth J. Johnson Xian B. Powers Joseph F. DeJesus Konstantinos D. Vogiatzis David M. Jenkins 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(24):8199-8202
Three five‐coordinate iron(IV) imide complexes have been synthesized and characterized. These novel structures have disparate spin states on the iron as a function of the R‐group attached to the imide, with alkyl groups leading to low‐spin diamagnetic (S=0) complexes and an aryl group leading to an intermediate‐spin (S=1) complex. The different spin states lead to significant differences in the bonding about the iron center as well as the spectroscopic properties of these complexes. Mössbauer spectroscopy confirmed that all three imide complexes are in the iron(IV) oxidation state. The combination of diamagnetism and 15N labeling allowed for the first 15N NMR resonance recorded on an iron imide. Multi‐reference calculations corroborate the experimental structural findings and suggest how the bonding is distinctly different on the imide ligand between the two spin states. 相似文献
124.
Kosuke Yasui Miharu Kamitani Mamoru Tobisu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(40):14295-14299
Concerted nucleophilic aromatic substitution (CSNAr) has emerged as a powerful mechanistic manifold, in which nucleophilic aromatic substitution can proceed in one step without the need to form a Meisenheimer intermediate. However, all of the CSNAr reactions reported thus far require a stoichiometric strong base or activating reagent, and no catalytic variants have yet been reported. Herein, we report an N‐heterocyclic carbene (NHC)‐catalyzed intramolecular cyclization of acrylamides that contain a 2‐fluorophenyl group on the nitrogen through a CSNAr reaction. By using this catalytic method, it is possible to synthesize an array of quinolin‐2‐one derivatives, which are common structural motifs in pharmaceuticals and organic materials. DFT calculations unambiguously revealed that this reaction proceeds through the concerted nucleophilic aromatic substitution of aryl fluorides, in which a stereoelectronic σ (Cipso‐Cβ)→ σ*(Cipso‐F) interaction critically contributes to the stabilization of the transition state for the cyclization. 相似文献
125.
Xin‐Shen Liang Rui‐Dong Li Xiao‐Chen Wang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(39):14023-14027
We have developed a method for the highly diastereo‐ and enantioselective construction of 2,3‐dihydrobenzofurans bearing tetrasubstituted carbon stereocenters by means of annulation reactions between carbenes and 2‐iminyl‐ or 2‐acyl‐substituted phenols through catalysis by readily accessible copper(I)/bisoxazoline catalysts under mild conditions. These reactions feature a unique mechanism in which the copper catalyst serves a dual function: first it reacts with the diazo compound to generate a metal carbene, and second, upon formation of an oxonium ylide, it acts as a Lewis acid to activate the imine or ketone for diastereo‐ and enantioselective cyclization. 相似文献
126.
Tingshun Zhu Yingguo Liu Marie Smetankova Shitian Zhuo Chengli Mou Huifang Chai Zhichao Jin Yonggui Robin Chi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(44):15925-15929
Multisubstituted arenes such as indanes with attached all‐carbon quaternary centers are unique scaffolds in synthetic functional molecules and sophisticated natural products. A key challenge in preparing such molecules lies in the enantioselective installation of the quaternary carbon centers. Conventional methods in this direction include asymmetric substitution reactions and substrate‐controlled cyclization reactions. These reactions lead to poor stereoselectivities and/or require long and tedious synthetic steps. Disclosed here is a one‐step organic catalytic strategy for enantioselective access to this class of molecules. The reaction involves an N‐heterocyclic carbene catalyzed process for direct benzene construction, indane formation, remote‐carbon desymmetrization, and excellent chirality control. This approach will enable the concise synthesis of arene‐containing molecules, including those with complex structures and challenging chiral centers. 相似文献
127.
The imidazo[1,2‐a]pyridines are an important target in organic synthetic chemistry and have attracted critical attention of chemists mainly due to the discovery of the interesting properties exhibited by a great number of imidazo[1,2‐a]pyridine derivatives. Although lots of synthetic methods of imidazo[1,2‐a]pyridines have been developed in the past years, the chemistry community faces continuing challenges to use green reagents, maximize atom economy and enrich the functional group diversity of product. Undoubtedly, with its low cost and lack of environmentally hazardous byproducts, cascade reactions and C?H functionalizations are ideal strategies for this field. In this record we highlight some of our progress toward the goal to synthesis of imidazo[1,2‐a]pyridine derivatives through carbene transformations or C?H functionalizations. 相似文献
128.
129.
130.
Tobias Ullrich Piermaria Pinter Julian Messelberger Philipp Haines Ramandeep Kaur Jun.-Prof. Dr. Max M. Hansmann Dr. Dominik Munz Prof. Dr. Dirk M. Guldi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(20):7980-7988
Herein, we present a new class of singlet fission (SF) materials based on diradicaloids of carbene scaffolds, namely cyclic (alkyl)(amino)carbenes (CAACs). Our modular approach allows the tuning of two key SF criteria: the steric factor and the diradical character. In turn, we modified the energy landscapes of excited states in a systematic manner to accommodate the needs for SF. We report the first example of intermolecular SF in solution by dimer self-assembly at cryogenic temperatures. 相似文献