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Yan Jin Si Li Zhen Han Bing‐Jie Yan Hai‐Yang Li Xi‐Yan Dong Shuang‐Quan Zang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(35):12271-12276
Chiral assembly and asymmetric synthesis are critically important for the generation of chiral metal clusters with chiroptical activities. Here, a racemic mixture of [K(CH3OH)2(18‐crown‐6)]+[Cu5(StBu)6]? ( 1?CH3OH ) in the chiral space group was prepared, in which the chiral red‐emissive anionic [Cu5(StBu)6]? cluster was arranged along a twofold screw axis. Interestingly, the release of the coordinated CH3OH of the cationic units turned the chiral 1?CH3OH crystal into a mesomeric crystal [K(18‐crown‐6)]+[Cu5(StBu)6]? ( 1 ), which has a centrosymmetric space group, by adding symmetry elements of glide and mirror planes through both disordered [Cu5(StBu)6]? units. The switchable chiral/achiral rearrangement of [Cu5(StBu)6]? clusters along with the capture/release of CH3OH were concomitant with an intense increase/decrease in luminescence. We also used cationic chiral amino alcohols to induce the chiral assembly of a pair of enantiomers, [d /l ‐valinol(18‐crown‐6)]+[Cu5(StBu)6]? ( d /l ‐Cu5V ), which display impressive circularly polarized luminescence (CPL) in contrast to the CPL‐silent racemic mixture of 1?CH3OH and mesomeric 1 . 相似文献
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Rick C. Betori Catherine M. May Karl A. Scheidt 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(46):16642-16646
Chemical transformations that install heteroatoms into C?H bonds are of significant interest because they streamline the construction of value‐added small molecules. Direct C?H oxyfunctionalization, or the one step conversion of a C?H bond to a C?O bond, could be a highly enabling transformation due to the prevalence of the resulting enantioenriched alcohols in pharmaceuticals and natural products,. Here we report a single‐flask photoredox/enzymatic process for direct C?H hydroxylation that proceeds with broad reactivity, chemoselectivity and enantioselectivity. This unified strategy advances general photoredox and enzymatic catalysis synergy and enables chemoenzymatic processes for powerful and selective oxidative transformations. 相似文献
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Qing-Xia Zhang Yao Li Jie Wang Chen Yang Cheng-Jun Liu Prof. Xin Li Prof. Jin-Pei Cheng 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(11):4580-4586
The enantioselective ketimine–ene reaction is one of the most challenging stereocontrolled reaction types in organic synthesis. In this work, catalytic enantioselective ketimine–ene reactions of 2-aryl-3H-indol-3-ones with α-methylstyrenes were achieved by utilizing a B(C6F5)3/chiral phosphoric acid (CPA) catalyst. These ketimine–ene reactions proceed well with low catalyst loading (B(C6F5)3/CPA=2 mol %/2 mol %) under mild conditions, providing rapid and facile access to a series of functionalized 2-allyl-indolin-3-ones with very good reactivity (up to 99 % yield) and excellent enantioselectivity (up to 99 % ee). Theoretical calculations reveal that enhancement of the acidity of the chiral phosphoric acid by B(C6F5)3 significantly reduces the activation free energy barrier. Furthermore, collective favorable hydrogen-bonding interactions, especially the enhanced N−H⋅⋅⋅O hydrogen-bonding interaction, differentiates the free energy of the transition states of CPA and B(C6F5)3/CPA, thereby inducing the improvement of stereoselectivity. 相似文献
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