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排序方式: 共有367条查询结果,搜索用时 218 毫秒
361.
为了研究铝阳极氧化过程中离子在阳极反应中的行为,利用第一性原理研究了氢原子对氧原子在铝(111)表面的吸附迁移行为的影响及氧原子向铝晶体内部的渗透行为的影响.结果表明,由于“抽象”(abstract)效应,氢原子的存在大大降低了氧进入铝晶体的能垒.氢原子的引入也影响了氧原子在铝晶体中的扩散,这可以显著降低氧原子在四面体间隙位置之间迁移的活化能(从1.23eV到0.35eV).这些结论助于我们了解阳极氧化过程和离子迁移过程. 相似文献
362.
Tonghui Zhao Mengting Li Dongdong Xiao Xiaoju Yang Lulu An Zhiping Deng Tao Shen Mingxing Gong Yi Chen Hongfang Liu Ligang Feng Xuan Yang Li Li Deli Wang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2024,136(5):e202315148
Tracking the trajectory of hydrogen intermediates during hydrogen electro-catalysis is beneficial for designing synergetic multi-component catalysts with division of chemical labor. Herein, we demonstrate a novel dynamic lattice hydrogen (LH) migration mechanism that leads to two orders of magnitude increase in the alkaline hydrogen oxidation reaction (HOR) activity on Pd@Pt over pure Pd, even ≈31.8 times mass activity enhancement than commercial Pt. Specifically, the polarization-driven electrochemical hydrogenation process from Pd@Pt to PdHx@Pt by incorporating LH allows more surface vacancy Pt sites to increase the surface H coverage. The inverse dehydrogenation process makes PdHx as an H reservoir, providing LH migrates to the surface of Pt and participates in the HOR. Meanwhile, the formation of PdHx induces electronic effect, lowering the energy barrier of rate-determining Volmer step, thus resulting in the HOR kinetics on Pd@Pt being proportional to the LH concentration in the in situ formed PdHx@Pt. Moreover, this dynamic catalysis mechanism would open up the catalysts scope for hydrogen electro-catalysis. 相似文献
363.
Dr. Shiyong Chu Prof. Duho Kim Gwanghyeon Choi Chunchen Zhang Haoyu Li Prof. Wei Kong Pang Yameng Fan Anita M. D'Angelo Prof. Shaohua Guo Prof. Haoshen Zhou 《Angewandte Chemie (International ed. in English)》2023,62(12):e202216174
Cation migration often occurs in layered oxide cathodes of lithium-ion batteries due to the similar ion radius of Li and transition metals (TMs). Although Na and TM show a big difference of ion radius, TMs in layered cathodes of sodium-ion batteries (SIBs) can still migrate to Na layer, leading to serious electrochemical degeneration. To elucidate the origin of TM migration in layered SIB cathodes, we choose NaCrO2, a typical layered cathode suffering from serious TM migration, as a model material and find that the TM migration is derived from the random desodiation and subsequent formation of Na-free layer at high charge potential. A Ru/Ti co-doping strategy is developed to address the issue, where the doped active Ru is first oxidized to create a selective desodiation and the doped inactive Ti can function as a pillar to avoid complete desodiation in Ru-contained TM layers, leading to the suppression of the Na-free layer formation and subsequent enhanced electrochemical performance. 相似文献
364.
Aniket Raut Haoyan Fang Yu-Chung Lin Shi Fu David Sprouster Ryuichi Shimogawa Anatoly I. Frenkel Chulsung Bae John C. Douglin Jaana Lillojad Kaido Tammeveski Zhiqiao Zeng Stoyan Bliznakov Miriam Rafailovich Dario R. Dekel 《Angewandte Chemie (International ed. in English)》2023,62(37):e202306754
Despite the recent progress in increasing the power generation of Anion-exchange membrane fuel cells (AEMFCs), their durability is still far lower than that of Proton exchange membrane fuel cells (PEMFCs). Using the complementary techniques of X-ray micro-computed tomography (CT), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX) spectroscopy, we have identified Pt ion migration as an important factor to explain the decay in performance of AEMFCs. In alkaline media Pt+2 ions are easily formed which then either undergo dissolution into the carbon support or migrate to the membrane. In contrast to PEMFCs, where hydrogen cross over reduces the ions forming a vertical “Pt line” within the membrane, the ions in the AEM are trapped by charged groups within the membrane, leading to disintegration of the membrane and failure. Diffusion of the metal components is still observed when the Pt/C of the cathode is substituted with a FeCo−N−C catalyst, but in this case the Fe and Co ions are not trapped within the membrane, but rather migrate into the anode, thereby increasing the stability of the membrane. 相似文献
365.
One-Carbon Homologation of α,β-Unsaturated Aldehydes: Access to α-Tertiary β,γ-Unsaturated Aldehydes
Dr. Arnaud Delbrassinne Boris Junior Takam Mba Laurent Collard Prof. Raphaël Robiette 《European journal of organic chemistry》2023,26(40):e202300765
An efficient protocol for the synthesis of enolizable α-substituted β,γ-unsaturated aldehydes is reported. The developed strategy involves two steps, epoxidation and Meinwald rearrangement, to result in a one-carbon homologation of α,β-unsaturated aldehydes enabling the insertion of a CHR unit. 相似文献
366.
Kester O. Ighodalo Wenjing Chen Zheng Liang Dr. Yongliang Shi Shenglong Chu Yihan Zhang Rashid Khan Hongmin Zhou Xu Pan Jiajiu Ye Prof. Zhengguo Xiao 《Angewandte Chemie (International ed. in English)》2023,62(5):e202213932
Ion migration is a notorious phenomenon observed in ionic perovskite materials. It causes several severe issues in perovskite optoelectronic devices such as instability, current hysteresis, and phase segregation. Here, we report that, in contrast to lead halide perovskites (LHPs), no ion migration or phase segregation was observed in tin halide perovskites (THPs) under illumination or an electric field. The origin is attributed to a much stronger Sn-halide bond and higher ion migration activation energy (Ea) in THPs, which remain nearly constant under illumination. We further figured out the threshold Ea for the absence of ion migration to be around 0.65 eV using the CsSnyPb1-y(I0.6Br0.4)3 system whose Ea varies with Sn ratios. Our work shows that ion migration does not necessarily exist in all perovskites and suggests metallic doping to be a promising way of stopping ion migration and improving the intrinsic stability of perovskites. 相似文献
367.
Qiuyu Li Jiajia Li Jie Zhang Shu Wu Yu Zhang Prof. Dr. Aijun Lin Prof. Dr. Hequan Yao 《Angewandte Chemie (International ed. in English)》2023,62(51):e202313404
Bicyclo[3.2.1]octadiene compounds and derivatives exist in a number of natural products and bioactive compounds. Nevertheless, catalytic enantioselective protocols for the synthesis of these skeletons have not been disclosed. Herein we reported a palladium-catalyzed asymmetric intramolecular alkene-alkyne coupling of alkyne-tethered cyclopentenes, affording a library of enantionenriched bicyclo[3.2.1]octadienes in excellent yields and enantioselectivities (mostly >99 % ee). Moreover, the products could undergo an unusual iodination-induced 1,2-acyl migration, forming iodinated bicyclo[3.2.1]octadienes with three vicinal stereocenters. The enone and isolated olefin motifs embedded in the products provide useful handles for downstream elaboration. 相似文献