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排序方式: 共有678条查询结果,搜索用时 672 毫秒
671.
Silène Engbers Yisong Guo Johannes E. M. N. Klein 《Angewandte Chemie (International ed. in English)》2023,62(46):e202313006
Isoporphyrins have recently been identified as remarkable species capable of turning the nucleophile attached to the porphyrin ring into an electrophile, thereby providing umpolung of reactivity (Inorg. Chem. 2022 , 61, 8105–8111). They are generated by nucleophilic attack on an iron(III) π-dication, a class of species that has received scant attention. Here, we explore the effect of the porphyrin meso-substituent and report a iron(III) π-dication bearing the meso-tetraphenylporphyrin (TPP) ligand. We provide an extensive study of the species by UV/Vis absorption, 2H NMR, EPR, applied field Mössbauer, and resonance Raman spectroscopy. We further explore the system's highly dynamic and tunable properties and address the nature of the axial ligands as well as the conformation of the porphyrin ring. The insights presented are essential for the rational design of catalysts for the umpolung of nucleophiles. Such catalytic avenues could for example provide a novel method for electrophilic chlorinations. We further examine the importance of electronic tuning of the porphyrin by nature of the meso-substituent as a factor in catalyst design. 相似文献
672.
Jin-Jiang Zhang Lin Yang Fupin Liu Gianluca Serra Yubin Fu Andrea Lucotti Alexey A. Popov Matteo Tommasini Ji Ma Xinliang Feng 《Angewandte Chemie (International ed. in English)》2023,62(48):e202312055
Heteroatom-doped peri-acenes (PAs) have recently attracted considerable attention considering their fascinating physical properties and chemical stability. However, the precise sole addition of boron atoms along the zigzag edges of PAs remains challenging, primarily due to the limited synthetic approach. Herein, we present a novel one-pot modular synthetic strategy toward unprecedented boron-doped PAs (B-PAs), including B-[4,2]PA ( 1 a-2 ), B-[4,3]PA ( 1 b-2 ) and B-[7,2]PA ( 1 c-3 ) derivatives, through efficient intramolecular electrophilic borylation. Their chemical structures are unequivocally confirmed with a combination of mass spectrometry, NMR, and single-crystal X-ray diffraction analysis. Notably, 1 b-2 exhibits an almost planar geometry, whereas 1 a-2 displays a distinctive bowl-like distortion. Furthermore, the optoelectronic properties of this series of B-PAs are thoroughly investigated by UV/Vis absorption and fluorescence spectroscopy combined with DFT calculation. Compared with their parent all-carbon analogs, the obtained B-PAs exhibit high stability, wide energy gaps, and high photoluminescence quantum yields of up to 84 %. This study reveals the exceptional ability of boron doping to finely tune the physicochemical properties of PAs, showcasing their potential applications in optoelectronics. 相似文献
673.
Binzhou Lin Hao Liu Dr. Ishwor Karki Dr. Erik C. Vik Dr. Mark D. Smith Dr. Perry J. Pellechia Prof. Dr. Ken D. Shimizu 《Angewandte Chemie (International ed. in English)》2023,62(28):e202304960
Stabilizing nitrogen pnictogen bond interactions were measured using molecular rotors. Intramolecular C=O⋅⋅⋅N interactions were formed in the bond rotation transition states which lowered the rotational barriers and increased the rates of rotation, as measured by EXSY NMR. The pnictogen interaction energies show a very strong correlation with the positive electrostatic potential on nitrogen, which was consistent with a strong electrostatic component. In contrast, the NBO perturbation and pyramidalization analyses show no correlation, suggesting that the orbital-orbital component is minor. The strongest C=O⋅⋅⋅N pnictogen interactions were comparable to C=O⋅⋅⋅C=O interactions and were stronger than C=O⋅⋅⋅Ph interactions, when measured using the same N-phenylimide rotor system. The ability of the nitrogen pnictogen interactions to stabilize transition states and enhance kinetic processes demonstrates their potential in catalysis and reaction design. 相似文献
674.
Dr. Peng Chen Shun-Zhong Tan Dr. Lei Zhu Prof. Dr. Qin Ouyang Prof. Dr. Zhi-Jun Jia Prof. Dr. Wei Du Prof. Dr. Ying-Chun Chen 《Angewandte Chemie (International ed. in English)》2023,62(23):e202301519
σ-Lewis base-catalyzed regio- and enantioselective aza-Morita–Baylis–Hillman (MBH) reaction of α,β,γ,δ-unsaturated systems remains a challenge due to the intrinsic covalent activation mode. Here we demonstrate that a Pd0 complex can mediate the dehydrogenative reaction of γ,δ-unsaturated compounds to give corresponding electron-poor dienes, which further undergo δ-regioselective umpolung Friedel–Crafts-type addition to imines via auto-tandem Pd0-π-Lewis base catalysis. After β-H elimination of in situ formed PdII-complexes, unprecedented and chemically inverse aza-MBH-type adducts are finally furnished with fair to outstanding enantioselectivity, and a diversity of functional groups and both ketimine and aldimine acceptors can be well tolerated. Moreover, switchable α-regioselective normal aza-MBH-type reaction also can be realized by tuning catalytic conditions, whereas moderate to good enantioselectivity with low to excellent Z/E-selectivity is attained. 相似文献
675.
676.
Tim Görlich Dr. Peter Coburger Eric S. Yang Prof. Dr. Jose M. Goicoechea Prof. Dr. Hansjörg Grützmacher Prof. Dr. Christian Müller 《Angewandte Chemie (International ed. in English)》2023,62(32):e202217749
We review the known chemistry of the cyaphide ion, (C≡P)−. This remarkable diatomic anion has been the subject of study since the late nineteenth century, however its isolation and characterization eluded chemists for almost a hundred years. In this mini-review, we explore the pioneering synthetic experiments that first allowed for its isolation, as well as more recent developments demonstrating that cyaphide transfer is viable in well-established salt-metathesis protocols. The physical properties of the cyaphide ion are also explored in depth, allowing us to compare and contrast the chemistry of this ion with that of its lighter congener cyanide (an archetypal strong field ligand and important organic functional group). Recent studies show that the cyaphide ion has the potential to be used as a versatile chemical regent for the synthesis of novel molecules and materials, hinting at many interesting future avenues of investigation. 相似文献
677.
Prof. Shujuan Han Abudukadi Tudi Wenbin Zhang Prof. Xueling Hou Prof. Zhihua Yang Prof. Shilie Pan 《Angewandte Chemie (International ed. in English)》2023,62(26):e202302025
The combination of SnII or SbIII with π, non-π-conjugated units has produced birefringent crystals with birefringence ranging from 0.005 to 0.468@1064 nm. It is proven that introducing SnII or SbIII into crystals is a feasible strategy to enlarge the birefringence, which not only promotes the miniaturization of fabricated devices, but also effectively modulates polarized light. Herein, recently discovered SnII, SbIII-based birefringent crystals with birefringence investigated are summarized, including their crystal structure and optical properties, especially birefringence. This review also presents the influence of SnII, SbIII with stereochemically active lone pair on the optical anisotropy. We hope that this work provides a clear perspective on the crystal chemistry of SnII, SbIII-based optical functional crystals and promotes the development of new birefringent crystals with large optical anisotropy. 相似文献
678.
Eric Bosch Bryce S. Moreno Nathan P. Bowling 《Acta Crystallographica. Section C, Structural Chemistry》2023,79(4):149-157
The present study evaluates the potential combination of charge-transfer electron-donor–acceptor π–π complexation and C—H hydrogen bonding to form colored cocrystals. The crystal structures of the red 1:1 cocrystals formed from the isomeric pyridines 4- and 3-{2-[4-(dimethylamino)phenyl]ethynyl}pyridine with 1-[2-(3,5-dinitrophenyl)ethynyl]-2,3,5,6-tetrafluorobenzene, both C14H4F4N2O4·C15H14N2, are reported. Intermolecular interaction energy calculations confirm that π-stacking interactions dominate the intermolecular interactions within each crystal structure. The close contacts revealed by Hirshfeld surface calculations are predominantly C—H interactions with N, O, and F atoms. 相似文献