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301.
Prof. Dr. Kazuaki Ishihara Kazuki Nishimura Katsuya Yamakawa 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(40):17794-17800
Catalytic enantioselective α-fluorination reactions of carbonyl compounds are among the most powerful and efficient synthetic methods for constructing optically active α-fluorinated carbonyl compounds. Nevertheless, α-fluorination of α-nonbranched carboxylic acid derivatives is still a big challenge because of relatively high pKa values of their α-hydrogen atoms and difficulty of subsequent synthetic transformation without epimerization. Herein we show that chiral copper(II) complexes of 3-(2-naphthyl)-l -alanine-derived amides are highly effective catalysts for the enantio- and site-selective α-fluorination of N-(α-arylacetyl) and N-(α-alkylacetyl) 3,5-dimethylpyrazoles. The substrate scope of the transformation is very broad (25 examples including a quaternary α-fluorinated α-amino acid derivative). α-Fluorinated products were converted into the corresponding esters, secondary amides, tertiary amides, ketones, and alcohols with almost no epimerization in high yield. 相似文献
302.
The photochromic [2.2]paracyclophane-bridged imidazole dimers show instantaneous coloration upon exposure to UV light and rapid fading in the dark. Experimental details for the enhancement of the photosensitivity and the unique photoisomerization of newly designed [2.2]paracyclophane-bridged imidazole dimers are demonstrated. We explored the structure-property relationships and demonstrated an efficient strategy for designing high-performance fast-photochromic molecules with increased photosensitivity to solar UVA radiation. The [2.2]paracyclophane-bridged imidazole dimer consists of two types of imidazole rings, Im1 and Im2. Im1 is characterized by a 6π electron system with an electron-donating characteristic, whereas Im2 is distinguished by a 4π electron system with an electron-withdrawing characteristic. The introduction of electron-donating substituents into the phenyl rings attached to the electron-withdrawing Im2 was proved to enhance the photosensitivity with the aid of the intramolecular charge transfer transitions. The unique photoisomerization resulting from the changes in the bonding manner between two imidazole rings was also investigated in detail. 相似文献
303.
Hiroto S Suzuki K Kamiya H Shinokubo H 《Chemical communications (Cambridge, England)》2011,47(25):7149-7151
The synthesis of a variety of diarylethenes through the Suzuki-Miyaura coupling reaction of 1,2-dichlorohexafluorocyclopentene with arylboronic acids and esters has been developed. Thiophenes with various substituents such as cyano and ester functionalities can be incorporated. 相似文献
304.
We present two distorted face-centered cubic (dfcc) structures of yttrium under high pressure, which have been found by a first-principles genetic algorithm technique. The structures are a tetragonal P43 (dfcc-I) and a triclinic P1¯ (dfcc-II), formed by slight distortions from a trigonal R3¯m structure reported as the dfcc phase earlier. The enthalpy difference between the two dfcc structures is less than 0.2 mRy/atom, and dfcc-I is marginally more stable than dfcc-II in lower pressure region. The enthalpy comparison among candidate structures indicates the structural phase transitions into dfcc-I at 41 GPa, into dfcc-II at 81 GPa, and into an orthorhombic Fddd structure at 106 GPa. 相似文献
305.
Katsuya Sako Yasufumi MugishimaTetsuo Iwanaga Shinji ToyotaHiroyuki Takemura Motonori WatanabeTeruo Shinmyozu Michito ShiotsukaHitoshi Tatemitsu 《Tetrahedron letters》2011,52(44):5865-5868
We have synthesized π-conjugated acceptor-type molecules 3a-d containing a cyanomethylene unit as the electron acceptor site and a 4,5-diazafluorene ligand for metal complexation. In the crystal, the planar 3a molecules stack along the b axis in the head-to-tail fashion. Compound 3a shows distinctive electrochromism and its three differently colored redox states (dianion (32−), anion radical (3−), neutral (3)) exhibit remarkable stability. 相似文献
306.
Jun Manabe Nagisa Sako Mizuki Ito Dr. Masaru Fujibayashi Dr. Chisato Kato Dr. Goulven Cosquer Prof. Katsuya Inoue Dr. Kiyonori Takahashi Prof. Takayoshi Nakamura Prof. Tomoyuki Akutagawa Dr. Seiya Shimono Dr. Hiroki Ishibashi Prof. Yoshiki Kubota Prof. Sadafumi Nishihara 《欧洲无机化学杂志》2023,26(34):e202300449
Materials exhibiting irreversible phase transitions, leading to changes in their properties, have a potential for novel application in electronic components such as a non-rewritable high-security memory. Here, we focused on the two salts, [(9-triptycylammonium)([18]crown-6)][Ni(dmit)2] ( 1 ) and [(9-triptycylammonium)([15]crown-5)][Ni(dmit)2] ( 2 ), which featured 2D sheet structures with alternately stacked cation and anion layers. Both salts exhibit similar cation arrangements, however, their anion arrangements differ significantly. The temperature-dependent magnetic susceptibilities of 1 and 2 were well reproduced by the alternating chain model (JAC1/kB=−306(8), JAC2/kB=−239(3) K) and the Curie-Weiss model (θ=−3.9(1) K), respectively. 1 experience a reversible phase transition around 40–60 K, causing anomalies in magnetic behavior. Moreover, an irreversible single-crystal-to-single-crystal phase transition to 1′ undergo at ~381 K, inducing a rearrangement of [Ni(dmit)2]− anions and a resistivity decrease from 6.5×106 to 6.5×102 Ω cm. The susceptibility curve of 1′ was reproduced by a combination of the Curie-Weiss and dimer models (Jdimer/kB=−407(5), θ=−26.7(5) K). The irreversible transition of 1 is the first example for such supramolecule and [Ni(dmit)2]− system to our knowledge, in opening potential new-type materials. 相似文献
307.