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101.
Young-Ho Oh Wonhyuck Yun Chul-Hee Kim Sung-Woo Jang Sung-Sik Lee Sungyul Lee Dong-Wook Kim 《Molecules (Basel, Switzerland)》2021,26(10)
We present the intra- and inter-molecular organocatalysis of SN2 fluorination using CsF by crown ether to estimate the efficacy of the promoter and to elucidate the reaction mechanism. The yields of intramolecular SN2 fluorination of the veratrole substrates are measured to be very small (<1% in 12 h) in the absence of crown ether promoters, whereas the SN2 fluorination of the substrate possessing a crown ether unit proceeds to near completion (~99%) in 12 h. We also studied the efficacy of intermolecular rate acceleration by an independent promoter 18-crown-6 for comparison. We find that the fluorinating yield of a veratrole substrate (leaving group = −OMs) in the presence of 18-crown-6 follows the almost identical kinetic course as that of intramolecular SN2 fluorination, indicating the mechanistic similarity of intra- and inter-molecular organocatalysis of the crown ether for SN2 fluorination. The calculated relative Gibbs free energies of activation for these reactions, in which the crown ether units act as Lewis base promoters for SN2 fluorination, are in excellent agreement with the experimentally measured yields of fluorination. The role of the metal salt CsF is briefly discussed in terms of whether it reacts as a contact ion pair or as a “free” nucleophile F−. 相似文献
102.
采用密度泛函理论(Density Functional Theory,DFT),对锰催化剂MnIII(salene)F作用下苄基C—H键氟化反应的机理进行了深入的理论研究。对该反应中涉及到的重要中间体和过渡态的能量、Mulliken电荷分布、前线分子轨道等进行了分析。计算结果表明采用[MnIV(OH)(salene)F]和[MnIV(salene)F2]为催化剂催化苄基C—H键氟化反应所需的能垒分别为11.5 kcal·mol-1和7.6 kcal·mol-1。可见采用双氟催化剂[MnIV(salene)F2],氟化反应的能垒较低,更有利于苄基C—H键的氟化。通过轨道分析,给出了反应过程中详细的电子转移情况,从本质上分析了苄基氟化反应的机理。研究表明中心金属上的氧原子可以获得和失去电子,在C—H活化过程中起到传递电子的作用。在电子转移过程中,Mn原子是最终的电子接受体。以上结果很好地解释了实验现象,为进一步研究金属催化C—H键氟化反应提供理论支持。 相似文献
103.
Aiming at clarifying the interplay on TiO2 photoactivity between particle morphology and surface fluorination, the photocatalytic performance of anatase nanocrystals, characterized by a pseudo-spherical shape or a nanosheet structure, is investigated in both a reduction and an oxidation reaction, either in the absence or in the presence of added fluoride anions. Cr(VI) photocatalytic reduction is strongly favored by a large exposure of anatase {001} facets; however, surface fluorination leads in this case to a morphology-independent photoactivity decrease, due to the decreased adsorption of the reaction substrate. More interestingly, a beneficial synergistic effect between the platelet-like anatase morphology and TiO2 surface fluorination is clearly outlined in Rhodamine B photocatalytic degradation, possibly resulting from the intrinsic ability of fluorinated {001} anatase facets of boosting ?OH radical mediated oxidation paths, due to their larger amount of surface –OH groups, as revealed using Fourier-transform infrared spectroscopy. 相似文献
104.
Reactions of hexafluoropropene oxide with SbV and BiV oxygen-containing compounds were studied. The E=O (E−O) groups were found to be transformed into the EF2 (E−F) (E=Sb or Bi) groups.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1652–1653, August, 1998. 相似文献
105.
Norihiko Yoneda 《Journal of fluorine chemistry》2004,125(1):7-17
The intriguing properties of iodine have drawn the attention of organic chemists. In this paper, we will describe the recent development of stereo- and/or regioselective synthesis of fluorine-containing organic compounds employing hypervalent iodine fluorides such as ArIF2 (1), IF5 (22), and (E)-2-fluoro-alk-1-enyl-4-aryl iodonium salts R(F)C=C(H)IF-Ar (12). The electrochemical fluorination procedures involving iodo-compounds will also be presented to prepare fluoro-organic compounds. 相似文献
106.
A. Daryl Ariawan Flora Mansour Nicole Richardson Mohan Bhadbhade Junming Ho Luke Hunter 《Molecules (Basel, Switzerland)》2021,26(13)
Histone deacetylase enzymes (HDACs) are potential targets for the treatment of cancer and other diseases, but it is challenging to design isoform-selective agents. In this work, we created new analogs of two established but non-selective HDAC inhibitors. We decorated the central linker chains of the molecules with specifically positioned fluorine atoms in order to control the molecular conformations. The fluorinated analogs were screened against a panel of 11 HDAC isoforms, and minor differences in isoform selectivity patterns were observed. 相似文献
107.
Julian G. West T. Aaron Bedell Prof. Erik J. Sorensen 《Angewandte Chemie (International ed. in English)》2016,55(31):8923-8927
The fluorination of unactivated C(sp3)?H bonds remains a desirable and challenging transformation for pharmaceutical, agricultural, and materials scientists. Previous methods for this transformation have used bench‐stable fluorine atom sources; however, many still rely on the use of UV‐active photocatalysts for the requisite high‐energy hydrogen atom abstraction event. Uranyl nitrate hexahydrate is described as a convenient, hydrogen atom abstraction catalyst that can mediate fluorinations of certain alkanes upon activation with visible light. 相似文献
108.
Iridium is one of the most important platinum group metals and is used in several alloys and in the automotive industry for the purposes of making catalysts. Therefore, its recycling is a very actual challenge for researchers working in the field of urban mining. Reactions of various tetrafluorobromates MBrF4 (M = K, Rb, Cs) and M’(BrF4)2 (M’ = Ba) with Ir metal have been investigated. Compositions of the obtained products have been determined, corresponding reaction schemes have been suggested, and proper conditions for the reactions have been established. 相似文献
109.
Effects of Aromatic Fluorine Substitution on Protonated Neurotransmitters: The Case of 2‐Phenylethylamine 下载免费PDF全文
M. Sc. Markus Schütz Dr. Aude Bouchet Prof. Barbara Chiavarino Prof. Maria Elisa Crestoni Prof. Simonetta Fornarini Prof. Otto Dopfer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(24):8124-8136
Fluorination of pharmaceutical compounds is a common tool to modulate their physiochemical properties. We determine the effects of site‐specific aromatic fluorine substitution on the geometric, energetic, vibrational, and electronic properties of the protonated neurotransmitter 2‐phenylethylamine (xF‐H+PEA, x=ortho, meta, para) by infrared multiphoton photodissociation (IRMPD) in the fingerprint range (600–1750 cm?1) and quantum chemical calculations at the B3LYP‐D3/aug‐cc‐pVTZ level. The IRMPD spectra of all ions are assigned to their folded gauche conformers stabilized by intramolecular NH+???π hydrogen bonds (H‐bonds) between the protonated amino group and the aromatic ring. H→F substitution reduces the symmetry and allows for additional NH+???F interactions in oF‐H+PEA, leading to three distinct gauche conformers. In comparison to oF‐H+PEA, the fluorination effects on the energy landscape (energy ordering and isomerization barriers) in pF‐H+PEA and mF‐H+PEA with one and two gauche conformers are less pronounced. The strengths of the intramolecular NH+???F and NH+???π bonds are analyzed by the noncovalent interaction (NCI) method. 相似文献
110.