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Bieniek M Michrowska A Usanov DL Grela K 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(3):806-818
The data reported in this paper demonstrate that great care must be taken when choosing an appropriate catalyst for a given metathesis reaction. First-generation catalysts were found to be useful in the metathesis of sterically unhindered substrates. Second-generation catalysts (under optimised conditions) showed good to excellent activities toward sterically hindered and electron-withdrawing group (EWG)-substituted alkenes that do not react using the first-generation complexes. A strong temperature effect was noted on all of the reactions tested. Interestingly, attempts to force a reaction by increasing the catalyst loading were much less effective. Therefore, when possible, it is suggested that metathesis transformations should be carried out with a second-generation catalyst at 70 degrees C in toluene. However, different second-generation catalysts proved to be optimal for different applications and no single catalyst outperformed all others in all cases. Nevertheless, some empirical rules can be deduced from the model experiments, providing preliminary hints for the selection of the optimal catalysts. 相似文献
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Prof. Dr. Jianxiao Li Yougui Luo Lihua Hu Lele Liu Prof. Dr. Yin-Long Lai Wenfang Xiong 《European journal of organic chemistry》2023,26(7):e202201387
An N-heterocyclic carbene palladium (NHC-palladium)-catalyzed cascade annulation of alkynoic acids with unactivated alkenes under an oxygen atmosphere in ionic liquids is described. This protocol enables facile access for the preparation of diverse alkyl substituted α-methylene-γ-lactones in moderate to good yields with excellent Z/E selectivity. Moreover, the ionic liquid not only acts as the green solvent, but also as the eco-friendly chlorine source, thus avoiding the use of excess metal halides such as cupric chloride. Some preliminary mechanistic studies were performed, which further revealed possible pathways for this cascade annulation. 相似文献
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Chenxi Wen Ting Li Prof. Dr. Zheng Huang Prof. Dr. Qi-Kai Kang 《Chemical record (New York, N.Y.)》2023,23(11):e202300146
Preparing valuable olefins from cheap and abundant alkane resources has long been a challenging task in organic synthesis, which mainly suffers from harsh reaction conditions and narrow scopes. Homogeneous transition metals catalyzed dehydrogenation of alkanes has attracted much attention for its excellent catalytic activities under relatively milder conditions. Among them, base metal catalyzed oxidative alkane dehydrogenation has emerged as a viable strategy for olefin synthesis for its usage of cheap catalysts, compatibility with various functional groups, and low reaction temperature. In this review, we discuss recent development of base metal catalyzed alkane dehydrogenation under oxidative conditions and their application in constructing complex molecules. 相似文献
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1,3-Dipolar cycloaddition (1,3-DC) reaction of 4-ethoxy-1,1,1-trifluoro-3-buten-2-one 1 with nitrile oxides was studied. It was found that besides its CC participating in the formation of isoxazole rings, trifluoromethyl activated CO also underwent 1,3-DC reaction with nitrile oxides to afford 1,4,2-dioxazole rings. Single crystal diffraction analysis also evidenced the diheterocyclic configuration. 相似文献
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手性含硫化合物在药物化学和不对称合成领域中应用广泛,发展这类化合物的新合成方法是有机合成化学的重要任务.烯烃的不对称亲电硫化反应为手性含硫化合物的合成提供了一条方便的途径,通过这种方式不仅可以在烯烃母体分子上引入一个含硫基团,同时也能够引入另外一个重要的官能团.我们课题组设计、合成了一系列手性双官能硒醚/硫醚催化剂,并成功将其应用在不同种类烯烃的分子内和分子间的不对称三氟甲硫基化、烷硫基化和芳硫基化反应,高对映选择性地合成了各种手性含硫化合物.总结了我们课题组在手性双官能硒醚/硫醚催化的烯烃不对称亲电硫化反应中的研究进展,并对该领域的发展进行展望. 相似文献
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Hengzhao Li Bin Zhang Yanhong Dong Ting Liu Yuntong Zhang Haiyu Nie Ruoyan Yang Xiaodong Ma Yun Ling Jie An 《Tetrahedron letters》2017,58(28):2757-2760
A new single electron transfer reaction for the reductive deuteration of activated alkenes has been developed for the selective synthesis of α,β-dideuterio compounds. A cheap, stable and commercially-available sodium dispersion with high specific surface area is employed as the electron donor to replace the traditionally used sodium/liquid ammonium system. Deuterium source is provided by EtOD-d1. Excellent yields and deuterium incorporations were obtained across a broad range of activated alkenes with good functional group tolerance. This method provided a cheap, efficient and operationally-simple method for the synthesis of deuterium labeled compounds. 相似文献