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121.
In this work, a novel, convenient, and efficient approach to the synthesis of pyrano[2,3-h]coumarins has been reported based on the multicomponent reaction. The one-pot reaction between 5,7-dihydroxy-4-methylcoumarin, dialkyl acetylenedicarboxylate and aromatic aldehydes catalyzed by sodium carbonate lead to the formation of a novel class of pyrano[2,3-h]coumarin derivatives. High atom-economy, excellent yields, simple procedure, and mild reaction conditions are the important features of this protocol. This method allows access to a variety of pyrano[2,3-h]coumarins via using a broad substrate scope. 相似文献
122.
Samanehsadat Sharifi Malek Taher Maghsoudlou Nourallah Hazeri Faramarz Rostami‐Charati 《中国化学会会志》2019,66(10):1347-1355
In this research, the green synthesis of chromen derivatives in good yields is described via three‐component reactions of 4‐hydroxycumarine, aldehydes or ketones, and methyl ketones in the presence of KF/clinoptilolite nanoparticles (KF/CP‐NPs) under solvent‐free conditions at 50°C in low time. The present methodology suggests some advantages such as low reaction time, easy and simple procedure, green method, inexpensive catalyst, high yield of product, and existence of different substrates for performing these reactions. In addition, it should be mentioned that antioxidant activity was studied for some prepared compounds, such as 4a–4d, by DPPH radical trapping and reducing potential tests of ferric ion and then comparing results with TBHQ and BHT as synthetic antioxidants. In this study, compounds 4c was shown to have moderate DPPH radical trapping, and compounds 4b and 4d displayed good reducing power of ferric ion. 相似文献
123.
A convenient metal-free decarbonylative radical conjugate addition of aliphatic aldehydes to electron-deficient alkenes is developed. With DTBP as an oxidant and radical-initiator, this reaction smoothly converts α-unsubstituted, α-mono-substituted and α-di-substituted aliphatic aldehydes into the corresponding primary, secondary and tertiary alkyl radicals, and subsequently allows for the cascade construction of C(sp3)C(sp3) bond via radical conjugate addition. 相似文献
124.
Copper‐Catalyzed Tandem Hydrocupration and Diastereo‐ and Enantioselective Borylalkyl Addition to Aldehydes 下载免费PDF全文
Won Jun Jang Prof. Jaesook Yun 《Angewandte Chemie (International ed. in English)》2018,57(37):12116-12120
We report the copper‐catalyzed stereoselective addition of in situ generated chiral boron‐α‐alkyl intermediates to various aldehydes including α,β‐unsaturated aldehydes under mild conditions. This tandem and multicomponent method facilitated the synthesis of enantiomerically enriched 1,2‐hydroxyboronates bearing contiguous stereocenters in good yield with high diastereo‐ and enantioselectivity up to a ratio greater than 98:2. In particular, α,β‐unsaturated aldehydes were successfully used as electrophiles in Cu?H catalysis through 1,2‐addition without significant reduction. The resulting 1,2‐hydroxyboronates were used in various transformations. 相似文献
125.
Natural products from the human microbiota may mediate host health and disease. However, discovery of the biosynthetic gene clusters that generate these metabolites has far outpaced identification of the molecules themselves. Here, we used an isolation-independent approach to access the probable products of a nonribosomal peptide synthetase-encoding gene cluster from Ruminococcus bromii, an abundant gut commensal bacterium. By combining bioinformatics with in vitro biochemical characterization of biosynthetic enzymes, we predicted that this pathway likely generates an N-acylated dipeptide aldehyde (ruminopeptin). We then used chemical synthesis to access putative ruminopeptin scaffolds. Several of these compounds inhibited Staphylococcus aureus endoproteinase GluC (SspA/V8 protease). Homologs of this protease are found in gut commensals and opportunistic pathogens as well as human gut metagenomes. Overall, this work reveals the utility of isolation-independent approaches for rapidly accessing bioactive compounds and highlights a potential role for gut microbial natural products in targeting gut microbial proteases. 相似文献
126.
Temperature‐Directed Biocatalysis for the Sustainable Production of Aromatic Aldehydes or Alcohols 下载免费PDF全文
Dr. Jun Ni Yan‐Yan Gao Dr. Fei Tao Hong‐Yu Liu Prof. Ping Xu 《Angewandte Chemie (International ed. in English)》2018,57(5):1214-1217
The biosynthesis of aromatic aldehydes and alcohols from renewable resources is currently receiving considerable attention because of an increase in demand, finite fossil resources, and growing environmental concerns. Here, a temperature‐directed whole‐cell catalyst was developed by using two novel enzymes from a thermophilic actinomycete. Ferulic acid, a model lignin derivative, was efficiently converted into vanillyl alcohol at a reaction temperature at 30 °C. However, when the temperature was increased to 50 °C, ferulic acid was mainly converted into vanillin with a productivity of 1.1 g L?1 h?1. This is due to the fact that the redundant endogenous alcohol dehydrogenases (ADHs) are not active at this temperature while the functional enzymes from the thermophilic strain remain active. As the biocatalyst could convert many other renewable cinnamic acid derivatives into their corresponding aromatic aldehydes/alcohols, this novel strategy may be extended to generate a vast array of valuable aldehydes or alcohols. 相似文献
127.
Giovanni Neri Giuseppe Rizzo Lidia De Luca Andrea Donato Maria Grazia Musolino Rosario Pietropaolo 《Reaction Kinetics and Catalysis Letters》2008,93(2):193-202
Selective catalytic reduction of campholenic aldehyde to naturanol was investigated over Sn-and Fe-doped SiO2, and Fe2O3-supported Pd catalysts. On Pd/SiO2 and Pd-Sn/SiO2 only saturated campholenic aldehyde is formed. Addition of Fe increases the C=O hydrogenation rate producing the corresponding
unsaturated alcohol with a good selectivity. Also Fe2O3-supported catalysts were found to be more selective towards carbonyl hydrogenation. Addition of tin to Pd/Fe2O3 contributes to a further selectivity enhancement towards naturanol. 相似文献
128.
在pH=7.5的水溶液中, Na2WO4•2H2O, NaAsO2, CoCl2•6H2O与对氨基吡啶反应, 得到了一种新的夹心型杂多钨酸盐Na6(C5H7N2){[Na(H2O)2]3Co(H2O)5[Co(H2O)]3(AsW9O33)2}•27H2O单晶, 用X射线单晶衍射法及元素分析确定了其结构, 晶体属三斜晶系, P 空间群, 其晶胞参数为: a=1.3276(8) nm, b=1.7581(10) nm, c=2.4381(14) nm, α=70.954(9)°, β=86.663(9)°, γ=72.885(9)°, V=5.136(5) nm3, Z=2, R1=0.0608, wR2=0.0848 [I>2σ(I)]. 在{[Na(H2O)2]3Co(H2O)5[Co(H2O)]3(AsW9O33)2}7-阴离子中, 一个Co2+与聚阴离子{[Na(H2O)2]3[Co(H2O)]3(AsW9O33)2}9-的一个端基氧共价连接, Co2+呈现出5和6两种配位数, 质子化的氨基吡啶正离子作为抗衡离子存在于晶体之中. 对标题化合物进行了IR, UV-Vis, TG-DSC表征. 对该化合物、Na2WO4•2H2O及CoCl2•6H2O催化H2O2氧化乙醛的活性进行了比较研究, 该化合物的催化活性远优于简单化合物Na2WO4•2H2O和CoCl2•6H2O. 相似文献
129.
Fe3+‐montmorillonite was used as a solid acidic catalyst for the synthesis of decahydroacridine derivatives through the condensation of aromatic aldehydes, dimedone and aniline in ethanol. The influence of reaction time, reaction temperature, and the amount of catalyst were studied. All the compounds were characterized by IR, Mp, 1H NMR and 13C NMR analysis. 相似文献
130.
活性MnO2 选择氧化紫苏醇合成紫苏醛 总被引:9,自引:0,他引:9
研究了活性MnO2液相选择氧化紫苏醇合成紫苏醛的反应。结果表明:以活性MnO:作氧化剂,乙酸乙酯作溶剂(15mL),紫苏醇0.76g(5mmol),m(紫苏醇):m(MnO2)=1:4,回流反应4h,紫苏醇转化率可达99.7%,紫苏醛收率在70%以上。 相似文献