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101.
反相高效液相色谱分离黄酮类化合物的研究 总被引:4,自引:0,他引:4
根据18种黄酮类化合物在C_3、C_(18)和CN三种固定相上的梯度洗脱反相高效液相色谱分离的研究,建立了一种连续快速分离植物提取物中黄酮类化合物的方法。此法可在55 min内完成一个样品的分离及柱平衡。最佳波长和温度分别是280nm和35℃。 相似文献
102.
Shiyang Xu Wei Zhang Caiyi Li Yanjing Li Hongxin Zeng Prof. Yingwei Wang Yang Zhang Prof. Dawen Niu 《Angewandte Chemie (International ed. in English)》2023,62(16):e202218303
We herein report a method that enables the generation of glycosyl radicals under highly acidic conditions. Key to the success is the design and use of glycosyl sulfinates as radical precursors, which are bench-stable solids and can be readily prepared from commercial starting materials. This development allows the installation of glycosyl units onto pyridine rings directly by the Minisci reaction. We further demonstrate the utility of this method in the late-stage modification of complex drug molecules, including the anticancer agent camptothecin. Experimental studies provide insight into the reaction mechanism. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2018,130(11):2998-3002
To tackle the problems associated with membrane protein (MP) instability in detergent solutions, we designed a series of glycosyl‐substituted dicarboxylate detergents (DCODs) in which we optimized the polar head to clamp the membrane domain by including, on one side, two carboxyl groups that form salt bridges with basic residues abundant at the membrane–cytoplasm interface of MPs and, on the other side, a sugar to form hydrogen bonds. Upon extraction, the DCODs 8 b , 8 c , and 9 b preserved the ATPase function of BmrA, an ATP‐binding cassette pump, much more efficiently than reference or recently designed detergents. The DCODs 8 a , 8 b , 8 f , 9 a , and 9 b induced thermal shifts of 20 to 29 °C for BmrA and of 13 to 21 °C for the native version of the G‐protein‐coupled adenosine receptor A2AR. Compounds 8 f and 8 g improved the diffraction resolution of BmrA crystals from 6 to 4 Å. DCODs are therefore considered to be promising and powerful tools for the structural biology of MPs. 相似文献
105.
M.T. Merino L. Humanes A. López-Ruiz J. Diez J.M. Roldán 《Journal of chromatography. A》1997,760(2):411-178
Ion-pairing reversed-phase HPLC has been used to separate and determine different derivatives of limonin, i.e. disodium limonoate, 17-dehydrolimonoate, limonoate A-ring lactone and 17-dehydrolimonoate A-ring lactone. Consequently, it has been possible to measure, by this chromatographic technique, the activities of the two enzymes that sequentially catalize the first two steps in limonin degradation: limonin D-ring lactone hydrolase and limonoate dehydrogenase. In both cases linear responses were found when using increasing enzyme amounts. The determination of limonoate dehydrogenase by HPLC measurements of limonoid products was compared with that obtained by the spectrophotometric method, based on pyridine nucleotides reduction. A good correlation was detected by using both procedures, which allows the proposition of the chromatographic method as an alternative to pyridine nucleotides determination. Besides, the chromatographic method appears to be a better assay than thin-layer chromatography or radioactive procedures, the methods traditionally used to measure limonin D-ring lactone hydrolase activity. 相似文献
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Leena Penttinen Vera Kouhi Rgis Faur Tatiana Skarina Peter Stogios Emma Master Edita Jurak 《Molecules (Basel, Switzerland)》2022,27(9)
Acetylated glucuronoxylan is one of the most common types of hemicellulose in nature. The structure is formed by a β-(1→4)-linked D-xylopyranosyl (Xylp) backbone that can be substituted with an acetyl group at O-2 and O-3 positions, and α-(1→2)-linked 4-O-methylglucopyranosyluronic acid (MeGlcpA). Acetyl xylan esterases (AcXE) that target mono- or doubly acetylated Xylp are well characterized; however, the previously studied AcXE from Flavobacterium johnsoniae (FjoAcXE) was the first to remove the acetyl group from 2-O-MeGlcpA-3-O-acetyl-substituted Xylp units, yet structural characteristics of these enzymes remain unspecified. Here, six homologs of FjoAcXE were produced and three crystal structures of the enzymes were solved. Two of them are complex structures, one with bound MeGlcpA and another with acetate. All homologs were confirmed to release acetate from 2-O-MeGlcpA-3-O-acetyl-substituted xylan, and the crystal structures point to key structural elements that might serve as defining features of this unclassified carbohydrate esterase family. Enzymes comprised two domains: N-terminal CBM domain and a C-terminal SGNH domain. In FjoAcXE and all studied homologs, the sequence motif around the catalytic serine is Gly-Asn-Ser-Ile (GNSI), which differs from other SGNH hydrolases. Binding by the MeGlcpA-Xylp ligand is directed by positively charged and highly conserved residues at the interface of the CBM and SGNH domains of the enzyme. 相似文献
110.
3-烷基/芳基-6-(1'-N-β-D-或-α-L-吡喃型全乙酰化糖基)- 均三唑并[3,4-b]-1,3,4-噻二唑的合成 总被引:5,自引:0,他引:5
通过2,3,4,6-四-O-乙酰基-β-D-吡喃型葡萄糖异硫氰酸酯(3)和2,3,4-三-O-乙酰基-α-L-吡喃型鼠李糖异硫氰酸酯(4)与3-烷基/芳基-4-氨基-5-巯基-1,2,4-三唑(5)在乙醇中回流,缩合得到了14个新的3-烷基/芳基-6-(1'-N-2',3',4',6'-四-O-乙酰基-β-D-吡喃型葡萄糖基或2',3',4'-三-O-乙酰基-α-L-吡喃型鼠李糖基)-均三唑并[3,4-b]-1,3,4-噻二唑类化合物(6a-6i,7a-7e),化合物结构经元素分析、IR和1H NMR确证. 相似文献