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51.
A. V. Soldatov 《Journal of Structural Chemistry》2008,49(1):102-108
N-(2-Hydroxyethyl)-β-alaninatonickel(II) was synthesized by the interaction of basic nickel carbonate with N-(2-hydroxyethyl)-β-alanine. The structures of the chelating agent and its nickel complex were studied by single crystal X-ray diffraction. In the synthesized compound, the nickel ion lies at the center of an octahedron of the N and 2O donor atoms of two tridentate ligands, each ligand having a meridional conformation. The ligands around the central atom are arranged in perpendicular planes. This coordination of two ligands yields two stereoisomers, whose cocrystallization affords a racemate. 相似文献
52.
Rehbein J Dietrich B Grynbaum MD Hentschel P Holtin K Kuehnle M Schuler P Bayer M Albert K 《Journal of separation science》2007,30(15):2382-2390
An overview upon modern analytical techniques for the isolation, separation, and structural identification of the essential bioactive carotenoid bixin is given. Isolation from biological matrices is performed by matrix solid phase dispersion (MSPD). The extract is separated with shape-selective C(30 )columns. Structural assignment of the separated compounds is done by online LC-MS and capillary HPLC-NMR. 相似文献
53.
快速气相色谱法测定蔬菜中菊酯类农药残留量 总被引:19,自引:0,他引:19
采用一种较快速,简单的方法测定蔬菜中菊酯类农药残留物。样本中农残经乙酸酯萃取,凝胶渗透色谱及固相提取净化后,用气相色谱-电子捕获检测器测定,色谱柱为HP-5小口长石英毛细管柱。本法对6种常用菊酯类农药的回收率范围为89.6%-99.7%,检测限为0.04mg/kg。对同一批普施用菊酯类农药的白菜样本进行化验,本法跟美国食物及药品管理局农药残留标准测定方法所得结果非常吻合。 相似文献
54.
The photodegradation mechanism of fenvalerate in water has been investigated by density functional theory(DFT).The geometries of reactants,transition states,intermediates and products are optimized at the B3LYP/6-31G* level.The calculated results indicate that the reaction process mainly includes the nucleophilic attack and the substitution reaction by hydroxyl radical to the carbonyl group.By vibrational frequency analysis and intrinsic reaction coordinate(IRC) method,the transition state and its reaction pathway are confirmed.Moreover,the changes of natural population analysis(NPA),calculated using the Natural bond orbital(NBO) method,are analyzed along with the degradation reaction which can explain the variation of chemical bonds.Additionally,the solvent effect is also investigated and the results show that the reaction preferably takes place in water. 相似文献
55.
《Acta Crystallographica. Section C, Structural Chemistry》2017,73(7):556-562
Unnatural cyclic α‐amino acids play an important role in the search for biologically active compounds and macromolecules. Enantiomers of natural amino acids with a d configuration are not naturally encoded, but can be chemically synthesized. The crystal structures of two enantiomers obtained by a method of stereoselective synthesis, namely (5R ,8S )‐8‐tert‐butyl‐7‐methoxy‐8‐methyl‐9‐oxa‐6‐azaspiro[4.5]decane‐2,10‐dione, (1), and (5S ,8R )‐8‐tert‐butyl‐7‐methoxy‐8‐methyl‐9‐oxa‐6‐azaspiro[4.5]decane‐2,10‐dione, (2), both C14H21NO4, were determined by X‐ray diffraction. Both enantiomers crystallize isostructurally in the space group P 21, with one molecule in the asymmetric unit and with the same packing motif. The crystal structures are stabilized by C—H…O hydrogen bonds, resulting in the formation of chains along the [100] and [010] directions. The conformation of the 3,6‐dihydro‐2H‐1,4‐oxazin‐2‐one fragment was compared with other crystal structures possessing this heterocyclic moiety. The comparison showed that the title compounds are not exceptional among structures containing the 3,6‐dihydro‐2H‐1,4‐oxazin‐2‐one fragment. The planar moiety was more frequently observed in derivatives in which this fragment was not condensed with other rings. 相似文献
56.
57.
Thetrans-{bis(4,6-diisopropyl-2,5-diphenyl-1,3,2,5-dioxaboraphosphorinane)}dichloroplatinum(II) complex was obtained by the interaction of 4,6-diisopropyl-2,5-diphenyl-1,3,2,5-dioxaboraphosphorinane with bis(benzonitrile)dichloroplatinum(II). In solution this complex occurs as a mixture of isomers. X-ray analysis revealed close contacts between the platinum atom and one oxygen atom of the ligands.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1040–1043, June, 1993. 相似文献
58.
59.
Six samples [(3R,14R,26R)-, (3R,14S,26R)-, (3S,14R,26S)-, and (3S,14S,26S)-1, a mixture of (3R,14R,26S)- and (3S,14R,26R)-1, and a mixture of (3R,14S,26S)- and (3S,14S,26R)-1] of miyakosyne A [1, (4E,24E)-14-methyloctacosa-4,24-diene-1,27-diyne-3,26-diol] were synthesized starting from the enantiomers of citronellal (2), employing olefin cross metathesis and R-selective asymmetric acetylation of a stereoisomeric mixture of acetylenic alcohols with vinyl acetate and lipase PS as key reactions. Separation of the eight stereoisomer of 1 by reversed phase HPLC at −56 °C was achieved after their esterification with (1R,2R)-2-(anthracene-2,3-dicarboximido)cyclohexanecarboxylic acid (16), and the natural miyakosyne A was found to be a mixture of 95.7% of (3R,14R,26R)-1 and 4.3% of (3R,14S,26R)-1. This is different from the (3R,14S,26R)-configuration of 1 as tentatively assigned by X-ray analysis. 相似文献
60.
研究了反式DV菊酸对映体在含有手性选择体酒石酸酯的水-有机相双相体系中的萃取分配行为,考察了有机稀释剂种类、酒石酸酯的浓度、温度、水相的pH值、酒石酸酯烷基链长度对分配系数(D)和分配因子(α)的影响.研究表明:三氯甲烷作稀释剂时萃取分离效果较好;温度升高使分配系数增大,分离因子减小;分配系数随pH的升高而降低,随着酒石酸酯浓度的增大而增大,分离因子随pH的升高和酒石酸酯浓度的增大先增加后降低,pH和酒石酸酯浓度分别为4.50和0.40mol/L时取得较好的分离效果;取代烷基链长对分配系数(D)和分离因子(α)亦有较大影响. 相似文献