全文获取类型
收费全文 | 81篇 |
免费 | 0篇 |
专业分类
化学 | 67篇 |
晶体学 | 2篇 |
数学 | 5篇 |
物理学 | 7篇 |
出版年
2022年 | 1篇 |
2021年 | 1篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 2篇 |
2017年 | 3篇 |
2016年 | 5篇 |
2015年 | 2篇 |
2014年 | 1篇 |
2013年 | 7篇 |
2012年 | 6篇 |
2011年 | 6篇 |
2010年 | 3篇 |
2009年 | 2篇 |
2007年 | 7篇 |
2006年 | 5篇 |
2005年 | 1篇 |
2004年 | 5篇 |
2003年 | 4篇 |
2002年 | 4篇 |
2001年 | 2篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1986年 | 1篇 |
1976年 | 2篇 |
排序方式: 共有81条查询结果,搜索用时 15 毫秒
21.
Lucía Rodríguez-Lpez Raquel Cela-Dablanca Avelino Núez-Delgado Esperanza lvarez-Rodríguez David Fernndez-Calvio Manuel Arias-Estvez 《Molecules (Basel, Switzerland)》2021,26(11)
In view of the rising relevance of emerging pollutants in the environment, this work studies the photodegradation of three antibiotics, evaluating the effects of the pH of the medium and the concentration of dissolved organic matter. Simulated light (with a spectrum similar to that of natural sunlight) was applied to the antibiotics Ciprofloxacin (Cip), Clarithromycin (Cla) and Trimethoprim (Tri), at three different pH, and in the presence of different concentrations of humic acids. The sensitivity to light followed the sequence: Cip > Cla > Tri, which was inverse for the half-life (Tri > Cla > Cip). As the pH increased, the half-life generally decreased, except for Cla. Regarding the kinetic constant k, in the case of Cip and Tri it increased with the rise of pH, while decreased for Cla. The results corresponding to total organic carbon (TOC) indicate that the complete mineralization of the antibiotics was not achieved. The effect of humic acids was not marked, slightly increasing the degradation of Cip, and slightly decreasing it for Tri, while no effect was detected for Cla. These results may be relevant in terms of understanding the evolution of these antibiotics, especially when they reach different environmental compartments and receive sunlight radiation. 相似文献
22.
Claudio Palomo Jesus M. Aizpurua Ana Benito Regina Galarza Uttam K. Khamrai Jordi Vazquez Beatriz de Pascual-Teresa Pedro M. Nieto Anthony Linden 《Angewandte Chemie (International ed. in English)》1999,38(20):3056-3058
Remarkable asymmetric induction is achieved in the alkylation of the lithium enolate of the β-lactam 1 . This allows the first time access to a new family of peptidomimetics 2 with predictable conformational constraints. 相似文献
23.
Esperanza Lafuente Milagros Piñol María Teresa Martínez Edgar Muñoz Luis Oriol José Luis Serrano 《Journal of polymer science. Part A, Polymer chemistry》2009,47(9):2361-2372
The synthesis and characterization of a series of nematic SWNT‐polyazomethine composites are described. The composites were prepared by in situ polymerization in the presence of 1 wt % of chemically modified SWNTs in such a way that they were either dispersed or covalently bonded to the polymeric matrix. The presence of the SWNTs did not alter the thermal behavior of the polymer matrix and, therefore, highly oriented fibers could be melt‐extruded from the composites at moderate temperatures, as revealed by structural and morphological studies. Preliminary tests on tensile properties indicate that strength and stiffness were improved when compared with fibers without CNTs, particularly when SWNTs were covalently bonded to the polymeric matrix. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2361–2372, 2009 相似文献
24.
Julio Duque Hctor Novoa de Armas Ramn Poms Hernndez Margarita Surez Navarro Estael Ochoa Rodríguez Esperanza Salfrn Yamila Verdecia Reyes Norbert. M Blaton Oswald M. Peeters Camiel J. De Ranter 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(11):1346-1347
In the title compound, C28H38N4O6, the 4‐aryl substituent occupies a pseudo‐axial position approximately orthogonal to the plane of the dihydropyridine ring [88.1 (3)°]. The dihydropyridine ring adopts a flattened boat conformation. The H atom on the pyridine N atom is involved in a bifurcated intramolecular hydrogen bond, the acceptors being the N atoms of the two piperidylmethyl groups [N?N 2.629 (4) and 2.695 (4) Å]. 相似文献
25.
Susana Río Segade M. Carmen Diéguez Albor Esperanza FernáNDEZ GÓMEZ Elena Falqué LÓPEZ 《International journal of environmental analytical chemistry》2013,93(4):343-356
Abstract The sampling performance of C18 cartridges coated with DNPH has been studied for twenty four C1-C9 carbonyls in experiments involving sampling of parts per billion levels of carbonyls in urban air. indoor air and laboratory experiments. The cartridge background carbonyl content in thirty six batches of cartridges averaged 85, 137 and 155 nanogram/cartridge for formaldehyde, acetaldehyde and acetone, respectively, and was below analytical detection for all other carbonyls. Carbonyl-DNPH derivative recovery from the cartridge was complete in the first elution with 2 mL acetonitrile, and this for twenty four carbonyls at concentrations of 0.02–73 μg carbonyl/cartridge. Studies carried out using two cartridges in series showed no breakthrough, for the sixteen carbonyls tested, at concentrations of 0.10–49 μg carbonyl/cartridge and volumes of air sampled = 6–370 L. Average relative standard deviations (RSD) for replicate analyses were 0.20–13.2% for twenty one carbonyls. Average RSD for co-located samples were 0.9–16.2% for eighteen carbonyls. Comparison of RSD for replicates and RSD for co-located samples for thirteen carbonyls indicated that the overall method precision was limited by sampling precision rather than by analytical precision. 相似文献
26.
27.
28.
29.
Mercedes Casado Laura Altimira Raquel Montero Esperanza Castejón Andrés Nascimento Belén Pérez-Dueñas Aida Ormazabal Rafael Artuch 《Analytical and bioanalytical chemistry》2014,406(18):4337-4343
The most widely used method for the biochemical screening of oligosaccharidoses is the analysis of the urinary oligosaccharide pattern by thin-layer chromatography on silica gel plates. However, this method is not always sensitive enough, and it is extremely time-consuming and laborious. In this work, the analysis of the urine oligosaccharide pattern was standardized for the first time by using capillary electrophoresis with laser-induced fluorescence (CE-LIF) detection (Beckman P/ACE MDQ) with a 488-nm argon ion laser module. All of the analyses were conducted using the Carbohydrate Labeling and Analysis Kit (Beckman-Coulter), which derivatizes samples with 8-aminopyrene-1,3,6-trisulfonate. Urine samples from 40 control subjects (age range, 1 week to 16 years) and from ten patients diagnosed with eight different lysosomal diseases (six of them included in the Educational Oligosaccharide Kit from ERNDIM EQA schemes) were analyzed. Two oligosaccharide excretion patterns were established in our control population according to age (younger or older than 1 year of age). Abnormal peaks with slower migration times than the tetrasaccharide position were observed for fucosidosis, α-mannosidosis, GM1 gangliosidosis, GM2 gangliosidosis variant 0, Pompe disease, and glycogen storage disease type 3. In conclusion, the first CE-LIF method to screen for oligosaccharidoses and related diseases, which also present oligosacchariduria, has been standardized. In all of the cases, the urine oligosaccharide analysis was strongly informative and showed abnormal patterns that were not present in any of the urine samples from the control subjects. Only urine from patients with aspartylglucosaminuria and Schindler disease displayed normal results. Figure
? 相似文献
30.
Antonio L. Braga Claudio C. Silveira Luciano Dornelles Gilson Zeni Flavia A. D. Galarza Ludger A. Wessjohann 《合成通讯》2013,43(20):3155-3162
Enol ethers are reacted with mercaptanes to give the corresponding O/S- or S/S-acetals in medium to high yield. Either product can be formed selectively depending on the acid catalyst and the reaction time applied. 相似文献