全文获取类型
收费全文 | 103篇 |
免费 | 1篇 |
专业分类
化学 | 47篇 |
力学 | 1篇 |
数学 | 10篇 |
物理学 | 46篇 |
出版年
2022年 | 2篇 |
2021年 | 1篇 |
2020年 | 2篇 |
2019年 | 1篇 |
2018年 | 4篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 1篇 |
2014年 | 3篇 |
2013年 | 4篇 |
2012年 | 10篇 |
2011年 | 5篇 |
2010年 | 3篇 |
2009年 | 4篇 |
2008年 | 7篇 |
2007年 | 4篇 |
2006年 | 3篇 |
2005年 | 2篇 |
2004年 | 2篇 |
2002年 | 1篇 |
2001年 | 2篇 |
2000年 | 5篇 |
1999年 | 3篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 7篇 |
1991年 | 5篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1983年 | 1篇 |
1976年 | 1篇 |
1972年 | 1篇 |
1960年 | 1篇 |
1948年 | 1篇 |
排序方式: 共有104条查询结果,搜索用时 31 毫秒
11.
Ernesto Brunet Jos L. Gracía-Ruano Miguel A. Hoyos Jesús H. Rodríguez Pilar Prados Felipe Alcudia 《Magnetic resonance in chemistry : MRC》1983,21(10):643-648
The conformational analysis of the diastereomeric 2-methylsulphinyl-1-phenylethanol and its O-methyl and O-acetyl derivatives has been performed by 1H NMR spectroscopy. The study of the influence of dilution and solvent polarity changes on the coupling constants has permitted the configurational assignment of each diastereoisomer. The role played by hydrogen bonding in the hydroxysulphoxides has also been studied by IR spectroscopy. 相似文献
12.
13.
Z.M. Babar Wan Mohd Azizi Solachuddin JA Ichwan Qamar Uddin Ahmed Abul Kalam Azad Imranul Mawa 《Natural product research》2019,33(15):2266-2270
The current study provides a way of extraction for both active NSO and WSE from Nigella sativa seeds using 98% methanol. About 1?kg of ground seeds was macerated by 1:2.5 w/v (g/mL) for 72?hours. After rotary evaporation and 7 days of continuous drying and chilling at 50 and 4?°C, NSO and WSE were obtained at the same instant. Solubility tests of 24 solvents and 11 thin layer chromatographic analyses while 2, 2-diphenyl-1-picrylhydrazyl free radical scavenging assay of NSO (73.66) , WSE (33.32) and NSO?+?WSE (78.22) against ascorbic acid (IC50?=?4.28?mg/mL) was performed. WSE was found to be highly soluble in water and 5% NaOH exhibiting the same Rf value of 0.95 for EtOH:DMSO (9:1) against the honey. WSE has revealed more than twofold higher anti-oxidant activity than others. Formulation of WSE with Tualang honey may provide better targeted hydrophilic drug delivery systems. 相似文献
14.
Laura Castoldi Laura Ielo Pilar Hoyos María J. Hernáiz Laura De Luca Andrés R. Alcántara Wolfgang Holzer Vittorio Pace 《Tetrahedron》2018,74(18):2211-2217
An effective stereocontrolled synthesis of the HIV protease inhibitor Nelfinavir is reported. Two transformations were identified crucial for achieving success: the formation of a densely functionalized α-chloroketone via the homologation of a Weinreb amide with chloromethyllithium (LiCH2Cl), followed by its erythro selective reduction into the corresponding chiral chlorohydrin. A commercially available enzyme P2-C02 was particularly well suited for this purpose, affording the key alcohol (in an excellent 99% de), which was then smoothly converted into the active biologically active agent. 相似文献
15.
We investigate the entanglement and nonlocality properties of two random XX spin-1/2 critical chains, in order to better understand the role of breaking translational invariance to achieve nonlocal states in critical systems. We show that breaking translational invariance is a necessary but not sufficient condition for nonlocality, as the random chains remain in a local ground state up to a small degree of randomness. Furthermore, we demonstrate that the random dimer model does not have the same nonlocality properties of the translationally invariant chain, even though they share the same universality class for a certain range of randomness. 相似文献
16.
17.
A new method, based on scaling analysis, is used to calculate fractal dimension and local roughness exponents to characterize in vivo 3-D tumor growth in the brain. Image acquisition was made according to the standard protocol used for brain radiotherapy and radiosurgery, i.e., axial, coronal and sagittal magnetic resonance T1-weighted images, and comprising the brain volume for image registration. Image segmentation was performed by the application of the k-means procedure upon contrasted images. We analyzed glioblastomas, astrocytomas, metastases and benign brain tumors. The results show significant variations of the parameters depending on the tumor stage and histological origin. 相似文献
18.
Verónica Hoyos 《ZDM》2012,44(6):775-786
This paper reviews existing research on how in-service high school teachers have learned about, worked on or thought about the incorporation of mathematics technology into their teaching practices. The paper reviews different scenarios of instruction issuing from important research related to teacher professional development. Specifically, we will deal with contributions to online in-service mathematics teacher education that refer to the use of digital technologies in classroom teaching practices. The different articles reviewed belong to a range of teams of researchers from several universities and countries, and who have implemented distinct online education approaches. That work has allowed the gaining of knowledge on the specificities of using Web 2.0 tools for mathematics professional development (MPD), the function that online teacher interaction has in teacher learning, and the actual classroom conditions in which mathematics technology is incorporated into instructional practice. This paper describes and discusses the design features of those approaches emphasizing the main concepts and their underpinning theoretical frames, noting important design elements, and specific results. Finally, the paper discusses how some of these research findings are connected with emergent issues in the field of MPD. 相似文献
19.
20.