全文获取类型
收费全文 | 73篇 |
免费 | 3篇 |
专业分类
化学 | 47篇 |
晶体学 | 2篇 |
力学 | 2篇 |
数学 | 8篇 |
物理学 | 14篇 |
综合类 | 3篇 |
出版年
2023年 | 1篇 |
2022年 | 4篇 |
2021年 | 3篇 |
2020年 | 1篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2014年 | 3篇 |
2013年 | 2篇 |
2012年 | 7篇 |
2011年 | 4篇 |
2010年 | 2篇 |
2009年 | 1篇 |
2008年 | 4篇 |
2007年 | 2篇 |
2006年 | 6篇 |
2005年 | 3篇 |
2004年 | 2篇 |
2003年 | 2篇 |
2002年 | 4篇 |
2000年 | 2篇 |
1991年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1970年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有76条查询结果,搜索用时 31 毫秒
51.
Polyketone resins have been prepared by the Friedel-Crafts polymerization of dithiophenylidenecyclopentanone (Ⅰ), dithiophenylidenecyclohexanone (Ⅱ) and dithiophenylideneacetone (Ⅲ) with adipoyl, sebacoyl and terephthaloyl dichlorides using boron trifluoride as catalyst and carbon disulphide as solvent. Polymers were characterized with IR, 1 H-NMR, and the results showed the presence of carbonyl of ketonic groups in the main chain. The polyketones have inherent viscosities of 0.40-0.70 dL/g. All the polymers are semicrystalline and most of them are partially soluble in most common organic solvents but freely soluble in aprotic solvents. The temperatures of 50% weight loss are as high as 185℃ to 280℃ in air, indicating that these aromatic polyketones have excellent thermal stability. All the polyketones were tested for their antimicrobial activity against bacteria and fungi. 相似文献
52.
T S Hale F Huq I Hipkin C Tucker 《The Journal of the Operational Research Society》2013,64(3):439-445
Transportation, distribution, and logistics professionals often need to estimate the distances that are used for the arc lengths between nodes on a network model. For example, a network model might be representative of roads and cities in which the actual distance from one city to the next may vary depending upon the actual source and destination within each of the respective cities. Hence, estimates for the arc lengths within the network model will contain error. This research presents two new models to estimate these inter-nodal distances for cases in which complete nodal representation of every source and destination is computationally prohibitive. 相似文献
53.
Gu Siyong Hsieh Chien-Te Huq Mohammad Mahmudul Hsu Jo-Pei Li Jianlin 《Journal of Solid State Electrochemistry》2019,23(11):3197-3207
Journal of Solid State Electrochemistry - In the present work, we report synthesis of MgCo2O4 (MCO)/Li4Ti5O12 (LTO) composites for Li-ion battery anodes by a co-precipitation method. The objective... 相似文献
54.
Dr. Syed A. Huq 《Mathematische Zeitschrift》1970,115(5):383-386
Sans résuméSubventionné par une bourse du N. R. C. à l'Université de Montréal. 相似文献
55.
This is an extension of a previous paper which examined the methods available for the determination of the anisotropy constant from torque curves when the anisotropy is governed by a single constant i.e. E = K1 sin2φ. The two methods singled out in that paper as being of special merit are briefly re-examined when the anisotropy energy takes the form E = K1 sin2φ + K2 sin4φ. 相似文献
56.
Gábor Braun Jonah Brown-Cohen Arefin Huq Sebastian Pokutta Prasad Raghavendra Aurko Roy Benjamin Weitz Daniel Zink 《Mathematical Programming》2017,165(2):643-662
Yannakakis (Proceedings of the STOC, pp 223–228, 1988; J Comput Syst Sci 43(3):441–466, 1991. doi: 10.1016/0022-0000(91)90024-Y) showed that the matching problem does not have a small symmetric linear program. Rothvoß (Proceedings of the STOC, pp 263–272, 2014) recently proved that any, not necessarily symmetric, linear program also has exponential size. In light of this, it is natural to ask whether the matching problem can be expressed compactly in a framework such as semidefinite programming (SDP) that is more powerful than linear programming but still allows efficient optimization. We answer this question negatively for symmetric SDPs: any symmetric SDP for the matching problem has exponential size. We also show that an O(k)-round Lasserre SDP relaxation for the asymmetric metric traveling salesperson problem yields at least as good an approximation as any symmetric SDP relaxation of size \(n^{k}\). The key technical ingredient underlying both these results is an upper bound on the degree needed to derive polynomial identities that hold over the space of matchings or traveling salesperson tours. 相似文献
57.
Hussin Muhammad Tengku Aideed Syah Tg Abu Bakar Muhamad Faizul Adhzim Yusery Norizah Awang Wan Mazlina Md. Saad Elda Nurafnie Ibnu Rasid Mohamad Fawzi Mahomoodally Maizatul Hasyima Omar 《Molecules (Basel, Switzerland)》2022,27(7)
Dioscorea hispida Dennst. locally known as “ubi gadung” has been used as a traditional remedy and source of carbohydrate among Malaysians. To assess the effect of Dioscorea hispida aqueous extract (DHAE) on the production of reactive oxygen species (ROS) and their effects on DNA damage in Sprague Dawley rat’s placental tissues, pregnant rats were randomly divided into four groups. The animals were orally treated with distilled water (negative control) and three different concentrations of DHAE (250, 500 and 1000 mg/kg body weight (BW)) from gestation day 6 until 20. The oxidative stress in placental tissues was evaluated at day 21 by measuring the level of ROS, superoxide dismutase (SOD) and lipid peroxidation biomarker, malondialdehyde (MDA) while comet assay was used for DNA damage. There was no significant production of ROS and SOD activities in all groups. Significant changes were observed in the MDA level at 1000 mg/kg BW DHAE. Comet assay revealed a significant increase (p < 0.05) of DNA damage on animals treated with 250 and 500 mg/kg BW DHAE but not at the highest concentration. It was postulated that the placental cells could have undergone necrosis which destroys all components including DNA. This occurrence simultaneously reduces the levels of DNA damage which can be represented by lower level of tail moments. This finding correlates with our histopathological examination where necrotic cells of spongiotrophoblast were observed in the basal zone of placental tissue. The high amount of hydrogen cyanide and other compounds in 1000 mg/kg BW DHAE could elevate the lipid peroxidation and directly induce cell necrosis which requires further investigation. 相似文献
58.
Global spread of microorganisms by ships 总被引:47,自引:0,他引:47
59.
Cysteine proteases are one of the largest groups of proteases and are involved in many important biological functions in all kingdoms of life. They are virulence factors of a range of eukaryotic, bacterial and viral pathogens and are involved in host invasion, pathogen replication and disruption of the host immune response. Their activity is regulated by a range of protease inhibitors. This review discusses the various families of cysteine protease inhibitors, their different modes of inhibition and their evolutionary relationships. These inhibitors as well as the recent discovery of propeptide and propeptide-like inhibitors provide insights into the structures that are important for particular inhibitory mechanisms, thus forming the foundation for the design of future therapeutics. 相似文献
60.
Polycrystalline Mg1−xZnxFe2O4 (x=0.0–0.6) ferrites have been prepared using solid-state reaction technique. The X-ray diffraction analysis revealed that the samples crystallize in a single-phase cubic spinel structure. The lattice parameter increases linearly with increase in zinc content obeying Vegard's law. The continuous decrease in Curie temperature (Tc) with an increase in Zn content is attributed to the weakening of A–B exchange interaction. Saturation magnetization (Ms) and magnetic moment are observed to increase up to x=0.4, and thereafter decrease due to the spin canting in B-sites. The initial permeability is found to increase with the addition of Zn2+ ions but the resonance frequency shifts towards the lower frequency. 相似文献