全文获取类型
收费全文 | 88篇 |
免费 | 2篇 |
国内免费 | 1篇 |
专业分类
化学 | 70篇 |
晶体学 | 2篇 |
力学 | 1篇 |
数学 | 3篇 |
物理学 | 15篇 |
出版年
2018年 | 1篇 |
2015年 | 2篇 |
2013年 | 1篇 |
2012年 | 5篇 |
2011年 | 5篇 |
2010年 | 4篇 |
2009年 | 2篇 |
2008年 | 4篇 |
2007年 | 1篇 |
2006年 | 4篇 |
2005年 | 2篇 |
2004年 | 4篇 |
2003年 | 7篇 |
2002年 | 11篇 |
2001年 | 1篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1974年 | 3篇 |
1972年 | 1篇 |
排序方式: 共有91条查询结果,搜索用时 31 毫秒
1.
G. J. Homer P. F. Smith J. D. Lewin S. J. Robertson J. U. D. Langridge D. Evans C. J. Brown M. Gonsalves A. K. Gyani 《Zeitschrift fur Physik C Particles and Fields》1992,55(4):549-554
The magnetic levitation technique has been used to test for fractional electric charge in sea water, using steel balls coated with sea water residue by evaporation. The objective was to reach concentration levels below 1 g?1 which might result from cosmic ray interactions. Four stages of increasing sensitivity are reported: (1) residue from direct evaporation of unprocessed sea water, (2) residue from sea water samples enriched by ion exchangen, (3) residue reduced by high temperature evaporation, and (4) hypothetical enrichment by dilution and separation of soluble residue. Stages 1–3 are based on the generally accepted preferential retention of fractional charge during evaporation, but stage 4 limits are subject to uncertainties in the enrichment process. No evidence for fractional charge was found in a total of about 130 samples tested in these four stages. Samples containing positive and negative ions were tested separately, and concentration limits are reported for each of the stages. Levels in the region 0.01–0.1g?1 were reached in stage 3, and 0.001 g?1 in stage 4. 相似文献
2.
3.
4.
Teresa M V D Pinho e Melo Cláudia S J Lopes António M d'A Rocha Gonsalves Ana M Beja José A Paix?o Manuela R Silva Luiz Alte da Veiga 《The Journal of organic chemistry》2002,67(1):66-71
Nucleophilic substitution reactions of 2-halo-2H-azirines 1a, 1b, 1d, and 1e with potassium phthalimide and aniline allowed the preparation of new substituted 2H-azirines 2-5. The reactions of 2-bromo-2H-azirine 1a with methylamine led to the synthesis of alpha-diimines 7 and 8. 2-Halo-2H-azirines were also established as building blocks for the synthesis of a range of heterocyclic compounds, namely, quinoxalines 10a-10d, 3-oxazoline 14, and 2H-[1,4]oxazines 18 and 20. X-ray crystal structures of alpha-diimine 7, 3-oxazoline 14, and 2H-[1,4]oxazine 18 are reported. 相似文献
5.
6.
Kenneth Gonsalves Lin Zhan-Ru Robert W. Lenz Marvin D. Rausch 《Journal of polymer science. Part A, Polymer chemistry》1985,23(6):1707-1722
Three types of isopropenylmetallocene monomers were synthesized and subjected to polymerization and copolymerization by cationic initiators; (1) isopropenylferrocene (IF); (2) (η5-isopropenylcyclopentadienyl)dicarbonylnitrosylmolybdenum (IDM); and (3) 1,1′-diisopropenylcyclopentadienylstannocene (DIS), and related derivatives of each. IF was synthesized by a three-step procedure involving the acetylation of ferrocene, conversion of the latter to 2-ferrocenyl-2-propanol, and dehydration of the carbinol. IF was homopolymerized under various cationic initiation conditions, but only low molecular weight homopolymers were obtained. Copolymerization of IF with styrene and with p-methoxy-α-methylstyrene also gave only low molecular weight products. The formation of only low molecular weight polymers in all polymerization reactions is believed to result from the effect of the unusually high stability of ferrocenyl carbenium ions on its propagation reaction. The observed polymerization behavior of α-trifluoromethylvinylferrocene is in accord with this conclusion. IDM and DIS did not form polymeric products under cationic conditions, although copolymers could be obtained for each of these monomers and styrene with a free radical polymerization initiator (AIBN). 相似文献
7.
Teresa M. V. D. Pinho e Melo Clara S. B. Gomes Maria I. L. Soares Antanio M. d'A Rocha Gonsalves Jos A. Paixo Ana M. Beja Manuela Ramos Silva 《Journal of heterocyclic chemistry》2004,41(4):493-497
3‐Carbethoxy‐5‐phenyl‐5H,7H‐thiazolo[3,4‐c]oxazol‐4‐ium‐1‐olate was generated from (2R,4R)‐N‐ethoxyoxalyl‐2‐phenylthiazolidine‐4‐carboxylic acid and its reactivity studied. This münchnone showed low reactivity as dipole although from the reaction with dimethyl acetylenedicarboxylate the corresponding (3R)‐3‐phenyl‐17H,3H‐pyrrolo[1,2‐c]thiazole‐5,6,7‐tricarboxylate could be isolated. The thermolysis of (2R,4R)‐N‐ethoxyoxalyl‐2‐phenylthiazolidine‐4‐carboxylic acid in refluxing acetic anhydride led to the synthesis of N‐(1‐ethoxycarbonyl‐2‐phenylvinyl)‐2‐phenyl‐4‐thioxo‐1,3‐thiazolidine. The structure of methyl (2R,4R)‐N‐ethoxyoxalyl‐2‐phenylthiazoliddine‐4‐carboxylate was determined by X‐ray crystallography. 相似文献
8.
A quantitative analysis of cutting thin stainless steel sheets with cw CO2 lasers using an oxygen gas jet assist is reported. Results are interpreted theoretically using a point source model. 相似文献
9.
Small-phase solution to the phase-retrieval problem 总被引:1,自引:0,他引:1
Gonsalves RA 《Optics letters》2001,26(10):684-685
A solution to the phase-retrieval problem when the unknown phase is small is presented. The solution specifies the even and odd parts of the unknown phase in two separate equations. The odd part requires a single intensity measurement, and the even part requires two measurements. Phase diversity is used for the second measurement, and computer simulations are given. 相似文献
10.
By combining the results of IR spectroscopy experiments, both in the transmission and diffuse reflectance modes, with data obtained by HRTEM, XRD and XPS an overall picture of AlN and GaN nanoparticle surface structures and functionality were deduced. The surface species from the IR data analysis indicated that the nanostructured AlN powder surfaces had acidic and weak basic sites in the form of Al3+ and Al3N–, respectively. Also present were -OH, -NH2, and -NH. For GaN, the bulk core of the particle had a zincblendel (FCC) structure with nitrogen vacancies, and the only functionality detected was Ga–H. The surface of the particles had a wurtzite(HCP) structure, with abundant NH and NH2 groups as well as OH and Ga3+ functionalities. 相似文献