全文获取类型
收费全文 | 241篇 |
免费 | 2篇 |
专业分类
化学 | 193篇 |
晶体学 | 1篇 |
数学 | 10篇 |
物理学 | 39篇 |
出版年
2022年 | 3篇 |
2021年 | 2篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2014年 | 8篇 |
2013年 | 28篇 |
2012年 | 15篇 |
2011年 | 7篇 |
2010年 | 12篇 |
2009年 | 13篇 |
2008年 | 11篇 |
2007年 | 8篇 |
2006年 | 8篇 |
2005年 | 6篇 |
2004年 | 3篇 |
2003年 | 5篇 |
2002年 | 3篇 |
1998年 | 3篇 |
1996年 | 1篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 1篇 |
1982年 | 7篇 |
1981年 | 10篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 1篇 |
1974年 | 3篇 |
1973年 | 1篇 |
1971年 | 2篇 |
1970年 | 3篇 |
1969年 | 2篇 |
1968年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有243条查询结果,搜索用时 15 毫秒
121.
Sudhansu Bhusan Dash Nilambar Baral Nrusingha C. Pati Padma L. Nayak 《Journal of polymer science. Part A, Polymer chemistry》1982,20(9):2371-2379
The kinetics of the aqueous polymerization of methyl methacrylate initiated by potassium peroxydisulfate–citric acid catalyzed by silver ion was investigated in nitrogen atmosphere. The rate of polymerization is proportional to the square root of peroxydisulfate concentration. The initial rate increases with increasing citric acid concentration up to 15 × 10?3M, after which it decreases. The rate of polymerization also increases initially with monomer concentration and decreases at higher monomer concentration. The effects of temperature and the addition of some solvents and salts on the rate of polymerization have also been studied and a suitable kinetic scheme has been proposed for the reaction. 相似文献
122.
A method is described for the flotation and determination of Mo(VI) in water at ng/ml levels. Mo(VI) is preconcentrated and separated by adsorbing colloid flotation employing aluminium(III) hydroxide as collector and sodium lauryl sulphate as surfactant at pH 5.3 ± 0.1. The molybdenum content in the froth is estimated by using the catalytic wave of Mo(VI) in the presence of nitrate by charging current compensated d.c. polarography (CCCDCP) or differential pulse polarography (DPP). The effect of variables such as pH, ionic strength, concentration of collector and surfactant, time of stirring and gas flow-rate on the recovery of Mo by flotation is reported. The effects of various cations and anions on the flotation and determination of Mo are studied. This method is employed for the determination of molybdenum in natural fresh water samples. 相似文献
123.
Venkatanarayanan A Spehar-Délèze AM Dennany L Pellegrin Y Keyes TE Forster RJ 《Langmuir : the ACS journal of surfaces and colloids》2008,24(19):11233-11238
The oxidative electropolymerization of [Ru(aphen)3](PF6)2 from an ionic liquid, 1-butyl-2,3-dimethylimidazolium bis[(trifluoromethyl)sulfonyl]imide (BDMITFSI), is reported; aphen is 5-amino-1,10-phenanthroline. The deposition rate in the ionic liquid is more than an order of magnitude faster than in conventional solvents such as anhydrous acetonitrile and aqueous sulfuric acid. The UV-vis absorbance, Raman, and emission spectra of the films grown in ionic liquid, acetonitrile, and sulfuric acid suggest that the polymer formed does not depend on the solvent. However, scanning electron microscopy shows that the film morphologies differ significantly; e.g., films deposited from BDMITFSI have high surface roughness, while films produced in acetonitrile and sulfuric acid are relatively smooth. The rate of homogeneous charge transport through films grown in ionic liquids is (6.4 +/- 1.2) x 10(-9) cm (2) s (-1), which is approximately 2 orders of magnitude faster than that found for films deposited from acetonitrile. Thin electropolymerized films generate electrochemiluminescence (ECL) in the presence of tripropylamine as a coreactant. Films produced from sulfuric acid are very thin compared to the ones produced in BDMITFSI; however, they produce an ECL signal of similar intensity. The ECL responses of films produced in anhydrous acetonitrile are significantly less intense. The ECL intensity within the films is approximately 5-fold higher than when they are dissolved and measured in solution. 相似文献
124.
125.
S. Padma V. Mahadevan M. Srinivasan 《Journal of polymer science. Part A, Polymer chemistry》1988,26(1):195-200
Polybenzoxazinones were prepared in two successive steps from methylene-4,4′-diaminodiphenyl-3,3′-dicarboxylic acid and azodicarbonyl chloride in 40–60% yield. These polymers were characterized by molecular weight and IR and NMR spectra. Their physical properties like solubility, viscosity, and thermal stability were also studied in detail. 相似文献
126.
Kurma Srimathi Dasari Gouthami Nukala Satheesh Kumar Ravula Sharada Kandukuri Padma Bandari Srinivas 《Russian Journal of General Chemistry》2022,92(7):1326-1332
Russian Journal of General Chemistry - A series of new quinoxaline-1,2,4-thiadiazoles amide hybrids has been synthesized and evaluated for their anti-proliferative activity on four different human... 相似文献
127.
5, 10, 15, 20-tetrakis-(4-chlorophenyl) porphyrin, H2TTPCl4, has been isolated as a new polymorph following the modified Adler’s method and its X-ray crystal structure solved. The new polymorph (I) crystallises in the monoclinic space group, P21/n with a?=?10.1574(5) Å, b?=?8.9827(4) Å, c?=?20.9350(8) Å, β?=?102.532(4)°, V?=?1864.62(15) Å3, Z?=?2. The previously found polymorph, prepared using Lindsay method was crystallised in monoclinic space group, P21/a with a?=?15.776 (13) Å, b?=?8.646 (3) Å, c?=?14.087 (5) Å, β?=?96.05 (5)°, V?=?1910.7 (3) Å3, Z?=?2. The main difference between the two polymorphs seems to be the different packing arrangement of molecules in their crystal lattices. The dramatic self aggregation property of new polymorph (I) has also been investigated. The investigation reveals that under certain conditions of solute concentration and pH of the media, the compound exhibits a strong tendency to exist in a prominent self aggregated state in head-to-tail type (j-aggregation) molecular alignment. The self association behaviour of (I) was confirmed by UV-Vis absorption spectra, performed in chloroform by varying concentrations and pH changes and 1H NMR spectra, performed in deuterated chloroform at varying concentrations and their results have been discussed in detail. 相似文献
128.
129.
130.
Lea Gimeno Dr. Errol Blart Dr. Jean-Noël Rebilly Marina Coupeau Magali Allain Thierry Roisnel Alexis Quarré de Verneuil Dr. Christophe Gourlaouen Prof. Chantal Daniel Dr. Yann Pellegrin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(51):11887-11899
A strategy is presented to improve the excited state reactivity of homoleptic copper–bis(diimine) complexes CuL2+ by increasing the steric bulk around CuI whereas preserving their stability. Substituting the phenanthroline at the 2-position by a phenyl group allows the implementation of stabilizing intramolecular π stacking within the copper complex, whereas tethering a branched alkyl chain at the 9-position provides enough steric bulk to rise the excited state energy E00. Two novel complexes are studied and compared to symmetrical models. The impact of breaking the symmetry of phenanthroline ligands on the photophysical properties of the complexes is analyzed and rationalized thanks to a combined theoretical and experimental study. The importance of fine-tuning the steric bulk of the N–N chelate in order to stabilize the coordination sphere is demonstrated. Importantly, the excited state reactivity of the newly developed complexes is improved as demonstrated in the frame of a reductive quenching step, evidencing the relevance of our strategy. 相似文献