全文获取类型
收费全文 | 698篇 |
免费 | 18篇 |
国内免费 | 3篇 |
专业分类
化学 | 459篇 |
晶体学 | 5篇 |
力学 | 11篇 |
数学 | 32篇 |
物理学 | 212篇 |
出版年
2024年 | 5篇 |
2023年 | 7篇 |
2022年 | 21篇 |
2021年 | 15篇 |
2020年 | 16篇 |
2019年 | 21篇 |
2018年 | 16篇 |
2017年 | 23篇 |
2016年 | 27篇 |
2015年 | 12篇 |
2014年 | 17篇 |
2013年 | 57篇 |
2012年 | 25篇 |
2011年 | 31篇 |
2010年 | 26篇 |
2009年 | 27篇 |
2008年 | 25篇 |
2007年 | 28篇 |
2006年 | 34篇 |
2005年 | 25篇 |
2004年 | 20篇 |
2003年 | 12篇 |
2002年 | 18篇 |
2001年 | 13篇 |
2000年 | 8篇 |
1999年 | 14篇 |
1998年 | 5篇 |
1997年 | 5篇 |
1996年 | 6篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 6篇 |
1991年 | 5篇 |
1989年 | 10篇 |
1988年 | 4篇 |
1987年 | 9篇 |
1986年 | 5篇 |
1985年 | 6篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1982年 | 15篇 |
1981年 | 13篇 |
1980年 | 9篇 |
1979年 | 10篇 |
1978年 | 10篇 |
1977年 | 6篇 |
1976年 | 6篇 |
1975年 | 4篇 |
1973年 | 9篇 |
1963年 | 3篇 |
排序方式: 共有719条查询结果,搜索用时 0 毫秒
31.
32.
33.
Padma L. Nayak Rajani K. Samal Mohan C. Nayak 《Journal of polymer science. Part A, Polymer chemistry》1979,17(1):1-7
The kinetics of thermal polymerization of methyl methacrylate initiated by the redox system Mn(III)–glycerol was studied in aqueous sulfuric acid in the temperature range of 30–40°C, and the rates of polymerization, Rp, and Mn3+ disappearance, etc., were measured. The effect of certain water-miscible organic solvents and certain cationic and anionic surfactants on the rates of polymerization has been investigated. A mechanism involving the formation of a complex between Mn3+ and glycerol whose decomposition yields the initiating free radical with the polymerization being terminated by the metal ion has been suggested. 相似文献
34.
The thermal stability of some boracites, CuB7O13Cl, NiB7O13Br and FeB7O13I, was investigated using thermogravimetry in air up to 1000°, DTA in air to 1200° and evolved gas analysis in vacuum to 1200°C. Only the FeI compound showed weight loss below 1000°C. The endothermic peaks associated with melting were CuCl (1025°C), NiBr (1150°C) and FeI) (965°C). Evolved gas analysis indicated major differences in the decomposition products of the three materials. 相似文献
35.
Divyaraj Puthran Boja Poojary Soukhyarani G. Nayak Nikil Purushotham Manjunath Bhat Hemant Hedge 《中国化学会会志》2020,67(7):1278-1288
2-amino-5-(3-fluoro-4-methoxyphenyl)thiophene-3-carbonitrile derivatives have been synthesized from 1-(3-fluoro-4-methoxyphenyl)ethanone, malononitrile, mild base, and sulfur powder using the Gewald method through a multistep reaction sequence. The structures of newly synthesized compounds were established on the basis of their elemental analyses, IR, 1H NMR, 13C NMR, and mass spectral data, and then synthesized compounds were screened for their in vitro antimicrobial activity. Among them, derivatives 3b (thiphene), 3f (pyrazole), and 3d (halogen) showed good activity and remaining derivatives exhibited moderate activity. 相似文献
36.
The graft copolymerization of methyl methacrylate onto poly-(ethylene terephthalate) using metal complexes of Mn3+, Co3+, and Fe3+ as initiators was studied. The rate of polymerization, Rp, increased with increasing complex concentrations. The rate of polymerization was also studied by varying monomer concentrations. Increasing monomer concentrations, the rate of polymerization increases significantly. The graft yield increases with increasing temperature within the range 60–75°C. The graft yield is medium dependent. A suitable kinetic scheme has been pictured and rate equations have been derived. 相似文献
37.
Ghosh K Semwal A Nayak SK Banerjee SB Banerjee M 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2007,66(4-5):1122-1125
[60]- and [70]Fullerenes have been shown to form 1:1 supramolecular complexes with bis[2-(5,11,17,23,29,35-hexa-tert-butyl-37,38,39,40,41-pentahydroxycalix[6]arenyl-oxy ethyl ether) (1) and 5,11,17,23,29,35-hexa-tert-butyl-37,38,40,41-tetra hydroxyl-39,42-(crown-4)calix[6]arene (2) in CHCl3 medium by electronic absorption spectroscopy. Formation constants (K) of the complexes of [60]- and [70]fullerenes with 1 and 2 have been determined at room temperature from which free energy of formation values of the complexes have been estimated. The very high formation constant value of [60]fullerene/1 complex (5900 dm3 mol-1) in indicative of formation of inclusion complex. Moreover, PM3 calculations reveal that intermolecular interaction between [60]fullerene and 1 proceeds through quite deep energy molecular orbital. 相似文献
38.
Jena Sudipta Ray Asit Sahoo Ambika Kamila Pradeep Kumar Nayak Sanghamitra Panda Pratap Chandra 《Chemistry of Natural Compounds》2021,57(6):1147-1149
Chemistry of Natural Compounds - 相似文献
39.
The MnIV complex of tetra-deprotonated 1,8-bis(2-hydroxybenzamide)-3,6-diazaoctane (MnIVL) engrossed in phenolate-amido-amine coordination is reduced by HSO3− and SO32− in the pH range 3.15–7.3 displaying biphasic kinetics, the MnIIIL− being the reactive intermediate. The MnIIIL− species has been characterized by u.v.–vis. spectra {λ max, (ε, dm3 mol−1 cm−1): 285(15 570), 330 sh (7570), 469(6472), 520 sh (5665), pH=5.42}. SO42− was the major oxidation product of SIV; dithionate is also formed (18 ± 2% of [MnIV]T) which suggests that dimerisation of SO3−• is competitive with its fast oxidation by MnIV/III. The rates and activation parameters for MnIVL + HSO3− (SO32−) → MnIIIL−; MnIIIL− + HSO3− (SO32−) → MnIIL2− are reported at 28.5–45.0 °C (I=0.3 mol dm−3, 10% (v/v) MeOH + H2O). Reduction by SO32− is ca. eight times faster than by HSO3− both for MnIVL and MnIIIL−. There was no evidence of HSO3−/SO32− coordination to the Mn centre indicating an outer sphere (ET) mechanism which is further supported by an isokinetic relationship. The self exchange rate constant (k22) for the redox couple, MnIIIL−/MnIVL (1.5 × 106 dm3 mol−1 s−1 at 25 °C) is reported. 相似文献
40.
Amal Halder Sandip K. Nayak Subrata Chattopadhyay Sumanta Bhattacharya 《Journal of solution chemistry》2012,41(2):223-240
The present article reports the host-guest complexation of a calix[4]arene derivative, namely 4-iso-propyl-calix[4]arene (1), with fullerenes (both C60 and C70) in toluene and benzonitrile solutions. It is observed that the charge-transfer (CT) absorption bands are located in the
ground state for the C60 and C70 complexes of 1. By utilizing the CT absorption bands, various important physicochemical parameters like the oscillator strength, resonance
energy, transition dipole moment, electronic coupling element and solvent reorganization energies have been estimated for
the C60-1 and C70-1 complexes. The CT transition energy is very helpful for determining the vertical ionization potential of 1 in solution. Jobs method of continuous variation was used to establish 1:1 stoichiometry for the fullerene complexes of 1. The most fascinating feature of the present study is that 1 binds C70 preferentially compared to C60 as obtained from binding constant (K) data. The effect of solvent on the complexation of fullerenes (C60 and C70) with 1 is clearly observed from the trend in the K values: in toluene and whereas in benzonitrile, and . Molecular mechanics force field (MMMF) calculations reveal fascinating features regarding the binding pattern of fullerenes
towards 1 in vacuo in terms of enthalpy of formation. MMMF calculations establish that during C70-1 complexation, C70 is directed in an end-on manner rather than the traditional side-on pattern. 相似文献