全文获取类型
收费全文 | 175篇 |
免费 | 6篇 |
国内免费 | 6篇 |
专业分类
化学 | 167篇 |
晶体学 | 1篇 |
数学 | 1篇 |
物理学 | 18篇 |
出版年
2023年 | 2篇 |
2022年 | 22篇 |
2021年 | 11篇 |
2020年 | 6篇 |
2019年 | 6篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 5篇 |
2014年 | 9篇 |
2013年 | 16篇 |
2012年 | 9篇 |
2011年 | 12篇 |
2010年 | 5篇 |
2009年 | 3篇 |
2008年 | 8篇 |
2007年 | 4篇 |
2006年 | 1篇 |
2005年 | 7篇 |
2004年 | 6篇 |
2003年 | 4篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1998年 | 2篇 |
1997年 | 4篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1983年 | 1篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有187条查询结果,搜索用时 948 毫秒
41.
An improved form of the radiative-Auger-cascade model is presented in which the shake-off contribution is incorporated into the model in a mathematically consistent way, avoiding the problem of double counting. The higher charge state distribution found in the photoionization experiment of the 1s electron in Ne is shown to be predominantly due to the shake-off effect during the formation of the 1s hole, and not during the cascade decays as previously assumed. This shake-off contribution is estimated in the sudden approximation, in terms of overlaps between the neutral and singly ionized ions. An excellent agreement with experiment is obtained in the case of Ne+ with 1s hole. The details of the X-ray and Auger spectra are also predicted by the new model both for the Ne and Mg ions. The shake-off effect on the resonant processes in general is discussed. 相似文献
42.
Ibrahim El-Sayed El-Kholy Mohamed Gaber Marei Morcos Michael Mishrikey 《Journal of heterocyclic chemistry》1979,16(4):737-743
A simple method for the synthesis of acetylenic β-diketones is described. They can be cyclized to the corresponding 4H-pyran-4-ones with acids. Their reaction with hydrazine hydrate gave pyrazole derivatives isomeric with those obtained from 4H-pyran-4-ones. With hydroxyl-amine hydrochloride in ethanol, 1-hydroxy-4-pyridones are formed. 相似文献
43.
Said Ahmed Soliman Ghozlan Ismail Abdelshafy Abdelhamid Mohamed Hilmy Elnagdi Hatem Moustafa Gaber 《Journal of heterocyclic chemistry》2005,42(6):1185-1189
3‐Diethylaminoacrylonitrile ( 1 ) reacts with hydrazonyl halides ( 2a‐d ) to yield 1,3‐disubstituted pyrazole‐4‐carbonitriles 5a‐d. The acetyl 1‐p‐chlorophenylpyrazole‐4‐carbonitrile ( 5a ) condensed with hydrazine hydrate to yield the bishydrazone 10 and with dimethylformamide dimethylacetal to yield 1‐aryl‐3‐(3‐dimethylamino)acryloyl pyrazole‐4‐carbonitrile ( 11 ). This enamine reacts with hydrazine hydrate to yield the pyrazolylpyrazole ( 12 ) and with naphthoquinone to yield the 3‐naphthofuranoyl pyrazole 13. The pyra‐zolyl pyridine derivative 14 was obtained upon treatment of 11 with acetylacetone in the presence of ammonium acetate. Compound 11 was coupled with p‐chlorobenzene diazonium chloride to yield the hydrazone 16 that was coupled further with p‐chlorobenzenediazonium chloride to yield the formazane 18. 相似文献
44.
A novel chemosensor, namely 3‐(4‐chlorophenyl)‐1‐(pyridin‐2‐yl)prop‐2‐en‐1‐one, CPPEO, and its metal complexes have been synthesized and characterized by using sets of chemical and spectroscopic techniques, such as elemental analysis, mass, Fourier transform‐infrared and UV–Vis spectral analysis. The thermal properties of the metal complexes have been investigated by thermogravimetric techniques. The decomposition mechanism of the titled complexes was suggested. The results showed that the Co2+ and Mn2+ complexes have an octahedral geometry, while Zn2+ and Cd2+ complexes have tetrahedral geometry. The kinetic and thermodynamic parameters of the thermal decomposition stages have been evaluated using the Coats–Redfern method. The optical sensing response of the investigated chemosensor to the different metal ions was investigated. It responds well to the tested metal ions as reflected from the significant change in both absorption and emission spectra upon adding different concentrations of the metal salts, confirming the intramolecular charge transfer of the chemosensor upon effective coordination with the used metal ions. This leads to enhancing ICT interaction, causing a significant shift in the presence of strongly complexing metal ions. This was fully reversible, where the solution of dye‐metal ion complex was decomplexed by adding an EDTA solution to revert the original spectrum of the dye. The stability constants, K, for the complexes of the investigated chemosensor with the mentioned metal ions were calculated, indicating that Co2+ is the most effectively detected, and the potential of the novel dye was highly efficient switchers for Co2+ ions. Additionally, the molecular modeling was carried out for the chemosensor and its metal complexes. Finally, the solid complexes have been tested for their in vitro antimicrobial activities against some bacterial strains (Gram +ve and Gram ?ve bacteria), as well as antifungal strains. 相似文献
45.
46.
M. Gaber A. F. Rehab D. F. Badr-Eldeen 《Journal of Thermal Analysis and Calorimetry》2008,91(3):957-962
The macrocyclic complexes of Co(II) and Ni(II) having chloride or thiocyanate ions in the axial position have been synthesized
and characterized. These complexes are synthesised by the template condensation of o-phenylenediamine or 2,3-butanedionedihydrazone with the appropriate aldehydes in NH4OH solution in the presence of the metal ions, Co(II) and Ni(II). The complexes were characterized by spectroscopic methods
(IR, UV-Vis and ESR) and magnetic measurements as well as thermal analysis (TG and DTA). The results obtained are commensurate
with the proposed formulae. Spectral studies indicate that these complexes have an octahedral structure. From conductivity
measurements the complexes are non-electrolytes. The kinetic of the thermal decomposition of the complexes was studied and
the thermodynamic parameters are reported. 相似文献
47.
The absorption and fluorescence characteristics of (4‐dimethylamino‐benzylidene)‐(4,6‐dimethyl‐pyrimidin‐2‐yl)‐amine (SB) have been investigated in different solvents. Both the absorption and emission spectra of SB exhibit red shifts as the solvent polarity increases. This indicats a change in dipole moment of molecules upon excitation as a result of intramolecular charge transfer interaction. The fluorescence quantum yield depends strongly on the properties of the solvents, which was discussed on the bases of positive and negative solvatokinetic effects. The effect of some divalent transition metal ions such as Mn2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, and Hg2+on the absorption and fluorescence spectra of SB is also investigated. The results were consistent with formation of highly colored metal‐ SB complex which is responsible for the extreme quenching of the fluorescence of SB. The variations of both the formation constant of the complex and Stern‐Volmer constant were correlated with the electronic structure of the used metal ion. 相似文献
48.
Gaber M. Abu El-Reash Kamal M. Ibrahim Tawfik H. Rakha 《Transition Metal Chemistry》1989,14(3):209-212
Summary Complexes of CuII, NiII, CoII, ZnII, CdII and HgII with 4-benzamido-1-o-aminoacetophenone-3-thiosemicarbazone (H2BATS) are reported and have been characterized by elemental analyses, molar conductivities, magnetic moments, spectral (visible, i.r.) and thermal (d.t.a., t.g., d.t.g.) measurements. I.r. spectra show that H2BATS behaves as a dianionic, monoanionic or neutral tetradentate ligand or as a monoanionic tridentate ligand. [Cu2(H2BATS)Cl2]·2H2O and [Cu2(H2BATS)Ac2]·2H2O complexes are diamagnetic while [Co(HBATS)OH]·2H2O and [Ni(HBATS)OH]·2H2O are octahedral. All the complexes are non-electrolytes. Generally, the solid metal acetate complexes have a unique decomposition exotherm profile which can be used as a rapid and sensitive tool for the detection of acetate-containing complexes. 相似文献
49.
M. Gaber S. S. Al-Shihry A. A. El-Bindary 《Journal of Thermal Analysis and Calorimetry》2005,82(1):63-68
Summary Proton-ligand dissociation constant of 2-mercapto-5-(2-hydroxynaphthylideamino)-1,3,4-thiadiazole (MHT) and the stepwise stability
constants of its metal complexes were determined potentiometrically in 40 mass/mass% ethanol-water mixture containing 0.1
M KCl. The stabilities of the complexes follow the order: Cu2+>Ni2+>Co2+>Mn2+. The dissociation constant (pKH) of MHT and the stability constants (logK) of its metal complexes were determined at different temperatures and the corresponding thermodynamic parameters were calculated
and discussed. The proton dissociation process is non-spontaneous, endothermic and entropically unfavoured. The formation
of the metal complexes was found to be spontaneous, endothermic and entropically favoured. 相似文献
50.
Gaber A. Elinany Fikry M. Ebeid Ahmed M. Zahra Farouk I. Ziedan 《Journal of Electroanalytical Chemistry》1976,72(3):363-369
The polarographic behavior of metal ions in perchlorate media containing gallic acid is described. Tungsten(VI) forms a complex with gallic acid which yields a single wave in these media, useful in the polarographic determination of tungsten. Evidence for complexation of chromium(III), copper(II), iron(III), molybdenum(VI), uranium(VI), vanadium(V), tungsten(VI), praseodymium(III), samarium(III), neodymium(III) and gadolinium(III) is obtained and the behavior of these metal ions is summarized. 相似文献