全文获取类型
收费全文 | 770篇 |
免费 | 35篇 |
国内免费 | 8篇 |
专业分类
化学 | 549篇 |
晶体学 | 6篇 |
力学 | 52篇 |
数学 | 93篇 |
物理学 | 113篇 |
出版年
2024年 | 1篇 |
2023年 | 6篇 |
2022年 | 14篇 |
2021年 | 18篇 |
2020年 | 54篇 |
2019年 | 41篇 |
2018年 | 40篇 |
2017年 | 36篇 |
2016年 | 44篇 |
2015年 | 44篇 |
2014年 | 46篇 |
2013年 | 87篇 |
2012年 | 60篇 |
2011年 | 62篇 |
2010年 | 42篇 |
2009年 | 50篇 |
2008年 | 27篇 |
2007年 | 20篇 |
2006年 | 20篇 |
2005年 | 21篇 |
2004年 | 17篇 |
2003年 | 10篇 |
2002年 | 4篇 |
2001年 | 3篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 6篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有813条查询结果,搜索用时 15 毫秒
11.
M. S. Masoud E. A. Khalil E. El-Sayed El-Shereafy S. A. El-Enein 《Journal of Thermal Analysis and Calorimetry》1990,36(3):1033-1038
The thermal behaviour of the entitled nickel(II) and copper(II) complexes of ¯4-acetylamino-2-hydroxy-5-methyl azobenzene has been studied by means of differential thermal analysis (DTA), thermogravimetry (TG), X-ray powder diffraction, IR and electrical conductivity. A light has been thrown on the nature of interaction of the solvents of crystallization with the host complex. Some of the kinetic parameters are calculated and discussed. 相似文献
12.
The reaction of an ethanolic solution 2,6‐pyridinedicarboxylic acid ( 1 , LH2) with TlNO3 in the presence of triethylamine led to the coordination polymer [Tl(LH)]n ( 2 ). The complex was characterized by elemental analysis, IR spectroscopy and single‐crystal X‐ray diffraction. Crystal data for 2 at –80 °C: monoclinic, space group I2/a, a = 696.1(1), b = 1190.6(2), c = 931.0(2) pm, β = 103.28(1)°, Z = 4, R1 = 0.0256. 相似文献
13.
M. I. El-Barghouthi N. A. Masoud J. K. Al-Kafawein M. B. Zughul A. A. Badwan 《Journal of inclusion phenomena and macrocyclic chemistry》2005,53(1-2):15-22
The solubility of risperidone (Risp) in aqueous buffered cyclodextrin (CD) solution was investigated for α-, β-, γ- and HP-β-CD. The effects of pH, ionic strength and temperature on complex stability were also explored. Neutral Risp tends to form
higher order complexes (1:2) with both β- and HP-β-CD, but only 1:1 type complexes with α-, and γ-CD. The tendency of Risp to complex with cyclodextrins is in the order β-CD > HP-β-CD > γ-CD > α-CD. The 1:1 complex formation constant of Risp/HP-β-CD increases with increasing ionic strength in an opposite trend to the inherent solubility (S
0) of Risp, thus indicating significant hydrophobic effect. The hydrophobic effect contributes to the extent of 72% towards
neutral Risp/HP-β-CD complex stability, while specific interactions contribute only 4.7 kJ/mol. Thermodynamic studies showed that 1:1 Risp/HP-β-CD complex formation is driven by a favorable enthalpy change (ΔH
0=−31.2 kJ/mol, ΔS
0=−7 J/mol.K) while the 1:2 complex is largely driven by entropy changes (ΔH
0=−5.0 kJ/mol, ΔS
0=42 J/mol.K). Complex stability was found to vary with pH, with a higher formation constant for neutral Risp. Molecular mechanical
computations using MM (atomic charges and bond dipole algorithms) and Amber force fields, which were carried out to explore
possible sites of interactions between Risp and CDs and to rationalize complex stoichiometry, produced similar results concerning
optimal inclusion complex geometries and stoichiometries. 相似文献
14.
The reaction of 2,6‐pyridinedicarboxylic acid ( 1 , LH2) with CeCl3·7H2O and Sm(NO3)3·6H2O in the presence of triethylamine led to the coordination polymer complexes [M(L)(LH)(H2O)2]·4H2O [M = Ce ( 2 ) and Sm ( 3 )]. Both complexes were characterized by elemental analyses, IR spectroscopy and the crystal structures of 2 and 3 . Crystal data for 2 at ?80 °C: monoclinic, space group P21/c, a = 1404.6(1), b = 1122.1(1), c = 1296.1(1) pm, β = 102.09(1)°, Z = 4, R1 = 0.0217 and for 3 at ?80 °C: monoclinic, space group P21/c, a = 1395.1(1), b = 1120.1(1), c = 1282.8(1) pm, β = 102.71(1)°, Z = 4, R1 = 0.019. 相似文献
15.
Alfy Badie Sakla Nabil Khalil Masoud Zaki Sawiris Wagih Sadik Ebaid 《Helvetica chimica acta》1974,57(2):481-487
Aryldiazophenyl sulfides prepared from diazotised arylamines and thiophenol at controlled pH, are coupled with β-naphthol yielding the corresponding azo dye. A kinetic study of the diazo coupling reaction of p-nitrobenzenediazo phenyl sulfide with β-naphthol under various conditions revealed that the reaction is of first order kinetics with respect to the diazo phenyl sulfide, and that the rate of coupling measured colorimetrically is influenced by the hydrogen ion concentration and by the ionising power of the medium. 相似文献
16.
Nabavizadeh SM 《Dalton transactions (Cambridge, England : 2003)》2005,(9):1644-1648
Methyltrioxorhenium (MTO) adduct formation with bidentate nitrogen donors 2,2'-bipyridine (bpy), 4,4'-dimethyl-2,2'-bipyridine (Me(2)bpy), 4,4'-di-tert-butyl-2,2'-bipyridine (tBu2bpy), 1,10-phenanthroline (phen), 5-methyl-1,10-phenanthroline (5-Mephen), 5-chloro-1,10-phenanthroline (5-Clphen), 4,7-dimethyl-1,10-phenanthroline (Me2phen) has been studied at different temperatures in CHCl3 solution. Spectrophotometeric measurements have been carried out to obtain the thermodynamic parameters. All complexes are enthalpy stabilized whereas the entropy changes counteract the adduct formation. The results are discussed in terms of different basicities of the bidentate N-donors. 相似文献
17.
Garbuzenko O Zalipsky S Qazen M Barenholz Y 《Langmuir : the ACS journal of surfaces and colloids》2005,21(6):2560-2568
The electrostatics of large unilamellar vesicles (LUVs) of various lipid compositions were determined and correlated with steric stabilization. The compositional variables studied include (a) degree of saturation, comparing the unsaturated egg phosphatidylcholine (EPC) and the fully hydrogenated soy phosphatidylcholine (HSPC) as liposome-forming lipids; (b) the effect of 40 mol % cholesterol; (c) the effect of mole % of three methyl poly(ethylene glycol) (mPEG)-lipids (the negatively charged mPEG-distearoyl phosphoethanolamine (DSPE) and two uncharged lipopolymers, mPEG-distearoyl glycerol (DSG) and mPEG-oxycarbonyl-3-amino-1,2-propanediol distearoyl ester (DS)); and (d) the negatively charged phosphatidyl glycerol (PG). The lipid phases were as follows: liquid disordered (LD) for the EPC-containing LUV, solid ordered (SO) for the HSPC-containing LUV, and liquid ordered (LO) for either of those LUV with the addition of 40 mol % cholesterol. The LUV zeta potential and electrical surface potential (psi(0)) were determined. It was found that progressive addition of mPEG(2k)-DSPE to liposomes increases negative surface potential and reduces surface pH to a similar extent as the addition of PG. However, due to the "hidden charge effect", zeta potential was more negative for liposomes containing PG than for those containing mPEG(2k)-DSPE. Replacing mPEG-DSPE with mPEG(2k)-DS or mPEG-DSG had no effect on surface pH and surface potential, and zeta potential was approximately zero. Addition of low concentrations of cationic peptides (protamine sulfate and melittin) to PG- or mPEG-DSPE-containing liposomes neutralized the liposome negative surface potential to a similar extent. However, only in liposomes containing PG, did liposome aggregation occur. Replacing the negatively charged lipopolymer mPEG-DSPE with the neutral lipopolymers mPEG-DS or mPEG-DSG eliminates or reduces such interactions. The relevance of this effect to the liposome performance in vivo is discussed. 相似文献
18.
Zheng Yuanzhou Yang Haoran Mazaheri Hossein Aghaei Alireza Mokhtari Namjoo Afrand Masoud 《Journal of Thermal Analysis and Calorimetry》2021,143(2):1425-1438
Journal of Thermal Analysis and Calorimetry - The purpose of this study is to numerically investigate flow field and turbulent heat transfer of hybrid nanofluid, water–DWCNT–TiO2 in a... 相似文献
19.
Molecular Diversity - Nowadays, one of the principal causes of death in the world is cancer. A series of 2-azetidinones containing anthraquinone moiety with various substituents were synthesized... 相似文献
20.
Alamdarlo Farzad Vaziri Solookinejad Ghahraman Zahakifar Fazel Jalal Masoud Rezvani Jabbari Masoud 《Journal of Radioanalytical and Nuclear Chemistry》2021,329(2):1033-1043
Journal of Radioanalytical and Nuclear Chemistry - In this work, graphene oxide (GO) and (aminomethyl)phosphonic acid–Graphene oxide (AMPA–GO) adsorbents were prepared by the modified... 相似文献