全文获取类型
收费全文 | 430篇 |
免费 | 18篇 |
国内免费 | 1篇 |
专业分类
化学 | 268篇 |
晶体学 | 7篇 |
力学 | 27篇 |
数学 | 21篇 |
物理学 | 126篇 |
出版年
2023年 | 5篇 |
2022年 | 4篇 |
2021年 | 11篇 |
2020年 | 9篇 |
2019年 | 10篇 |
2018年 | 16篇 |
2017年 | 4篇 |
2016年 | 23篇 |
2015年 | 11篇 |
2014年 | 14篇 |
2013年 | 27篇 |
2012年 | 22篇 |
2011年 | 30篇 |
2010年 | 28篇 |
2009年 | 20篇 |
2008年 | 26篇 |
2007年 | 21篇 |
2006年 | 30篇 |
2005年 | 19篇 |
2004年 | 17篇 |
2003年 | 14篇 |
2002年 | 6篇 |
2001年 | 6篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1998年 | 6篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 5篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1975年 | 1篇 |
1965年 | 1篇 |
1964年 | 1篇 |
1934年 | 1篇 |
1931年 | 1篇 |
排序方式: 共有449条查询结果,搜索用时 15 毫秒
441.
Perumal Rajakumar Venkatesan KalpanaShanmugam Ganesan Pichai Maruthamuthu 《Tetrahedron letters》2011,52(44):5812-5816
Synthesis of novel dendrimers with benzothiazole as surface group and triazole as branching unit is achieved through click chemistry. The presence of more number of benzothiazole and triazole units increases the molar absorption coefficient and alters the fluorescence as well as electrochemical behaviors in the dendrimers. Dye-sensitized solar cell (DSSC) studies reveal that dendrimers with more number of benzothiazole and triazole groups exhibit better current generating capacity than the dendrimers with lesser number of benzothiazole and triazole groups. Dendrimer 2b shows the maximum current conversion efficiency (η) of 7.1%. 相似文献
442.
Damodharan U Ganesan R Radhakrishnan UC 《Applied biochemistry and biotechnology》2011,165(5-6):1245-1252
Matrix metalloproteinases (MMPs) are a family of zinc-dependent neutral endopeptidases, collectively capable of degrading essentially all matrix components. Elevated levels of distinct MMPs are detected in tumor tissue or serum of patients with advanced cancer, and they are the major prognostic indicators in cancer. Inhibition of MMPs has been explored as a therapeutic goal for almost two decades. Nitric oxide (NO), a free radical plays an important role in signaling pathways in regulation of MMP expression. In the present study, we demonstrated the role of exogenous NO levels in the regulation of MMP2 and MMP9 (gelatinases A and B) in colon cancer cell line WiDr and its inhibition with emodin (a naturally occurring anthraquinone). 相似文献
443.
A new class of macrobicyclic azacryptand containing dipyrrolylmethane subunits with nitrogen bridgeheads was synthesized by the Mannich reaction of the dipyrrolylmethane in the presence of aqueous ammonia. The azacryptand exhibits a staggered conformation in the solid state, but is in a dynamic equilibrium with the eclipsed conformation in solution studied by the variable-temperature (1)H NMR methods. The azacryptand has a specific size suitable only for fluoride ion; large anions such as NO(3)(-) bind in the clefts of the macrobicycle as shown by the X-ray structures of its fluoride ion inclusion and the nitrate anion complexes. The anion binding studies showed that it has high selectivity and affinity for fluoride ion in acetone over other anions studied, which was supported by (1)H and (19)F NMR methods. The azacryptand has fast fluoride ion-mediated proton-deuterium exchanges with acetone-d(6) studied by the (19)F NMR method. 相似文献
444.
M. Ganesan 《Ionics》2008,14(5):395-401
Chromium-substituted Li4Ti5O12 has been investigated as a negative electrode for future lithium batteries. It has been synthesized by a solid-state method
followed by quenching leading to a micron-sized material. The minimum formation temperature of Li4Ti2.5Cr2.5O12 was found to be around 600 °C using thermogravimetric and differential thermal analysis. X-ray diffraction, scanning electron
microscopy, cyclic voltammetry (CV), impedance spectroscopy, and charge–discharge cycling were used to evaluate the synthesized
Li4Ti2.5Cr2.5O12. The particle size of the powder was around 2–4 μm. CV studies reveal a shift in the deintercalation potential by about 40
mV, i.e., from 1.54 V for Li4Ti5O12 to 1.5 V for Li4Ti2.5Cr2.5O12. High-rate cyclability was exhibited by Li4Ti2.5Cr2.5O12 (up to 5 C) compared to the parent compound. The conduction mechanism of the compound was examined in terms of the dielectric
constant and dissipation factor. The relaxation time has been evaluated and was found to be 0.07 ms. The mobility was found
to be 5.133 × 10−6 cm2 V−1 s−1. 相似文献
445.
Motivated by recent experiments, we examine within a percolation model whether there is a quantitative equivalence in the glass transition temperatures of polymer thin films and polymer nanocomposites. Our results indicate that, while the qualitative behaviors of these systems are similar, a quantitative equivalence cannot be established in general. However, we propose a phenomenological scaling collapse of our results which suggests a simple framework by which the results of the thin films may be used to quantitatively predict the properties of polymer nanocomposites. 相似文献
446.
A.P.A. Faiyas E.M. Vinod R. Ganesan 《Journal of magnetism and magnetic materials》2010,322(4):400-10131
Nanoparticles of Fe3O4 were synthesized by co-precipitation in an aqueous solution containing ferrous and ferric salts (1:2) at varying pH with ammonia as a base. It was found that the value of pH influences the reaction mechanism for the formation of Fe3O4. Furthermore, the addition of mercaptoethanol significantly reduced the crystalline size of Fe3O4 nanoparticles from 15.03 to 8.02 nm. X-ray diffraction (XRD) spectra revealed that the synthesized nanoparticles were ε-Fe2O3 or Fe3O4 phase. To further prove the composition of the product, as-prepared Fe3O4 were examined by X-ray photoelectron spectroscopy (XPS). Magnetic properties of the obtained particles were determined by vibrating sample magnetometer (VSM). Further analysis of the X-ray studies shows that while maintaining a pH value of 6 and 9 in a solution containing iron salts II and III ions produces ε-Fe2O3. Whereas a pH value of 11 produces magnetite (Fe3O4) phase. All of these results show that the pH has a major role in the observed phase formation of (Fe3O4) nanoparticles. 相似文献
447.
Pranay Amruth Maroju Ramakrishnan Ganesan Jayati Ray Dutta 《Macromolecular bioscience》2023,23(12):2300296
Surface derivatization is essential for incorporating unique functionalities into biodegradable polymers. Nonetheless, its precise effects on enzymatic biodegradation still lack comprehensive understanding. In this study, a facile solution-based method is employed to surface derivatize poly(ε-caprolactone) films and electrospun fibers with lysozyme, aiming to impart antimicrobial properties and examine the impact on enzymatic degradation. The derivatized films and fibers have shown high antibacterial efficacy against Escherichia coli and Staphylococcus aureus. Through gravimetric analysis, it is observed that the degradation rate experiences a slight decrease upon lysozyme derivatization. However, this reduction is effectively countered by the inclusion of Tween-20, as affirmed by isothermal titration calorimetry. Comparing films and fibers, the latter undergoes degradation at a more accelerated pace, coupled with a rapid decline in molecular weight. This study provides valuable insights into the factors influencing the degradation of surface-derivatized biopolymers through electrospinning, offering a simple strategy to mitigate biomaterial-associated infections. 相似文献
448.
Ananya Tiwari Mamta Yadav Devesh Kumar Singh Vellaichamy Ganesan 《Electroanalysis》2023,35(2):e202200106
This work reports an electrochemical sensing framework for nicotine determination based on glassy carbon electrode (GC) immobilized with Fe(bpy)32+ (where bpy is 2,2’-bipyridyl) supported by Nafion and multi-walled carbon nanotubes (Nf-MWCNTs). Fe(bpy)32+ immobilized Nf-MWCNTs modified GC (GC/Nf-MWCNTs/Fe(bpy)32+) manifests stable redox peaks, characteristics of Fe(bpy)32+. The GC/Nf-MWCNTs/Fe(bpy)32+ exhibits effective electrochemical oxidation of nicotine, diminishing the overpotential relative to GC/Nf-MWCNTs. The limit of detection is 0.1 μM (experimentally observed) with two different linear calibration ranges between 0.1 to 600 μM and 600 to 3000 μM. Electrocatalytic responses observed at GC/Nf-MWCNTs/Fe(bpy)32+ indicate superior performance for nicotine determination with acceptable selectivity, stability, and reproducibility. Additionally, the nicotine present in real samples such as beedi and tobacco are also analyzed with satisfactory recovery percentages. 相似文献
449.
A reaction between 2, 8-dichloro-4, 10-dinitro-5, 11-dehydro-5H, 11H-benzotriazolo[2, 1-a]-benzotriazole 8 and sodium azide in dimethyl sulfoxide produced 3, 9-diazido-4, 10-dinitro-5, 11-dehydro-5H, 11H-benzotriazolo [2, 1-a]benzotriazole 10 rather than the 2.8-diazido isomer 9 expected by direct displacement. Thermolytic elimination of nitrogen (2 moles) converted the dinitro diazide 10 to 3,4,9,10-bisfuroxano-5, 11-dehydro-5H, 11H-benzotriazolo[2, 1-a]benzotriazole 11 that was subsequently nitrated to give the 2,8-dinitro derivative 12 . Similar nitration converted the dinitro diazide 9 to the trinitro 15 and tetranitro 14 derivatives: thermolysis of the latter gave 1,2,7,8-bisfuroxano-4, 10-dinitro-5, 11-dehydro-5H, 11H-benzotriazolo[2, 1-a]-benzotriazole 16 . Nitration (100% HNO3, CF3SO3H) converted compound 16 to the 3,4,10-trinitro derivative 17 , whereas a similar nitration (100% HNO3, FSO3H) gave the title compound BTBB, an insensitive high-energy, high-density (d 2.03 g/cc) molecule. © 1995 John Wiley & Sons, Inc. 相似文献