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21.
J. K. Puri H. Kaur A. Singla 《Phosphorus, sulfur, and silicon and the related elements》2013,188(10):1433-1441
Abstract Here, we report on synthesis of some novel derivatives of dibutyltin dichloride/oxide with assorted drugs containing a labile proton of carboxylic acid or alcohol moiety. Ligands used in these reactions are ampicillin trihydrate (ABP), ibuprofen (BPPA), acetylsalicylic acid (ASA), and acetaminophen (APAP). Characterization and structure elucidation of the complexes was achieved by elemental analysis, infrared spectroscopy and multinuclear (1H, 13C, and 119Sn) NMR spectroscopic studies. Their protonation behavior and stability constants were investigated and corresponding thermodynamic parameters were calculated using pH-potentiometric technique. It was suggested on basis of potentiometric studies that the complexes formed are invariably of 1:2 stoichiometry irrespective of ligand-to-metal ratio. The stability constants represented by log β values at 298 K were found to be in the order: ABP > APAP > BPPA > ASA. The free energy of formation of these complexes has a negative value, which shows that formation of the complexes is a spontaneous process. Also, the negative value of standard enthalpy change indicates that reaction of ligands with metal ion is exothermic and this validates the decrease in the value of log β with increasing temperature. Entropy change is positive which seems to be the driving force for complex formation. 相似文献
22.
A Soibel SS Banerjee Y Myasoedov ML Rapparort E Zeldov S Ooi T Tamegai 《Pramana》2002,58(5-6):893-898
Using a novel differential magneto-optical imaging technique we investigate the phenomenon of vortex lattice melting in crystals
of Bi2Sr2CaCu2O8 (BSCCO). The images of melting reveal complex patterns in the formation and evolution of the vortex solid-liquid interface
with varying field (H)/temperature (T). We believe that the complex melting patterns are due to a random distribution of material disorder/inhomogeneities across
the sample, which create fluctuations in the local melting temperature or field value. To study the fluctuations in the local
melting temperature/field, we have constructed maps of the melting landscape T
m(H, r), viz., the melting temperature (T
m) at a given location (r) in the sample at a given field (H). A study of these melting landscapes reveals an unexpected feature: the melting landscape is not fixed, but changes rather
dramatically with varying field and temperature along the melting line. It is concluded that the changes in both the scale
and shape of the landscape result from the competing contributions of different types of quenched disorder which have opposite
effects on the local melting transition. 相似文献
23.
A Gurtu P K Malhotra I S Mittra P M Sood SC Gupta VK Gupta GL Kaul LK Mangotra Y Prakash NK Rao ML Sharma 《Pramana》1974,3(5):311-322
This is a continuation of our earlier investigation (Gurtuet al 1974Phys. Lett. 50 B 391) on multiparticle production in proton-nucleus collisions based on an exposure of emulsion stack to 200 GeV/c beam at the NAL. It is found that the ratioR em = 〈n s〉/〈n ch〉, where 〈n ch〉 is the charged particle multiplicity in pp-collisions, increases slowly from about 1 at 10 GeV/c to 1·6 at 68 GeV/c and attains a constant value of 1·71 ± 0·04 in the region 200 to 8000 GeV/c. Furthermore,R em = 1·71 implies an effectiveA-dependence ofR A =A 0.18,i.e., a very weak dependence. Predictions ofR em on various models are discussed and compared with the emulsion data. Data seem to favour models of hadron-nucleon collisions in which production of particles takes place through adouble step mechanism,e.g., diffractive excitation, hydrodynamical and energy flux cascade as opposed to models which envisage instantaneous production. 相似文献
24.
Conductivity, static fluorescence and (1)H NMR measurements have been carried out to study the micellar behavior of aqueous solutions of dodecyldimethylethylammonium bromide (DDAB), dodecyltrimethylammonium chloride (DTAC) and tetradecyltrimethylammonium chloride (TDAC) in absence and presence of alpha-cyclodextrin (alpha-CD), beta-cyclodextrin (beta-CD), hydroxypropyl-beta-cyclodextrin (HPbeta-CD) and gamma-cyclodextrin (gamma-CD). The conductivity measurements were carried out at 298.15 K. The influence of cyclodextrins on the micellar parameters, such as cmc* (apparent critical micellar concentration), beta (degree of ionization) have been analyzed. Thermodynamics of the systems was discussed in terms of the change in standard free energy of micellization, DeltaG(m)(0). Micellization was found to be less spontaneous in presence of cyclodextrins. The fluorescence intensity of the surfactant solutions is enhanced by the addition of cyclodextrins. The association constants obtained from conductivity and fluorescence data suggest the binding of gamma-CD with the surfactants to be strongest among all the cyclodextrins used. (1)H NMR chemical shift changes provide powerful means for probing the cyclodextrin-micellar interactions and inclusion of surfactant is shown by the change in the chemical shift of some of the guest and host protons in comparison with the chemical shifts of the same protons in the free compounds. 相似文献
25.
Paramjyot Kumar Jha Jasmeet Kaur Gill Gourav Singla K. Singh O. P. Pandey 《Ionics》2012,18(8):759-767
Composition (100?x) ZrO2 (x) Bi2O3 (x?=?15, 20, 25) is synthesized by solid-state reaction method to study the effect of Bi2O3 doping on ZrO2. The as-prepared samples are characterized by various methods. The X-ray diffraction pattern of all these samples exhibits three phases, namely, m-ZrO2, ??III-Bi2O3, and ??-Bi2O3. The differential thermal analysis curves do not show any phase transition/decomposition, which clearly indicated the stabilization of ??-Bi2O3 phase. The conductivity changes in all the samples are discussed in terms of different phase formations and their volume fractions. The microstructural and energy dispersive analyses indicate the presence of different phases. A maximum conductivity at high temperature (800?°C) was observed for the x?=?25 composition, i.e., ???=?4.21?×?10?2 S/cm. 相似文献
26.
Aaron G Filler Garth T Whiteside Mark Bacon Martyn Frederickson Franklyn A Howe Miri D Rabinowitz Alan J Sokoloff Terrence W Deacon Chris Abell Raj Munglani John R Griffiths B Anthony Bell Andrew ML Lever 《BMC neuroscience》2010,11(1):1-26
Background
Targeted delivery of pharmaceutical agents into selected populations of CNS (Central Nervous System) neurons is an extremely compelling goal. Currently, systemic methods are generally used for delivery of pain medications, anti-virals for treatment of dermatomal infections, anti-spasmodics, and neuroprotectants. Systemic side effects or undesirable effects on parts of the CNS that are not involved in the pathology limit efficacy and limit clinical utility for many classes of pharmaceuticals. Axonal transport from the periphery offers a possible selective route, but there has been little progress towards design of agents that can accomplish targeted delivery via this intraneural route. To achieve this goal, we developed a tripartite molecular construction concept involving an axonal transport facilitator molecule, a polymer linker, and a large number of drug molecules conjugated to the linker, then sought to evaluate its neurobiology and pharmacological behavior.Results
We developed chemical synthesis methodologies for assembling these tripartite complexes using a variety of axonal transport facilitators including nerve growth factor, wheat germ agglutinin, and synthetic facilitators derived from phage display work. Loading of up to 100 drug molecules per complex was achieved. Conjugation methods were used that allowed the drugs to be released in active form inside the cell body after transport. Intramuscular and intradermal injection proved effective for introducing pharmacologically effective doses into selected populations of CNS neurons. Pharmacological efficacy with gabapentin in a paw withdrawal latency model revealed a ten fold increase in half life and a 300 fold decrease in necessary dose relative to systemic administration for gabapentin when the drug was delivered by axonal transport using the tripartite vehicle.Conclusion
Specific targeting of selected subpopulations of CNS neurons for drug delivery by axonal transport holds great promise. The data shown here provide a basic framework for the intraneural pharmacology of this tripartite complex. The pharmacologically efficacious drug delivery demonstrated here verify the fundamental feasibility of using axonal transport for targeted drug delivery. 相似文献27.
Rohit Singla Deepika Gautam Poonam Gautam 《Phosphorus, sulfur, and silicon and the related elements》2016,191(5):740-745
A simple, efficient, and eco-friendly procedure for the synthesis of thiazolidin-4-one derivatives in water from cyclocondensation reaction of thiosemicarbazone derivatives and dimethylacetylene dicarboxylate (DMAD) in good yield is reported. The regiochemistry of the cyclized products is established by elemental analysis, IR, NMR, and mass spectral data. A single crystal X-ray diffraction study of a representative compound, 3f, is reported. 相似文献
28.
29.
Manisha Singla Pavan Mathur 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2009,74(2):536-543
A pentakis benzimidazole based penta-amide ligand diethylenetriamine—N,N,N′,N′,N″-pentakis(2-methyl benzimidazolyl)penta-amide [GBDTPA] has been synthesized and utilized to prepare Mn (II) complexes of general composition [Mn2(GBDTPA)X4], where X is an exogenous anionic ligand (X = Cl−, NO3− and Br−). The oxidation of alcohols has been investigated using [Mn2(GBDTPA)Cl4] as the catalyst and TBHP as an alternate source of oxygen. The respective aldehydic products have been isolated and characterized by 1H NMR. 相似文献
30.
Caviglia AD Scherwitzl R Popovich P Hu W Bromberger H Singla R Mitrano M Hoffmann MC Kaiser S Zubko P Gariglio S Triscone JM Först M Cavalleri A 《Physical review letters》2012,108(13):136801
We report on ultrafast optical experiments in which femtosecond midinfrared radiation is used to excite the lattice of complex oxide heterostructures. By tuning the excitation energy to a vibrational mode of the substrate, a long-lived five-order-of-magnitude increase of the electrical conductivity of NdNiO(3) epitaxial thin films is observed as a structural distortion propagates across the interface. Vibrational excitation, extended here to a wide class of heterostructures and interfaces, may be conducive to new strategies for electronic phase control at THz repetition rates. 相似文献