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51.
C. R. Jejurkar Jayrang S. Dave Pratik R. Patel Meera R. Menon 《Molecular Crystals and Liquid Crystals》2013,570(1):753-758
Abstract Four macrocyclic liquid crystalline ligands derived from 1,8 dihydroxy ethyl 1,3,6,8,10,13 hexa aza cyclotetradecane(DHAT) and trans-4-n-alkoxy cinnamoyl chloride have been synthesised and their metal complexes using Cu(II),Ni(II),Pb(II), V(V) and U(VI) metal ions have been isolated. The ligands and their metal complexes were characterised by elemental analysis, FTIR,NMR,X-Ray and DSC studies. Polarising microscope was used to identify mesomorphic textures of the ligands and the complexes. The transition temperature and mesophase textures of the ligands and complexes have been compared. The effect of presence of different metal ions on mesomorphic properties has been discussed. 相似文献
52.
The dielectric response in a magnetic field is routinely used to probe the existence of coupled magnetic and elastic order in the multiferroics. However, here we demonstrate that magnetism is not necessary to produce a magnetocapacitance when the material is inhomogeneous. By considering a two-dimensional, two-component composite medium, we find a characteristic dielectric resonance that depends on magnetic field. We propose this as a possible signature of inhomogeneities and we argue that this behavior has already been observed in nanoporous silicon and some manganites. 相似文献
53.
pH and temperature play critical roles in multistep enzymatic conversions. In such conversions, the optimal pH for individual
steps differs greatly. In this article, we describe the production of glucoamylase (from Aspergillus oryzae MTCC152 in solid-state fermentation) and glucose isomerase (from Streptomyces griseus NCIM2020 in submerged fermentation), used in industries for producing high-fructose syrup. Optimum pH for glucoamylase was
found to be 5.0. For glucose isomerase, the optimum pH ranged between 7.0 and 8.5, depending on the type of buffer used. Optimum
temperature for glucoamylase and glucose isomerase was 50 and 60°C, respectively. When both the enzymatic conversions were
performed simultaneously at a compromised pH of 6.5, both the enzymes showed lowered activity. We also studied the kinetics
at different pHs, which allows the two-step reaction to take place simultaneously. This was done by separating two steps by
a thin layer of urease. Ammonia generated by the hydrolysis of urea consumed the hydrogen ions, thereby allowing optimal activity
of glucose isomerase at an acidic pH of 5.0. 相似文献
54.
B. P. Chandra Yuvaraj Rahangdale Meera Ramrakhiani M. H. Aansari Y. K. Sharma 《Crystal Research and Technology》1992,27(4):561-568
The present paper reports on a statistical model of the mechanoluminescence (ML) excitation in crystals where attempts have been made to explain stress, temperature-, strain rate-, activator concentration dependence and several other aspects of ML. It is found that ML emission should take place only during the period at which stress will change with time. The total ML intensity should be directly proportional to the square of the stress and there should be phase difference between the ML pulse and the applied stress pulse. It is found that the ML intensity should decrease faster with temperature as compared to the corresponding photoluminescence intensity. within the limit of concentration quenching the ML intensity should increase directly with the defect centre concentration. The ML intensity should increase with the stress rate or strain rate of the solids. Furthermore, the concept of mechanoluminescent and non-mechanoluminescent materials is explored. 相似文献
55.
B. P. Chandra S. Tiwari Meera Ramrakhiani M. H. Ansari 《Crystal Research and Technology》1991,26(6):767-781
The paper reports that the mechanoluminescence (ML) is not an inherent property of only the non-centrosymmetric crystals. The ML may appear in number of centrosymmetric crystals due to variety of processes. The ML of 82 centrosymmetric crystals are reported and different models are proposed for the ML excitation. The models proposed are: space charge electrification model, triboelectrification model, phase transformation model, gas adsorption model, chemical reaction model, thermal population model, molecular deformation model, cleavage electrification model, defective piezoelectric phase model, dislocation defect stripping model, dislocation unpinning model, dislocation annihilation model, charged dislocation model and incandecent light emission model. It is shown that on the basis of the proposed model, intense mechanoluminescent materials with desired nature and characteristics may be prepared. 相似文献
56.
A novel method has been found to enhance the metastable zone width of solutions in their supersaturated region in order to grow large size crystals. In which, the incorporation of a small quantity of Ethylenediamine tetra acetic acid (EDTA), a well‐known chelating agent, enhances the zone width significantly due to its chelating action. Also this incorporation reduces the nucleation rate and enhances the growth rate of the crystal. X‐ray rocking curve experiment for the grown crystals reveals that EDTA addition does not affect the crystalline quality. This concept was first realized with Potassium acid phthalate (KAP) solutions and then confirmed with Potassium dihydrogen phosphate (KDP) and Triglycine Sulphate (TGS). 相似文献
57.
Nidhi Adhlakha K.L. YadavAmit Kumar Piyush Kumar PatelJyoti Rani Meera Rawat 《Physica B: Condensed Matter》2012,407(17):3427-3433
We report the study of structural, optical and magnetic properties of (1−x)ZnO–xMgO (x=0.35, 0.40, 0.45 and 0.50) composites prepared by solid state reaction method. X-ray diffraction pattern confirms the presence of both the phases associated with ZnO (hexagonal) and MgO (cubic), which is revealed through the existence of (1 1 1) and (2 0 0) peaks in addition to ZnO peaks. The lattice parameter c as calculated using X-ray analysis undergoes shrinkage with increasing content of MgO. Microstructural analysis suggests that there is no variation in spherical elongated shape of grains with increasing concentration of MgO, where the average grain size is found to be ∼600 nm. The band gap as calculated from optical absorption spectra obtained by diffuse reflectance method recorded at room temperature is tuned from 3.16 to 3.55 eV. Photoluminescence spectra consist of near band edge UV emission (389 nm) and defect level emission (503 nm). The increase of MgO concentration leads to blue shift of UV emission peaks. The magnetic measurements conducted using SQUID at 5 K temperature reveals ferromagnetism along with paramagnetic and superparamagnetic components. Saturation magnetisation (Ms) is observed to be enhanced with MgO doping. 相似文献
58.
Drishty Satpati Archana Mukherjee Meera Venkatesh Sharmila Banerjee 《Journal of Radioanalytical and Nuclear Chemistry》2011,290(1):89-93
The over-expression of folate receptors in variety of neoplastic tissues makes radiolabeled folate conjugates potential agents
for imaging and therapy of such cancers. With the aim of preparing an imaging agent for targeting folate receptors, folic
acid has been conjugated with homocysteine for complexation with [99mTc(CO)3(H2O)3]+ core. The radiolabeled complex of the homocysteine-folate could be obtained in >95% radiochemical yield as observed by HPLC.
Stability of complex in saline was studied and challenge studies with histidine and cysteine revealed kinetic stability of
the complex. Lipophilicity of the radiolabeled complex (log P) was found to be 0.45. In vitro uptake of 99mTc(CO)3-labeled folic acid derivative was studied in KB cells and inhibition studies were carried out using 3H-folic acid and cold homocysteine–folate conjugate. The in vitro studies indicated loss of binding affinity of the derivative
towards folate receptors. 相似文献
59.
Rubel Chakravarty Ramu Ram K. C. Jagdeesan Meera Venkatesh Ashutosh Dash 《Chromatographia》2011,74(7-8):531-540
The present work demonstrates the utility of polymer embedded nanocrystalline titania (TiP) as a new, accessible and viable solid sorbent for the chromatographic separation of high specific activity 77As from neutron irradiated natural GeO2. Experimental parameters such as distribution ratios (K d), equilibrium sorption capacity, breakthrough capacity and separation yields were determined. A two-step ion-exchange procedure was developed to avail 77As, from irradiated Ge in alkaline medium. The first step involved removal of the bulk Ge from 77As by selective sorption of Ge ions on a TiP column at pH 13. Subsequently, the effluent solution containing 77As was further purified and concentrated by sorption on a small TiP column at pH 10. 77As could be eluted from the second column in 2?C3?mL of 0.1?M NaOH solution with >80% radiochemical yield. The 77As obtained by this method was found to have insignificantly small level of radiocontaminants. 相似文献
60.