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451.
The adsorption isotherms of Cr(VI) on kaolinite, montmorillonite, and alumina were adequately treated with Langmuir model showing behavior characteristic of single-layer adsorption. The efficiency of the adsorbents in removing Cr(VI) from water follows the order alumina > kaolinite > montmorillonite > silica. Speciation studies indicate that hydrogen chromate ions were the major adsorbed species and simultaneous adsorption of dichromate ion occurred at concentrations greater than approximately 10(-3) mol L(-1). It is most probable that the mechanism of adsorption of the hydrogen chromate ion at the surface of alumina is predominantly electrostatic adsorption, with outer sphere complex formation.  相似文献   
452.
This paper reports a study of vibrational, structural and morphological properties of molybdenum oxide nanoribbons. Temperature‐dependent Raman spectroscopy measurements in MoO3 nanoribbons revealed morphological changes in the 150–350 °C temperature range. No structural phase transitions were observed, thus showing that the orthorhombic phase is stable from room temperature (nanoribbons) up to 650 °C (bulk‐like phase) where large plates have been formed by the coalescence of the nanoribbons. The interpretation of temperature‐dependent Raman data (wavenumber and linewidths) is supported by scanning electron microscopy that is used to directly probe the morphological changes in MoO3 samples. The observed phenomena in the Raman data for MoO3 nanoribbons can be applied to other nanomaterials. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   
453.
We report the first observation of photoluminescence enhancement in Er3+ doped GeO2–Bi2O3 glasses containing silicon nanocrystals (Si-NCs) excited by a laser operating at 980 nm. The growth of ≈200% in the intensity of the Er3+ transition 4S3/24I15/2 (545 nm) and of ≈100% for transitions 2H11/24I15/2 (525 nm), 4F9/24I15/2 (660 nm), and 4I5/24I13/2 (1530 nm) was observed in comparison with a reference sample that does not contain Si-NCs. The results open a new road for obtaining efficient Stokes and anti-Stokes emissions in germanate composites doped with rare-earth ions.  相似文献   
454.
We demonstrate the potential application of silver-pectin nanoparticles on photodynamic therapy, on a solution-base platform. Photodynamic therapy is a medical technique which uses a combination of photosensitizing drugs and light to induce selective damage on the target tissue, by electronically excited and highly reactive singlet state of oxygen. Metal enhanced singlet oxygen generation in riboflavin water solution with silver-pectin nanoparticles was observed and quantified. Here 13 nm silver nanospheres enclosed by a pectin layer were synthesized and it interaction with riboflavin molecule was analyzed. Pectin, a complex carbohydrate found in plants primary cell walls, was used to increase the biocompatibility of the silver nanoparticles and to improve metal enhanced singlet oxygen generation (28.5 %) and metal-enhanced fluorescence (30.7 %) processes at room temperature. The singlet oxygen sensor fluorescent green reagent was used to quantify the enhancement of the riboflavin singlet oxygen production induced by the silver colloid. We report a 1.7-fold increase of riboflavin emission and a 1.8-fold enhancement of singlet oxygen production.  相似文献   
455.
456.
Crude oil distillates are a highly useful industrial product, mainly for energy generation. Unfortunately, they are rarely studied, mainly due to the low accessibility to products directly obtained from the distillation process, which is a laborious, expensive, and time-consuming operation. This work presents and discusses the use of time-domain nuclear magnetic resonance (TD-NMR) as a simple, affordable, and straightforward tool for the development of correlations supported on the transverse relaxation time (T2) and boiling temperature. The results point out a high convergence between TD-NMR experimental data and the ASTM D2892 method for distillates from light, medium, and heavy oils, with up to 52.20% of accumulated mass and boiling point temperature (Tb) up to 400°C. Furthermore, an unprecedented relationship between T2 values and the accumulated mass of the distillates is first demonstrated. This new insight opens new perspectives for future prediction of accumulated mass for unknown crude oils, placing the TD-NMR relaxometry as an appeal spectroscopy approach with a potential to meaningfully contribute to the daily refining petrochemical industry field operations.  相似文献   
457.
Organic-inorganic hybrid materials with excellent heavy metal ions chelating properties were synthesized by covalent bonding of multifunctional polymers of polyamidoamine (PAA) type onto silica. Two series of polyamidoamine-silica hybrid materials differing in the PAA chemical structure were prepared and their thermal properties were investigated. Differential Scanning Calorimetry was used to study the effects of chain immobilization and ion chelation on the glass-transition temperature (Tg) of the polymers. The Tg of PAA-hybrid materials was elevated with respect to ungrafted PAAs. Complex formation with metal ions such as Cu++ or Co++ caused total suppression of Tg for both linear polymers as well as the corresponding hybrid materials. Finally, the silica particles slightly influenced the decomposition temperatures of linear polymers increasing their thermal stability.  相似文献   
458.
Mass-variation measurements were carried out on carbon black (CB)-poly(vinyl chloride) (PVC) composite film with 40% by weight of di(2-ethylhexyl)-phthalate (DOP), cast on resonant piezo-layer (RPL) elements of lead zirconat titanate (PZT). Even if anomalous diffusion is predicted by fitting the data with Mt/M=ktα, the fractional uptake Mt/M is linear with the square root of the time up to Mt/M=0.6, suggesting Fickian behavour. The anomalous values of α are probably due to experimental time lag. A dependence of the diffusion on the morphology of the material and the penetrant shape and flexibility has been found.  相似文献   
459.
A Deep Eutectic Solvent, choline chloride/glycerol (1 : 2 mol mol−1), proved to be an effective and sustainable reaction medium to promote telescoped, one-pot Mizoroki-Heck cross-coupling/reduction processes between 2,3-dihydrofuran or 3,4-dihydro-2H-pyran and several (hetero)aryl halides to easily access valuable 2-(hetero)aryl tetrahydrofuran (THF) or tetrahydropyran derivatives in up to 95 % yield. Notably, the whole transformation takes place under aerobic conditions, in the absence of additional ligands, and with a good substrate scope. The practicability of the method is also exemplified by the sustainable synthesis of two key THF derivatives, which are side chains of pharmacologically relevant inhibitors of Kv1.2 channel.  相似文献   
460.
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