首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   172篇
  免费   4篇
  国内免费   4篇
化学   141篇
力学   1篇
数学   10篇
物理学   28篇
  2023年   2篇
  2022年   14篇
  2021年   21篇
  2020年   4篇
  2019年   9篇
  2018年   5篇
  2017年   3篇
  2016年   2篇
  2015年   7篇
  2014年   3篇
  2013年   17篇
  2012年   11篇
  2011年   8篇
  2010年   12篇
  2009年   9篇
  2008年   8篇
  2007年   10篇
  2006年   6篇
  2005年   4篇
  2004年   1篇
  2003年   2篇
  2002年   4篇
  2001年   3篇
  2000年   3篇
  1999年   3篇
  1996年   2篇
  1993年   1篇
  1992年   1篇
  1991年   1篇
  1989年   1篇
  1988年   1篇
  1973年   1篇
  1971年   1篇
排序方式: 共有180条查询结果,搜索用时 265 毫秒
101.
Commiphora gileadensis (CG) is a small tree distributed throughout the Middle East. It was traditionally used in perfumes in countries in this area. In Saudi Arabia, it was used to treat wounds burns and as an antidote to scorpion stings. This study aimed to evaluate the antimicrobial activity and cutaneous wound healing efficiency of the CG extracts using microbiological tests, rate of wound contraction and histopathological changes. CG plant were extracted using the methanol extraction technique; then, the methanolic extract was characterized using liquid chromatography coupled with mass spectrometry (LC–MS). Afterwards, a six-millimetre (mm) excision wound was induced in 60 male Balb/c mice. Mice were classified into two classes; each class consisted of three groups of 10 mice. In the non-infected wound class, the group I was assigned as control and received normal saline. Group II received gentamicin treatment, and group III treated with CG-methanolic extract. In the Staphylococcus aureus-infected class, group IV received normal saline, and groups V and VI were treated with gentamicin and CG-methanolic extract, respectively. The colonization of infected wounds was determined using colony-forming units (CFUs), and the percentage of wound contraction was measured in all groups. Finally, the histopathologic semi-quantitative determination of wound healing was evaluated by inflammatory cell infiltration, the presence of collagen fibres and granulation tissue, and the grade of re-epithelization. Composition analysis of the methanolic extract confirmed the presence of a high amount of ceramide (69%) and, to a lesser extent, hexosylceramide (18%) and phosphatidylethanolamine (7%) of the total amount. Additionally, there was a statistically significant difference between the percentage of wound contraction in the CG-treated and control groups in both Staphylococcus aureus-infected and non-infected wounds (p < 0.01). The colonization of the infected wounds was lower in the group treated with CG than in the control group (p < 0.01). In both non-infected and infected wounds, the CG-treated group showed significant statistical differences in inflammatory cell infiltration, collagen fibres, re-epithelization and granulation tissue formation compared with the control group (p < 0.01). The CG extract possesses antibacterial and anti-inflammatory properties that induce wound healing.  相似文献   
102.
This work was intended to characterize aspirin solubilized in microemulsion systems comprising clove oil, 1-butanol and water. Microemulsions demonstrated the unique ability to solubilize aspirin in polar media, thus having good potential in drug delivery. After incorporation of aspirin, four samples were selected in microstructure and be investigated by conductivity measurements, transmission electron microscope (TEM), and spectroscopic studies (1H-NMR, UV-visible spectroscopy, and IR spectra). The percolation behavior with variation of weight fraction of aqueous phase (?) was confirmed by conductivity measurements. In order to study the effect of aspirin, the conductivity results of aspirin-loaded samples were compared with non-loaded ones. The proton transfer and The competitive H-bonding interactions between aspirin with butanol and water were also discussed in details using 1H-NMR, UV-visible spectroscopy, and IR spectra. These measurements confirmed that the hydrogen-bonded ion pair structure dominated in the solutions.  相似文献   
103.
This paper studies and analyzes a preconditioned Krylov solver for Helmholtz problems that are formulated with absorbing boundary layers based on complex coordinate stretching. The preconditioner problem is a Helmholtz problem where not only the coordinates in the absorbing layer have an imaginary part, but also the coordinates in the interior region. This results into a preconditioner problem that is invertible with a multigrid cycle. We give a numerical analysis based on the eigenvalues and evaluate the performance with several numerical experiments. The method is an alternative to the complex shifted Laplacian and it gives a comparable performance for the studied model problems.  相似文献   
104.
Simple and sensitive spectrophotometric and spectrofluorimetric methods are described for analysis of acebutolol hydrochloride. The proposed methods are based on oxidation of the selected drug with cerium(IV) ion in acidic medium with subsequent measurement of either the decrease in absorbance at 320 nm or the fluorescence intensity of the produced cerous(III) ion at 363 nm (excitation at 250 nm). Beer's law obeyed from 1.0-7.0 microg ml(-1) and 0.25-2.5 microg ml(-1) acebutolol hydrochloride, using the spectrophotometric and spectrofluorimetric method, respectively. The proposed methods were successfully applied for determination of the selected drug in its pharmaceutical preparation with good recoveries.  相似文献   
105.
106.
A new heterogeneous catalyst composed of Pd nanoparticles immobilized within a HypoGel resin has been prepared in the absence of any ligands using an extensive cross-linking method. This new-ly develop...  相似文献   
107.
108.
This study investigates the influence of treatment frequency (1–150 kHz) on the atmospheric plasma activation of both silicone and polyethylene terephthalate (PET) particles. These polymer particles with diameters in the range 3–5 mm, were treated using either helium or helium/oxygen gas mixtures, in a barrel atmospheric plasma system. The level of polymer particles activation was monitored using water contact angle measurements. The effect of plasma treatment frequency on barrel heating was monitored using an infrared thermographic camera, the maximum barrel temperature after 15 min treatment was found to be 98 °C at a frequency of 130 kHz. Optical emission spectroscopy was used as a diagnostic tool to monitor changes in atomic and molecular species spectral intensity with experimental conditions, as well as a change in electron energy distribution function. Electrical characterisation studies demonstrated an increase in plasma power with increasing frequency, in the range investigated. X-ray photoelectron spectroscopy analysis indicate an increase of oxygen content on polymer surfaces after plasma treatment. For silicone particles, the minimum polymer water contact angle was obtained by using a frequency of 130 kHz. After 15 min treatment time, the water contact angle decreased from 141° to 11°. While for PET particles the optimum treatment frequency was found to be 70 kHz, resulting in a water contact angle decreased from 94° to 32°. This lower frequency was used due to the partial melting of the PET (Tg of 80 °C), when treated at the higher frequency.  相似文献   
109.
The effect of triton‐X‐100 micelles on the aquation of Fe(C10H6N2O)3 2+ has been investigated with triton‐X‐100 as solvent. In liquid triton‐X‐100, over a range of [H2O] T (0.0–3 M), significant rate enhancement factors of 50–150 are observe. Acid inhibits the rate of aquation at fixed [H2O] T . A mechanism based on effective solvent participation in a chemical environment similar to that in reversed micelles is proposed in liquid triton‐X‐100 with dispersed water pockets. This mechanism predicts direct H2O substitution into the coordination sphere of Fe(C10H6N2O)3 2+ in the highly polar water pockets or cavities where the Fe (II) complex molecules are solubilized. Changes in the tumbling rate, structure, and activity of water are suggested to account for the observed changes in the rate of aquation as a function OH [H2O] T . All k ψ–[H2O] T profiles are structured and exhibit maxima with k ψ(max) shifted to progressively higher [H2O] T as the fixed concentration [H+] T is increased.  相似文献   
110.
Zirconium-89 (89Zr) can be produced in a cyclotron by focusing the proton beam on an yttrium-89 (89Y) foil target. Optimal combination of beam energy and target assembly configuration enables maximum production of 89Zr while minimizing the formation of contaminant nuclides such as 88Zr and 88Y to allow efficient and effective radiopharmaceutical labeling. Accurate modeling of the proton beam and the target is therefore an essential step to assure the best beam and target specification. We used the radiation transport code MCNPX to simulate the transport of protons through the irradiation assembly and the nuclear reaction code TALYS to obtain the production cross sections of various nuclides from proton-89Y reactions. Results from simulating the irradiation of 14 mm diameter targets with aluminum (Al) degrader at 19.8 mA for 1 h suggested that the 0.15 mm thick one would produce 227 MBq while the 0.3 mm thick one would produce 413 MBq of 89Zr with less than 1 % uncertainty. These results show excellent agreement with experimental work in literature. This work provides the basis for further experimental and theoretical assessments of the use of 89Zr as radiopharmaceutical labels.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号