全文获取类型
收费全文 | 158篇 |
免费 | 4篇 |
国内免费 | 4篇 |
专业分类
化学 | 112篇 |
力学 | 4篇 |
数学 | 10篇 |
物理学 | 40篇 |
出版年
2023年 | 2篇 |
2022年 | 1篇 |
2021年 | 12篇 |
2020年 | 4篇 |
2019年 | 5篇 |
2018年 | 5篇 |
2017年 | 3篇 |
2016年 | 4篇 |
2015年 | 2篇 |
2014年 | 8篇 |
2013年 | 11篇 |
2012年 | 11篇 |
2011年 | 14篇 |
2010年 | 9篇 |
2009年 | 12篇 |
2008年 | 21篇 |
2007年 | 8篇 |
2006年 | 2篇 |
2005年 | 7篇 |
2004年 | 7篇 |
2003年 | 1篇 |
2002年 | 3篇 |
2001年 | 1篇 |
2000年 | 7篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1994年 | 2篇 |
1980年 | 1篇 |
排序方式: 共有166条查询结果,搜索用时 15 毫秒
1.
Abstract Homopolymer of linseed oil and its four copolymers with styrene, 1-decene, isodecyl acrylate and octyl acrylate, respectively, have been synthesized in this present context. The prepared polymers are characterized by NMR and FTIR spectroscopy. The molecular weights have been measured by gel permeation chromatography. Their effectiveness as pour point depressant (PPD), viscosity index improver (VII) and their shear stability in terms of permanent shear stability index have been evaluated in lube oil. The copolymers acted as better PPDs than the homopolymer whereas the homopolymer of linseed oil excelled as VII. Further it was observed that all the prepared polymers were stable enough under severe mechanical shear. 相似文献
2.
The present work describes the formulation of alginate microspheres containing diltiazem hydrochloride by the emulsification-internal gelation method with the use of barium carbonate as a cross-linking agent. The effect of various factors (the concentration of alginate and barium chloride) on the drug loading efficiency and in vitro release were investigated. Fourier transform infrared microscopy (FTIR) and differential scanninig calorimetry (DSC) analysis confirmed the absence of any drug polymer interaction. X-ray diffraction (XRD) pattern showed that there is a decrease crystallinity of the drug. The in vitro drug release profile could be altered significantly by changing various processing parameters to give a controlled release of drug from microcapsules. The stability studies of drug-loaded microcapsules showed that the drug was stable at different storage conditions. 相似文献
3.
Diltiazem is an established cardiovascular drug mainly used for the management of hypertension specifically for the angina pectoris. Fluoroquinolones are widely prescribed against the treatment of severe infections. In vitro relations of diltiazem with fluoroquinolones (ciprofloxacin, levofloxacin, norfloxacin, and ofloxacin) were examined using spectrophotometric and separation techniques, i.e., RP-HPLC. Diltiazem’s availabilities were observed to be predisposed highly in the presence of fluoroquinolones. To investigate the mechanism of interaction in a variety of dissolution environments, i.e., simulating body environments with regard to pH on these interactions has been studied. Moreover, complex of diltiazem–fluoroquinolones were prepared and elucidated through IR spectroscopy and confirmed by computational molecular modeling. 相似文献
4.
Facile LC‐UV methods for simultaneous monitoring of ciprofloxacin and rosuvastatin in API,formulations and human serum 下载免费PDF全文
An efficient, selective and cost‐effective liquid chromatographic assay was developed and validated for the simultaneous quantification of ciprofloxacin and rosuvastatin in Active Pharmaceutical Ingredients (API), pharmaceutical formulations and in human serum. The chromatographic system consisted of mobile phase methanol–water, 90:10 v/v at pH 3.0 adjusted with o‐phosphoric acid, pumped at 1.0 mL/min through a prepacked Purospher Star C18 (5 µm, 25 × 0.46 cm) column and effluent was monitored at the isosbestic point (255 nm) as well as at the λmax of individual drugs (243 and 271 nm). The method was validated over a linear concentration range of 0.25–15 µg/mL for ciprofloxacin and 0.33–20 µg/mL for rosuvastatin (r2 ≥ 0.999). The ranges of reliable response (limits of detection and quantitation) for ciprofloxacin were 3–15 and 9–45 ng/mL and 17–29 and 52–88 ng/mL, respectively, for rosuvastatin in all API, pharmaceutical formulations and human serum. Analytical recovery from human serum was >98% and relative standard deviation (RSD) was <2. The accuracies were 97.13–102.55 and 97.41–101.31% and precisions in RSD were 0.04–1.90 and 0.02–1.23% for ciprofloxacin and rosuvastatin, respectively. No matrix interferences, ion suppression/enhancement and carry‐over were detected. The total assay run time was less than 5 min. In another study, for optimum performance the detector was programmed for multiwavelength scanning at the absorption maxima of each component. Consequently, the linearity range was improved and limit of detection and quantitation values were down to 1–4 and 4–12 ng/mL for ciprofloxacin and 3–5 and 9–15 ng/mL for rosuvastatin, respectively. The validation parameters fitted ICH guidelines through the isosbestic and individual λmax approach. The small sample volume and simplicity of preparation make this method suitable for use in human serum samples, pharmaceutical formulations, quality control, drug–drug interaction studies, clinical laboratories, drug research centers and forensic medical centers. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
5.
Sultana Ferdous Marios A. Ioannidis Dale Henneke 《Journal of nanoparticle research》2011,13(12):6579-6589
The pendant drop technique was used to characterize the adsorption behavior of n-dodecane-1-thiol and n-hexane-1-thiol-capped gold nanoparticles at the hexane–water interface. The adsorption process was studied by analyzing the
dynamic interfacial tension versus nanoparticle concentration, both at early times and at later stages (i.e., immediately
after the interface between the fluids is made and once equilibrium has been established). A series of gold colloids were
made using nanoparticles ranging in size from 1.60 to 2.85 nm dissolved in hexane for the interfacial tension analysis. Following
free diffusion of nanoparticles from the bulk hexane phase, adsorption leads to ordering and rearrangement of the nanoparticles
at the interface and formation of a dense monolayer. With increasing interfacial coverage, the diffusion-controlled adsorption
for the nanoparticles at the interface was found to change to an interaction-controlled assembly and the presence of an adsorption
barrier was experimentally verified. At the same bulk concentration, different sizes of n-dodecane-1-thiol nanoparticles showed different absorption behavior at the interface, in agreement with the findings of Kutuzov
et al. (Phys Chem Chem Phys 9:6351–6358, 2007). The experiments additionally demonstrated the important role played by the capping agent. At the same concentration, gold
nanoparticles stabilized by n-hexane-1-thiol exhibited greater surface activity than gold nanoparticles of the same size stabilized by n-dodecane-1-thiol. These findings contribute to the design of useful supra-colloidal structures by the self-assembly of alkane-thiol-capped
gold nanoparticles at liquid–liquid interfaces. 相似文献
6.
Shahid Hussain Arshad Muhammad Nawaz Naeem Nazra Sultana Zafar Iqbal Abdul Ghafar Shah 《Archive of Applied Mechanics (Ingenieur Archiv)》2011,81(8):999-1016
In the present work, vibration characteristics of thin functionally graded cylindrical shells are studied under the influence
of various boundary conditions. Fabrication of FGM cylindrical shell is carried out by using exponential volume fraction law.
Strain- and curvature-displacements relationships are taken from Love’s thin shell theory. The frequency equation in the form
of eigenvalue problem is obtained by adapting the Rayleigh-Ritz method. Characteristic beam functions are assumed to approximate
the axial modal dependence. Effects of exponential volume fraction law on the natural frequencies of the FGM cylindrical shells
for various boundary conditions are studied against circumferential wave number, length to radius ratio and thickness to radius
ratio for different values of power law exponents. Results evaluated show good agreement with those available in the literature. 相似文献
7.
Jasmin Sultana Nageshwar D. Khupse Srijita Chakrabarti Pronobesh Chattopadhyay Diganta Sarma 《Tetrahedron letters》2019,60(16):1117-1121
Using catalytic amount of Ag2CO3 a simple, efficient and copper free green protocol has been developed to synthesize 1,4-disubstituted 1,2,3-triazoles regioselectively. Here, the cationic surfactant, cetylpyridinium chloride (CPyCl) in water provides a micellar media and accelerates the subsequent Ag(I)-catalysed azide-alkyne cycloaddition (AgAAC) reaction by increasing the concentration of reactants in the micellar pseudophase. Our method is found to be environmentally friendly from E-factor measurement. The surfactant, CPyCl is found to be nontoxic. 相似文献
8.
9.
A rapid and sensitive high-performance liquid chromatographic (HPLC) assay for the simultaneous determination and quantification
of cefpirome and cetirizine or cefpirome and levocetirizine in pharmaceutical formulations and human plasma without changing
the chromatographic conditions is described. Chromatographic separations were performed on a prepacked Nucleosil 120, C18 (5 μm, 12.5 ± 0.46 mm) column using CH3CN: H2O (75: 25, v/v) as a mobile phase at a flow rate of 1 mL/min while UV detection was performed at 232 nm for monitoring the
effluent. A number of other brands of C18 columns were also employed which had a significant effect on the separation. The method has been validated over the concentration
range of 0.5–50 μg/mL (r
2 > 0.999). The limit of detection (LOD) and quantification (LOQ) for cefpirome and levocetirzine in pharmaceutical formulations
and serum were in the range 0.24–1.31 μg/mL. Analytical recovery from human plasma was >98%, and the within and between-day
relative standard deviation was <3.1%. The small sample volume and simplicity of preparation make this method suitable for
use in pharmaceutical industries, drug research centers, clinical laboratories, and forensic medical centers.
The text was submitted by the authors in English. 相似文献
10.
A rapid and sensitive high‐performance liquid chromatographic method was developed and validated for the simultaneous determination and quantification of atenolol, rosuvastatin, spirnolactone, glibenclamide and naproxen sodium in bulk drugs, pharmaceutical formulations and in human plasma in the presence of internal standard (flurbiprofen). Chromatograms were developed with methanol and water (80:20, v/v) solvent system on a Purospher start, C18 (5 μm, 250 × 4.6 mm) column and pH was adjusted to 3.40 with ortho‐phosphoric acid. Mobile phase was pumped with a flow rate of 0.90 mL/minute with 235 nm UV detection. Standard curves were linear over the concentration range 0.25‐30 μg/mL?1. The coefficients of variation (C.V.%), were < 3% and LOD and LOQ were <0.0154 & 0.06 for inter‐ and intra‐day, respectively. The method was applied to drug interaction studies of atenolol with rosuvastatin, spironolactone, glibenclamide and naproxen to illustrate the scope and application of the methods to manage four different therapeutic classes of drugs, as they are co‐administered. 相似文献