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   251篇
  免费   18篇
电工技术   1篇
化学工业   110篇
金属工艺   3篇
机械仪表   5篇
建筑科学   15篇
能源动力   7篇
轻工业   56篇
水利工程   1篇
石油天然气   1篇
无线电   2篇
一般工业技术   37篇
冶金工业   9篇
原子能技术   1篇
自动化技术   21篇
  2023年   4篇
  2022年   33篇
  2021年   33篇
  2020年   12篇
  2019年   5篇
  2018年   14篇
  2017年   3篇
  2016年   7篇
  2015年   8篇
  2014年   11篇
  2013年   14篇
  2012年   11篇
  2011年   13篇
  2010年   6篇
  2009年   10篇
  2008年   17篇
  2007年   12篇
  2006年   5篇
  2005年   4篇
  2004年   5篇
  2003年   5篇
  2002年   5篇
  2001年   4篇
  2000年   7篇
  1999年   2篇
  1998年   3篇
  1996年   3篇
  1994年   4篇
  1993年   2篇
  1991年   4篇
  1989年   1篇
  1979年   1篇
  1974年   1篇
排序方式: 共有269条查询结果,搜索用时 15 毫秒
11.
Herbal remedies are increasing in popularity as treatments for metabolic conditions such as obesity and Type 2 Diabetes. One potential therapeutic option is fenugreek seeds (Trigonella foenum-graecum), which have been used for treating high cholesterol and Type 2 diabetes. A proposed mechanism for these benefits is through alterations in the microbiome, which impact mammalian host metabolic function. This study used untargeted metabolomics to investigate the fenugreek-induced alterations in the intestinal, liver, and serum profiles of mice fed either a 60% high-fat or low-fat control diet each with or without fenugreek supplementation (2% w/w) for 14 weeks. Metagenomic analyses of intestinal contents found significant alterations in the relative composition of the gut microbiome resulting from fenugreek supplementation. Specifically, Verrucomicrobia, a phylum containing beneficial bacteria which are correlated with health benefits, increased in relative abundance with fenugreek. Metabolomics partial least squares discriminant analysis revealed substantial fenugreek-induced changes in the large intestines. However, it was observed that while the magnitude of changes was less, significant modifications were present in the liver tissues resulting from fenugreek supplementation. Further analyses revealed metabolic processes affected by fenugreek and showed broad ranging impacts in multiple pathways, including carnitine biosynthesis, cholesterol and bile acid metabolism, and arginine biosynthesis. These pathways may play important roles in the beneficial effects of fenugreek.  相似文献   
12.
In the development of pH-responsive chitosan-based hydrogels, achieving reproducible porosity and swelling behavior is essential for the design of hydrogel networks. Herein, we enhance the level of control in hydrogel microarchitecture by incorporating poly(ethylene glycol) (PEG) into the chitosan–genipin matrix. Hydrogels, varied in composition, were synthesized under mild conditions (37°C, 1 atm, 24 hr), yielding microporous structures with a pore diameter ranging from 11 to 57 μm and an average cross-sectional porosity of approximately 40–64%. Compared to chitosan–genipin hydrogels without PEG, presence of PEG in concentrations up to 1.9 mM generated the same effect as would increase in genipin content, yielding structures with a smaller pore diameter, a lower swelling degree in pH 2 buffer and a higher elastic modulus. Considering cost effectiveness and scale-up, reducing genipin content by the addition of PEG is favorable. Importantly, hydrogel samples containing higher concentrations of PEG (2.9 mM and above) showed a sudden increase in the swelling degree accompanied with a decrease in the elastic modulus. Findings showcase the potential variation in the composition of these hydrogels has in yielding scaffolds with significantly different physico-chemical behaviors.  相似文献   
13.
We deposited BiFeO3 films on stainless steel substrates using a simple low-temperature wet-chemical route. Bismuth and iron nitrates were used as metal source and citric acid as chelating agent to prepare a water solution and deposit the film by dipping the steel substrate in the viscous solution. We have investigated the composition, crystallinity and structure of the BiFeO3 film on steel by X-ray diffraction, X-ray photoelectron spectroscopy, high resolution scanning electron microscopy, conventional and high resolution transmission electron microscopy, and energy dispersive spectroscopy techniques. The film deposited on the steel substrate has two sublayers: a very thin (about 100 nm) nanocrystalline layer, with crystallite size of few nanometers, and a thicker (below 1 μm) crystalline layer.  相似文献   
14.
Ultrathin PZT film was prepared using a chemical solution deposition method from polymeric citrate precursors. The PZT solution was spin-coated on an amorphous silica layer formed on a Si(1 0 0) substrate. The films were thermally treated from the substrate side with a low heating rate (1°/min) up to 700 °C and finally annealed for 10 h. Ultrathin PZT films without microstructural instability were prepared in spite of high temperature and long annealing time. AFM and HRTEM investigations revealed the formation of a well-developed dense microstructure consisting of spherical crystallites (4–7 nm). Low roughness (2.2 nm) of a ~26 nm thick layer was obtained for a two-layered PZT film. The grazing incidence X-ray diffraction (GIXRD) measurements confirmed the polycrystalline structure of ultrathin PZT films. Also, GIXRD and electron energy dispersive X-ray (EDS) analysis showed that compositional variations were smaller than expected, in spite of the long annealing time.  相似文献   
15.

Object  

Polyunsaturated omega-6 fatty acids (PUFAs) have been shown to promote prostate cancer. Here, we describe the use of HRMAS NMR spectroscopy to detect omega-6 PUFA species in prostate tissues.  相似文献   
16.
BACKGROUND: The European Union has forbidden the use of antibiotics as additives in animal feed. Zn‐bacitracin (Zn‐BC) and nystatin (NYS) were frequently used for their growth‐promoting effects and for feed conversion in poultry, pigs and cattle. An HPTLC method has been developed for separating Zn‐BC and NYS in the mixture, for routine quality control. RESULTS: The separation was obtained using RP‐18 F254S coated HPTLC plates with acetonitrile/methanol (equal volumes):toluene:KH2PO4/KOH (buffer, pH 6.8) = 57:3:40 (v/v/v), adjusted with HCl to pH 8.2, as a mobile phase. The densitograms were monitored at 192, 215 and 305 nm and both antibiotics were assayed at 215 nm. The method was shown to be specific, accurate (recoveries were 98.7 ± 0.5% and 104.8 ± 0.7% for Zn‐BC and NYS, respectively), linear over the tested range (correlation coefficients, 0.9982 and 0.9884), and precise (intermediate precision RSD below 2.2% for both analytes) with efficient separation (Rs = 3.5). CONCLUSION: The method was applied for determining Zn‐BC and NYS as additives in spiked matrices of commercial animal feedstuffs. According to LOD values for each antibiotic, the minimum detectable amount in feed is 4.5 and 5.5 ppm of Zn‐BC and NYS, respectively. Copyright © 2008 Society of Chemical Industry  相似文献   
17.
This paper compares conditions and costs for RES-E grid connection in selected European countries. These are Germany, the Netherlands, the United Kingdom, Sweden, Austria, Lithuania and Slovenia. Country specific case studies are presented for wind onshore and offshore, biomass and photovoltaic power systems, as based on literature reviews and stakeholder interviews. It is shown that, especially for wind offshore, the allocation of grid connection costs can form a significant barrier for the installation of new RES-E generation if the developer has to bear all such costs. If energy policy makers want to reduce the barriers for new large-scale RES-E deployment, then it is concluded that the grid connection costs should be covered by the respective grid operator. These costs may then be recouped by increasing consumer tariffs for the use of the grid.  相似文献   
18.
Type 2 diabetes (T2D), one of the most prevalent noncommunicable diseases, is often preceded by insulin resistance (IR), which underlies the inability of tissues to respond to insulin and leads to disturbed metabolic homeostasis. Mitochondria, as a central player in the cellular energy metabolism, are involved in the mechanisms of IR and T2D. Mitochondrial function is affected by insulin resistance in different tissues, among which skeletal muscle and liver have the highest impact on whole-body glucose homeostasis. This review focuses on human studies that assess mitochondrial function in liver, muscle and blood cells in the context of T2D. Furthermore, different interventions targeting mitochondria in IR and T2D are listed, with a selection of studies using respirometry as a measure of mitochondrial function, for better data comparison. Altogether, mitochondrial respiratory capacity appears to be a metabolic indicator since it decreases as the disease progresses but increases after lifestyle (exercise) and pharmacological interventions, together with the improvement in metabolic health. Finally, novel therapeutics developed to target mitochondria have potential for a more integrative therapeutic approach, treating both causative and secondary defects of diabetes.  相似文献   
19.
Micro and nanofibrillated cellulose is an essentially one‐dimensional high aspect‐ratio particle material, which can undergo two‐dimensional layer (band) structuring under shear. Controlling the evolving rheological properties in aqueous suspension is essential for industrial applications in composite materials. This study focuses on an as yet considered to be unreported phenomenon of structure hardening under low shear. The timescale of the quasi gelation‐controlled structure formation under low shear is studied using the large gap vane‐in‐cup geometry of the Brookfield viscometer. It is proposed that localized structure forms within continuous shear bands, similar to quasi liquid‐crystal formation. By extrapolating a characteristic structure growth parameter to the rotation speed at which it becomes zero, the strain‐induced structure time constant, tgel, can be obtained as (= f (Ω)) = 1/tgel for the range Ω = 10–100/min. The time constant of low shear structure formation is shown to be separable from the static viscoelastic structure build under oscillation in concentrated composite suspension using plate‐plate geometry, which is manifest by a Weissenberg normal force response on switching to applied shear, when the time constant of structuration tgel is long. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42827.  相似文献   
20.
A mathematical model was developed to estimate the release of gentamicin sulfate from a bioactive textile material as a transdermal system for wound dressing. The gentamicin sulfate released from the antibiotic/chitosan hydrogel complexes was measured in vitro by the Franz diffusion cell technique. The diffusive transport of gentamicin sulfate through three connected compartments, that is, chitosan hydrogel, membrane, and solution, was considered by the formulation of a model based on Fick's second law. Initially, the total amount of gentamicin sulfate was placed within an already swollen chitosan hydrogel. The value of the diffusivity coefficient of the drug through the chitosan hydrogel was calculated for every initial amount of the active substance. For the initial concentration of gentamicin sulfate, which was lower than 2.81 × 104 μg/mL, the diffusion coefficient was approximately constant. A higher amount of gentamicin sulfate in the hydrogel reduced its own transport as a consequence of an increase in the intensity of the interaction field between the molecules of gentamicin sulfate. The model provides the possibility of optimizing the process of drug release by ensuring a compromise between a higher value of the diffusivity coefficient and a desirable amount of gentamicin sulfate and a constant concentration within the solution over 48 h. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010  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