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   159篇
  免费   24篇
电工技术   2篇
综合类   1篇
化学工业   31篇
金属工艺   1篇
机械仪表   4篇
建筑科学   7篇
能源动力   6篇
轻工业   71篇
无线电   7篇
一般工业技术   13篇
冶金工业   17篇
自动化技术   23篇
  2024年   1篇
  2023年   5篇
  2022年   2篇
  2021年   10篇
  2020年   1篇
  2019年   1篇
  2018年   16篇
  2017年   18篇
  2016年   11篇
  2015年   6篇
  2014年   10篇
  2013年   23篇
  2012年   12篇
  2011年   11篇
  2010年   8篇
  2009年   6篇
  2008年   6篇
  2007年   5篇
  2006年   3篇
  2005年   2篇
  2004年   6篇
  2003年   2篇
  2002年   3篇
  2000年   1篇
  1999年   1篇
  1998年   2篇
  1997年   1篇
  1996年   1篇
  1994年   2篇
  1989年   1篇
  1988年   2篇
  1987年   1篇
  1982年   1篇
  1977年   1篇
  1974年   1篇
排序方式: 共有183条查询结果,搜索用时 203 毫秒
31.
Multiple sclerosis (MS) represents the leading cause of neurological deficit among young adults, affecting women more frequently than men. In MS, the extent of central nervous system lesions is determined by the net balance between self-reactive and regulatory T-cells at any given time, among other factors, as well as by the effect of inflammatory response. Here, we studied both CD4+ and CD8+ T(Reg) in parallel in blood and CSF during MS relapse. A recruitment of both regulatory CD4+ and CD8+ T cells (T(Reg)) within the cerebrospinal fluid (CSF) takes place during MS relapse. Not previously described, the presence of CD4+ T(Reg) in CSF was higher in women than in men, which could account for the sexual dimorphism in the incidence of MS. A direct correlation between plasma oestradiol (E2) and IL-2 levels was observed, in line with a putative circuit of E2 and perforin expression by CD4+ T(Reg) playing a role in MS. Also, serum IFN-alpha was higher in females, with direct correlation with serum E2 levels. This is the first study to analyze perforin expression by CD4+ T(Reg) in MS, which was greatly enhanced in CSF, what points out a relevant role of this molecule in the suppressive effects of the CD4+ T(Reg) in MS, and contributes to the understanding of MS pathophysiology.  相似文献   
32.
33.
34.
The aim of this work was to develop and evaluate the effect of an edible coating produced with protein isolate and gum from the Cajanus cajan seed to be applied to strawberries (Fragaria spp.). The films were formulated using 1 and 2% gum, and 5 and 10% protein isolate, as well as glycerol (2%) as a plasticizer. The formulated films were evaluated in terms of water vapor permeability (WVP), opacity, color, scanning electron microscopy, and texture. Once the ideal formulation with sufficiently low WVP and opacity was selected, it was applied to the strawberries, which were evaluated in terms of mass loss, color, firmness, acidity, pH, soluble solids, anthocyanin content, vitamin C content, and acceptability degree by an untrained consumer panel. Results showed that film made from 5% of protein isolate and 1% of gum had the lowest WVP of all treatments. Applied to strawberries, the coating resulted in a reduction of the total soluble solid content, the consumption of citric acid, and the mass loss of coated with respect to uncoated strawberries after 10 days of storage at 5 °C, without causing sensorial changes.  相似文献   
35.
Beef from cattle less than 30 months old at the point of slaughter are generally sold in meat markets. Though the age of the animal can generally be estimated by dentition, this method cannot be applied to a carcass or a piece of meat from which the teeth have been removed. Since gas chromatography of volatile organic compounds has been used to classify biological samples, this technique was used for classifying meat obtained from cattle aged over 30 months (OTM) at point of slaughter. Volatile organic compounds of fresh meat (M. longissimus dorsi) samples obtained from cattle of different age and dentition (two, four, and six teeth) at point of slaughter were analyzed using gas chromatography/mass spectrum (GC/MS). Six volatile organic compounds were selected (hexanoic acid, benzoic acid, octanoid acid, tridecane, tetradecane, and 4-formylbenzoic acid) and confirmed by using chemical standards and Kovat’s indexes. The chromatogram data were used to train two classifiers, one based on the partial least square (PLS) method and another based on support vector machine (SVM), but only SVM showed high accuracy. Data exploration based on the principal component analysis allowed for comprehension of the data distribution, proposing a new version of PLS in a parallel configuration. This modified version of the PLS algorithm showed better accuracy than the SVM classifier. In conclusion, volatile organic compounds analyzed by GC/MS–solid-phase microextraction can be used to recognize OTM beef.  相似文献   
36.
37.
Probiotics are live microorganisms that confer a number of health benefits when consumed in adequate amounts, mostly due to improvement of intestinal microflora. Bacterial strains from the genera Lactobacillus, Bifidobacterium, and Bacillus have been widely studied and are used to prepare ready‐to‐eat foods. However, the physicochemical stability and bioavailability of these bacteria have represented a challenge for many years, particularly in nonrefrigerated foodstuffs. Microencapsulation (ME) helps to improve the survival of these bacteria because it protects them from harsh conditions, such as high temperature, pH, or salinity, during the preparation of a final food product and its gastrointestinal passage. The most common coating materials used in the ME of probiotics are ionic polysaccharides, microbial exopolysaccharides, and milk proteins, which exhibit different physicochemical features as well as mucoadhesion. Structurally, the survival of improved bacteria depends on the quantity and strength of the functional groups located in the bacterial cell walls, coating materials, and cross‐linkers. However, studies addressing the role of these interacting groups and the resulting metabolic impacts are still scarce. The fate of new probiotic‐based products for the 21st century depends on the correct selection of the bacterial strain, coating material, preparation technique, and food vehicle, which are all briefly reviewed in this article.  相似文献   
38.
39.
Therapeutic deep eutectic solvents (THEDES) are an emerging family of eutectic mixtures gaining increasing interest in the biomedical space. The immobilization of THEDES into polymer networks allows bioactive eutectogels to expand their application scope to topical drug delivery. Herein, this work presents the first set of elastomeric eutectogels constructed by supporting a therapeutic eutectic system with skin permeation ability in a protein scaffold dynamically crosslinked by a natural polyphenol. In this ionic eutectic, gelatin undergoes gelation through an unexpected mechanism in striking contrast with classical hydrogels, which is herein thoroughly studied. Interestingly, the polyphenol controls the conformation of the protein structure, enabling tuning up the mechanical and viscoelastic behavior of the dynamic eutectogel networks from elastic to hyperelastic. The resultant protein eutectogels exhibit strain-hardening behavior, thermoreversible gel-to-sol transition, and excellent adhesive performance. Furthermore, these versatile materials retain the bioactivity of the liquid THEDES and favor skin occlusion, assisting the delivery of both hydrophilic and hydrophobic substances in ex vivo porcine skin in a time-dependent penetration process. These ultrastretchable eutectogels show new interplays between protein scaffolds and eutectic mixtures, paving the way for innovative therapeutic soft materials.  相似文献   
40.
The multiangular Rahman–Pinty–Verstraete modified (MRPV) semi-empirical model uses three parameters (ρ0, Θ, and k) for describing the anisotropy of an arbitrary target. They have been usefully proved to characterize some forest attributes and land covers. However, there is no enough evaluation of the consistency of this product, and the possible affection from different factors in the reliability of them. Here, we explored the consistency of the MRPV parameters provided in the MISR L2 Land Surface (MIL2ASLS) product, with data from Mainland Spain, grouping MISR images into close time pairs. Thus, it was studied the three MRPV parameters through retrieving Spearman’s rank correlation coefficient (ρ) and mean relative differences related to every pair of images. The results showed the ρ0 parameter presented higher consistency than the others, with ρ over 0.85 and meant relative differences around 15%. The k parameter showed ρ over 0.65 and average relative disagreements over 8%. Finally, the Θ parameter reached ρ around 0.60. The Θ mean differences were over 25% unless the combination of the blue band which was especially bad and its values were up to 50%. So, it is crucial having into account when the parameters of this product are used to look into the band and the own parameter.  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