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   272篇
  免费   4篇
  国内免费   3篇
化学   202篇
晶体学   2篇
力学   1篇
数学   34篇
物理学   40篇
  2023年   2篇
  2022年   11篇
  2021年   10篇
  2020年   9篇
  2019年   6篇
  2018年   5篇
  2017年   3篇
  2016年   8篇
  2015年   8篇
  2014年   9篇
  2013年   21篇
  2012年   16篇
  2011年   11篇
  2010年   16篇
  2009年   14篇
  2008年   13篇
  2007年   17篇
  2006年   14篇
  2005年   9篇
  2004年   11篇
  2003年   9篇
  2002年   6篇
  2001年   1篇
  2000年   2篇
  1999年   1篇
  1995年   1篇
  1988年   1篇
  1985年   1篇
  1980年   1篇
  1979年   2篇
  1976年   2篇
  1975年   1篇
  1973年   1篇
  1948年   2篇
  1944年   4篇
  1943年   6篇
  1942年   1篇
  1939年   5篇
  1938年   2篇
  1937年   1篇
  1936年   3篇
  1935年   3篇
  1934年   3篇
  1933年   4篇
  1932年   2篇
  1931年   1篇
排序方式: 共有279条查询结果,搜索用时 15 毫秒
91.
Due to their unique features, most nanostructured lipid carriers (NLCs) in association with vegetable oils that exhibit UV filtering properties and bioactivity could be used in many cosmetic formulations. Therefore, in this work, a new application of pomegranate seed oil (PSO) in the cosmetic sector was developed, based on the synthesis of bioactive lipid nanocarriers loaded with various UV filters by the hot high pressure homogenization technique. To get broad spectrum photoprotection, different UVA and UVB filters have been used (Avobenzone — AVO, Octocrylen-OCT, Bemotrizinol — BEMT). The influence of the solid lipids combined with PSO on the particle size, physical stability and entrapment efficiency was investigated using 8 nanocarrier systems. An improved physical stability and an appropriate size were obtained for NLCs prepared with Emulgade, carnauba wax and PSO (e.g. ?30.9÷-36.9 mV and 160÷185 nm). NLCs showed an entrapment efficiency above 90% and assured slow release rates of UV filters, especially for BEMT (5%). The developed nanocarriers have been formulated into safe and effective sunscreens containing low amounts of synthetic UV filters coupled with a high percent of natural ingredients. The highest SPF of 34.3 was obtained for a cream comprising of 11% PSO and 3.7% BEMT
  相似文献   
92.
Considering the valuable information provided by glycosphingolipids as molecular markers and the limited data available for their detection and characterization in patients suffering from Type 2 diabetic kidney disease (DKD), we developed and implemented a superior method based on high-resolution (HR) mass spectrometry (MS) and tandem MS (MS/MS) for the determination of gangliosides in the urine of DKD patients. This study was focused on: (i) testing of the HR MS and MS/MS feasibility and performances in mapping and sequencing of renal gangliosides in Type 2 DM patients; (ii) determination of the changes in the urine gangliosidome of DKD patients in different stages of the disease—normo-, micro-, and macroalbuminuria—in a comparative assay with healthy controls. Due to the high resolution and mass accuracy, the comparative MS screening revealed that the sialylation status of the ganglioside components; their modification by O-acetyl, CH3COO, O-fucosyl, and O-GalNAc; as well as the composition of the ceramide represent possible markers for early DKD detection, the assessment of disease progression, and follow-up treatment. Moreover, structural investigation by MS/MS demonstrated that GQ1d(d18:1/18:0), GT1α(d18:1/18:0) and GT1b(d18:1/18:0) isomers are associated with macroalbuminuria, meriting further investigation in relation to their role in DKD.  相似文献   
93.
Flavonoids, stilbenes, lignans, and phenolic acids, classes of polyphenols found in grape pomace (GP), were investigated as an important alternative source for active substances that could be used in the management of oxidative stress and inflammation. The benefic antioxidant and anti-inflammatory actions of GP are presented in the literature, but they are derived from a large variety of experimental in vitro and in vivo settings. In these in vitro works, the decrease in reactive oxygen species, malondialdehyde, and thiobarbituric acid reactive substances levels and the increase in glutathione levels show the antioxidant effects. The inhibition of nuclear factor kappa B and prostaglandin E2 inflammatory pathways and the decrease of some inflammatory markers such as interleukin-8 (IL-8) demonstrate the anti-inflammatory actions of GP polyphenols. The in vivo studies further confirmed the antioxidant (increase in catalase, superoxide dismutase and glutathione peroxidase levels and a stimulation of endothelial nitric oxide synthase -eNOS gene expression) and anti-inflammatory (inhibition of IL-1𝛼, IL-1β, IL-6, interferon-𝛾, TNF-α and C-reactive protein release) activities. Grape pomace as a whole extract, but also different individual polyphenols that are contained in GP can modulate the endogenous pathway responsible in reducing oxidative stress and chronic inflammation. The present review analyzed the effects of GP in oxidative stress and inflammation, suggesting that it could become a valuable therapeutic candidate capable to reduce the aforementioned pathological processes. Grape pomace extract could become an adjuvant treatment in the attempt to reduce the side effects of the classical anti-inflammatory medication like non-steroidal anti-inflammatory drugs (NSAIDs).  相似文献   
94.
Elaeis guineensis Jacq. has gained a reputation in the food industry as an incredible crop capable of supplying the world’s largest edible oil production. In Ecuador, an important oil palm-producing country, this crop is affected in a high percentage by the bud rot disease, which is responsible for palm death. The main objective of the investigation was dedicated to understanding the palm defense mechanism facing bud rot disease, translated in the induction of reactive oxygen species, activation of defensive machinery comprising enzymatic and non-enzymatic antioxidative components, secondary metabolites, carotenoids accumulation in the palm during all stages of disease infection. For this, a survey was conducted in different oil palm plantations in the Esmeraldas province, one of the most representative for its highest incidence of bud rot disease. The survey completed DPPH, FRAP, ABTS, and other spectrophotometric analyses to underline the biochemical, biological, and physiological palm response front of bud rot incidence. The palm defense strategy in each disease stage could be represented by the phenolic compound’s involvement, an increment of antioxidant activity, and the high enzymatic activity of phenylalanine ammonia-lyase (PAL). The results of the investigation made understandable the palm defense strategy front of this disease, respectively, the antioxidative defense and the palm secondary compounds involved.  相似文献   
95.
    
Ohne Zusammenfassung  相似文献   
96.
97.
98.
99.
A simple and rapid, inexpensive spectrophotometric method was proposed for magnesium assay in pharmaceutical preparations by sequential injection analysis (SIA). The method is based on the reaction between o-cresolphthalein complexone (CPC) and Mg(II) in alkaline media, yielding a pink colored complex with absorption maximum at 570 nm. Since the formation constant between Ca-CPC and Mg-CPC is similar, initially a sample/standard solution was aspirated into the holding coil followed by a mixture of masking-buffer solutions. This was done because masking of calcium should be accomplished before Mg-CPC complexation. Then the reagent was introduced into the reaction coil to produce a colored complex, which is measured spectrophotometrically at 570 nm. In this way the interference of calcium was reduced. Furthermore, all the parameters that affect the reaction were evaluated. The calibration curve is linear over a range of 0-20 mg l−1 of Mg(II) with a detection limit of 0.24 mg l−1. A sample throughput of 80 samples per hour and relative standard deviation <2.0% were achieved. The proposed method was successfully applied for the assay of magnesium in three different compositions of pharmaceutical preparations (tablets). The results were found to be in good agreement with the manual flame atomic absorption spectrophotometry (FAAS) and UV-Vis spectrophotometry methods and with the claimed values by the manufactures. The t-test shows no significant difference at 95% confidence level.  相似文献   
100.
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