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   4758篇
  免费   389篇
  国内免费   50篇
电工技术   28篇
综合类   113篇
化学工业   433篇
金属工艺   11篇
机械仪表   43篇
建筑科学   19篇
矿业工程   8篇
能源动力   47篇
轻工业   4151篇
水利工程   14篇
石油天然气   18篇
武器工业   2篇
无线电   24篇
一般工业技术   145篇
冶金工业   11篇
原子能技术   2篇
自动化技术   128篇
  2024年   39篇
  2023年   102篇
  2022年   198篇
  2021年   255篇
  2020年   225篇
  2019年   216篇
  2018年   180篇
  2017年   191篇
  2016年   205篇
  2015年   182篇
  2014年   208篇
  2013年   324篇
  2012年   369篇
  2011年   346篇
  2010年   222篇
  2009年   182篇
  2008年   166篇
  2007年   302篇
  2006年   242篇
  2005年   225篇
  2004年   150篇
  2003年   119篇
  2002年   99篇
  2001年   79篇
  2000年   62篇
  1999年   47篇
  1998年   39篇
  1997年   25篇
  1996年   27篇
  1995年   19篇
  1994年   18篇
  1993年   28篇
  1992年   20篇
  1991年   11篇
  1990年   6篇
  1989年   11篇
  1988年   4篇
  1987年   12篇
  1986年   12篇
  1985年   8篇
  1984年   8篇
  1983年   3篇
  1982年   2篇
  1981年   2篇
  1980年   5篇
  1979年   2篇
排序方式: 共有5197条查询结果,搜索用时 250 毫秒
71.
72.
《分离科学与技术》2012,47(18):3082-3090
ABSTRACT

This study aimed at extracting and separating anthocyanins from Nitraria tangutorun Bobr. fruit using deep eutectic solvent (DES) combined with macroporous resins. Choline chloride/1,2-propanediol (ChCl-Prop)-based DESs produced higher extraction yields of total anthocyanins from N. tangutorun fruit than pure water and ethanol/methanol/acetone aqueous solutions did, and LX-32 macroporous resin was used to separate total anthocyanins from the DES (recovery>95%). Additionally, a green and efficient HPLC-DAD method was used for the analysis of total anthocyanins using ethanol and a tartaric acid aqueous solution as mobile phases, and 13 anthocyanins were identified from N. tangutorun fruit using a UPLC-Q-TOF-MS method.

Abbreviations: DES, deep eutectic solvent; ChCl-Prop, choline chloride/1,2-propanediol.  相似文献   
73.
74.
The effect of cranberry extracts and juices during cranberry juice processing on the antiproliferative properties against colon cancer cells was investigated. Two colon cancer cell lines HT-29 and LS-513 were treated with different concentrations of cranberry phenolic extracts from fruits, puree, depectinised puree and pomace and different concentration of three juices (raw, filtered and concentrated juices). The phenolic extracts consisted of water-soluble phenolic compounds, apolar phenolic compounds and anthocyanins. These phenolic extracts and juices were tested against two cell lines at pH 2.5 (natural juice pH) and at pH 7.0 (physiological pH). All cranberry extracts and juices could inhibit the growth of both cell lines with the IC50 values (the concentration of phenolic content required to inhibit 50% the growth of cancer cells) varied from 3.8 to 179.2 μg gallic acid equivalent/ml. It was found that three types of extracts from fruit at pH 7.0 were the most effective at inhibiting the growth of HT-29 cell line. Extracts containing anthocyanins from fruit and from pomace were the most and the least efficient, respectively, in inhibiting the growth of both cancer cell lines. Further, three juices at natural pH (pH 2.5) were more effective at inhibiting the growth of two cell lines as compared to juices at pH 7.0. Concentrated juice at both pH values was the most effective at growth inhibition of two cancer cell lines compared to two other juices.  相似文献   
75.
76.
The oxidative stability of refined olive oil with incorporated Pistacia khinjuk fruit oil (PKFO; 0.5%, 1%, 2%, 5%, and 10%) during thermal processing at 170ºC for 8 h was evaluated. The conjugated diene values, carbonyl values, acid values, oil/oxidative stability indices, and total tocopherol content were measured during thermal processing. Olive oil containing 0.5% PKFO was identified as the most oxidative stable oil followed by oils containing 100 ppm TBHQ and 1, 5, 10, and 2% PKFO. No significant difference between samples of olive oil containing 100 ppm TBHQ and 1% PKFO was observed. Thus, it was concluded that PKFO at levels lower than 1% could provide stronger antioxidation activity in comparison with TBHQ (the strongest syntactic antioxidant used in the food industry). Moreover, reduction in tocopherol compounds during thermal processing was higher in olive oil containing TBHQ as compared to those in pure olive oil.  相似文献   
77.
78.
Peaches are popular, nutritious and widely consumed. Being a tree crop, it is considered a low risk fruit, with no direct water contact, and no previous foodborne disease outbreaks associated with its consumption. However, in 2014 the pioneer association between stone fruit and a foodborne illness was reported, linking Listeria monocytogenes to stone fruit. This highlights the need for better understanding of risk associated with contaminated fresh stone fruit, in order to implement adequate preventative measures. No information is available on the presence of foodborne pathogens on peaches in the supply chain. A case study approach was therefore followed to assess foodborne pathogen presence on the farm, focusing on the impact of irrigation water, facility sanitation and hygiene by collecting various fruit and environmental samples (n = 428). This study demonstrates the effectiveness of integrating basic microbial testing with safety management and risk assessment tools that can be collectively used to improve the food safety management system. No Salmonella Typhimurium was detected from samples, however, Escherichia coli O157:H7, Listeria spp. and Staphylococcus aureus were detected on fruit and environmental samples. Despite the GlobalG.A.P. certification status of the farm, livestock frequented water sources which lead to E. coli O157:H7 contamination. This conclusion was based on positive detection of foodborne pathogens from the water sources and subsequent removal of livestock which resulted in a definite decrease in pathogen detection. A number of E. coli O157:H7 and S. aureus were detected during the second year of monitoring from environmental samples and it was observed that the personal hygiene and facility sanitation was not adequately enforced. Based on feedback given to the farmer, enforcement was improved and a definite decrease in foodborne pathogens was observed in the following sampling cycle. Areas of risk that were still identified following the fourth year of monitoring included the water source used for irrigation and poor sanitation in the production and processing facilities. Limited foodborne pathogen prevalence on peaches over the full study period as well as the extended export supply chain at controlled temperatures resulted in low-to-medium calculated consumer risk. The correct and meticulous implementation of integrated and holistic pre- and post-harvest food safety management systems is therefore essential to prevent produce contamination, reduce the consumer risk and therefore ensure overall product safety.  相似文献   
79.
80.
BACKGROUND: Sugars, acids and vitamin C are essential components influencing the sensory and nutritional properties of currants (Ribes sp.). In this study the effects of growth latitude and weather conditions on these components in red, white and green currant cultivars were systematically investigated for the first time. RESULTS: Red Dutch (a red Ribes rubrum cultivar) contained more malic acid but fewer sugars and had a lower sugar/acid ratio than Vertti (a green Ribes nigrum cultivar) and White Dutch (a white R. rubrum cultivar). Fructose (27–56 g L?1 juice) and glucose (21–54 g L?1) were the major sugars in all currant samples, but sucrose (7–20 g L?1) was present only in Vertti. Vertti contained the most ascorbic acid. Sugars, malic acid and the sugar/acid ratio in Red Dutch were 11–28% higher in southern Finland than in northern Finland. The corresponding values in Vertti were 6–16% lower in the south than in the north, but no differences were found in White Dutch. As the relative humidity decreased, the amounts of citric acid and total acid increased in all cultivars, while the amount of sugars increased in Vertti but decreased in White Dutch and Red Dutch. In Red Dutch, high temperature and radiation levels increased the sugar content. CONCLUSION: The influence of latitude and weather conditions on qualitative parameters of currants varies with the cultivar. This study provides important guidance for currant cultivation and for further physiological and enzymological studies. Copyright © 2009 Society of Chemical Industry  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