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   781篇
  免费   14篇
化学工业   229篇
金属工艺   7篇
机械仪表   6篇
建筑科学   20篇
矿业工程   5篇
能源动力   8篇
轻工业   174篇
水利工程   4篇
石油天然气   6篇
无线电   49篇
一般工业技术   68篇
冶金工业   114篇
自动化技术   105篇
  2024年   6篇
  2023年   7篇
  2022年   35篇
  2021年   30篇
  2020年   19篇
  2019年   16篇
  2018年   24篇
  2017年   23篇
  2016年   21篇
  2015年   22篇
  2014年   25篇
  2013年   52篇
  2012年   42篇
  2011年   38篇
  2010年   40篇
  2009年   35篇
  2008年   35篇
  2007年   39篇
  2006年   16篇
  2005年   16篇
  2004年   22篇
  2003年   20篇
  2002年   19篇
  2001年   15篇
  2000年   6篇
  1999年   10篇
  1998年   14篇
  1997年   12篇
  1996年   8篇
  1995年   11篇
  1994年   6篇
  1993年   5篇
  1992年   4篇
  1990年   7篇
  1989年   5篇
  1988年   4篇
  1987年   9篇
  1986年   3篇
  1985年   4篇
  1984年   5篇
  1983年   8篇
  1982年   5篇
  1981年   5篇
  1980年   3篇
  1979年   5篇
  1978年   6篇
  1977年   3篇
  1976年   7篇
  1975年   3篇
  1973年   3篇
排序方式: 共有795条查询结果,搜索用时 0 毫秒
751.
Methanolic and acetonic extracts of apple pomace were evaluated for phenolic profiles, antioxidant properties and antiviral effect against herpes simplex virus type 1 (HSV-1) and 2 (HSV-2). Acetone extraction yielded the higher amounts of phenolic compounds. The extraction method influenced the phenolic composition although antioxidant activity correlated weakly with phenols concentration. Among the polyphenols analysed, quercetin glycosides were the most important family, followed by dihydrochalcones. Apple pomace extracts were able to inhibit both HSV-1 and HSV-2 replication in Vero cells by more than 50%, at non-cytotoxic concentrations. Selectivity indexes (SI) ranged from 9.5 to 12.2.  相似文献   
752.
The levels of free and total tryptophan and of 5-hydroxytryptophan (5-HTP) were investigated in green and roasted grains and beverages of Coffea arabica L. (Arabica) and Coffea canephora Pierre var. robusta (Robusta). Grains were light, medium and dark roasted. Free and protein tryptophan were extracted before and after hydrolysis. The levels of tryptophan and 5-HTP were quantified simultaneously by ion-pair HPLC and fluorimetric detection after derivatisation with o-phthalaldehyde. Robusta green coffee had higher total and protein tryptophan, whereas Arabica had higher free tryptophan levels. 5-HTP was not detected in the samples before and after roasting. Free tryptophan was completely degraded during roasting. Roasting significantly affected protein tryptophan. The rate of loss was smaller in Arabica compared to Robusta at every roasting degree. A beverage prepared the Brazilian way with a medium-roasted coffee provided 1.4–2.5 mg tryptophan/50 ml cup.  相似文献   
753.
To estimate the dietary exposure of the main minerals and trace elements from retail food typically consumed by the French population, samples were purchased and then prepared and cooked prior to analysis. A total of 1080 individual food composites samples were collected and analysed for 18 elements (arsenic, lead, cadmium, aluminium, mercury, antimony, chrome, calcium, manganese, magnesium, nickel, copper, zinc, lithium, sodium, molybdenum, cobalt and selenium). Intakes were calculated from different food consumption patterns found in France for average and high consumers among adults and children. Dietary exposures of those consumers estimated from the France 2000 Total Diet Study (FTDS) are reported, and compared with existing nutritional reference values (Lowest threshold Intake, LTI) or toxicological reference values (Provisional Tolerable Weekly Intake, PTWI or Upper Level, UL) of the respective element and from previous French studies. This study confirms for the populations concerned, the low probability of nutritional or health risks due to food consumption.  相似文献   
754.
An HPLC study of the carotenoid composition of fresh, frozen and canned papaya fruit slices was done. There were no qualitative differences between the carotenoid patterns of fresh and frozen papaya fruit slices (cultivar Sunrise). The major carotenoids found in papaya extracts were lycopene and carotenol fatty acid esters of-cryptoxanthin and-cryptoxanthin-5, 6-epoxide. Other xanthophylls detected were-crypto-xanthin,trans-zeaxanthin and cryptoflavin. It was possible to determine the quantitative losses of carotenoids in papaya slices as a result of the freezing process and frozen storage, since samples of these fruits were available before processing. The pigment pattern of the canned product showed lycopene as being a major pigment. Thermal treatment induced the degradation of carotenol fatty acid esters of xanthophylls. The freezing and canning processing of papaya slices led to significant decreases in the total carotenoids quantified by HPLC, with frozen female slices and canned samples showing lower amounts of pigments. Hunter colour values of frozen slices were similar to those of fresh papaya fruit slices.  相似文献   
755.
We have investigated the bacteria and yeast ecology of the typical Italian Ciauscolo salami that is produced in Central Italy using a polyphasic approach based on culture-dependent and -independent methods. The physico-chemical analyses showed a progressive drop in pH and water activity (aw) during ripening. The viable counts revealed a dominance of lactic acid bacteria (LAB) over coagulase negative cocci (CNC) and yeasts. From the molecular identification of the isolates, the prevalence of Lactobacillus curvatus, Lb. plantarum and Staphylococcus xylosus was shown among the bacteria, while Debaryomyces hansenii was the prevalent species among the yeasts, and it was isolated throughout the whole ripening process. Minority species, namely Rhodotorula mucillaginosa and Trichosporon brassicae, were also recovered from the meat batter. The total microbial community was profiled without cultivation by analyzing the DNA that was directly extracted from the salami samples. Moreover, the cultivable community was profiled by analyzing the DNA recovered from bulk cells that were obtained by harvesting the colonies from serial-dilution agar plates. The 16S rRNA gene V1 and V3 regions were used as targets in the denaturing gradient gel electrophoresis (DGGE) profiling of the LAB and CNC communities, respectively, while the diversity and dynamics of the yeast population were assessed by analyzing a portion of the 28S rRNA gene. Our findings suggest that the microbial diversity of fermented meat products can be successfully investigated by this polyphasic approach that is based on the assessment of both the total and the cultivable community diversity.  相似文献   
756.
大麻休闲服和工作服的整理   总被引:5,自引:0,他引:5  
本文提供了符合环境要求的大麻织物的整理方法,这些方法能改善织物的析皱和收缩倾向并且具有阻燃保护功能,此整理为大麻时装,休闲服,运动服及工作服市场化提供了可能性。  相似文献   
757.
758.
The European Union co-funded COMUNICAR (communication multimedia unit inside car) project designed and developed an integrated multimedia human–machine interface (HMI) able to manage a wide variety of driver information systems (from entertainment to safety). COMUNICAR proposed an innovative information provision paradigm, in which the on-vehicle HMI is able to tailor the delivery of the information in real time according to the actual driving context and the drivers workload. COMUNICAR adopted a user-centred design process involving an iterative development based on extensive user tests since the early phases of the project. This approach was particularly useful to define and improve the layout of the user interface and specify the rules that decide the scheduling and the modalities of the delivery of the information messages to the driver. This paper introduces the COMUNICAR concept and the user-centred flow of design. Then, a concrete case of user-test driven, iterative improvement of a systems functionality is presented. We also briefly describe two software tools that we have designed to enhance the development process in a user-centred perspective. Finally, the future evolution of the concept of smart and safe information scheduling is sketched and discussed.
F. BellottiEmail:
A. De GloriaEmail:
R. MontanariEmail:
D. MorrealeEmail:
  相似文献   
759.
While speech recognition technology has long held the potential for improving the effectiveness of military operations, it has only been within the last several years that speech systems have enabled the realization of that potential. Commercial speech recognition technology developments aimed at improving robustness for automotive and cellular phone applications have capabilities that can be exploited in various military systems. This paper discusses the results of two research efforts directed toward applying commercial-off-the-shelf speech recognition technology in the military domain. The first effort discussed is the development and evaluation of a speech recognition interface to the Theater Air Planning system responsible for the generation of air tasking orders in a military Air Operations Center. The second effort examined the utility of speech versus conventional manual input for tasks performed by operators in an unmanned aerial vehicle control station simulator. Both efforts clearly demonstrate the military benefits obtainable from the proper application of speech technology.  相似文献   
760.

In the last decades, the socio-demographic evolution of the population has substantially changed mobility demand, posing new challenges in minimizing urban congestion and reducing environmental impact. In this scenario, understanding how different modes of transport can efficiently share (partially or totally) a common infrastructure is crucial for urban development. To this aim, we present a stochastic model-based analysis of critical intersections shared by tram traffic and private traffic, combining a microscopic model of the former with a macroscopic model of the latter. Advanced simulation tools are typically used for such kind of analyses, by playing various traffic scenarios. However, simulation is not an exhaustive approach, and some critical, possibly rare, event may be ignored. For this reason, our aim is instead to adopt suitable analytical solution techniques and tools that can support instead a complete, exhaustive analysis, so being able to take into account rare events as well. Transient analysis of the overall traffic model using the method of stochastic state classes is adopted to support the evaluation of relevant performance measures, namely the probability of traffic congestion over time and the average number of private vehicles in the queue over time. A sensitivity analysis is performed with respect to multiple parameters, notably including the arrival rate of private vehicles, the frequency of tram rides, and the time needed to recover from traffic congestion.

  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