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   491篇
  免费   35篇
  国内免费   2篇
电工技术   2篇
化学工业   206篇
金属工艺   1篇
机械仪表   15篇
建筑科学   21篇
矿业工程   1篇
能源动力   13篇
轻工业   122篇
水利工程   1篇
石油天然气   4篇
无线电   11篇
一般工业技术   60篇
冶金工业   20篇
原子能技术   1篇
自动化技术   50篇
  2023年   2篇
  2022年   47篇
  2021年   45篇
  2020年   21篇
  2019年   10篇
  2018年   17篇
  2017年   15篇
  2016年   20篇
  2015年   12篇
  2014年   20篇
  2013年   36篇
  2012年   43篇
  2011年   39篇
  2010年   21篇
  2009年   25篇
  2008年   24篇
  2007年   17篇
  2006年   15篇
  2005年   12篇
  2004年   7篇
  2003年   11篇
  2002年   7篇
  2001年   2篇
  2000年   8篇
  1999年   6篇
  1998年   3篇
  1997年   2篇
  1996年   7篇
  1995年   5篇
  1994年   3篇
  1993年   5篇
  1992年   3篇
  1991年   1篇
  1989年   2篇
  1988年   3篇
  1987年   1篇
  1986年   2篇
  1984年   1篇
  1983年   2篇
  1982年   2篇
  1977年   1篇
  1974年   1篇
  1973年   1篇
  1972年   1篇
排序方式: 共有528条查询结果,搜索用时 15 毫秒
41.
Falling films in wash down process are of major interest for pharmaceutical isolators, which are used for processing of highly potent pharmaceutical products. In this study multiple process parameters were examined with common materials of isolator systems. The importance of material and surface finish in respect of cleanability and complete wetting as well as a combination of process parameters are presented and discussed. For cleaning validation an effect of high interest was discovered: swab sampling areas changed their properties over many repeated cycles and showed decreased cleanability.  相似文献   
42.
Patulin is a mycotoxin produced by certain species of Penicillium and Aspergillus, often detectable in mouldy fruits and their derivatives. On the basis of a PMTDI of 0.4 mu g/kg bw, limit values of 50 mu g/kg or 50 mu g/l of patulin have been set in fruit derivatives. To estimate the quantity of patulin that can be taken in with the diet, we analysed by HPL C samples of apples and apple derivatives which are most likely to be contaminated with patulin. In apple juices and in homogenized babyfoods, the mycotoxin concentration was always below the established limits, while in some samples of juice with pulp the mycotoxin content exceeded the safe levels. In rotten apples, not only was the amount of patulin extraordinarily high in the rotten area, but the mycotoxin had also spread to the part unaffected by mould. The data presented in this study indicate that the intake of patulin with apple derivatives is usually below the tolerable level of 0.4 mu g/kg bw/day, but since the patulin content in apples can vary considerably, the quality of fruits used in the production of apple derivatives should be strictly controlled in order not to exceed the safe limits.  相似文献   
43.
A confirmatory method for fusariotoxin analysis in maize meal, based on liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS), was developed, and compared with a previously published screening method, based on the same technique. By eluting selectively from a Carbograph-4 clean-up cartridge trichothecenes, fumonisins and macrocyclic lactones, and optimizing LC–MS/MS conditions for every chemical class, a sensitive and reliable determination was performed. Method quantification limits for confirmatory and screening methods were in the range 0.001–0.019 mg/kg and 0.003–0.125 mg/kg, respectively.  相似文献   
44.
Among sugar substitutes, an important role is played by xylitol, an aliphatic pentitol provided with some interesting properties which make it a high value product for pharmaceutical, odontological and food industries. Its production by biotechnological methods is based on fermentation of agro-industrial residues and could potentially compete with the traditional chemical way. However, crystallization is an important stage of xylitol production, since in many respects it determines the yield and quality of the target product. In the present work tests were made in order to determine the best conditions to clarify fermented media, which were then subjected to isothermal crystallization in the presence or in the absence of residual xylose and varying xylitol concentration as well as cooling temperature (−10 ≤ Tc ≤ 15 °C). Besides, the kinetics of xylitol crystallization from fermented solutions was investigated as function of the initial solution supersaturation and cooling temperature. The effect of the presence of residual xylose on the rate of crystallization was also evaluated. The best clarifying treatment was found to be 20 g l−1 activated charcoal at room temperature for 1 h. The study of xylitol crystallization revealed the positive effect of the presence of residual xylose, which ensured a 1.6-fold increase in the crystallization yield (from 0.27 to 0.42).  相似文献   
45.
46.
The main aim of the EC-financed R&D project PlantLIBRA (PLANT food supplements: Levels of Intake, Benefit and Risk Assessment) is to foster the safe use of food supplements containing plants or botanical preparations, by enabling science-based decision making by regulators and stakeholders. To make informed decisions, competent authorities and industry need more accessible and quality-assured information, as well as better tools (e.g., databases) and procedures for safety and benefit assessments, supported by broadly accepted methodologies. Consequently, PlantLIBRA is working to develop, validate and disseminate data and methodologies for risk and benefit assessment of plant food supplements, and to implement sustainable international cooperation. International cooperation will help ensure the quality of botanicals imported in the EU. Moreover, the project will provide data on intake by conducting a harmonized consumption survey. Existing composition and safety data will be collated into a meta-database. New analytical data and methods will be investigated and validated. The consortium is working closely with competent authorities and stakeholders.  相似文献   
47.
Ostreopsis cf. ovata, a benthic dinoflagellate often blooming along the Mediterranean coasts, has been associated with toxic events ranging from dyspnea to mild dermatitis. In late September 2009, an Ostreopsis cf. ovata bloom occurred in the Gulf of Trieste (Northern Adriatic Sea; Italy), causing pruritus and mild dermatitis in beachgoers. An integrated study was initiated to characterize Ostreopsis cells by light and confocal microscopy, PCR techniques, immunocytochemistry, and high resolution liquid chromatography-mass spectrometry (HR LC-MS). The presence of Ostreopsis cf. ovata of the Atlantic/Mediterranean clade was unambiguously established by morphological and genetic analyses in field samples. Several palytoxin-like compounds (ovatoxin-a,-b,-c,-d,-e) were identified by HR LC-MS, ovatoxin-a being the most abundant (45-64 pg/cell). Surprisingly, no palytoxin was detected. For the first time, monoclonal and polyclonal antipalytoxin antibodies revealed the intracellular cytoplasmic localization of ovatoxins, suggesting their cross-reactivity with these antibodies. Since harmful dinoflagellates do not always produce toxins, the immunocytochemical localization of ovatoxins, although qualitative, can provide an early warning for toxic Ostreopsis cells before their massive diffusion and/or concentration in seafood.  相似文献   
48.
Surface plasmon resonance imaging (SPRi) was used as the transduction principle for the development of optical-based sensing for transgenes detection in human cell lines. The objective was to develop a multianalyte, label-free, and real-time approach for DNA sequences that are identified as markers of transgenosis events. The strategy exploits SPRi sensing to detect the transgenic event by targeting selected marker sequences, which are present on shuttle vector backbone used to carry out the transfection of human embryonic kidney (HEK) cell lines. Here, we identified DNA sequences belonging to the Cytomegalovirus promoter and the Enhanced Green Fluorescent Protein gene. System development is discussed in terms of probe efficiency and influence of secondary structures on biorecognition reaction on sensor; moreover, optimization of PCR samples pretreatment was carried out to allow hybridization on biosensor, together with an approach to increase SPRi signals by in situ mass enhancement. Real-time PCR was also employed as reference technique for marker sequences detection on human HEK cells. We can foresee that the developed system may have potential applications in the field of antidoping research focused on the so-called gene doping.  相似文献   
49.
50.
Three poly(ethylene terephthalate) films were prepared having the same crystallinity but different morphology. They were colored with azo dyes XC6H4N = NC6H4N(C2H5)2 (where X is H, OCH3, CN, and COOC2H5). The kinetics of the thermal cis-trans isomerization of these dyes has been studied below the glass transition temperature in the range 25–56°C. The isomerization process was found to be the result of a multiplicity of first-order reactions. The kinetic parameters have been correlated with the order degree at molecular level of the polymer. Lightfastness of the dyes in the polymer matrices has been also investigated: it appeared to be in relation with the supermolecular structure of the film.  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