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   3670篇
  免费   230篇
  国内免费   3篇
电工技术   49篇
综合类   3篇
化学工业   1185篇
金属工艺   45篇
机械仪表   81篇
建筑科学   127篇
矿业工程   3篇
能源动力   122篇
轻工业   405篇
水利工程   18篇
无线电   329篇
一般工业技术   662篇
冶金工业   159篇
原子能技术   48篇
自动化技术   667篇
  2024年   8篇
  2023年   45篇
  2022年   247篇
  2021年   269篇
  2020年   114篇
  2019年   103篇
  2018年   130篇
  2017年   128篇
  2016年   161篇
  2015年   143篇
  2014年   152篇
  2013年   238篇
  2012年   226篇
  2011年   284篇
  2010年   201篇
  2009年   207篇
  2008年   173篇
  2007年   154篇
  2006年   142篇
  2005年   102篇
  2004年   89篇
  2003年   73篇
  2002年   57篇
  2001年   40篇
  2000年   34篇
  1999年   40篇
  1998年   54篇
  1997年   39篇
  1996年   40篇
  1995年   18篇
  1994年   27篇
  1993年   15篇
  1992年   11篇
  1991年   6篇
  1989年   10篇
  1988年   5篇
  1987年   2篇
  1986年   8篇
  1985年   12篇
  1984年   9篇
  1983年   17篇
  1982年   10篇
  1981年   11篇
  1980年   12篇
  1979年   7篇
  1978年   5篇
  1977年   10篇
  1976年   4篇
  1975年   2篇
  1973年   2篇
排序方式: 共有3903条查询结果,搜索用时 15 毫秒
91.
92.
93.
94.
Glyphosate and glufosinate are broad spectrum herbicides, widely used in agriculture and in inhabited or industrialised areas, and aminomethylphosphonic acid is a degradation product of glyphosate. In 2015, the International Agency for Research on Cancer reported that glyphosate is a probable carcinogenic. In 2017, however, a scientific opinion of the European Chemicals Agency concluded that glyphosate is not proven to be carcinogenic, mutagenic or to have negative effects on reproduction. Nevertheless, aminomethylphosphonic acid was not considered. Due to their chemical-physical characteristics, these molecules present difficulties that have not yet allowed routine monitoring to be carried out. For these reasons, we developed and validated a simple and versatile liquid extraction, before IC-HRMS analysis, of three different complex matrices: honey, bass fish and bovine muscle. Among the satisfactory validation parameters, the LOQs in the range of 4.30–9.26 ng g?1 demonstrated high method sensitivity, compared to the few works present in literature. Finally, the method was applied to real commercial samples, which showed no traces of the selected pesticides.  相似文献   
95.
The aim of this study was to assess the microbial populations causing the spoilage of chilled beef during storage and to evaluate the effect of the use of an antimicrobial packaging for the meat storage. A nisin activated antimicrobial packaging was developed by using a nisin, HCL and EDTA solution and used for the storage of beef cuts at 1 °C. The common spoilage related microbial groups were monitored during the storage of beef in activated and non activated plastic bags by using selective media. The use of the antimicrobial packaging caused an overall significant reduction of viable counts of Gram positive bacteria such as carnobacteria, lactic acid bacteria and Brochotrix thermosphacta whose development was inhibited for at least 11 days of storage compared to the control. Moreover, a 1–3 log cycles reduction of enterobacteria was also registered between 22 and 32 days of storage. The microbiota was assessed at species level by using Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis of 16S rRNA gene of DNA extracted directly from meat and from bulk cells from selective media plates and showed that the species occurring within the targeted microbial groups did not change according to storage conditions. In conclusion, the use of the nisin activated packaging reduced the number of spoilage populations but did not affect the species diversity. Improved antimicrobial packaging is needed, possibly coupled with vacuum storage, to possibly achieve a simultaneous inhibition of more spoilage microbial groups and to preserve the microbiological quality of beef during chilled storage.  相似文献   
96.
In this study, Enterocin 416K1, a bacteriocin produced by Enterococcus casseliflavus IM 416K1, was entrapped in an organic-inorganic hybrid coating applied to a LDPE (low-density polyethylene) film for its potential use in the active food packaging field. The antibacterial activity of the coated film was evaluated against Listeria monocytogenes NCTC 10888 by qualitative modified agar diffusion assay, quantitative determination in listeria saline solution suspension and direct contact with artificially contaminated food samples (frankfurters and fresh cheeses) stored at room and refrigeration temperatures. All investigations demonstrated that enterocin-activated coatings have a good anti-listeria activity. Qualitative tests showed a clear zone of inhibition in the indicator lawn in contact with and around the coated film. During the quantitative antibacterial evaluation the L. monocytogenes viable counts decreased to 1.5 log units compared to the control. The inhibitory capability was confirmed also in food-contact assays. In all food samples packed with coated films we observed a significant decrease in L. monocytogenes viable counts in the first 24 h compared to the control. This difference was generally maintained up to the seventh day and then decreased, with the exception of the cheese samples stored at refrigeration temperature.  相似文献   
97.
Results of an extensive 5 year study on a full-scale plant with the specific aim to investigate polychlorinated dibenzo-p-dioxin (PCDD) and polychlorinated dibenzo furan (PCDF) formation and release in a secondary aluminum casting plant are reported. PCDD and PCDF concentrations were evaluated for all the gaseous and solid streams (no liquid stream was present) as well as for the flue gas upstream and downstream of every single unit of the flue gas cleaning system. The study highlights PCDD and PCDF formation particularly in the narrow 320-360 degrees C range. To prevent formation reactions and/or minimize PCDD and PCDF concentration at the stack, effects of the fabric filter substitution, a quenching chamber and a postcombustor installation together with working conditions are investigated. The flue gas cleaning system results in PCDD and PCDF emission at stack of 0.1-0.2 ng I-TEQ/N m3 and in a mass flow of 250-550 nmol/h. The total PCDD and PCDF release into the environment is 0.06 g I-TEQ/yr and the corresponding emission factor, 0.35 microg I-TEQ/ton. It is shown that the global effects of the technological innovation on the reaction mechanisms are the prevention of PCDD/F formation by de novo synthesis and the minimization of their emission.  相似文献   
98.
Demand for honey is increasing, especially if it is organic and if its nutritional properties are linked to untreated environments in order to guarantee quality for health. Sources of contamination of honey can be divided into environmental and apicultural. Therefore, the distribution of persistent organic pollutants, pesticides and antibiotic residues from geographical areas with different contamination sources (high anthropic impact, intensive farming, husbandry and low anthropic impact) was investigated in order to confirm the potential transfer of xenobiotics into the supply chain and to give beekeepers tools for the selection of areas dedicated to organic production. The presence of polychlorinated biphenyls, polybrominated diphenyl ether and polycyclic aromatic hydrocarbons was confirmed, not only in proximity to highly urbanised centres, where the concentrations were higher, but in all environment contexts, confirming their ubiquity. No antibiotics or neonicotinoids were detected in 95 organic honeys, demonstrating the absence of apicultural treatments and consequently the good quality of honey of different areas. These results are important due to the undefined regulatory European situation on honey antibiotic limits.  相似文献   
99.
100.
Production of the traditional Italian Focaccia bread (FcBread) requires reformulation to meet the new rules for healthier foods. We tested the applicability of a short-fermented (15 h) liquid sourdough (LS) (dough yield, DY, 250), obtained using quinoa (Q) or amaranth (Am) flour fermented with a Weissella cibaria strain (C43-11) producing exopolysaccharides (EPS) as fat replacer in yeast-leavened FcBread. The LSs were applied during the FcBread-making process at industrial pilot plant, reducing the added fat amount by 20% (FcBread-QLS and FcBread-AmLS) and products were compared with reference samples not containing EPS. All the products were analysed for physico-chemical properties (pH, TTA, organic acids, protein content and profile, instrumental colour), textural properties, sensory quality and glycemic index. The application of both pseudo-cereal-based W. cibaria LSs in FcBread allowed obtaining products with a reduced amount of fat, increased protein amount, mainly due to the albumin and glutenin/glutelin fractions, reduced glycemic index, improved texture and preserved in the traditional sensory profile of ‘focaccia’.  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