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   5107篇
  免费   505篇
  国内免费   15篇
电工技术   25篇
综合类   6篇
化学工业   1452篇
金属工艺   183篇
机械仪表   294篇
建筑科学   74篇
能源动力   171篇
轻工业   759篇
水利工程   29篇
石油天然气   4篇
无线电   806篇
一般工业技术   1051篇
冶金工业   227篇
原子能技术   46篇
自动化技术   500篇
  2024年   7篇
  2023年   89篇
  2022年   143篇
  2021年   227篇
  2020年   158篇
  2019年   176篇
  2018年   192篇
  2017年   218篇
  2016年   275篇
  2015年   202篇
  2014年   322篇
  2013年   364篇
  2012年   394篇
  2011年   480篇
  2010年   360篇
  2009年   288篇
  2008年   288篇
  2007年   219篇
  2006年   172篇
  2005年   168篇
  2004年   122篇
  2003年   111篇
  2002年   100篇
  2001年   89篇
  2000年   60篇
  1999年   61篇
  1998年   95篇
  1997年   53篇
  1996年   42篇
  1995年   25篇
  1994年   22篇
  1993年   17篇
  1992年   10篇
  1991年   13篇
  1990年   14篇
  1989年   11篇
  1988年   9篇
  1987年   7篇
  1986年   7篇
  1985年   4篇
  1984年   3篇
  1983年   2篇
  1982年   2篇
  1978年   1篇
  1977年   1篇
  1975年   2篇
  1970年   1篇
  1966年   1篇
排序方式: 共有5627条查询结果,搜索用时 28 毫秒
1.
International Journal of Information Security - Machine learning techniques have been widely used and shown remarkable performance in various fields. Along with the widespread utilization of...  相似文献   
2.
3.
Bacteria with antibiotic-resistant could seriously threaten to human health, increasing the treatment cost for infections and negatively affecting treatment outcomes. Stress adaptation is one possible mechanism for the acquisition or enhancement of antibiotic resistance in bacteria as a result of cross-protection. In this study, the effects of acid, salt, and cold stress on the antibiotic resistance of Salmonella Enteritidis, Listeria monocytogenes, and Escherichia coli O157:H7 were investigated using the disc diffusion method. For S. Enteritidis, acidic growth conditions increased resistance to ciprofloxacin and erythromycin (p < .05), and addition of 4% NaCl to growth media decreased resistance to chloramphenicol (p < .05). Irrespective of pH and the NaCl concentration of the growth medium, refrigerated E. coli O157:H7 showed increased resistance to amoxycillin, ciprofloxacin, gentamicin, streptomycin, and erythromycin (p < .05). Acid-adapted L. monocytogenes showed decreased the resistance to amoxycillin, ampicillin, chloramphenicol, ciprofloxacin, erythromycin, gentamicin, streptomycin, and tetracycline (p < .05). In conclusion, prolonged exposure of foodborne pathogens to acid, salt, and cold stress alters their antibiotic resistance. However, the effect of acid, salt, and cold stress on bacterial antibiotic resistance depend on both the bacterial species and the specific antibiotic. Therefore, multiple factors need to be considered for a foodborne antimicrobial resistant risk assessment.  相似文献   
4.
5.
Evaluation of kinetic distribution and behaviors of nanoparticles in vivo provides crucial clues into their roles in living organisms. Extracellular vesicles are evolutionary conserved nanoparticles, known to play important biological functions in intercellular, inter‐species, and inter‐kingdom communication. In this study, the first kinetic analysis of the biodistribution of outer membrane vesicles (OMVs)—bacterial extracellular vesicles—with immune‐modulatory functions is performed. OMVs, injected intraperitoneally, spread to the whole mouse body and accumulate in the liver, lung, spleen, and kidney within 3 h of administration. As an early systemic inflammation response, increased levels of TNF‐α and IL‐6 are observed in serum and bronchoalveolar lavage fluid. In addition, the number of leukocytes and platelets in the blood is decreased. OMVs and cytokine concentrations, as well as body temperature are gradually decreased 6 h after OMV injection, in concomitance with the formation of eye exudates, and of an increase in ICAM‐1 levels in the lung. Following OMV elimination, most of the inflammatory signs are reverted, 12 h post‐injection. However, leukocytes in bronchoalveolar lavage fluid are increased as a late reaction. Taken together, these results suggest that OMVs are effective mediators of long distance communication in vivo.  相似文献   
6.
7.
8.
While exercise training (ET) is an efficient strategy to manage obesity, it is recommended with a dietary plan to maximize the antiobesity functions owing to a compensational increase in energy intake. Capsiate is a notable bioactive compound for managing obesity owing to its capacity to increase energy expenditure. We aimed to examine whether the antiobesity effects of ET can be further enhanced by capsiate intake (CI) and determine its effects on resting energy expenditure and metabolic molecules. Mice were randomly divided into four groups (n = 8 per group) and fed high-fat diet. Mild-intensity treadmill ET was conducted five times/week; capsiate (10 mg/kg) was orally administered daily. After 8 weeks, resting metabolic rate and metabolic molecules were analyzed. ET with CI additively reduced the abdominal fat rate by 18% and solely upregulated beta-3-adrenoceptors in adipose tissue (p = 0.013) but did not affect the metabolic molecules in skeletal muscles. Surprisingly, CI without ET significantly increased the abdominal fat rate (p = 0.001) and reduced energy expenditure by 9%. Therefore, capsiate could be a candidate compound for maximizing the antiobesity effects of ET by upregulating beta-3-adrenoceptors in adipose tissue, but CI without ET may not be beneficial in managing obesity.  相似文献   
9.
10.
The electrochemical reduction of carbon dioxide (CO2) to hydrocarbons is a challenging task because of the issues in controlling the efficiency and selectivity of the products. Among the various transition metals, copper has attracted attention as it yields more reduced and C2 products even while using mononuclear copper center as catalysts. In addition, it is found that reversible formation of copper nanoparticle acts as the real catalytically active site for the conversion of CO2 to reduced products. Here, it is demonstrated that the dinuclear molecular copper complex immobilized over graphitized mesoporous carbon can act as catalysts for the conversion of CO2 to hydrocarbons (methane and ethylene) up to 60%. Interestingly, high selectivity toward C2 product (40% faradaic efficiency) is achieved by a molecular complex based hybrid material from CO2 in 0.1 m KCl. In addition, the role of local pH, porous structure, and carbon support in limiting the mass transport to achieve the highly reduced products is demonstrated. Although the spectroscopic analysis of the catalysts exhibits molecular nature of the complex after 2 h bulk electrolysis, morphological study reveals that the newly generated copper cluster is the real active site during the catalytic reactions.  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