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   63550篇
  免费   3234篇
  国内免费   212篇
电工技术   981篇
综合类   107篇
化学工业   12547篇
金属工艺   2351篇
机械仪表   3472篇
建筑科学   1360篇
矿业工程   54篇
能源动力   2477篇
轻工业   4651篇
水利工程   283篇
石油天然气   216篇
武器工业   2篇
无线电   11153篇
一般工业技术   12723篇
冶金工业   6350篇
原子能技术   704篇
自动化技术   7565篇
  2023年   602篇
  2022年   974篇
  2021年   1613篇
  2020年   1147篇
  2019年   1184篇
  2018年   1555篇
  2017年   1576篇
  2016年   1945篇
  2015年   1538篇
  2014年   2367篇
  2013年   3974篇
  2012年   3696篇
  2011年   4523篇
  2010年   3402篇
  2009年   3585篇
  2008年   3257篇
  2007年   2786篇
  2006年   2523篇
  2005年   2169篇
  2004年   2077篇
  2003年   1912篇
  2002年   1796篇
  2001年   1418篇
  2000年   1331篇
  1999年   1306篇
  1998年   2388篇
  1997年   1546篇
  1996年   1307篇
  1995年   1019篇
  1994年   786篇
  1993年   732篇
  1992年   529篇
  1991年   516篇
  1990年   439篇
  1989年   429篇
  1988年   339篇
  1987年   289篇
  1986年   267篇
  1985年   237篇
  1984年   210篇
  1983年   166篇
  1982年   156篇
  1981年   137篇
  1980年   138篇
  1979年   108篇
  1978年   97篇
  1977年   130篇
  1976年   167篇
  1975年   82篇
  1974年   82篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
Journal of Mechanical Science and Technology - This study delivers equations useful for low-height pleated fibrous filter design: two pressure drop equations and one set of optimum design equations...  相似文献   
33.
34.
Phytoalexins are inducible secondary metabolites possessing antimicrobial activity against phytopathogens. Rice produces a wide array of phytoalexins in response to pathogen attacks and environmental stresses. With few exceptions, most phytoalexins identified in rice are diterpenoid compounds. Until very recently, flavonoid sakuranetin was the only known phenolic phytoalexin in rice. However, recent studies have shown that phenylamides are involved in defense against pathogen attacks in rice. Phenylamides are amine-conjugated phenolic acids that are induced by pathogen infections and abiotic stresses including ultra violet (UV) radiation in rice. Stress-induced phenylamides, such as N-trans-cinnamoyltryptamine, N-p-coumaroylserotonin and N-cinnamoyltyramine, have been reported to possess antimicrobial activities against rice bacterial and fungal pathogens, an indication of their direct inhibitory roles against invading pathogens. This finding suggests that phenylamides act as phytoalexins in rice and belong to phenolic phytoalexins along with sakuranetin. Phenylamides also have been implicated in cell wall reinforcement for disease resistance and allelopathy of rice. Synthesis of phenolic phytoalexins is stimulated by phytopathogen attacks and abiotic challenges including UV radiation. Accumulating evidence has demonstrated that biosynthetic pathways including the shikimate, phenylpropanoid and arylmonoamine pathways are coordinately activated for phenolic phytoalexin synthesis, and related genes are induced by biotic and abiotic stresses in rice.  相似文献   
35.
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   
36.
37.
38.
39.
40.
The cover image is based on the Research Article V2O5/RGO/Pt nanocomposite on oxytetracycline degradation and pharmaceutical effluent detoxification by Mohan, H et al., DOI: 10.1002/jctb.6238 .

  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