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   161363篇
  免费   14991篇
  国内免费   8535篇
电工技术   11756篇
技术理论   4篇
综合类   11694篇
化学工业   23687篇
金属工艺   9665篇
机械仪表   10192篇
建筑科学   12045篇
矿业工程   4040篇
能源动力   4906篇
轻工业   11823篇
水利工程   3682篇
石油天然气   7256篇
武器工业   1675篇
无线电   20443篇
一般工业技术   18751篇
冶金工业   7898篇
原子能技术   1928篇
自动化技术   23444篇
  2024年   625篇
  2023年   2193篇
  2022年   4359篇
  2021年   6192篇
  2020年   4477篇
  2019年   3611篇
  2018年   4060篇
  2017年   4914篇
  2016年   4491篇
  2015年   6289篇
  2014年   8192篇
  2013年   9992篇
  2012年   11568篇
  2011年   12533篇
  2010年   11398篇
  2009年   10981篇
  2008年   10808篇
  2007年   10297篇
  2006年   9645篇
  2005年   7903篇
  2004年   5739篇
  2003年   5022篇
  2002年   5190篇
  2001年   4487篇
  2000年   3418篇
  1999年   2986篇
  1998年   2386篇
  1997年   2080篇
  1996年   1822篇
  1995年   1501篇
  1994年   1172篇
  1993年   926篇
  1992年   724篇
  1991年   555篇
  1990年   467篇
  1989年   361篇
  1988年   290篇
  1987年   217篇
  1986年   177篇
  1985年   146篇
  1984年   112篇
  1983年   88篇
  1982年   78篇
  1981年   68篇
  1980年   58篇
  1979年   40篇
  1978年   34篇
  1977年   33篇
  1976年   54篇
  1973年   21篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
Removal of imidacloprid and acetamiprid in tea infusions by microfiltration membrane using dead‐end model was investigated in the present study. The results showed that microfiltration significantly promoted the removal of both pesticides (P < 0.05) in tea infusions. Furthermore, the extent of removal was strongly influenced by the pore size of membrane, operational pressure and the concentrations of tea infusions. The initial concentration of imidacloprid and acetamiprid showed no significant effect on their removal rates. The maximum removal rates were 79.7% for imidacloprid and 81.9% acetamiprid. The changes in major chemical components of tea infusions after microfiltration were evaluated. The results indicated that microfiltration caused no considerable changes in total polyphenols and total free amino acids, and small but statistically significant losses (6.3–18.0%) of eight catechins and three methylxanthines when filtration volume reached to 200 mL. The present study validated the application of microfiltration as a potentially feasible and promising method for the removal of imidacloprid and acetamiprid residues from tea infusions.  相似文献   
3.
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   
4.
5.
文章首先对暑期学校的发展历史和现状进行了分析,指出了现阶段国内高校暑期学校发展中的问题和瓶颈。针对提出的问题,文章剖析了开设暑期学校的理论支撑和实践基础,并结合山东大学九年办学实践经验说明暑期学校在深化教学改革、创新人才培养模式、提高教学质量和办学水平、扩大学校影响力,全面提升学校国际化的积极作用。  相似文献   
6.
针对不合格品的高效处置、数据的有效分析对企业质量控制具有深远的意义,其是装备制造领域质量管理研究的重点。文章以SAP接口二次开发、IQS流程建模、数据库建立、系统实用价值等方面展开详细论述,确保质量信息可追溯分析。  相似文献   
7.
8.
Cerebral microbleeds (CMBs) are small hemosiderin deposits indicative of prior cerebral microscopic hemorrhage and previously thought to be clinically silent. Recent population‐based cross‐sectional studies and prospective longitudinal cohort studies have revealed association between CMB and cognitive dysfunction. In the general population, CMBs are associated with age, hypertension, and cerebral amyloid angiopathy. In the chronic kidney disease (CKD) population, diminished estimated glomerular filtration rate has been found to be an independent risk factor for CMB, raising the possibility that a uremic milieu may predispose to microbleeds. In the end‐stage renal disease (ESRD) population on hemodialysis, the incidence of microbleeds is significantly higher compared with a control group without history of CKD or stroke. We present an ESRD patient on chronic hemodialysis with a history of gradual cognitive decline and progressive CMBs. Through this case and literature review, we illustrate the need to develop detection and prediction models to treat this frequent development in ESRD patients.  相似文献   
9.
10.
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