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   148729篇
  免费   9549篇
  国内免费   3183篇
电工技术   4899篇
技术理论   2篇
综合类   3928篇
化学工业   27709篇
金属工艺   6723篇
机械仪表   9183篇
建筑科学   6169篇
矿业工程   1729篇
能源动力   5448篇
轻工业   10374篇
水利工程   1443篇
石油天然气   3198篇
武器工业   438篇
无线电   22261篇
一般工业技术   25516篇
冶金工业   12021篇
原子能技术   1800篇
自动化技术   18620篇
  2024年   267篇
  2023年   1700篇
  2022年   3124篇
  2021年   4777篇
  2020年   3432篇
  2019年   3463篇
  2018年   4037篇
  2017年   4020篇
  2016年   4491篇
  2015年   4454篇
  2014年   6211篇
  2013年   9075篇
  2012年   8997篇
  2011年   10555篇
  2010年   8306篇
  2009年   8471篇
  2008年   8212篇
  2007年   7115篇
  2006年   6784篇
  2005年   5709篇
  2004年   5017篇
  2003年   4739篇
  2002年   4745篇
  2001年   3925篇
  2000年   3354篇
  1999年   3192篇
  1998年   4318篇
  1997年   3052篇
  1996年   2605篇
  1995年   2037篇
  1994年   1576篇
  1993年   1380篇
  1992年   1040篇
  1991年   970篇
  1990年   859篇
  1989年   821篇
  1988年   641篇
  1987年   545篇
  1986年   437篇
  1985年   411篇
  1984年   331篇
  1983年   253篇
  1982年   230篇
  1981年   200篇
  1980年   190篇
  1979年   153篇
  1978年   142篇
  1977年   173篇
  1976年   238篇
  1975年   110篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
1.
Zhao  Jiandong  Lei  Wei  Li  Zijian  Zhao  Dongfeng  Han  Mingmin  Hou  Xiaoqing 《Multimedia Tools and Applications》2022,81(4):4753-4780
Multimedia Tools and Applications - The crowding in bus is an important factor affecting passenger satisfaction and bus dispatching level. However, how to use video images to detect crowding...  相似文献   
2.
Hepatic fibrosis occurs when liver tissue becomes scarred from repetitive liver injury and inflammatory responses; it can progress to cirrhosis and eventually to hepatocellular carcinoma. Previously, we reported that neoagarooligosaccharides (NAOs), produced by the hydrolysis of agar by β-agarases, have hepatoprotective effects against acetaminophen overdose-induced acute liver injury. However, the effect of NAOs on chronic liver injury, including hepatic fibrosis, has not yet been elucidated. Therefore, we examined whether NAOs protect against fibrogenesis in vitro and in vivo. NAOs ameliorated PAI-1, α-SMA, CTGF and fibronectin protein expression and decreased mRNA levels of fibrogenic genes in TGF-β-treated LX-2 cells. Furthermore, downstream of TGF-β, the Smad signaling pathway was inhibited by NAOs in LX-2 cells. Treatment with NAOs diminished the severity of hepatic injury, as evidenced by reduction in serum alanine aminotransferase and aspartate aminotransferase levels, in carbon tetrachloride (CCl4)-induced liver fibrosis mouse models. Moreover, NAOs markedly blocked histopathological changes and collagen accumulation, as shown by H&E and Sirius red staining, respectively. Finally, NAOs antagonized the CCl4-induced upregulation of the protein and mRNA levels of fibrogenic genes in the liver. In conclusion, our findings suggest that NAOs may be a promising candidate for the prevention and treatment of chronic liver injury via inhibition of the TGF-β/Smad signaling pathway.  相似文献   
3.
4.
5.
6.
7.
International Journal of Information Security - This paper deals with a well-known problem in the area of the smudge attacks: when a user draws a pattern to unlock the pattern lock on a smartphone...  相似文献   
8.
9.
Di(2-ethylhexyl) phthalate (DEHP) is widely used as a plasticizer in the manufacture of polyvinylchloride plastics and has been associated with concerns regarding male reproductive toxicity. In this study, we hypothesized that maternal exposure to DEHP induces transgenerational inheritance of adult-onset adverse reproductive outcomes through the male germline in the F1, F2, and F3 generations of male offspring. Pregnant rats were treated with 5 or 500 mg of DEHP/kg/day through gavage from gestation day 0 to birth. The offspring body weight, anogenital distance (AGD), anogenital index (AGI), sperm count, motility, and DNA fragmentation index (DFI) were measured for all generations. Methyl-CpG binding domain sequencing was performed to analyze sperm DNA methylation status in the F3. DEHP exposure at 500 mg/kg affected AGD, AGI, sperm count, mean DFI, and %DFI in the F1; AGD, sperm count, and mean DFI in the F2; and AGD, AGI, mean DFI, and %DFI in the F3. DEHP exposure at 5 mg/kg affected AGD, AGI, sperm count, and %DFI in the F1; sperm count in the F2; and AGD and AGI in F3. Compared with the control group, 15 and 45 differentially hypermethylated genes were identified in the groups administered 5 mg/kg and 500 mg/kg DEHP, respectively. Moreover, 130 and 6 differentially hypomethylated genes were observed in the groups administered 5 mg/kg and 500 mg/kg DEHP. Overall, these results demonstrated that prenatal exposure to DEHP caused transgenerational epigenetic effects, which may explain the observed phenotypic changes in the male reproductive system.  相似文献   
10.
Pathogens pose a serious challenge to environmental sanitation and a threat to public health.The frequent use of chemicals for sterilization in recent years has not only caused secondary damage to the environment but also increased pathogen resistance to drugs,which further threatens public health.To address this issue,the use of non-chemical antibacterial means has become a new trend for environmental disinfection.In this study,we developed red phosphorus nanoparticles(RPNPs),a safe and degradable photosensitive material with good photocatalytic and photothermal properties.The red phosphorus nanoparticles were prepared using a template method and ultrasonication.Under the irradiation of simulated sunlight for 20 min,the RPNPs exhibited an efficiency of 99.98%in killing Staphylococcus aureus due to their excellent photocatalytic and photothermal abilities.Transmission electron microscopy and ultraviolet–visible spectroscopy revealed that the RPNPs exhibited degradability within eight weeks.Both the RPNPs and their degradation products were nontoxic to fibroblast cells.Therefore,such RPNPs are expected to be used as a new type of low-cost,efficient,degradable,biocompatible,and eco-friendly photosensitive material for environmental disinfection.  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