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   11007篇
  免费   826篇
  国内免费   73篇
电工技术   210篇
综合类   38篇
化学工业   3055篇
金属工艺   281篇
机械仪表   291篇
建筑科学   426篇
矿业工程   23篇
能源动力   708篇
轻工业   1172篇
水利工程   109篇
石油天然气   217篇
无线电   1066篇
一般工业技术   1869篇
冶金工业   482篇
原子能技术   116篇
自动化技术   1843篇
  2023年   220篇
  2022年   467篇
  2021年   581篇
  2020年   449篇
  2019年   506篇
  2018年   659篇
  2017年   545篇
  2016年   579篇
  2015年   411篇
  2014年   563篇
  2013年   994篇
  2012年   546篇
  2011年   744篇
  2010年   536篇
  2009年   503篇
  2008年   436篇
  2007年   340篇
  2006年   296篇
  2005年   242篇
  2004年   214篇
  2003年   182篇
  2002年   153篇
  2001年   122篇
  2000年   128篇
  1999年   111篇
  1998年   143篇
  1997年   88篇
  1996年   85篇
  1995年   66篇
  1994年   68篇
  1993年   79篇
  1992年   64篇
  1991年   55篇
  1990年   56篇
  1989年   42篇
  1988年   52篇
  1987年   54篇
  1986年   45篇
  1985年   40篇
  1984年   49篇
  1983年   40篇
  1982年   35篇
  1981年   25篇
  1980年   33篇
  1979年   25篇
  1978年   33篇
  1977年   27篇
  1976年   39篇
  1975年   32篇
  1974年   28篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Obesity and hyperlipidemia are major risk factors for developing vascular diseases. Bee bread (BB) has been reported to exhibit some biological actions, including anti-obesity and anti-hyperlipidemic. This study aims to investigate whether bee bread can ameliorate vascular inflammation and impaired vasorelaxation activity through eNOS/NO/cGMP pathway in obese rats. Forty male Sprague-Dawley rats were randomly divided into four groups (n = 10/group), namely: control (normal group), obese rats (OB group), obese rats treated with bee bread (0.5 g/kg/day, OB/BB group) and obese rats treated with orlistat (10 mg/kg/day, OB/OR group). The latter three groups were given a high-fat diet (HFD) for 6 weeks to induced obesity before being administered with their respective treatments for another 6 weeks. After 12 weeks of the total experimental period, rats in the OB group demonstrated significantly higher Lee obesity index, lipid profile (total cholesterol, triglyceride, low-density lipoprotein), aortic proinflammatory markers (tumor necrosis factor-α, nuclear factor-κβ), aortic structural damage and impairment in vasorelaxation response to acetylcholine (ACh). Bee bread significantly ameliorated the obesity-induced vascular damage manifested by improvements in the lipid profile, aortic inflammatory markers, and the impaired vasorelaxation activity by significantly enhancing nitric oxide release, promoting endothelial nitric oxide synthase (eNOS) and cyclic guanosine monophosphate (cGMP) immunoexpression. These findings suggest that the administration of bee bread ameliorates the impaired vasorelaxation response to ACh by improving eNOS/NO/cGMP-signaling pathway in obese rats, suggesting its vascular therapeutic role.  相似文献   
2.
Journal of Materials Science: Materials in Electronics - Nano Mn0.95M0.05S (M ≡ Cu, Mg) samples were produced using molten salt solid state reaction method. Rietveld analysis of X-ray...  相似文献   
3.
4.
5.
6.
7.
8.
Watermelon peel residues were used to produce a new biochar by dehydration method. The new biochar has undergone two methods of chemical modification and the effect of this chemical modification on its ability to adsorb Cr(VI) ions from aqueous solution has been investigated. Three biochars, Melon-B, Melon-BO-NH_2 and Melon-BO-TETA, were made from watermelon peel via dehydration with 50% sulfuric acid to give Melon-B followed by oxidation with ozone and amination using ammonium hydroxide to give Melon-BO-NH_2 or Triethylenetetramine(TETA) to give Melon-BO-TETA. The prepared biochars were characterized by BET, BJH,SEM, FT-IR, TGA, DSC and EDAX analyses. The highest removal percentage of Cr(VI) ions was 69% for Melon-B,98% for Melon-BO-NH_2 and 99% for Melon-BO-TETA biochars of 100 mg·L~(-1) Cr(VI) ions initial concentration and 1.0 g·L~(-1) adsorbents dose. The unmodified biochar(Melon-B) and modified biochars(Melon-BO-NH_2 and Melon-BO-TETA) had maximum adsorption capacities(Qm) of 72.46, 123.46, and 333.33 mg·g~(-1), respectively.The amination of biochar reduced the pore size of modified biochar, whereas the surface area was enhanced.The obtained data of isotherm models were tested using different error function equations. The Freundlich,Tempkin and Langmuir isotherm models were best fitted to the experimental data of Melon-B, Melon-BO-NH_2 and Melon-BO-TETA, respectively. The adsorption rate was primarily controlled by pseudo-second–order rate model. Conclusively, the functional groups interactions are important for adsorption mechanisms and expected to control the adsorption process. The adsorption for the Melon-B, Melon-BO-NH_2 and Melon-BO-TETA could be explained for acid–base interaction and hydrogen bonding interaction.  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