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   1520558篇
  免费   27990篇
  国内免费   6952篇
电工技术   34472篇
综合类   6392篇
化学工业   266036篇
金属工艺   65045篇
机械仪表   43318篇
建筑科学   46410篇
矿业工程   11503篇
能源动力   50707篇
轻工业   110899篇
水利工程   15529篇
石油天然气   37187篇
武器工业   134篇
无线电   198347篇
一般工业技术   290187篇
冶金工业   172436篇
原子能技术   34258篇
自动化技术   172640篇
  2021年   15653篇
  2020年   12073篇
  2019年   14902篇
  2018年   17283篇
  2017年   16704篇
  2016年   22286篇
  2015年   17788篇
  2014年   29133篇
  2013年   88675篇
  2012年   36874篇
  2011年   50379篇
  2010年   44138篇
  2009年   52427篇
  2008年   46408篇
  2007年   43884篇
  2006年   45484篇
  2005年   40517篇
  2004年   42342篇
  2003年   42189篇
  2002年   41015篇
  2001年   37611篇
  2000年   36037篇
  1999年   35357篇
  1998年   48268篇
  1997年   40920篇
  1996年   36403篇
  1995年   30880篇
  1994年   28772篇
  1993年   28686篇
  1992年   25737篇
  1991年   22907篇
  1990年   23377篇
  1989年   22288篇
  1988年   20795篇
  1987年   19128篇
  1986年   18545篇
  1985年   21886篇
  1984年   22060篇
  1983年   19942篇
  1982年   18997篇
  1981年   19105篇
  1980年   17709篇
  1979年   18216篇
  1978年   17500篇
  1977年   17251篇
  1976年   18169篇
  1975年   15774篇
  1974年   15292篇
  1973年   15398篇
  1972年   12879篇
排序方式: 共有10000条查询结果,搜索用时 671 毫秒
981.
982.
Targeting the tumor cell mitochondrion could produce novel anticancer agents. We designed an aryl−urea fatty acid ( 1 g ; 16({[4-chloro-3-(trifluoromethyl)phenyl]carbamoyl}amino)hexadecanoic acid) that disrupted the mitochondrion and decreased MDA-MB-231 breast cancer cell viability. To optimize the aryl−ureas the present study evaluated mitochondrial targeting by 1 g analogues containing alkyl chains between 10–17 carbons. Using the dye JC-1, the C12−C17 analogues efficiently disrupted the mitochondrial membrane potential (IC50s 3.5±1.2 to 7.6±1.1 μM) and impaired ATP production; shorter analogues were less active. 7-Aminoactinomycin D/annexin V staining and flow cytometry showed that these agents activated the killing mechanisms of necrosis and apoptosis to varying extents (7-aminoactinomycin D/annexin V staining ratios 4.3–6.0). Indeed, 1 g and its C17 analogue preferentially activated necrosis and apoptosis, respectively (ratios 2.1 and 16). Taken together, alkyl chain length is a determinant of mitochondrial targeting by aryl−ureas and can be varied to develop analogues that activate apoptosis or necrosis in a regulated fashion.  相似文献   
983.
The solvent-dependent polymorphism of the active pharmaceutical ingredient (API) carbamazepine is interpreted from calculations of the solid-state and API-solvent intermolecular interactions. These simulations suggested that apolar solute-solute interactions could be disrupted by apolar solvents. In contrast, the polar solute-solute interactions were found to be easily disrupted by polar and protic solvents. This is consistent with experimental observations that the crystallization of the metastable form II is more dominant in apolar solvents. The Mercury program remains the gold standard in terms of usability; however, further expansion into more complex simulation techniques could make this package of even greater use in pharmaceutical manufacturing workflows.  相似文献   
984.
FeO-doped TiO2 nanoparticle photocatalysts were immobilized onto the surface of fibrous activated carbon (ACF) via a sol-gel process. As an adsorbent and photocatalyst, FeO-TiO2 on immobilized ACFs (FeO-TiO2/ACF) greatly improved the photocatalysis rate of hydrogen production as compared with pure TiO2 and ACF-TiO2 under UV irradiation and visible light. The addition of ACFs surface significantly reduced the photogenerated pairs of electrons-hole recombination, thereby promoting the photocatalysis action of doped photo-metal oxides of FeO-TiO2. Co-doping of FeO onto the lattice of the TiO2 approach can improve the absorption activity of visible light through photo-metal oxide of TiO2 and further enhance hydrogen production under visible light. The photocatalytic fabrics (FeO-TiO2/ACF) were effortlessly split out from the experimental solution for re-utilization and exhibited high stability even after five complete regeneration cycles.  相似文献   
985.
Bakry  A. R.  Hashim  M. D.  Elwy  A. M. 《Radiochemistry》2020,62(3):359-367
Radiochemistry - Leaching of uranium and REEs with oxalic acid from the Egyptian Abu-Tartur phosphate rock (PR) was studied. The effect exerted on the leaching process by oxalic acid concentration,...  相似文献   
986.
Technical Physics Letters - The magnetoelectric (ME) effect in a planar amorphous ferromagnet–piezoelectric lead zirconate titanate (PZT) composite structure can be effectively excited by...  相似文献   
987.
988.
989.
990.
A new constitutive equation of thermoelasticity for crystals is presented based on the interatomic potential and solid mechanics at finite temperature. Using the new constitutive equation, the calculations for crystal copper and graphene are carried out under different loading paths at different temperatures. The calculated results are in good agreement with those of the previous thermoelasticity constitutive equation based on quantum mechanics, which clearly indicates that our new constitutive equation of thermoelasticity is correct. A lot of comparisons also show that the present theory is more concise and efficient than the previous thermal stress theory in the practical application.  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