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   1538266篇
  免费   27646篇
  国内免费   7018篇
电工技术   34230篇
综合类   6444篇
化学工业   269848篇
金属工艺   64499篇
机械仪表   42940篇
建筑科学   47112篇
矿业工程   11369篇
能源动力   50233篇
轻工业   117447篇
水利工程   15780篇
石油天然气   37286篇
武器工业   133篇
无线电   196534篇
一般工业技术   287738篇
冶金工业   187174篇
原子能技术   33859篇
自动化技术   170304篇
  2021年   15505篇
  2020年   11885篇
  2019年   14667篇
  2018年   15130篇
  2017年   14279篇
  2016年   21171篇
  2015年   17347篇
  2014年   28749篇
  2013年   87894篇
  2012年   36109篇
  2011年   48427篇
  2010年   42296篇
  2009年   50464篇
  2008年   45327篇
  2007年   42545篇
  2006年   45579篇
  2005年   40007篇
  2004年   42258篇
  2003年   42096篇
  2002年   41129篇
  2001年   38479篇
  2000年   36543篇
  1999年   36199篇
  1998年   53294篇
  1997年   43979篇
  1996年   38402篇
  1995年   32526篇
  1994年   30273篇
  1993年   30084篇
  1992年   26504篇
  1991年   23811篇
  1990年   23949篇
  1989年   23006篇
  1988年   21645篇
  1987年   19792篇
  1986年   19212篇
  1985年   22561篇
  1984年   22560篇
  1983年   20550篇
  1982年   19465篇
  1981年   19566篇
  1980年   18197篇
  1979年   18713篇
  1978年   17940篇
  1977年   18108篇
  1976年   19840篇
  1975年   16163篇
  1974年   15649篇
  1973年   15737篇
  1972年   13187篇
排序方式: 共有10000条查询结果,搜索用时 453 毫秒
891.
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   
892.
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   
893.
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   
894.
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   
895.
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   
896.
897.
898.
899.
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   
900.
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