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   1586148篇
  免费   29092篇
  国内免费   7959篇
电工技术   35937篇
技术理论   5篇
综合类   7471篇
化学工业   277258篇
金属工艺   66343篇
机械仪表   45796篇
建筑科学   48240篇
矿业工程   12034篇
能源动力   50679篇
轻工业   122153篇
水利工程   16295篇
石油天然气   38865篇
武器工业   371篇
无线电   200529篇
一般工业技术   297433篇
冶金工业   195311篇
原子能技术   34424篇
自动化技术   174055篇
  2021年   16220篇
  2020年   12300篇
  2019年   15025篇
  2018年   18092篇
  2017年   17621篇
  2016年   22738篇
  2015年   18188篇
  2014年   29457篇
  2013年   89068篇
  2012年   38664篇
  2011年   52959篇
  2010年   45795篇
  2009年   53587篇
  2008年   48715篇
  2007年   46610篇
  2006年   47281篇
  2005年   42228篇
  2004年   43336篇
  2003年   43012篇
  2002年   41767篇
  2001年   38848篇
  2000年   37119篇
  1999年   36725篇
  1998年   55400篇
  1997年   45364篇
  1996年   39237篇
  1995年   32914篇
  1994年   30575篇
  1993年   30477篇
  1992年   26741篇
  1991年   23869篇
  1990年   24180篇
  1989年   23252篇
  1988年   21834篇
  1987年   20000篇
  1986年   19409篇
  1985年   22707篇
  1984年   22684篇
  1983年   20567篇
  1982年   19457篇
  1981年   19626篇
  1980年   18208篇
  1979年   18703篇
  1978年   17928篇
  1977年   17988篇
  1976年   19609篇
  1975年   16149篇
  1974年   15640篇
  1973年   15728篇
  1972年   13170篇
排序方式: 共有10000条查询结果,搜索用时 7 毫秒
901.
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   
902.
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   
903.
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   
904.
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   
905.
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   
906.
907.
908.
909.
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   
910.
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