首页 | 官方网站   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   1464980篇
  免费   27305篇
  国内免费   6943篇
工业技术   1499228篇
  2021年   15340篇
  2020年   11819篇
  2019年   14611篇
  2018年   14528篇
  2017年   13724篇
  2016年   20778篇
  2015年   17211篇
  2014年   28639篇
  2013年   87665篇
  2012年   34899篇
  2011年   46649篇
  2010年   41452篇
  2009年   49986篇
  2008年   43778篇
  2007年   40774篇
  2006年   44505篇
  2005年   38802篇
  2004年   41185篇
  2003年   41129篇
  2002年   40245篇
  2001年   37106篇
  2000年   35513篇
  1999年   34394篇
  1998年   42195篇
  1997年   37352篇
  1996年   33160篇
  1995年   29416篇
  1994年   27663篇
  1993年   27483篇
  1992年   25387篇
  1991年   22543篇
  1990年   22931篇
  1989年   21794篇
  1988年   20411篇
  1987年   18712篇
  1986年   18174篇
  1985年   21563篇
  1984年   21894篇
  1983年   19876篇
  1982年   18913篇
  1981年   18961篇
  1980年   17584篇
  1979年   18204篇
  1978年   17434篇
  1977年   16919篇
  1976年   17344篇
  1975年   15731篇
  1974年   15286篇
  1973年   15379篇
  1972年   12892篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
952.
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   
953.
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   
954.
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   
955.
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   
956.
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   
957.
958.
959.
960.
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-23

京公网安备 11010802026262号