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   251110篇
  免费   1582篇
  国内免费   402篇
化学   114954篇
晶体学   3156篇
力学   13578篇
综合类   7篇
数学   39713篇
物理学   81686篇
  2019年   1172篇
  2018年   10432篇
  2017年   11289篇
  2016年   6590篇
  2015年   2422篇
  2014年   2540篇
  2013年   6437篇
  2012年   9318篇
  2011年   18808篇
  2010年   11515篇
  2009年   11637篇
  2008年   16455篇
  2007年   20083篇
  2006年   5606篇
  2005年   11980篇
  2004年   7913篇
  2003年   7317篇
  2002年   5322篇
  2001年   4493篇
  2000年   3631篇
  1999年   2613篇
  1998年   2286篇
  1997年   2203篇
  1996年   2156篇
  1995年   2001篇
  1994年   1931篇
  1993年   1750篇
  1992年   2019篇
  1991年   2155篇
  1990年   1944篇
  1989年   1962篇
  1988年   1915篇
  1987年   1812篇
  1986年   1738篇
  1985年   2248篇
  1984年   2405篇
  1983年   1961篇
  1982年   2141篇
  1981年   2030篇
  1980年   1948篇
  1979年   2116篇
  1978年   2294篇
  1977年   2081篇
  1976年   2160篇
  1975年   2057篇
  1974年   2107篇
  1973年   2139篇
  1972年   1379篇
  1971年   1222篇
  1968年   1177篇
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
51.
52.
In the last decade, catalytic chemical vapor deposition (CVD) has been intensively explored for the growth of single-layer graphene (SLG). Despite the scattering of guidelines and procedures, variables such as the surface texture/chemistry of catalyst metal foils, carbon feedstock, and growth process parameters have been well-scrutinized. Still, questions remain on how best to standardize the growth procedure. The possible correlation of procedures between different CVD setups is an example. Here, two thermal CVD reactors were explored to grow graphene on Cu foil. The design of these setups was entirely distinct, one being a “showerhead” cold-wall type, whereas the other represented the popular “tubular” hot-wall type. Upon standardizing the Cu foil surface, it was possible to develop a procedure for cm2-scale SLG growth that differed only by the carrier gas flow rate used in the two reactors.  相似文献   
53.
54.
Molecular dynamics simulation was performed to study the formation of cluster structure, interfaces, and surfaces with different curvature radii in a perfect nanocrystal passed through by a nonlinear wave. It is shown that this process is a type of nanostructure self-organization in response to an external energy flux with subsequent development of a strong rotational field.  相似文献   
55.
Echabaane  M.  Hfaiedh  S.  Smiri  B.  Saidi  F.  Dridi  C. 《Journal of Solid State Electrochemistry》2021,25(6):1797-1806
Journal of Solid State Electrochemistry - The fast and sensitive detection of copper ions would be essential for water monitoring. Herein, we report a novel development of an impedimetric sensor...  相似文献   
56.
Journal of Thermal Analysis and Calorimetry - Novel porous carbon sheets were developed as green, renewable, cost-effective, and efficient flame retardant material for thermoplastic polymers....  相似文献   
57.
Journal of Thermal Analysis and Calorimetry - The paper focuses on the analytical analysis of the propagation of a normal shock wave in an adiabatic gas flow with nanoparticles. A modified...  相似文献   
58.
A new derivative of dioxouranium(VI) salen complex, [UO2(L)(pyridine)], where [L = N,N′-Bis(2-hydroxybenzylidene)-2,2-dimethyl-1,3-propanediamine] is synthesized and characterized by elemental analysis (C, H, N), FT-IR, ESI-MS spectrometry, UV/Vis, fluorescence, 1H and 13C NMR spectroscopy and thermal gravimetric (TG) study. Furthermore, the single crystal X-ray diffraction measurements of the complex were carried out at 100 and 273 K. The crystal structure measurements revealed that the complex has distorted pentagonal bipyramidal geometry with uranium atom located at the centre and bonded to two phenoxy oxygen and two azomethine nitrogen in tetradenate fashion and one nitrogen from pyridine making it seven coordinated. In addition, the photoluminescence property of the complex was also recorded.  相似文献   
59.
Russian Journal of Organic Chemistry - Selenopheno[2,3-d]pyrimidine- and selenopheno[2,3-d][1,2,3]triazine-containing compounds were synthesized starting from...  相似文献   
60.
The biomimetic sol—gel synthesis of silicon—chitosan-containing glycerohydrogels was carried out using silicon tetraglycerolate as a precursor. It was found that chitosan accelerates gel formation in weakly acidic media. In more acidic media, the kinetics of the process changes according to the curve with a maximum, which can be attributed to different mechanisms of silanol condensation before and after the isoelectric point. The investigated silicon—chitosan-containing glycerohydrogels exhibit antibacterial, anti-inflammatory, and wound healing activity. The synthesized hybrid glycerohydrogels are promising materials for biomedical applications.  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