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   2129篇
  免费   94篇
  国内免费   22篇
化学   1497篇
晶体学   13篇
力学   86篇
综合类   1篇
数学   344篇
物理学   304篇
  2024年   6篇
  2023年   25篇
  2022年   44篇
  2021年   145篇
  2020年   105篇
  2019年   89篇
  2018年   87篇
  2017年   74篇
  2016年   124篇
  2015年   72篇
  2014年   80篇
  2013年   194篇
  2012年   132篇
  2011年   147篇
  2010年   88篇
  2009年   80篇
  2008年   101篇
  2007年   95篇
  2006年   77篇
  2005年   78篇
  2004年   60篇
  2003年   60篇
  2002年   36篇
  2001年   23篇
  2000年   15篇
  1999年   16篇
  1998年   8篇
  1997年   5篇
  1996年   15篇
  1995年   6篇
  1994年   8篇
  1993年   13篇
  1992年   14篇
  1991年   10篇
  1990年   7篇
  1989年   3篇
  1988年   4篇
  1987年   3篇
  1986年   10篇
  1985年   9篇
  1984年   6篇
  1983年   9篇
  1982年   10篇
  1980年   10篇
  1979年   9篇
  1978年   8篇
  1976年   4篇
  1975年   5篇
  1974年   2篇
  1971年   2篇
排序方式: 共有2245条查询结果,搜索用时 31 毫秒
31.
Research on Chemical Intermediates - This study presents the synthesis of rare earth-doped Y (RE Y) zeolite, its application in formulation of a fluid catalytic cracking (FCC) catalyst and the...  相似文献   
32.
In this work, we propose and analyze the pressure stabilization method for the unsteady incompressible Brinkman‐Forchheimer equations. We present a time discretization scheme which can be used with any consistent finite element space approximation. Second‐order error estimate is proven. Some numerical results are also given.© 2017 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 33: 1949–1965, 2017  相似文献   
33.
Eissa  Shimaa  Zourob  Mohammed 《Mikrochimica acta》2017,184(7):2281-2289
Microchimica Acta - The authors describe a voltammetric immunosensor for morphine (MOR) that is based on a graphene screen printed electrode (GSPE) modified with gold nanoparticles (AuNP) which...  相似文献   
34.
A simple and expedient multicomponent protocol was developed to synthesize 4-thiazolidinones by employing VOSO4 as a catalyst under ultrasonic irradiation. The significant features of this protocol includes shorter reaction time, high yields, low catalyst loading, and also the catalyst can be recovered and reused up to next four cycles without significant loss in catalytic activity. All the synthesized novel indazole compounds were evaluated for their antibacterial and anti-biofilm activities. Compounds 9n, 9o and 9q showed promising activity (MIC value of 3.9?µg/mL) against K. planticola (MTCC 530). They also exhibited significant bactericidal activity against K. planticola (MTCC 530) (MBC value of 15.6?µg/mL). Additionally, 9n, 9o and 9q inhibited biofilm formation (IC50 values ranging between 20.28–20.79?μg/mL) in this organism.  相似文献   
35.
In the present study, we have investigated the self-association, mixed micellization, and thermodynamic studies of a cationic gemini (dimeric) surfactant, hexanediyl-1,6-bis(dimethylcetylammonium bromide (16-6-16)) and a cationic conventional (monomeric) surfactant, cetyltrimethylammonium bromide (CTAB). The critical micelle concentration (CMC) of pure (16-6-16 and CTAB) and mixed (16-6-16+CTAB) surfactants was measured by electrical conductivity, dye solubilization, and surface tension measurements. The surface properties (viz., C20 (the surfactant concentration required to reduce the surface tension by 20 mN/m), ΠCMC (the surface pressure at the CMC), Γmax (maximum surface excess concentration at the air/water interface), Amin (the minimum area per surfactant molecule at the air/water interface), etc.) of micellar (16-6-16 or CTAB) and mixed micellar (16-6-16+CTAB) surfactant systems were evaluated. The thermodynamic parameters of the micellar (16-6-16 and CTAB) and mixed micellar (16-6-16+CTAB) surfactant systems were also evaluated.  相似文献   
36.
37.
Rapid determination of gross alpha and beta emitters in urine by liquid scintillation counting is discussed. This method is based on direct addition of urine into scintillation cocktail. 241Am, 239Pu and 90Sr were selected as model radionuclides. The LSA Hidex 300 SL equipped with Triple-Double-Coincidence-Ratio technique was used for sample measurement. The work focused on optimizing the LSC cocktail to urine volume ratio with respect to the model radionuclides. The overall efficiencies for 241Am, 239Pu and 90Sr were greater than 92 %; therefore, this method would be suitable for rapid determination of gross alpha/beta activity.  相似文献   
38.
In this paper, we study the tensor product structure of the category of finite dimensional modules over Drinfeld doubles of Taft Hopf algebras. Tensor product decomposition rules for all finite dimensional indecomposable modules are explicitly given.  相似文献   
39.
The aim of this work is to establish the existence of multi-peak solutions for the following class of quasilinear problems
$$ - \mbox{div} \bigl(\epsilon^{2}\phi\bigl(\epsilon|\nabla u|\bigr)\nabla u \bigr) + V(x)\phi\bigl(\vert u\vert\bigr)u = f(u)\quad\mbox{in } \mathbb{R}^{N}, $$
where \(\epsilon\) is a positive parameter, \(N\geq2\), \(V\), \(f\) are continuous functions satisfying some technical conditions and \(\phi\) is a \(C^{1}\)-function.
  相似文献   
40.
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