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   657篇
  免费   26篇
  国内免费   15篇
化学   465篇
晶体学   2篇
力学   43篇
数学   76篇
物理学   112篇
  2023年   2篇
  2022年   8篇
  2021年   12篇
  2020年   26篇
  2019年   25篇
  2018年   35篇
  2017年   33篇
  2016年   60篇
  2015年   38篇
  2014年   41篇
  2013年   99篇
  2012年   52篇
  2011年   73篇
  2010年   28篇
  2009年   34篇
  2008年   26篇
  2007年   24篇
  2006年   11篇
  2005年   14篇
  2004年   9篇
  2003年   18篇
  2002年   11篇
  2001年   4篇
  2000年   2篇
  1996年   1篇
  1995年   1篇
  1994年   2篇
  1990年   2篇
  1989年   1篇
  1988年   1篇
  1987年   2篇
  1984年   1篇
  1976年   2篇
排序方式: 共有698条查询结果,搜索用时 15 毫秒
81.
Research on Chemical Intermediates - In this paper, tributyl(carboxymethyl)phosphonium bromotrichloroferrate as a new magnetic ionic liquid bearing acetic acid tags was synthesized and...  相似文献   
82.
Summary In the present study the effects of addition of iron on the catalytic activity and Si tolerability of Pt/g-Al2O3in the total oxidation of volatile organic compounds were investigated. Preliminary results showed that there is a noticeable improvement effect on Si-tolerance of catalyst, particularly for short term poison exposure. Bulk analysis of deposited silicon on the catalyst surface indicated that both Pt/g-Al2O3and iron-doped pellets had roughly the same silicone uptakes. Deactivation of catalyst was reversible and much faster for iron doped sample. The promoting effects of iron were related to its electronegativity and, to blocking of fewer Pt sites when iron is present at the surface of the catalyst.  相似文献   
83.
Individuals may have biased perceptions of health and safety risks. We conjecture perceptions of mortality risk from various risk measures using parametric and non-parametric methods. We investigate how risk perceptions are measured and what rational explanations can be found for these measures with implication for risk and solvency.  相似文献   
84.
The mean centering of ratio kinetic profiles method was used for the simultaneous determination of binary mixtures of Ni(II) and Zn(II) in water samples, without prior separation steps. The method is based on the difference in the rate of the reaction of Ni(II) and Zn(II) with xylenol orange at pH 5.3. The method allows rapid and accurate determination of Ni(II) and Zn(II). The analytical characteristics of the methods for the simultaneous determination of binary mixtures of Ni(II) and Zn(II) were calculated. The linear range was 0.025‐2.400 μg mL?1 and 0.025‐2.20 μg mL?1 for Zn(II) and Ni(II), respectively. Interference effects of common anions and cations were studied, and the method was successfully applied to the simultaneous determination of Zn(II) and Ni(II) in water samples.  相似文献   
85.
The combination of the Biginelli reaction with click chemistry has been used for the one-pot synthesis of 1,2,3-triazole linked dihydropyrimidinones from azides, aromatic aldehydes containing a propargyl ether group, urea, and 1,3-dicarbonyl compounds using Cu(OAc)2/sodium ascorbate as catalyst in acetic acid under mild reaction conditions.  相似文献   
86.
The present paper deals with the study of semilinear and non-homogeneous Schrödinger equations on a manifold with conical singularity. We provide a suitable constant by Sobolev embedding constant and for p ∈ (2, 2?) with respect to non-homogeneous term g(x) ∈ L 2 n/2 (B), which helps to find multiple solutions of our problem. More precisely, we prove the existence of two solutions to the problem 1.1 with negative and positive energy in cone Sobolev space H 2,0 1,n/2 (B). Finally, we consider p = 2 and we prove the existence and uniqueness of Fuchsian-Poisson problem.  相似文献   
87.
The electrical characteristics of a double-gate armchair silicene nanoribbon field-effect-transistor(DG ASi NR FET)are thoroughly investigated by using a ballistic quantum transport model based on non-equilibrium Green's function(NEGF) approach self-consistently coupled with a three-dimensional(3D) Poisson equation. We evaluate the influence of variation in uniaxial tensile strain, ribbon temperature and oxide thickness on the on-off current ratio, subthreshold swing, transconductance and the delay time of a 12-nm-length ultranarrow ASi NR FET. A novel two-parameter strain magnitude and temperature-dependent model is presented for designing an optimized device possessing balanced amelioration of all the electrical parameters. We demonstrate that employing Hf O2 as the gate insulator can be a favorable choice and simultaneous use of it with proper combination of temperature and strain magnitude can achieve better device performance.Furthermore, a general model power(GMP) is derived which explicitly provides the electron effective mass as a function of the bandgap of a hydrogen passivated ASi NR under strain.  相似文献   
88.
89.
90.
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