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   552篇
  免费   11篇
化学   217篇
力学   9篇
数学   75篇
物理学   262篇
  2022年   5篇
  2020年   5篇
  2018年   5篇
  2017年   7篇
  2016年   7篇
  2015年   8篇
  2014年   9篇
  2013年   23篇
  2012年   21篇
  2011年   15篇
  2010年   9篇
  2009年   12篇
  2008年   20篇
  2007年   22篇
  2006年   13篇
  2005年   28篇
  2004年   14篇
  2003年   14篇
  2002年   17篇
  2001年   13篇
  2000年   13篇
  1999年   8篇
  1996年   12篇
  1995年   10篇
  1994年   26篇
  1993年   22篇
  1992年   17篇
  1991年   11篇
  1990年   5篇
  1989年   9篇
  1988年   5篇
  1986年   5篇
  1985年   4篇
  1984年   3篇
  1983年   5篇
  1982年   5篇
  1981年   7篇
  1979年   6篇
  1978年   10篇
  1977年   10篇
  1976年   7篇
  1975年   8篇
  1974年   8篇
  1973年   5篇
  1972年   5篇
  1971年   4篇
  1967年   6篇
  1932年   3篇
  1928年   3篇
  1916年   4篇
排序方式: 共有563条查询结果,搜索用时 15 毫秒
51.
The current study provides a way of extraction for both active NSO and WSE from Nigella sativa seeds using 98% methanol. About 1?kg of ground seeds was macerated by 1:2.5 w/v (g/mL) for 72?hours. After rotary evaporation and 7 days of continuous drying and chilling at 50 and 4?°C, NSO and WSE were obtained at the same instant. Solubility tests of 24 solvents and 11 thin layer chromatographic analyses while 2, 2-diphenyl-1-picrylhydrazyl free radical scavenging assay of NSO (73.66) , WSE (33.32) and NSO?+?WSE (78.22) against ascorbic acid (IC50?=?4.28?mg/mL) was performed. WSE was found to be highly soluble in water and 5% NaOH exhibiting the same Rf value of 0.95 for EtOH:DMSO (9:1) against the honey. WSE has revealed more than twofold higher anti-oxidant activity than others. Formulation of WSE with Tualang honey may provide better targeted hydrophilic drug delivery systems.  相似文献   
52.
53.
Summary We present an approximation method of a space-homogeneous transport equation which we prove is convergent. The method is very promising for numerical computation. Comparison of a numerical computation with an exact solution is given for the Master equation.  相似文献   
54.
55.
56.
A Generalized Optical Logic Element or GOLE is device that performs any of the 16 Boolean logic operations on signals in an optical beam with very fast switching among functions. The advantages of a generalized or universal gate in manufacturing are obvious. Extremely flexible functioning becomes possible if the GOLE functionality is switched in response to earlier computations. Likewise Field Programmable Gate Arrays or FPGAs can be used to fix the GOLE functions, making one of the most powerful and flexible processor units ever designed - called a Field GOLE. Such systems can be made in bulk optics to utilize Spatial Light Modulator or SLM capabilities, but integrated optics on silicon will be the choice for most applications. GOLEs can be generalized in several ways to become Fredkin gates and generalized Fredkin gates. They can also be cascaded similarly to electronic gates.  相似文献   
57.
58.
In good conductors optical phonons are usually screened, and therefore not observed. However, sharp features due to infrared-active modes in the copper-oxygen planes are observed in the optical conductivity of Pr1.85Ce0.15CuO4 and YBa2Cu3O6.95. Oscillator strengths indicate that the screening of these modes is poor or totally absent. These materials are compared with eta-Mo4O11, in which lattice modes appear suddenly below the charge-density wave transition. It is proposed that poor screening in the cuprates originates from fluctuating charge inhomogeneities in the copper-oxygen planes.  相似文献   
59.
60.
Benzocyclobutene 10 and 3-oxabicyclo [3.2.0]hepta-1, 4-diene 11 are formed by gas-phase pyrolysis of the title compound 9 . The results are discussed with reference to the estimated reaction parameters. It is found that the activation due to oxygen in 9 is relatively weak in comparison to its effect on the reactivity of oxaquadricyclanes 1 .  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