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   636199篇
  免费   10175篇
  国内免费   5877篇
化学   317931篇
晶体学   8922篇
力学   34367篇
综合类   339篇
数学   92483篇
物理学   198209篇
  2021年   6387篇
  2020年   7108篇
  2019年   7870篇
  2018年   14330篇
  2017年   14509篇
  2016年   15805篇
  2015年   8283篇
  2014年   12813篇
  2013年   26790篇
  2012年   24280篇
  2011年   32289篇
  2010年   22981篇
  2009年   22975篇
  2008年   29272篇
  2007年   30973篇
  2006年   21153篇
  2005年   21819篇
  2004年   18870篇
  2003年   17554篇
  2002年   16485篇
  2001年   16367篇
  2000年   12819篇
  1999年   9854篇
  1998年   8620篇
  1997年   8291篇
  1996年   7915篇
  1995年   7065篇
  1994年   7095篇
  1993年   6776篇
  1992年   7053篇
  1991年   7518篇
  1990年   7234篇
  1989年   7074篇
  1988年   6833篇
  1987年   6594篇
  1986年   6332篇
  1985年   7921篇
  1984年   8253篇
  1983年   6972篇
  1982年   7240篇
  1981年   6708篇
  1980年   6377篇
  1979年   6944篇
  1978年   7183篇
  1977年   6997篇
  1976年   7056篇
  1975年   6730篇
  1974年   6553篇
  1973年   6918篇
  1972年   5094篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
161.
Journal of Thermal Analysis and Calorimetry - This article considers viscoelastic effects on the enhancement of transportation of heat in thin-film flow when the relaxation time phenomenon is...  相似文献   
162.
Journal of Computer-Aided Molecular Design - Accurate predictions of acid dissociation constants are essential to rational molecular design in the pharmaceutical industry and elsewhere. There has...  相似文献   
163.
Journal of Thermal Analysis and Calorimetry - Coal O2/CO2 combustion is a promising carbon capture and storage technology for coal-fired power plant. Char consumption rate prediction is essential...  相似文献   
164.
This mini-review highlights key structural features that should be taken into account when creating ambipolar redox-active closed-shell metal-free molecules. This type of compound is strongly required for the fabrication of all-organic ‘poleless’ batteries and semiconductors. The suggested strategies aimed at stabilization of both oxidized (cationic) and reduced (anionic) redox-states are based on the comprehensive analysis of the most successful structures taken from the recent publications.  相似文献   
165.
Journal of Experimental and Theoretical Physics - We suggest that the principle of holographic duality be extended beyond conformal invariance and AdS isometry. Such an extension is based on a...  相似文献   
166.
167.
Applied Magnetic Resonance - The suggested approach allowed us to derive analytical expressions for modeling the shape of solid-echo signal and its time evolution for a system of three-spin groups...  相似文献   
168.
Temperature dependences of the relative reactivity of potassium aryloxides XC6H4O?K+ toward 2,4‐dinitrophenyl benzoate in 50 mol% dimethylformamide (DMF)–50 mol% H2O mixture have been studied using the competitive reactions technique. Correlation analyses of the relative rate constants kX/kH and differences in the activation parameters (ΔΔН and ΔΔS) of the competitive reactions have revealed the existence of two isokinetic series of the reactions of 2,4‐dinitrophenyl benzoate with potassium aryloxides with electron‐donating substituent (EDS) and electron‐withdrawing substituent (EWS), respectively. We have investigated the effect of the substituent X on the activation parameters for each isokinetic series and concluded that the mechanism of the reactions of 2,4‐dinitrophenyl benzoate with potassium aryloxides XC6H4O?K+ in 50 mol% DMF–50 mol% H2O mixture is the same as in DMF. Analysis of the obtained data with using the method of two‐dimensional reaction coordinate diagram leads to the conclusion that the variation of the solvent from DMF to 50 mol% DMF–50 mol% H2O mixture affects the reaction pathway. The rate constant kX for the reaction of 3‐nitrophenyl benzoate with potassium 4‐methoxyphenoxide and the relative rate constants kX/kH for the reaction of 3‐nitrophenyl benzoate with potassium aryloxides XC6H4O?K+ with EDS were measured in 50 mol% DMF–50 mol% H2O mixtures at 25°C, and it has been shown that the addition of water to DMF does not change the mechanism but slows down these reactions.  相似文献   
169.
170.
In many organic electronic devices functionality is achieved by blending two or more materials, typically polymers or molecules, with distinctly different optical or electrical properties in a single film. The local scale morphology of such blends is vital for the device performance. Here, a simple approach to study the full 3D morphology of phase‐separated blends, taking advantage of the possibility to selectively dissolve the different components is introduced. This method is applied in combination with AFM to investigate a blend of a semiconducting and ferroelectric polymer typically used as active layer in organic ferroelectric resistive switches. It is found that the blend consists of a ferroelectric matrix with three types of embedded semiconductor domains and a thin wetting layer at the bottom electrode. Statistical analysis of the obtained images excludes the presence of a fourth type of domains. The criteria for the applicability of the presented technique are discussed. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1231–1237  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