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   1423742篇
  免费   29738篇
  国内免费   7813篇
化学   717663篇
晶体学   21058篇
力学   77241篇
综合类   107篇
数学   250052篇
物理学   395172篇
  2021年   13589篇
  2020年   16006篇
  2019年   16133篇
  2018年   16720篇
  2017年   15365篇
  2016年   29783篇
  2015年   21320篇
  2014年   30661篇
  2013年   74729篇
  2012年   42448篇
  2011年   43984篇
  2010年   41013篇
  2009年   42788篇
  2008年   41958篇
  2007年   38982篇
  2006年   39889篇
  2005年   35415篇
  2004年   34585篇
  2003年   31662篇
  2002年   31720篇
  2001年   31550篇
  2000年   26644篇
  1999年   23411篇
  1998年   21385篇
  1997年   21251篇
  1996年   21291篇
  1995年   19304篇
  1994年   18791篇
  1993年   18372篇
  1992年   18672篇
  1991年   18892篇
  1990年   18098篇
  1989年   18140篇
  1988年   17734篇
  1987年   17667篇
  1986年   16582篇
  1985年   22963篇
  1984年   24043篇
  1983年   20151篇
  1982年   21770篇
  1981年   21008篇
  1980年   20322篇
  1979年   20671篇
  1978年   21870篇
  1977年   21487篇
  1976年   21195篇
  1975年   19902篇
  1974年   19561篇
  1973年   19979篇
  1972年   14471篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
291.
292.
ABSTRACT

A new density functional for the study of associating inhomogeneous fluids based on Wertheim's first-order thermodynamic perturbation theory is presented and compared to the most currently used associating density functionals. This functional is developed using the weighted density approximation in the range of association of hard spheres. We implement this functional within the framework of classical density functional theory together with modified fundamental measure theory to account for volume exclusion of hard spheres. This approach is tested against molecular simulations from literature of pure associating hard spheres and mixtures of non-associationg and associating hard spheres with different number of bonding sites close to a hard uniform wall. Furthermore, we compare and review our results with the performance of associating functionals from literature, one based on fundamental measure theory and the inhomogeneous version of Wertheim's perturbation theory. Results obtained with classical DFT and the three functionals show excellent agreement with molecular simulations in systems with one hard wall. For the cases of small pores where only one or two layers of fluid are allowed discrepancies between results with classical DFT and molecular simulations were found.  相似文献   
293.
294.
295.
296.
Journal of Structural Chemistry - Thermodynamic characteristics are calculated for aqueous alkanolamine solutions that are obtained by substituting alkyl radicals for the protons in the amino group...  相似文献   
297.
Physics of Particles and Nuclei Letters - Resonance structure of the beta decay strength function Sβ(E) for GT β–-decay of halo nuclei 6He and 11Li is analyzed. Compare experimental...  相似文献   
298.
The first immobilized catalyst for Ir‐catalyzed asymmetric allylic aminations is described. The catalyst is a cationic (π‐allyl)Ir complex bound by cation exchange to an anionic silica gel support. Preparation of the catalyst is facile, and the supported catalyst displayed considerably enhanced activity compared with the parent homogeneous catalyst. Up to 43 consecutive amination runs were possible in recycling experiments.  相似文献   
299.
The current work utilizes three separate techniques to study the physical aging process in amorphous poly(ethylene furanoate) (PEF), which is a recently introduced engineering thermoplastic with enhanced properties compared to petroleum‐sourced poly(ethylene terephthalate). Differential scanning calorimetry aging experiments were conducted at multiple aging temperatures and times, and the resultant enthalpic recovery values compared to the theoretical maximum enthalpy loss evaluated from calculations involving extrapolation of the equilibrium liquid line. Density measurements reveal densification of the matrix for the aged versus unaged samples, and provide an estimate for the reduction in free volume for the aged samples. Complementary oxygen permeation and pressure‐decay sorption experiments provide independent verification of the free volume reduction mechanism for physical aging in glassy polymers. The current work provides the first detailed aging study for PEF. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 389–399  相似文献   
300.
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