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   451797篇
  免费   6234篇
  国内免费   1257篇
化学   244879篇
晶体学   6626篇
力学   19111篇
综合类   13篇
数学   52585篇
物理学   136074篇
  2021年   3927篇
  2020年   4436篇
  2019年   4763篇
  2018年   6042篇
  2017年   5948篇
  2016年   9385篇
  2015年   6083篇
  2014年   9084篇
  2013年   21242篇
  2012年   16720篇
  2011年   20268篇
  2010年   14117篇
  2009年   13869篇
  2008年   18561篇
  2007年   18349篇
  2006年   17081篇
  2005年   15292篇
  2004年   14142篇
  2003年   12466篇
  2002年   12227篇
  2001年   13650篇
  2000年   10321篇
  1999年   8075篇
  1998年   6724篇
  1997年   6477篇
  1996年   6292篇
  1995年   5628篇
  1994年   5537篇
  1993年   5375篇
  1992年   5974篇
  1991年   6038篇
  1990年   5759篇
  1989年   5573篇
  1988年   5602篇
  1987年   5476篇
  1986年   5212篇
  1985年   6750篇
  1984年   6851篇
  1983年   5409篇
  1982年   5514篇
  1981年   5507篇
  1980年   5063篇
  1979年   5480篇
  1978年   5617篇
  1977年   5502篇
  1976年   5439篇
  1975年   5012篇
  1974年   4958篇
  1973年   4975篇
  1972年   3503篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
201.
Journal of Analytical Chemistry - A new liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) method has been developed and validated for alfuzosin quantification in...  相似文献   
202.
Russian Chemical Bulletin - Gradient polymer composites were prepared by melt-mixing of carbon black and polypropylene in a compounder and subsequent hot pressing of pellets. The thermally treated...  相似文献   
203.
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   
204.
205.
206.
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   
207.
208.
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   
209.
Radiophysics and Quantum Electronics - We propose and experimentally test a numerical method for correction of the influence of fluctuations in the distance to objects during noncontact probing in...  相似文献   
210.
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