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   436370篇
  免费   4924篇
  国内免费   1436篇
化学   238395篇
晶体学   6527篇
力学   17496篇
综合类   8篇
数学   51586篇
物理学   128718篇
  2020年   3720篇
  2019年   4242篇
  2018年   5609篇
  2017年   5422篇
  2016年   8163篇
  2015年   5109篇
  2014年   7729篇
  2013年   20062篇
  2012年   14974篇
  2011年   18046篇
  2010年   12351篇
  2009年   12064篇
  2008年   16598篇
  2007年   16841篇
  2006年   15502篇
  2005年   14235篇
  2004年   12733篇
  2003年   11336篇
  2002年   11148篇
  2001年   12061篇
  2000年   9351篇
  1999年   7190篇
  1998年   6128篇
  1997年   6143篇
  1996年   5821篇
  1995年   5150篇
  1994年   5097篇
  1993年   5146篇
  1992年   5535篇
  1991年   5615篇
  1990年   5348篇
  1989年   5287篇
  1988年   5268篇
  1987年   5094篇
  1986年   4886篇
  1985年   6574篇
  1984年   6882篇
  1983年   5594篇
  1982年   6120篇
  1981年   5940篇
  1980年   5633篇
  1979年   5846篇
  1978年   6151篇
  1977年   6024篇
  1976年   6196篇
  1975年   5677篇
  1974年   5706篇
  1973年   6180篇
  1972年   3973篇
  1971年   3245篇
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
171.
Kim  F. H.  Moylan  S. P.  Phan  T. Q.  Garboczi  E. J. 《Experimental Mechanics》2020,60(7):987-1004
Experimental Mechanics - Insufficient data are available to fully understand the effects of metal additive manufacturing (AM) defects for widespread adoption of the emerging technology....  相似文献   
172.
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   
173.
π-Extended molecules are key components for the development of materials science. In fact, polyaromatic structures are fundamental for the scientific and technological progress of fields such as organic electronics and bio-applications. Beneficial properties of π-extended structures are absorption in the visible region, often luminescence, high electron mobilities and stability. Common approaches to adjust the properties of polyaromatic structures to functional setups involve changes in shape and size at the molecular level. Recently, incorporating hetero-elements emerged as successful approach. In this regard, organophosphorus conjugated molecules are new materials holding great promise for potential applications. In this review, we comprehensively discuss the design/development of polyaromatic phosphorus materials and their applicability. We establish structure/property/applicability relationships to provide key guidelines for the engineering of newer, future applications. This article thus provides a source of information for the further development of this rapidly evolving field of research.  相似文献   
174.
175.
176.
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   
177.
178.
Optics and Spectroscopy - The population kinetics of a two-level system has been theoretically investigated taking into account the transfer of spontaneous radiation under continuous optical...  相似文献   
179.
We describe the synthesis and the physical properties of polyaromatic hydrocarbons (PAHs) containing a phosphorus atom at the edge. In particular, the impact of the successive addition of aromatic rings on the electronic properties was investigated by experimental (UV/Vis absorption, fluorescence, cyclic voltammetry) and theoretical studies (DFT). The physical properties recorded in solution and in the solid state showed that the P‐containing PAHs exhibit properties expected for an emitter in white organic light‐emitting diodes (WOLEDs).  相似文献   
180.
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