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   375079篇
  免费   4704篇
  国内免费   1508篇
化学   202729篇
晶体学   5586篇
力学   16136篇
综合类   8篇
数学   42707篇
物理学   114125篇
  2020年   2695篇
  2019年   2995篇
  2018年   3400篇
  2017年   3339篇
  2016年   5712篇
  2015年   4157篇
  2014年   5889篇
  2013年   17412篇
  2012年   13089篇
  2011年   16305篇
  2010年   10464篇
  2009年   10555篇
  2008年   14768篇
  2007年   14856篇
  2006年   13877篇
  2005年   12919篇
  2004年   11563篇
  2003年   10191篇
  2002年   10021篇
  2001年   11608篇
  2000年   8824篇
  1999年   6870篇
  1998年   5608篇
  1997年   5556篇
  1996年   5299篇
  1995年   4907篇
  1994年   4628篇
  1993年   4598篇
  1992年   5059篇
  1991年   5079篇
  1990年   4674篇
  1989年   4647篇
  1988年   4687篇
  1987年   4532篇
  1986年   4301篇
  1985年   6146篇
  1984年   6241篇
  1983年   5115篇
  1982年   5561篇
  1981年   5354篇
  1980年   5183篇
  1979年   5221篇
  1978年   5464篇
  1977年   5269篇
  1976年   5417篇
  1975年   4996篇
  1974年   5045篇
  1973年   5347篇
  1972年   3255篇
  1971年   2424篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
112.
Homogenous amphiphilic crosslinked polymer films comprising of poly(ethylene oxide) and polysiloxane were synthesized utilizing thiol‐ene “ click ” photochemistry. A systematic variation in polymer composition was Carried out to obtain high quality films with varied amount of siloxane and poly(ethylene oxide). These films showed improved gas separation performance with high gas permeabilities with good CO2/N2 selectivity. Furthermore, the resulting films were also tested for its biocompatibility, as a carrier media which allow human adult mesenchymal stem cells to retain their capacity for osteoblastic differentiation after transplantation. The obtained crosslinked films were characterized using differential scanning calorimetry, dynamic mechanical analysis, thermogravimetric analysis, FTIR, Raman‐IR , and small angle X‐ray scattering. The synthesis ease and commercial availability of the starting materials suggests that these new crosslinked polymer networks could find applications in wide range of applications. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1548–1557  相似文献   
113.
Russian Journal of Organic Chemistry - The Reformatsky reaction of (3R,4R)-4-acetoxy-3-((1R)-1-{[tert-butyl(dimethyl)silyl]oxy}ethyl)­azetidin-2-one with ethyl 4-bromo-3-oxopentanoate gave...  相似文献   
114.
115.
116.
Journal of Thermal Analysis and Calorimetry - The operating temperature of Li-ion batteries used in modern electric vehicles should be maintained within an allowable range to avoid thermal runaway...  相似文献   
117.
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   
118.
Li  C.  Zhang  D.  Cheng  G.  Zhu  Y. 《Experimental Mechanics》2020,60(3):329-343
Experimental Mechanics - There have been relatively few studies on mechanical properties of nanomaterials under high strain rates, mainly due to the lack of capable nanomechanical testing devices....  相似文献   
119.
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   
120.
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