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   219661篇
  免费   4063篇
  国内免费   2564篇
化学   117586篇
晶体学   3657篇
力学   11204篇
综合类   197篇
数学   23537篇
物理学   70107篇
  2021年   2478篇
  2020年   2610篇
  2019年   3176篇
  2018年   4124篇
  2017年   4148篇
  2016年   5580篇
  2015年   3091篇
  2014年   5199篇
  2013年   9825篇
  2012年   8339篇
  2011年   9630篇
  2010年   7596篇
  2009年   7627篇
  2008年   8764篇
  2007年   8545篇
  2006年   7640篇
  2005年   6827篇
  2004年   6356篇
  2003年   5797篇
  2002年   5868篇
  2001年   6083篇
  2000年   4566篇
  1999年   3513篇
  1998年   2980篇
  1997年   3017篇
  1996年   2792篇
  1995年   2443篇
  1994年   2512篇
  1993年   2396篇
  1992年   2682篇
  1991年   2780篇
  1990年   2673篇
  1989年   2721篇
  1988年   2615篇
  1987年   2606篇
  1986年   2472篇
  1985年   3094篇
  1984年   3134篇
  1983年   2625篇
  1982年   2583篇
  1981年   2547篇
  1980年   2344篇
  1979年   2715篇
  1978年   2672篇
  1977年   2870篇
  1976年   2872篇
  1975年   2665篇
  1974年   2604篇
  1973年   2712篇
  1972年   2085篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
4D printing is an exciting branch of additive manufacturing. It relies on established 3D printing techniques to fabricate objects in much the same way. However, structures which fall into the 4D printed category have the ability to change with time, hence the “extra dimension.” The common perception of 4D printed objects is that of macroscopic single-material structures limited to point-to-point shape change only, in response to either heat or water. However, in the area of polymer 4D printing, recent advancements challenge this understanding. A host of new polymeric materials have been designed which display a variety of wonderful effects brought about by unconventional stimuli, and advanced additive manufacturing techniques have been developed to accommodate them. As a result, the horizons of polymer 4D printing have been broadened beyond what was initially thought possible. In this review, we showcase the many studies which evolve the very definition of polymer 4D printing, and reveal emerging areas of research integral to its advancement.  相似文献   
2.
Nikolaev  N. N. 《JETP Letters》2022,115(11):639-643
JETP Letters - A new approach to search for axions in the storage ring experiments, applicable at a short coherence time of the in-plane polarization as is the case for protons is discussed. The...  相似文献   
3.
Russian Journal of General Chemistry - Aminophosphabetaines, i.e., isobutyl {[alkyl(dimethyl)ammonio]methyl}phosphonates with higher alkyl substituents at the nitrogen atom, were obtained by a...  相似文献   
4.
5.
Journal of Structural Chemistry - A new polymorph of the [ReCl3(MeCN)(PPh3)2] complex is synthesized and characterized by single crystal X-ray diffraction (XRD). Its recrystallization from the...  相似文献   
6.
Russian Chemical Bulletin - New representatives of (O-Si)-chelate compounds, N-(fluorosilyl)methyl derivatives of N-methylacetamide, N-methylbenzamide, N-phenylacetamide, and N-phenylbenzamide,...  相似文献   
7.
Russian Journal of General Chemistry - A mechanochemical method was developed for the synthesis of ferromagnetic Pd–Fe–Co–Ni composites based on the natural biopolymer chitosan,...  相似文献   
8.
Aqueous self-assembly of short peptides has attracted growing attention for the construction of supramolecular materials for various bioapplications. Herein, we describe how the thermolysin-assisted biocatalytic construction of a dipeptide hydrazide from an N-protected amino acid and an amino acid hydrazide leads to the formation of thermally stable supramolecular hydrogels. In addition, we demonstrate the post-assembly modification of the supramolecular architectures constructed in situ tethering hydrazide groups as a chemical handle by means of fluorescence imaging.  相似文献   
9.
Journal of Structural Chemistry - Atomic and electronic structures of cyclic organosilicon compound 9,9,10,10-tetraethynyl-9,10-dihydrodisilaanthracene are studied by the density functional theory....  相似文献   
10.
Russian Journal of Applied Chemistry - A method for the disposal of hydrolysis lignin waste based on its modification with ZnCl2 and FeCl3 and subsequent carbonization at 800°C was proposed....  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