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   422676篇
  免费   3289篇
  国内免费   1436篇
化学   228453篇
晶体学   6623篇
力学   17264篇
综合类   8篇
数学   48414篇
物理学   126639篇
  2021年   3358篇
  2020年   3903篇
  2019年   4424篇
  2018年   5259篇
  2017年   5107篇
  2016年   7658篇
  2015年   4590篇
  2014年   7160篇
  2013年   18927篇
  2012年   13832篇
  2011年   16928篇
  2010年   11699篇
  2009年   11454篇
  2008年   15631篇
  2007年   15854篇
  2006年   14629篇
  2005年   13405篇
  2004年   12019篇
  2003年   10808篇
  2002年   10655篇
  2001年   11776篇
  2000年   9098篇
  1999年   6956篇
  1998年   5966篇
  1997年   5998篇
  1996年   5607篇
  1995年   5007篇
  1994年   4914篇
  1993年   4998篇
  1992年   5390篇
  1991年   5488篇
  1990年   5217篇
  1989年   5179篇
  1988年   5166篇
  1987年   4993篇
  1986年   4796篇
  1985年   6433篇
  1984年   6731篇
  1983年   5507篇
  1982年   6026篇
  1981年   5827篇
  1980年   5528篇
  1979年   5774篇
  1978年   6076篇
  1977年   5951篇
  1976年   6140篇
  1975年   5607篇
  1974年   5668篇
  1973年   6125篇
  1972年   3949篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
82.
83.
84.
The anti-atherogenic potentials of total ginger (Zingiber officinale) extract (TGE) or curcuminoids extracted from turmeric (Curcuma longa), members of family Zingiberaceae, were compared in hypercholesterolaemia. Rabbits were fed either normal or atherogenic diet. The rabbits on atherogenic diet received treatments with TGE or curcumenoids and placebo concurrently for 6 weeks (n = 6). The anti-atherogenic effects of curcuminoids and ginger are mediated via multiple mechanisms. This effect was correlated with their ability to lower cholesteryl ester transfer protein activity. Ginger extract exerted preferential effects on plasma lipids, reverse cholesterol transport, cholesterol synthesis and inflammatory status. Curcuminoids, however, showed superior antioxidant activity.  相似文献   
85.
A “turn‐on” pattern Fe3+‐selective fluorescent sensor was synthesized and characterized that showed high fluorescence discrimination of Fe3+ over Fe2+ and other tested ions. With a 62‐fold fluorescence enhancement towards Fe3+, the probe was employed to detect Fe3+ in vivo in HeLa cells and Caenorhabditis elegans, and it was also successfully used to elucidate Fe3+ enrichment and exchange infected by innexin3 (Inx3) in hemichannel‐closed Sf9 cells.  相似文献   
86.
87.
88.
We report the addition of M–H bonds (M = Al, Zn, Mg) to a Rh(iii) intermediate generated from the reductive elimination of triethylsilane from [Cp*Rh(H)2(SiEt3)2]. A series of new heterobimetallic complexes possessing Rh–M bonds have been isolated and characterised by a number of spectroscopic (1H, 29Si, 13C, 103Rh NMR, infrared, and X-ray diffraction) and computational techniques (NBO and QTAIM analysis). Experimental and computational data are consistent with cleavage of the M–H bond upon addition to rhodium with formation of new Rh–M and Rh–H bonds. Upon photolysis the Al analogue of this series undergoes a further elimination reaction producing triethylsilane and a highly unusual Rh2Al2H4 containing cluster proposed to contain an Al(i) bridging ligand.  相似文献   
89.
DNA-based aptamers are commonly used recognition elements in biosensors for a range of target molecules. Here, the development of a wavelength-shifting optical module for a DNA-based adenosine-binding aptamer is described. It applies the combination of two photostable cyanine-styryl dyes as covalent modifications. This energy-transfer pair is postsynthetically attached to oligonucleotides via a copper(I)-catalyzed azide–alkyne cycloaddition by two structurally different approaches: 1) as nucleotide modifications at the 2′-position of uridines and 2) as nucleotide substitutions using (S)-amino-1,2-propanediol as acyclic linker between the phosphodiester bridges. Both dyes exhibit a remarkable photostability. A library of DNA aptamers consisting of different combinations of the two dyes in diagonal orientations were evaluated by their emission color contrast as readout. Further optimization led to aptasensors with improved fluorescent readout as compared with previously reported aptasensors. This approach described is synthetically facile using simple propargylated phosphoramidites as DNA building blocks. As such, this approach could be applied for other dyes and other chemical/biological applications.  相似文献   
90.
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