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   268308篇
  免费   2522篇
  国内免费   778篇
化学   142716篇
晶体学   4174篇
力学   11968篇
综合类   14篇
数学   29579篇
物理学   83157篇
  2019年   2342篇
  2018年   3148篇
  2017年   3157篇
  2016年   4535篇
  2015年   2707篇
  2014年   4332篇
  2013年   10749篇
  2012年   8167篇
  2011年   9961篇
  2010年   7129篇
  2009年   6911篇
  2008年   9363篇
  2007年   9557篇
  2006年   8935篇
  2005年   8094篇
  2004年   7448篇
  2003年   6751篇
  2002年   6674篇
  2001年   7337篇
  2000年   5680篇
  1999年   4379篇
  1998年   3881篇
  1997年   3862篇
  1996年   3597篇
  1995年   3344篇
  1994年   3496篇
  1993年   3199篇
  1992年   3676篇
  1991年   3676篇
  1990年   3607篇
  1989年   3462篇
  1988年   3572篇
  1987年   3466篇
  1986年   3288篇
  1985年   4361篇
  1984年   4637篇
  1983年   3873篇
  1982年   4008篇
  1981年   3931篇
  1980年   3909篇
  1979年   3877篇
  1978年   4191篇
  1977年   4107篇
  1976年   4173篇
  1975年   3849篇
  1974年   3893篇
  1973年   4050篇
  1972年   2851篇
  1971年   2378篇
  1970年   2177篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
22.
Journal of Analytical Chemistry - Silver nanoparticles modified with Eu3+ ions increase the intensity of the fluorescence signal by a factor of 125 in an analytical system containing doxycycline as...  相似文献   
23.
Crystallography Reports - Two LiInSe2 single crystals, grown under different conditions, have been studied. Characteristics of these crystals for neutron detection have been compared using...  相似文献   
24.
Crystallography Reports - The orientation of grains and the special boundaries formed by them in multicrystalline silicon has been studied by electron backscattered diffraction. It is found that...  相似文献   
25.
Crystallography Reports - The specific features of the formation of crystallites in gallium arsenide crystals grown by the Czochralski method have been investigated. The crystallites are found to...  相似文献   
26.
27.
To achieve efficient proton pumping in the light-driven proton pump bacteriorhodopsin (bR), the protein must be tightly coupled to the retinal to rapidly convert retinal isomerization into protein structural rearrangements. Methyl group dynamics of bR embedded in lipid nanodiscs were determined in the dark-adapted state, and were found to be mostly well ordered at the cytosolic side. Methyl groups in the M145A mutant of bR, which displays only 10 % residual proton pumping activity, are less well ordered, suggesting a link between side-chain dynamics on the cytosolic side of the bR cavity and proton pumping activity. In addition, slow conformational exchange, attributed to low frequency motions of aromatic rings, was indirectly observed for residues on the extracellular side of the bR cavity. This may be related to reorganization of the water network. These observations provide a detailed picture of previously undescribed equilibrium dynamics on different time scales for ground-state bR.  相似文献   
28.
Herein, we report the synthesis of specific silica-supported Co/Co3O4 core–shell based nanoparticles prepared by template synthesis of cobalt-pyromellitic acid on silica and subsequent pyrolysis. The optimal catalyst material allows for general and selective hydrogenation of pyridines, quinolines, and other heteroarenes including acridine, phenanthroline, naphthyridine, quinoxaline, imidazo[1,2-a]pyridine, and indole under comparably mild reaction conditions. In addition, recycling of these Co nanoparticles and their ability for dehydrogenation catalysis are showcased.  相似文献   
29.
Far-red emitting fluorescent labels are highly desirable for spectral multiplexing and deep tissue imaging. Here, we describe the generation of frFAST (far-red Fluorescence Activating and absorption Shifting Tag), a 14-kDa monomeric protein that forms a bright far-red fluorescent assembly with (4-hydroxy-3-methoxy-phenyl)allylidene rhodanine (HPAR-3OM). As HPAR-3OM is essentially non-fluorescent in solution and in cells, frFAST can be imaged with high contrast in presence of free HPAR-3OM, which allowed the rapid and efficient imaging of frFAST fusions in live cells, zebrafish embryo/larvae, and chicken embryos. Beyond enabling the genetic encoding of far-red fluorescence, frFAST allowed the design of a far-red chemogenetic reporter of protein–protein interactions, demonstrating its great potential for the design of innovative far-red emitting biosensors.  相似文献   
30.
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