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   204976篇
  免费   2620篇
  国内免费   509篇
化学   113557篇
晶体学   2656篇
力学   8022篇
综合类   11篇
数学   19805篇
物理学   64054篇
  2020年   1896篇
  2019年   2082篇
  2018年   2305篇
  2017年   2445篇
  2016年   3752篇
  2015年   2418篇
  2014年   3820篇
  2013年   9374篇
  2012年   6926篇
  2011年   8473篇
  2010年   5970篇
  2009年   5882篇
  2008年   7508篇
  2007年   7395篇
  2006年   6994篇
  2005年   6297篇
  2004年   5752篇
  2003年   5283篇
  2002年   5054篇
  2001年   6247篇
  2000年   4707篇
  1999年   3591篇
  1998年   2531篇
  1997年   2568篇
  1996年   2455篇
  1995年   2433篇
  1994年   2341篇
  1993年   2153篇
  1992年   2784篇
  1991年   2686篇
  1990年   2636篇
  1989年   2646篇
  1988年   2668篇
  1987年   2670篇
  1986年   2514篇
  1985年   3242篇
  1984年   3252篇
  1983年   2531篇
  1982年   2649篇
  1981年   2714篇
  1980年   2492篇
  1979年   2833篇
  1978年   2835篇
  1977年   2956篇
  1976年   2791篇
  1975年   2532篇
  1974年   2474篇
  1973年   2439篇
  1972年   1677篇
  1968年   1702篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Crystallography Reports - Crystals of mutants of uridine phosphorylase from Shewanella oneidensis MR-1 at the active-site threonine residue were obtained, and the three-dimensional structures of...  相似文献   
12.
13.
Russian Physics Journal - The process of radiative decay of a Higgs boson into a fermion-antifermion pair $$ H\Rightarrow \overline{ff}\upgamma . $$ is investigated within the framework of the...  相似文献   
14.
Differential Equations - Galathea traps for confining plasma in a magnetic field created by current-carrying conductors immersed in the plasma volume constitute a promising class of objects for...  相似文献   
15.
Journal of Applied Spectroscopy - The elemental composition of one- and two-rupee coins issued in different years by the Reserve Bank of India (RBI) was investigated using laser-induced breakdown...  相似文献   
16.
17.
18.
A facile biosynthesis route was followed to prepare zinc oxide nanoparticles (ZnO NPs) using Euphorbia milii (E. milii) leaf constituents. The SEM images exhibited presence of spherical ZnO NPs and the corresponding TEM images disclosed monodisperse nature of the ZnO NPs with diameter ranges between 12 and 20 nm. The Brunauer–Emmett–Teller (BET) analysis revealed that the ZnO NPs have specific surface area of 20.46 m2/g with pore diameter of 2 nm–10 nm and pore volume of 0.908 cm3/g. The EDAX spectrum exemplified the existence of Zn and O elements and non-appearance of impurities that confirmed pristine nature of the ZnO NPs. The XRD pattern indicated crystalline peaks corresponding to hexagonal wurtzite structured ZnO with an average crystallite size of 16.11 nm. The FTIR spectrum displayed strong absorption bands at 512 and 534 cm?1 related to ZnO. The photocatalytic action of ZnO NPs exhibited noteworthy degradation of methylene blue dye under natural sunlight illumination. The maximum degradation efficiency achieved was 98.17% at an illumination period of 50 min. The reusability study proved considerable photostability of the ZnO NPs during photocatalytic experiments. These findings suggest that the E. milii leaf constituents can be utilized as suitable biological source to synthesis ZnO NPs for photocatalytic applications.  相似文献   
19.
20.
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   
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