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   363976篇
  免费   4691篇
  国内免费   1062篇
化学   183340篇
晶体学   5547篇
力学   16499篇
综合类   12篇
数学   44776篇
物理学   119555篇
  2021年   3412篇
  2020年   3783篇
  2019年   4099篇
  2018年   5656篇
  2017年   5898篇
  2016年   8331篇
  2015年   4870篇
  2014年   7841篇
  2013年   17645篇
  2012年   13942篇
  2011年   16530篇
  2010年   12167篇
  2009年   11872篇
  2008年   14795篇
  2007年   14672篇
  2006年   13531篇
  2005年   11779篇
  2004年   10916篇
  2003年   9557篇
  2002年   9425篇
  2001年   11029篇
  2000年   8224篇
  1999年   6358篇
  1998年   5326篇
  1997年   5150篇
  1996年   4919篇
  1995年   4268篇
  1994年   4261篇
  1993年   4169篇
  1992年   4597篇
  1991年   4640篇
  1990年   4449篇
  1989年   4330篇
  1988年   4063篇
  1987年   4219篇
  1986年   3965篇
  1985年   5087篇
  1984年   5106篇
  1983年   4248篇
  1982年   4358篇
  1981年   4083篇
  1980年   4030篇
  1979年   4282篇
  1978年   4258篇
  1977年   4261篇
  1976年   4205篇
  1975年   4002篇
  1974年   3929篇
  1973年   3915篇
  1972年   2755篇
排序方式: 共有10000条查询结果,搜索用时 765 毫秒
51.
Foundations of Computational Mathematics - We present a finite element variational integrator for compressible flows. The numerical scheme is derived by discretizing, in a structure-preserving way,...  相似文献   
52.
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   
53.
Crystallography Reports - Some questions related to the establishment, development, and prospects of physical studies using inelastic thermal-neutron scattering are briefly reviewed. The directions...  相似文献   
54.
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   
55.
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   
56.
57.
Russian Physics Journal - The paper shows that the values of zero-point energy and vibrations of atoms in a crystal determined by the uncertainty principle, depend on the dynamic response of atoms....  相似文献   
58.
59.
60.
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