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   332291篇
  免费   4022篇
  国内免费   1448篇
化学   166868篇
晶体学   5408篇
力学   15676篇
综合类   36篇
数学   38851篇
物理学   110922篇
  2021年   3257篇
  2020年   3483篇
  2019年   3916篇
  2018年   5339篇
  2017年   5567篇
  2016年   7541篇
  2015年   4332篇
  2014年   7220篇
  2013年   16140篇
  2012年   12654篇
  2011年   15116篇
  2010年   11241篇
  2009年   11134篇
  2008年   13464篇
  2007年   13361篇
  2006年   12295篇
  2005年   10662篇
  2004年   9925篇
  2003年   8748篇
  2002年   8752篇
  2001年   10441篇
  2000年   7706篇
  1999年   6027篇
  1998年   5004篇
  1997年   4858篇
  1996年   4538篇
  1995年   3923篇
  1994年   3862篇
  1993年   3738篇
  1992年   4111篇
  1991年   4330篇
  1990年   4110篇
  1989年   4021篇
  1988年   3789篇
  1987年   3920篇
  1986年   3689篇
  1985年   4632篇
  1984年   4682篇
  1983年   3886篇
  1982年   3974篇
  1981年   3697篇
  1980年   3648篇
  1979年   3913篇
  1978年   3901篇
  1977年   3906篇
  1976年   3879篇
  1975年   3675篇
  1974年   3615篇
  1973年   3650篇
  1972年   2603篇
排序方式: 共有10000条查询结果,搜索用时 156 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.
Understanding the thermal aggregation behavior of metal atoms is important for the synthesis of supported metal clusters. Here, derived from a metal–organic framework encapsulating a trinuclear FeIII2FeII complex (denoted as Fe3) within the channels, a well-defined nitrogen-doped carbon layer is fabricated as an ideal support for stabilizing the generated iron nanoclusters. Atomic replacement of FeII by other metal(II) ions (e.g., ZnII/CoII) via synthesizing isostructural trinuclear-complex precursors (Fe2Zn/Fe2Co), namely the “heteroatom modulator approach”, is inhibiting the aggregation of Fe atoms toward nanoclusters with formation of a stable iron dimer in an optimal metal–nitrogen moiety, clearly identified by direct transmission electron microscopy and X-ray absorption fine structure analysis. The supported iron dimer, serving as cooperative metal–metal site, acts as efficient oxygen evolution catalyst. Our findings offer an atomic insight to guide the future design of ultrasmall metal clusters bearing outstanding catalytic capabilities.  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