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   1306511篇
  免费   33575篇
  国内免费   10488篇
化学   649213篇
晶体学   20135篇
力学   75371篇
综合类   325篇
数学   240496篇
物理学   365034篇
  2021年   14353篇
  2020年   16705篇
  2019年   16889篇
  2016年   28098篇
  2015年   21537篇
  2014年   31527篇
  2013年   75795篇
  2012年   36946篇
  2011年   31423篇
  2010年   36414篇
  2009年   39223篇
  2008年   30983篇
  2007年   25673篇
  2006年   33734篇
  2005年   24886篇
  2004年   27014篇
  2003年   26046篇
  2002年   27475篇
  2001年   26791篇
  2000年   23857篇
  1999年   22417篇
  1998年   21273篇
  1997年   21322篇
  1996年   21380篇
  1995年   19471篇
  1994年   18813篇
  1993年   18275篇
  1992年   18079篇
  1991年   18371篇
  1990年   17625篇
  1989年   17631篇
  1988年   17163篇
  1987年   17199篇
  1986年   16017篇
  1985年   22443篇
  1984年   23740篇
  1983年   19919篇
  1982年   21593篇
  1981年   20808篇
  1980年   20122篇
  1979年   20279篇
  1978年   21594篇
  1977年   21198篇
  1976年   20835篇
  1975年   19492篇
  1974年   19129篇
  1973年   19555篇
  1972年   14106篇
  1968年   11992篇
  1967年   12388篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
131.
Ukrainian Mathematical Journal - We establish new criteria of compatibility for a linear system of equations (equivalent to the Kronecker–Capelli theorem) or inequalities (equivalent to the...  相似文献   
132.
Chen  R. J.  Chen  W.  Kong  F. L. 《Analysis Mathematica》2022,48(1):19-28

Restricted testing conditions were considered recently. For the maximal operator, Hytönen, Li and Sawyer [8] first obtained parental testing condition. Later, they [9] showed that it suffices to restrict testing to doubling cubes. Chen and Lacey [3] gave a similar restricted testing condition. In our paper, we discuss a version of the latter in the multilinear setting.

  相似文献   
133.
Journal of Fourier Analysis and Applications - We develop a theory of Sobolev orthogonal polynomials on the Sierpiński gasket ( $$SG$$ ), which is a fractal set that can be viewed as a limit...  相似文献   
134.
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   
135.
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   
136.
Theoretical and Mathematical Physics - The fractional derivative method is used to take wave dispersion into account in the wave equation when describing the propagation of gravitational soliton...  相似文献   
137.
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   
138.
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   
139.
Crystallography Reports - Methods of coherent X-ray diffraction imaging of the spatial structure of noncrystalline objects and nanocrystals (nanostructures) are considered. Particular attention is...  相似文献   
140.
Aequationes mathematicae - For $$p\in (1,\infty )$$ , we establish several criteria of one-sided invertibility on spaces $$l^p=l^p(\mathbb {Z})$$ for discrete band-dominated operators being either...  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