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   16161篇
  免费   1623篇
  国内免费   1667篇
化学   3589篇
晶体学   210篇
力学   1944篇
综合类   305篇
数学   10784篇
物理学   2619篇
  2024年   19篇
  2023年   160篇
  2022年   171篇
  2021年   254篇
  2020年   398篇
  2019年   383篇
  2018年   364篇
  2017年   441篇
  2016年   485篇
  2015年   351篇
  2014年   673篇
  2013年   1194篇
  2012年   819篇
  2011年   956篇
  2010年   944篇
  2009年   1029篇
  2008年   1129篇
  2007年   1192篇
  2006年   979篇
  2005年   900篇
  2004年   825篇
  2003年   863篇
  2002年   725篇
  2001年   572篇
  2000年   496篇
  1999年   450篇
  1998年   418篇
  1997年   338篇
  1996年   290篇
  1995年   255篇
  1994年   214篇
  1993年   156篇
  1992年   154篇
  1991年   114篇
  1990年   94篇
  1989年   75篇
  1988年   71篇
  1987年   55篇
  1986年   60篇
  1985年   64篇
  1984年   52篇
  1983年   25篇
  1982年   61篇
  1981年   44篇
  1980年   31篇
  1979年   30篇
  1978年   18篇
  1977年   13篇
  1976年   13篇
  1972年   7篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
《Mendeleev Communications》2022,32(6):742-744
A solution of a histone-like protein from Spiroplasma melliferum (HUSpm) was examined by small-angle X-ray scattering (SAXS). The experimental SAXS curve was compared with those calculated for the HUSpm structures from the PDB databank obtained by both X-ray diffraction analysis and nuclear magnetic resonance spectroscopy. The model of the HUSpm structure in solution, which best agrees with the experimental SAXS data, has a shorter distance between the centers of mass of the HUSpm monomers compared to the crystal structure, indicating that the HUSpm monomers can be located closer to each other in solution than in the crystalline state.  相似文献   
22.
23.
24.
25.
We study the existence of a time‐periodic solution with pointwise decay properties to the Navier–Stokes equation in the whole space. We show that if the time‐periodic external force is sufficiently small in an appropriate sense, then there exists a time‐periodic solution { u , p } of the Navier–Stokes equation such that | ? j u ( t , x ) | = O ( | x | 1 ? n ? j ) and | ? j p ( t , x ) | = O ( | x | ? n ? j ) ( j = 0 , 1 , ) uniformly in t R as | x | . Our solution decays faster than the time‐periodic Stokes fundamental solution and the faster decay of its spatial derivatives of higher order is also described.  相似文献   
26.
Jia-Hui Wang 《中国物理 B》2021,30(11):110204-110204
We fabricated a microfluidic chip with simple structure and good sealing performance, and studied the influence of the electric field on THz absorption intensity of liquid samples treated at different times by using THz time domain spectroscopy system. The tested liquids were deionised water and CuSO4, CuCl2, NaHCO3, Na2CO3 and NaCl solutions. The transmission intensity of the THz wave increases as the standing time of the electrolyte solution in the electric field increases. The applied electric field alters the dipole moment of water molecules in the electrolyte solution, which affects the vibration and rotation of the whole water molecules, breaks the hydrogen bonds in the water, increases the number of single water molecules and leads to the enhancement of the THz transmission spectrum.  相似文献   
27.
In this article, we consider the asymptotic behavior of the classical solution to the 3‐dimensional Vlasov‐Poisson plasma interacting repulsively with N point charges. The large time behavior in terms of diameters of its velocity‐spatial supports is improved to O(t2/3+ϵ) for any ϵ>0.  相似文献   
28.
The flow behavior in non-parallel walls is an important factor of any physical model including cavity flow and canals, which is applicable for diverging/converging channel. The present communication explains that the flow of the hybrid nanomaterial subjected to the convergent/divergent channel has non-parallel walls. It is assumed that the hybrid nanomaterial movement is in the porous region. A Darcy-Forchheimer medium of porosity is considered to interpret the porosity features. A useful similarity function is adopted to get the strong ordinary coupled equations. Numerical solutions are achieved through the Runge-Kutta-Fehlberg(RKF) fourth-fifth order method, and they are validated with the existing results. Physical nature of the involving constraints is reported with the help of plots. It is explored that the velocity of divergent channel decreases, and convergent channel enhances for the higher solid volume faction. Further, the presence of inertia coefficient and porosity parameter amplifies the velocity at the wall.  相似文献   
29.
The(3+1)-dimensional Burgers equation, which describes nonlinear waves in turbulence and the interface dynamics,is considered. Two types of semi-rational solutions, namely, the lump–kink solution and the lump–two kinks solution, are constructed from the quadratic function ansatz. Some interesting features of interactions between lumps and other solitons are revealed analytically and shown graphically, such as fusion and fission processes.  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