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   748430篇
  免费   9611篇
  国内免费   2561篇
化学   404746篇
晶体学   11058篇
力学   32451篇
综合类   23篇
数学   92291篇
物理学   220033篇
  2021年   5488篇
  2020年   6220篇
  2019年   6715篇
  2018年   8995篇
  2017年   8872篇
  2016年   13365篇
  2015年   8950篇
  2014年   13047篇
  2013年   33832篇
  2012年   25418篇
  2011年   30897篇
  2010年   21116篇
  2009年   20781篇
  2008年   27795篇
  2007年   27744篇
  2006年   25774篇
  2005年   25083篇
  2004年   23040篇
  2003年   19936篇
  2002年   18704篇
  2001年   20856篇
  2000年   16024篇
  1999年   12720篇
  1998年   10557篇
  1997年   10334篇
  1996年   10209篇
  1995年   9217篇
  1994年   9077篇
  1993年   8919篇
  1992年   9933篇
  1991年   9772篇
  1990年   9440篇
  1989年   9288篇
  1988年   9328篇
  1987年   9165篇
  1986年   8672篇
  1985年   11579篇
  1984年   11878篇
  1983年   9717篇
  1982年   10238篇
  1981年   10012篇
  1980年   9463篇
  1979年   10012篇
  1978年   10498篇
  1977年   10218篇
  1976年   10247篇
  1975年   9493篇
  1974年   9432篇
  1973年   9711篇
  1972年   6651篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Russian Journal of General Chemistry - Hybrid liquid crystal systems with different ratios of the components have been prepared on the basis of 5,5′-di(heptadecyl)-2,2′-bipyridine...  相似文献   
72.
73.
The European Physical Journal Special Topics - The removal of suspended particles from the interior of a thermocapillary liquid bridge via a finite-particle-size effect restricting the particle...  相似文献   
74.
75.
Palladium nanoparticle‐incorporated metal–organic framework MIL‐101 (Pd/MIL‐101) was successfully synthesized and characterized using X‐ray diffraction, nitrogen physisorption, X‐ray photoelectron, UV–visible and infrared spectroscopies, and transmission electron microscopy. The characterization techniques confirmed high porosity and high surface area of MIL‐101 and high stability of nano‐size palladium particles. Pd/MIL‐101 nanocomposite was investigated for the Sonogashira cross‐coupling reaction of aryl and heteroaryl bromides with various alkynes under copper‐free conditions. The reusability of the catalyst was tested for up to four cycles without any significant loss in catalytic activity. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
76.
We study the full counting statistics of transport electrons through a semiconductor two-level quantum dot with Rashba spin–orbit (SO) coupling, which acts as a nonabelian gauge field and thus induces the electron transition between two levels along with the spin flip. By means of the quantum master equation approach, shot noise and skewness are obtained at finite temperature with two-body Coulomb interaction. We particularly demonstrate the crucial effect of SO coupling on the super-Poissonian fluctuation of transport electrons, in terms of which the SO coupling can be probed by the zero-frequency cumulants. While the charge currents are not sensitive to the SO coupling.  相似文献   
77.
78.
79.
80.
In this paper, we present an approach of dynamic mesh adaptation for simulating complex 3‐dimensional incompressible moving‐boundary flows by immersed boundary methods. Tetrahedral meshes are adapted by a hierarchical refining/coarsening algorithm. Regular refinement is accomplished by dividing 1 tetrahedron into 8 subcells, and irregular refinement is only for eliminating the hanging points. Merging the 8 subcells obtained by regular refinement, the mesh is coarsened. With hierarchical refining/coarsening, mesh adaptivity can be achieved by adjusting the mesh only 1 time for each adaptation period. The level difference between 2 neighboring cells never exceeds 1, and the geometrical quality of mesh does not degrade as the level of adaptive mesh increases. A predictor‐corrector scheme is introduced to eliminate the phase lag between adapted mesh and unsteady solution. The error caused by each solution transferring from the old mesh to the new adapted one is small because most of the nodes on the 2 meshes are coincident. An immersed boundary method named local domain‐free discretization is employed to solve the flow equations. Several numerical experiments have been conducted for 3‐dimensional incompressible moving‐boundary flows. By using the present approach, the number of mesh nodes is reduced greatly while the accuracy of solution can be preserved.  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