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   291991篇
  免费   5425篇
  国内免费   2815篇
化学   140533篇
晶体学   4232篇
力学   15645篇
综合类   110篇
数学   44141篇
物理学   95570篇
  2021年   1634篇
  2020年   1845篇
  2019年   1844篇
  2018年   11062篇
  2017年   11955篇
  2016年   7376篇
  2015年   3673篇
  2014年   3614篇
  2013年   9141篇
  2012年   12312篇
  2011年   22317篇
  2010年   13492篇
  2009年   13587篇
  2008年   19332篇
  2007年   22880篇
  2006年   8170篇
  2005年   14746篇
  2004年   10183篇
  2003年   9101篇
  2002年   6936篇
  2001年   6597篇
  2000年   5253篇
  1999年   3974篇
  1998年   3079篇
  1997年   3037篇
  1996年   3123篇
  1995年   2688篇
  1994年   2522篇
  1993年   2338篇
  1992年   2590篇
  1991年   2550篇
  1990年   2280篇
  1989年   2230篇
  1988年   2228篇
  1987年   2144篇
  1986年   2047篇
  1985年   2978篇
  1984年   2938篇
  1983年   2375篇
  1982年   2545篇
  1981年   2414篇
  1980年   2369篇
  1979年   2317篇
  1978年   2393篇
  1977年   2268篇
  1976年   2232篇
  1975年   2202篇
  1974年   2105篇
  1973年   2214篇
  1972年   1244篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
We summarize the results of our recent work on Bäcklund transformations (BTs), particularly focusing on the relation between BTs and infinitesimal symmetries. We present a BT for an associated Degasperis–Procesi (aDP) equation and its superposition principle and investigate the solutions generated by applying this BT. Following our general methodology, we use the superposition principle of the BT to generate the infinitesimal symmetries of the aDP equation.  相似文献   
22.
Mesoscopic modeling at the pore scale offers great promise in exploring the underlying structure transport performance of flow through porous media. The present work studies the fluid flow subjected to capillarity-induced resonance in porous media characterized by different porous structure and wettability. The effects of porosity and wettability on the displacement behavior of the fluid flow through porous media are discussed. The results are presented in the form of temporal evolution of percentage saturation and displacement of the fluid front through porous media. The present study reveals that the vibration in the form of acoustic excitation could be significant in the mobilization of fluid through the porous media. The dependence of displacement of the fluid on physicochemical parameters like wettability of the surface, frequency along with the porosity is analyzed. It was observed that the mean displacement of the fluid is more in the case of invading fluid with wetting phase where the driving force strength is not so dominant.  相似文献   
23.
24.
25.
26.
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   
27.
28.
29.
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