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   652171篇
  免费   7511篇
  国内免费   2301篇
化学   336396篇
晶体学   10200篇
力学   30356篇
综合类   18篇
数学   80782篇
物理学   204231篇
  2021年   5191篇
  2020年   5661篇
  2019年   6402篇
  2018年   8302篇
  2017年   8494篇
  2016年   12491篇
  2015年   7586篇
  2014年   12122篇
  2013年   30447篇
  2012年   22814篇
  2011年   27835篇
  2010年   19840篇
  2009年   19721篇
  2008年   25151篇
  2007年   24949篇
  2006年   23297篇
  2005年   20763篇
  2004年   19075篇
  2003年   17039篇
  2002年   16804篇
  2001年   19822篇
  2000年   15014篇
  1999年   11747篇
  1998年   9726篇
  1997年   9572篇
  1996年   8979篇
  1995年   8066篇
  1994年   7897篇
  1993年   7749篇
  1992年   8680篇
  1991年   8761篇
  1990年   8365篇
  1989年   8207篇
  1988年   8025篇
  1987年   8112篇
  1986年   7581篇
  1985年   10079篇
  1984年   10244篇
  1983年   8487篇
  1982年   8904篇
  1981年   8469篇
  1980年   8330篇
  1979年   8742篇
  1978年   9037篇
  1977年   8902篇
  1976年   8984篇
  1975年   8274篇
  1974年   8375篇
  1973年   8698篇
  1972年   5860篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
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   
92.
93.
94.
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   
95.
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   
96.
97.
98.
99.
100.
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