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   372369篇
  免费   4401篇
  国内免费   1474篇
化学   194178篇
晶体学   5711篇
力学   17370篇
综合类   10篇
数学   41999篇
物理学   118976篇
  2020年   2783篇
  2019年   3023篇
  2018年   3715篇
  2017年   3637篇
  2016年   5932篇
  2015年   4039篇
  2014年   6123篇
  2013年   16553篇
  2012年   12842篇
  2011年   16075篇
  2010年   10760篇
  2009年   10839篇
  2008年   14742篇
  2007年   14681篇
  2006年   14062篇
  2005年   12809篇
  2004年   11748篇
  2003年   10231篇
  2002年   10121篇
  2001年   11717篇
  2000年   8957篇
  1999年   6967篇
  1998年   5657篇
  1997年   5576篇
  1996年   5393篇
  1995年   4900篇
  1994年   4724篇
  1993年   4708篇
  1992年   5053篇
  1991年   5171篇
  1990年   4705篇
  1989年   4663篇
  1988年   4703篇
  1987年   4533篇
  1986年   4289篇
  1985年   6053篇
  1984年   6181篇
  1983年   5031篇
  1982年   5373篇
  1981年   5190篇
  1980年   4928篇
  1979年   5064篇
  1978年   5173篇
  1977年   5107篇
  1976年   5176篇
  1975年   4838篇
  1974年   4824篇
  1973年   4926篇
  1972年   3260篇
  1971年   2541篇
排序方式: 共有10000条查询结果,搜索用时 421 毫秒
61.
62.
Journal of Solid State Electrochemistry - The “shuttle effect” of polysulfides is a serious issue, resulting in a decrease in the life-cycle of lithium-sulfur (Li-S) batteries. To...  相似文献   
63.
Journal of Thermal Analysis and Calorimetry - In recent decades, the growth of heat transfer using nanomaterials in the conventional base fluid has caught the attention of researchers...  相似文献   
64.
65.
66.
67.
68.
69.
Injection-moulding is one of the most common manufacturing processes used for polymers. In many applications, the mechanical properties of the product is of great importance. Injection-moulding of thin-walled polymer products tends to leave the polymer structure in a state where the mechanical properties are anisotropic, due to alignment of polymer chains along the melt flow direction. The anisotropic elastic-viscoplastic properties of low-density polyethylene, that has undergone an injection-moulding process, are therefore examined in the present work. Test specimens were punched out from injection-moulded plates and tested in uniaxial tension. Three in-plane material directions were investigated. Because of the small thickness of the plates, only the in-plane properties could be determined. Tensile tests with both monotonic and cyclic loading were performed, and the local strains on the surface of the test specimens were measured using image analysis. True stress vs. true strain diagrams were constructed, and the material response was evaluated using an elastic-viscoplasticity law. The components of the anisotropic compliance matrix were determined together with the direction-specific plastic hardening parameters.  相似文献   
70.
Erosion and sediments transport processes have a great impact on industrial structures and on water quality. Despite its limitations, the Saint‐Venant‐Exner system is still (and for sure for some years) widely used in industrial codes to model the bedload sediment transport. In practice, its numerical resolution is mostly handled by a splitting technique that allows a weak coupling between hydraulic and morphodynamic distinct softwares but may suffer from important stability issues. In recent works, many authors proposed alternative methods based on a strong coupling that cure this problem but are not so trivial to implement in an industrial context. In this work, we then pursue 2 objectives. First, we propose a very simple scheme based on an approximate Riemann solver, respecting the strong coupling framework, and we demonstrate its stability and accuracy through a number of numerical test cases. However, second, we reinterpret our scheme as a splitting technique and we extend the purpose to propose what should be the minimal coupling that ensures the stability of the global numerical process in industrial codes, at least, when dealing with collocated finite volume method. The resulting splitting method is, up to our knowledge, the only one for which stability properties are fully demonstrated.  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