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   435991篇
  免费   3918篇
  国内免费   1194篇
化学   234326篇
晶体学   6623篇
力学   18987篇
综合类   15篇
数学   50487篇
物理学   130665篇
  2019年   4019篇
  2018年   5554篇
  2017年   5464篇
  2016年   7805篇
  2015年   4568篇
  2014年   7307篇
  2013年   18199篇
  2012年   13571篇
  2011年   16559篇
  2010年   11793篇
  2009年   11508篇
  2008年   15672篇
  2007年   15924篇
  2006年   14865篇
  2005年   13453篇
  2004年   12123篇
  2003年   11053篇
  2002年   10941篇
  2001年   11814篇
  2000年   9289篇
  1999年   7098篇
  1998年   6232篇
  1997年   6250篇
  1996年   5854篇
  1995年   5165篇
  1994年   5360篇
  1993年   5115篇
  1992年   5682篇
  1991年   5706篇
  1990年   5593篇
  1989年   5427篇
  1988年   5463篇
  1987年   5355篇
  1986年   5117篇
  1985年   6770篇
  1984年   7127篇
  1983年   5857篇
  1982年   6253篇
  1981年   6070篇
  1980年   5842篇
  1979年   6024篇
  1978年   6390篇
  1977年   6315篇
  1976年   6377篇
  1975年   5954篇
  1974年   5994篇
  1973年   6219篇
  1972年   4341篇
  1971年   3670篇
  1967年   3693篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
Physics of Atomic Nuclei - We have studied the mechanisms influencing production of cumulative pions and protons in the fragmentation of the incident deuterons into cumulative pions and protons...  相似文献   
82.
Journal of Thermal Analysis and Calorimetry - The role of method of synthesis on the size of flakes, dispersion stability and thermophysical properties of aqua based reduced graphene oxide (rGO)...  相似文献   
83.
Journal of Thermal Analysis and Calorimetry - Modeling and computations are performed to study the ND-Co3O4/EG hybrid nanoliquid mixed convective flow past a vertical porous cylinder. The flow...  相似文献   
84.
85.
86.
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   
87.
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   
88.
89.
90.
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