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   230167篇
  免费   2262篇
  国内免费   953篇
化学   127439篇
晶体学   3380篇
力学   8771篇
综合类   36篇
数学   25342篇
物理学   68414篇
  2021年   1926篇
  2020年   2165篇
  2019年   2460篇
  2018年   3379篇
  2017年   3250篇
  2016年   4616篇
  2015年   2688篇
  2014年   4200篇
  2013年   10047篇
  2012年   7539篇
  2011年   9160篇
  2010年   6583篇
  2009年   6418篇
  2008年   8817篇
  2007年   8922篇
  2006年   8224篇
  2005年   7533篇
  2004年   6737篇
  2003年   6221篇
  2002年   6106篇
  2001年   6380篇
  2000年   5091篇
  1999年   3755篇
  1998年   3243篇
  1997年   3217篇
  1996年   3061篇
  1995年   2571篇
  1994年   2638篇
  1993年   2639篇
  1992年   2794篇
  1991年   2840篇
  1990年   2757篇
  1989年   2682篇
  1988年   2612篇
  1987年   2591篇
  1986年   2498篇
  1985年   3256篇
  1984年   3417篇
  1983年   2720篇
  1982年   3001篇
  1981年   2860篇
  1980年   2663篇
  1979年   2878篇
  1978年   2970篇
  1977年   3029篇
  1976年   2971篇
  1975年   2821篇
  1974年   2796篇
  1973年   2933篇
  1972年   1949篇
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
41.
42.
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   
43.
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   
44.
45.
In this study, the functional interaction of HPLW peptide with VEGFR2 (Vascular Endothelial Growth Factor Receptor 2) was determined by using fast 15N‐edited NMR spectroscopic experiments. To this aim, 15N uniformly labelled HPLW has been added to Porcine Aortic Endothelial Cells. The acquisition of isotope‐edited NMR spectroscopic experiments, including 15N relaxation measurements, allowed a precise characterization of the in‐cell HPLW epitope recognized by VEGFR2.  相似文献   
46.
47.
48.
Journal of Thermal Analysis and Calorimetry - In the present study, numerical simulations have been carried out on thermal characteristics and second-law analysis of turbulent Cu–H2O...  相似文献   
49.
50.
Journal of Solid State Electrochemistry - In this work, the use of neodymium electrodes as a basis for the immobilization of magnetite nanoparticles has been carried out. The sensitivity and...  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