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   197054篇
  免费   3494篇
  国内免费   443篇
化学   112810篇
晶体学   2620篇
力学   7722篇
综合类   3篇
数学   21795篇
物理学   56041篇
  2021年   1545篇
  2020年   1882篇
  2019年   1918篇
  2018年   2656篇
  2017年   2528篇
  2016年   4096篇
  2015年   2983篇
  2014年   3810篇
  2013年   8976篇
  2012年   8271篇
  2011年   9459篇
  2010年   6293篇
  2009年   5961篇
  2008年   8782篇
  2007年   8581篇
  2006年   8095篇
  2005年   7565篇
  2004年   6705篇
  2003年   5956篇
  2002年   5683篇
  2001年   6430篇
  2000年   4730篇
  1999年   3600篇
  1998年   2534篇
  1997年   2594篇
  1996年   2572篇
  1995年   2232篇
  1994年   2293篇
  1993年   2103篇
  1992年   2606篇
  1991年   2645篇
  1990年   2445篇
  1989年   2421篇
  1988年   2327篇
  1987年   2355篇
  1986年   2140篇
  1985年   2799篇
  1984年   2788篇
  1983年   2157篇
  1982年   2302篇
  1981年   2099篇
  1980年   2058篇
  1979年   2330篇
  1978年   2399篇
  1977年   2292篇
  1976年   2263篇
  1975年   2114篇
  1974年   2105篇
  1973年   2112篇
  1972年   1348篇
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
51.
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   
52.
53.
54.
55.
56.
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   
57.
This study compares the physicochemical properties of six electrolytes comprising of three salts: LiFTFSI, NaFTFSI and KFTFSI in two solvent mixtures, the binary (3EC/7EMC) and the ternary (EC/PC/3DMC). The transport properties (conductivity, viscosity) as a function of temperature and concentration were modeled using the extended Jones-Dole-Kaminsky equation, the Arrhenius model, and the Eyring theory of transition state for activated complexes. Results are discussed in terms of ionicity, solvation shell, and cross-interactions between electrolyte components. The application of the six formulated electrolytes in symmetrical activated carbon (AC)//AC supercapacitors (SCs) was characterized by cyclic voltammetry (CV), galvanostatic cycling with potential limitation (GCPL), electrochemical impedance spectroscopy (EIS) and accelerated aging. Results revealed that the geometrical flexibility of the FTFSI anion allows it to access and diffuse easily in AC whereas its counter ions (Li+, Na+ or K+) can remain trapped in porosity. However, this drawback was partially resolved by mixing LiFTFSI and KFTFSI salts in the electrolyte.  相似文献   
58.
59.
60.
Molecular Diversity - Hypertension is a medical condition that affects millions of people worldwide. Despite the high efficacy of the current antihypertensive drugs, they are associated with...  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