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   304881篇
  免费   3953篇
  国内免费   2085篇
化学   168822篇
晶体学   4443篇
力学   12662篇
综合类   18篇
数学   35046篇
物理学   89928篇
  2020年   2687篇
  2019年   2930篇
  2018年   3834篇
  2017年   3806篇
  2016年   5840篇
  2015年   3747篇
  2014年   5450篇
  2013年   13230篇
  2012年   10798篇
  2011年   12890篇
  2010年   8837篇
  2009年   8703篇
  2008年   11650篇
  2007年   11788篇
  2006年   10863篇
  2005年   9959篇
  2004年   9382篇
  2003年   8141篇
  2002年   7991篇
  2001年   8105篇
  2000年   6350篇
  1999年   4891篇
  1998年   4309篇
  1997年   4209篇
  1996年   4030篇
  1995年   3656篇
  1994年   3781篇
  1993年   3515篇
  1992年   3958篇
  1991年   3879篇
  1990年   3793篇
  1989年   3614篇
  1988年   3721篇
  1987年   3607篇
  1986年   3430篇
  1985年   4586篇
  1984年   4830篇
  1983年   4029篇
  1982年   4137篇
  1981年   4071篇
  1980年   4013篇
  1979年   3997篇
  1978年   4282篇
  1977年   4194篇
  1976年   4254篇
  1975年   3928篇
  1974年   3967篇
  1973年   4139篇
  1972年   2898篇
  1971年   2425篇
排序方式: 共有10000条查询结果,搜索用时 468 毫秒
81.
82.
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   
83.
84.
Bruzy  N.  Coret  M.  Huneau  B.  Kermouche  G.  Mondon  M.  Bertrand  E.  Stainier  L. 《Experimental Mechanics》2019,59(8):1145-1157

The allotropic phase change from ferrite to austenite represents a moment of massive interplay between the microstructural and mechanical states of iron. The difference of compacity between the two phases induces a microplastic accommodation in the material at grain scale. However, mechanical heterogeneities resulting from the transformation process remain challenging to characterise due to the high temperature conditions it is associated with. We developed experimental equipment for in situ observation of α ? γ and γ ? α transformations. Images of the surface of an iron sample taken by an optical camera were used as input for a Digital Image Correlation (DIC) routine. Special care was taken to maximize image resolution to capture sub-grain phenomena. Observations show that, at the mesoscopic scale, shear strain fields exhibit strong localisations that are evidence of transformations that are occurring.

  相似文献   
85.
Radiophysics and Quantum Electronics - Wind-related weather hazards remain difficult to recognize targets for weather radars. Methods that use estimates of the width of the reflected-signal...  相似文献   
86.
Russian Journal of General Chemistry - Highly dispersed CaO has been synthesized by heating an aqueous solution of calcium nitrate and D-glucose up to 800°C. Calcium oxide is formed with an...  相似文献   
87.
Exosomes are nanovesicles secreted by most cellular types that carry important biochemical compounds throughout the body with different purposes, playing a preponderant role in cellular communication. Because of their structure, physicochemical properties and stability, recent studies are focusing in their use as nanocarriers for different therapeutic compounds for the treatment of different diseases ranging from cancer to Parkinson's disease. However, current bioseparation protocols and methodologies are selected based on the final exosome application or intended use and present both advantages and disadvantages when compared among them. In this context, this review aims to present the most important technologies available for exosome isolation while discussing their advantages and disadvantages and the possibilities of being combined with other strategies. This is critical since the development of novel exosome‐based therapeutic strategies will be constrained to the effectiveness and yield of the selected downstream purification methodologies for which a thorough understanding of the available technological resources is needed.  相似文献   
88.
Journal of Analytical Chemistry - HPTLC is a widely used tool in standardization of herbs because of its ability to estimate the presence of active components in samples. HPTLC-bioautography is a...  相似文献   
89.
Journal of Solid State Electrochemistry - In this study, galvanostatic electrolysis, through the use of the platinum supported on Ti (Ti/Pt) and Ti/TiO2-nanotubes/PbO2 anodes, was conducted in an...  相似文献   
90.
Journal of Applied Spectroscopy - Aqueous solutions of human hemoglobin have been studied by the multi-angle static light scattering method. The tendency of sickle-shaped erythrocytes to aggregate...  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