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   462682篇
  免费   4020篇
  国内免费   1619篇
化学   231405篇
晶体学   7432篇
力学   23615篇
综合类   28篇
数学   61474篇
物理学   144367篇
  2019年   3687篇
  2018年   11840篇
  2017年   12423篇
  2016年   10265篇
  2015年   4630篇
  2014年   6670篇
  2013年   16044篇
  2012年   15208篇
  2011年   24210篇
  2010年   16422篇
  2009年   16630篇
  2008年   21854篇
  2007年   24664篇
  2006年   12228篇
  2005年   16117篇
  2004年   12804篇
  2003年   12001篇
  2002年   10305篇
  2001年   10980篇
  2000年   8393篇
  1999年   6362篇
  1998年   5231篇
  1997年   5270篇
  1996年   5191篇
  1995年   4655篇
  1994年   4617篇
  1993年   4405篇
  1992年   5134篇
  1991年   5159篇
  1990年   5036篇
  1989年   5108篇
  1988年   4996篇
  1987年   5018篇
  1986年   4657篇
  1985年   6141篇
  1984年   6219篇
  1983年   5212篇
  1982年   5365篇
  1981年   5272篇
  1980年   5001篇
  1979年   5513篇
  1978年   5734篇
  1977年   5687篇
  1976年   5649篇
  1975年   5332篇
  1974年   5167篇
  1973年   5336篇
  1972年   3790篇
  1968年   3430篇
  1967年   3472篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
121.
122.
Syrovatka  R. A.  Lipaev  A. M.  Naumkin  V. N.  Klumov  B. A. 《JETP Letters》2022,116(12):869-874
JETP Letters - A quasi-two-dimensional plasma crystal in (3 + 1) dimensions has been experimentally observed for the first time; i.e., three spatial coordinates of each microparticles of the...  相似文献   
123.

A procedure was suggested for preparing brominated polyols of reduced viscosity for the synthesis of foamed polyurethanes of reduced flammability. The flame-retarding action of the synthesized polyol tetrabromophthalate in polyurethane was studied in comparison with that of other widely used flame retardants. Evaluation of the effect exerted on the flammability of the polurethane compound by the polyol tetrabromophthalate synthesized, melamine, and aluminum hydroxide shows that all the samples containing flame retardants are self-extinguishing. The shortest combustion time was observed for the sample containing 6% polyol tetrabromophthalate synthesized. The sample containing as a flame retardant additive solely the synthesized polyole tetrabromophthalate also exhibits the highest performance as a heat-insulating material from the viewpoint of thermal conductivity.

  相似文献   
124.
Crystallography Reports - The specific features of the formation of concentration inhomogeneities in crystals grown by the Czochralski method (GaSb:Te, Ge:Ga) and by the Bridgman method...  相似文献   
125.
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   
126.
Vorob’ev  N. T.  Lantsetova  E. D. 《Mathematical Notes》2021,110(5-6):655-665
Mathematical Notes - It is proved that the lattice of all Fitting classes of finite groups is not distributive, and conditions under which Fitting classes satisfy the distributive and modular laws...  相似文献   
127.
128.
Doklady Mathematics - An Erratum to this paper has been published: https://doi.org/10.1134/S1064562421330012  相似文献   
129.
Ding  Q.  Yao  M.  Wu  Sh.  Zeng  M.  Xue  N.  Wu  D.  Xu  J. 《Journal of Applied Spectroscopy》2022,89(4):712-718
Journal of Applied Spectroscopy - Based on partial least squares (PLS) analysis, the effects of different smoothing points and different preprocessing methods on the accuracy and precision of the...  相似文献   
130.
Xu  H. J.  Zhang  Q. G.  Debenest  G. 《Transport in Porous Media》2021,140(3):625-627
Transport in Porous Media - The theme of coupling problems for adsorption, absorption and thermochemical transport in porous media is very important for engineering applications. Based on the...  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