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   654716篇
  免费   6202篇
  国内免费   1764篇
化学   333649篇
晶体学   9656篇
力学   32357篇
综合类   22篇
数学   85500篇
物理学   201498篇
  2021年   5827篇
  2020年   6363篇
  2019年   7197篇
  2018年   9593篇
  2017年   9681篇
  2016年   13559篇
  2015年   7597篇
  2014年   12453篇
  2013年   29267篇
  2012年   22674篇
  2011年   27089篇
  2010年   19856篇
  2009年   19651篇
  2008年   25400篇
  2007年   25353篇
  2006年   23225篇
  2005年   20811篇
  2004年   19440篇
  2003年   17486篇
  2002年   17221篇
  2001年   18479篇
  2000年   14386篇
  1999年   11138篇
  1998年   9515篇
  1997年   9371篇
  1996年   8773篇
  1995年   7977篇
  1994年   7856篇
  1993年   7592篇
  1992年   8153篇
  1991年   8574篇
  1990年   8226篇
  1989年   8009篇
  1988年   7915篇
  1987年   7719篇
  1986年   7343篇
  1985年   9370篇
  1984年   9966篇
  1983年   8325篇
  1982年   8716篇
  1981年   8312篇
  1980年   7881篇
  1979年   8347篇
  1978年   8701篇
  1977年   8560篇
  1976年   8584篇
  1975年   8150篇
  1974年   7983篇
  1973年   8371篇
  1972年   5963篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
261.
262.
Radiophysics and Quantum Electronics - We propose and experimentally test a numerical method for correction of the influence of fluctuations in the distance to objects during noncontact probing in...  相似文献   
263.
The aim of the study presented in this paper was to characterize quantitatively the erosion of aluminum cathodes in high-current vacuum arcs. The experimental setup comprised two current generators. The first one, capable of generating a current of amplitude up to 350 kA, was used to produce a plasma jet, that is, the object to be investigated. The second generator was used to produce a source of probe radiation for imaging the object under investigation in soft x rays of energy ?ν ≈ 0.5–3 keV. The findings of the study are based on experimental data obtained by electrophysical and radiographic methods. It has been shown that the cathode erosion rate in a high-current vacuum arc is a function of the charge passed through the cathode.  相似文献   
264.
Optics and Spectroscopy - The population kinetics of a two-level system has been theoretically investigated taking into account the transfer of spontaneous radiation under continuous optical...  相似文献   
265.
The hydrophobicity of silicone elastomers can compromise their utility in some biomaterials applications. Few effective processes exist to introduce hydrophilic groups onto a polysiloxane backbone and subsequently crosslink the material into elastomers. This problem can be overcome through the utilization of metal‐free click reactions between azidoalkylsilicones and alkynyl‐modified silicones and/or PEGs to both functionalize and crosslink silicone elastomers. Alkynyl‐functional PEG was clicked onto a fraction of the available azido groups of a functional polysiloxane, yielding azido reactive PDMS‐g‐PEG rake surfactants. The reactive polymers were then used to crosslink alkynyl‐terminated PDMS of different molecular weights. Using simple starting materials, this generic yet versatile method permits the preparation and characterization of a library of amphiphilic thermoset elastomers that vary in their composition, crosslink density, elasticity, hydrogel formation, and wettability. An appropriate balance of PEG length and crosslink density leads to a permanently highly wettable silicone elastomer that demonstrated very low levels of protein adsorption. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1082–1093  相似文献   
266.
267.
Submicron CaZrO3 powder is obtained in combustion reactions (solution combustion synthesis—SCS) with glycine. It is found that SCS reduces the sintering temperature of CaZrO3 powders. The dielectric properties of calcium zirconate ceramics are studied by the electrochemical impedance method. It is shown that a ceramics of powders obtained by the SCS method has high dielectric characteristics.  相似文献   
268.
269.
Russian Chemical Bulletin - The study is concerned with structural rearrangements in the crystals of heterospin complexes Cu(hfac)2 with nitroxide radicals LR (hfac is hexafluoroacetylacetonate, LR...  相似文献   
270.
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