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   522543篇
  免费   4901篇
  国内免费   1369篇
化学   250952篇
晶体学   6974篇
力学   26479篇
综合类   9篇
数学   75189篇
物理学   169210篇
  2021年   3889篇
  2020年   4291篇
  2019年   4819篇
  2018年   12557篇
  2017年   13217篇
  2016年   12382篇
  2015年   6094篇
  2014年   9265篇
  2013年   21598篇
  2012年   19345篇
  2011年   28491篇
  2010年   19681篇
  2009年   19641篇
  2008年   25494篇
  2007年   27855篇
  2006年   16662篇
  2005年   19128篇
  2004年   15839篇
  2003年   14463篇
  2002年   12928篇
  2001年   14134篇
  2000年   10690篇
  1999年   8175篇
  1998年   6799篇
  1997年   6583篇
  1996年   6346篇
  1995年   5585篇
  1994年   5401篇
  1993年   5165篇
  1992年   5780篇
  1991年   5916篇
  1990年   5647篇
  1989年   5523篇
  1988年   5312篇
  1987年   5507篇
  1986年   5131篇
  1985年   6667篇
  1984年   6799篇
  1983年   5751篇
  1982年   5900篇
  1981年   5506篇
  1980年   5440篇
  1979年   5888篇
  1978年   5931篇
  1977年   5790篇
  1976年   5838篇
  1975年   5550篇
  1974年   5499篇
  1973年   5699篇
  1972年   3913篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
Journal of Mathematical Chemistry - The analytical solutions of an asymmetric double well potential $$V(x)=a\, x^2-b\, x^3+c\, x^4$$ are found to be a triconfluent Heun function $$H_{T}(\alpha ,...  相似文献   
63.
Russian Physics Journal - The paper shows that the values of zero-point energy and vibrations of atoms in a crystal determined by the uncertainty principle, depend on the dynamic response of atoms....  相似文献   
64.
Journal of Applied and Industrial Mathematics - We study the problem of optimal location of the ambulance fleet at the base stations. The objective is to minimize the average waiting time for...  相似文献   
65.
A liquid dewetting method for the determination of the viscoelastic properties of ultrathin polymer films has been extended to study thickness effects on the properties of ultrathin polycarbonate (PC) films. PC films with film thicknesses ranging from 4 to 299 nm were placed on glycerol at temperatures from below the macroscopic glass transition temperature (Tg) to above it with the dewetting responses being monitored. It is found that the isothermal creep results for films of the same thickness, but dewetted at different temperatures can be superposed into one master curve, which is consistent with the fact of PC being a thermorheologically simple material. Furthermore, the results show that the Tg of PC thin films is thickness dependent, but the dependence is weaker than the results for freely standing films and similar to literature data for PC films supported on rigid substrates. It was also found that the rubbery plateau region for the PC films stiffens dramatically, but still less than what has been observed for freely standing polycarbonate films. The rubbery stiffening is discussed in terms of a recently reported model that relates macroscopic segmental dynamics with the stiffening. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1559–1566  相似文献   
66.
67.
68.
Russian Physics Journal - A relationship between the structural-morphological and physical-mechanical properties of macro-porous calcium phosphate (CaP) coatings on the surface of titanium implants...  相似文献   
69.
The design of new solid-state proton-conducting materials is a great challenge for chemistry and materials science. Herein, a new anionic porphyrinylphosphonate-based MOF ( IPCE-1Ni ), which involves dimethylammonium (DMA) cations for charge compensation, is reported. As a result of its unique structure, IPCE-1Ni exhibits one of the highest value of the proton conductivity among reported proton-conducting MOF materials based on porphyrins (1.55×10−3 S cm−1 at 75 °C and 80 % relative humidity).  相似文献   
70.
The change in the free-electron density in ultrathin (5 nm) superconducting NbN films in the initial state and after irradiation by O+ ions to doses of (0.1–0.9) × 1017 cm–2 has been studied by electron energy-loss spectroscopy (EELS). The analysis has been performed on cross section samples prepared by the focused ion beam method, using plasmon oscillations with energies up to 50 eV. The radiation-induced replacement of nitrogen atoms with oxygen atoms in niobium nitride is found to change the electrical properties of the material, which leads to a decrease in the free-electron density with an increase in the irradiation dose.  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