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   475361篇
  免费   4153篇
  国内免费   1623篇
化学   234391篇
晶体学   7621篇
力学   24108篇
综合类   12篇
数学   73706篇
物理学   141299篇
  2020年   3301篇
  2019年   3719篇
  2018年   14458篇
  2017年   14265篇
  2016年   12690篇
  2015年   5123篇
  2014年   7269篇
  2013年   18108篇
  2012年   16497篇
  2011年   25766篇
  2010年   16651篇
  2009年   16995篇
  2008年   20702篇
  2007年   22613篇
  2006年   13804篇
  2005年   13513篇
  2004年   12703篇
  2003年   12052篇
  2002年   10915篇
  2001年   12223篇
  2000年   9426篇
  1999年   7268篇
  1998年   5988篇
  1997年   5846篇
  1996年   5665篇
  1995年   5160篇
  1994年   4980篇
  1993年   4908篇
  1992年   5591篇
  1991年   5628篇
  1990年   5375篇
  1989年   5331篇
  1988年   5396篇
  1987年   5293篇
  1986年   5014篇
  1985年   6642篇
  1984年   6838篇
  1983年   5418篇
  1982年   5693篇
  1981年   5655篇
  1980年   5363篇
  1979年   5796篇
  1978年   5864篇
  1977年   5907篇
  1976年   5792篇
  1975年   5286篇
  1974年   5307篇
  1973年   5295篇
  1972年   3708篇
  1968年   3146篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
121.
The behavior of real disperse systems with organic impurities was examined under conditions of destabilization by inorganic coagulants. A number of physicochemical methods of analysis and a simulation method were used to identify the character and type of the complexes formed and to calculate their stability constants.  相似文献   
122.
C Dufour  K Dumesnil  P H Mangin 《Pramana》2006,67(1):173-190
Rare earths exhibit complex magnetic phase diagrams resulting from the competition between various contributions to the magnetic energy: exchange, anisotropy and magnetostriction. The epitaxy of a rare-earth film on a substrate induces (i) a clamping to the substrate and (ii) pseudomorphic strains. Both these effects are shown to lead to modifications of the magnetic properties in (0 0 1)Dy, (0 0 1)Tb and (1 1 0)Eu films. In Dy and Tb films, spectacular variations of the Curie temperature have been evidenced. Additionally, Tb films exhibit a new large wavelength magnetic modulation. In Eu films, one of the helical magnetic domains disappears at low temperature whereas the propagation vectors of the other helices are tilted. The link between structural and magnetic properties is underlined via magnetoelastic models. Moreover, molecular beam epitaxy permits the growth of Sm in a metastable dhcp phase. The magnetic structure of dhcp Sm has been elucidated for the first time. In this review, neutron scattering is shown to be a powerful technique to reveal the magnetic structures of rare-earth films.  相似文献   
123.
A standard model Lagrangian is constructed making the pseudo-Finsleroid generalization of the Yang-Mills field equation by the conformal method. The Higgs field potential is suggested that ensures generation of particle masses caused by the spontaneous symmetry breaking. After transition to the conformal coordinates, the expressions obtained assume the standard form that in many cases allows the results of pseudo-Euclidean theory to be used in calculations of the Feynman diagrams. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 44–51, April, 2006.  相似文献   
124.
A method for suppressing self-modulation in backward-wave tubes is proposed. Additional delay is introduced into the feedback circuit, owing to which the output signal amplitude affects the electron beam current that enters into the interaction space. Numerical simulations demonstrate that the operating current in the single-frequency oscillation mode may be increased roughly twofold.  相似文献   
125.
Ascidia malaca gametes before fertilization incubated in 10?5 or 10?7 M solutions of tributyltin(IV) chloride, TBTCl, for 3 h appear highly damaged under transmission electron microscopy observation. Also, the fertilization process is affected by the compound: the damaged spermatozoa are present in the vitelline coat and the egg does not cleave. An increase of microbodies, structurally similar to peroxisomes, have been detected in the egg peripheral cytoplasm, probably in relation to their role in alleviating damage to some cellular components. The results have shown that the reproduction of ascidians under unfavourable environmental conditions is prevented. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   
126.
127.
128.
129.
130.
Optics and Spectroscopy - The fluorescence of the nematic liquid crystal n-butyl-n′-methoxyazoxybenzene (BMAOB) in the form of a layer and in porous glasses with pores of different diameter...  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