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   214384篇
  免费   1903篇
  国内免费   685篇
化学   109329篇
晶体学   3530篇
力学   9519篇
综合类   6篇
数学   24351篇
物理学   70237篇
  2021年   1748篇
  2020年   1903篇
  2019年   2101篇
  2018年   2783篇
  2017年   2687篇
  2016年   3957篇
  2015年   2461篇
  2014年   3787篇
  2013年   9583篇
  2012年   7696篇
  2011年   9254篇
  2010年   6309篇
  2009年   6152篇
  2008年   8416篇
  2007年   8605篇
  2006年   8216篇
  2005年   7362篇
  2004年   6847篇
  2003年   5990篇
  2002年   5889篇
  2001年   6527篇
  2000年   5045篇
  1999年   3907篇
  1998年   3148篇
  1997年   3183篇
  1996年   2963篇
  1995年   2726篇
  1994年   2567篇
  1993年   2448篇
  1992年   2805篇
  1991年   2769篇
  1990年   2720篇
  1989年   2489篇
  1988年   2553篇
  1987年   2531篇
  1986年   2374篇
  1985年   3121篇
  1984年   3392篇
  1983年   2761篇
  1982年   3011篇
  1981年   2952篇
  1980年   2792篇
  1979年   2872篇
  1978年   2960篇
  1977年   2945篇
  1976年   3023篇
  1975年   2787篇
  1974年   2781篇
  1973年   2897篇
  1972年   1837篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
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   
62.
Disordered Sr2FeMoO6 shows a drastic reduction in saturation magnetization compared to highly ordered samples, moreover magnetization as a function of the temperature for different disordered samples shows qualitatively different behaviours. We investigate the origin of such diversity by performing spatially resolved photoemission spectroscopy on various disordered samples. Our results establish that extensive electronic inhomogeneity, arising most probably from an underlying chemical inhomogeneity in disordered samples, is responsible for the observed magnetic inhomogeneity. It is further pointed out that these inhomogeneities are connected with composition fluctuations of the type Sr2Fe1+x Mo1-x O6 with Fe-rich (x > 0) and Mo-rich (x < 0) regions. Dedicated to Prof J Gopalakrishnan on his 62nd birthday.  相似文献   
63.
64.
An interconnection strategy with built-in adaptive controllersis presented which achieves synchronization of scalar linearsystems: the closed-loop network forces all outputs to followthe same signal asymptotically while maintaining the open-loopcharacteristics. In the design of the output feedback controllers,no knowledge of system parameters is assumed, but each systemmust have the same poles and be high-gain-stable. The proofof the main theorem relies critically on derived systems-theoreticresults and the special system topology as a network of interconnectedsystems. The topology is explained by first solving the simplerproblem of signal synchronization.  相似文献   
65.
A formulation of an implicit characteristic-flux-averaging method for the unsteady Euler equations with real gas effects is presented. Incorporation of a real gas into a general equation of state is achieved by considering the pressure as a function of density and specific internal energy. The Ricmann solver as well as the flux-split algorithm are modified by introducing the pressure derivatives with respect to density and internal energy. Expressions for calculating the values of the flow variables for a real gas at the cell faces are derived. The Jacobian matrices and the eigenvectors are defined for a general equation of state. The solution of the system of equations is obtained by using a mesh-sequencing method for acceleration of the convergence. Finally, a test case for a simple form of equation of state displays the differences from the corresponding solution for an ideal gas.  相似文献   
66.
67.
68.
New polyimidates were prepared from bisphenols and mono- and dicarboxylic acid imidoyl chlorides. The structures of the polymers were determined, and their physicochemical, chemical, and thermal properties were studied. The possibility of preparing film and compression materials with good mechanical characteristics from these polymers was examined.  相似文献   
69.
Monomial ideals     
In this paper, we study the numeric characteristics (the Hilbert function and graded Betti numbers) of monomial ideals in the polynomial ring and in the exterior algebra. __________ Translated from Sovremennaya Matematika i Ee Prilozheniya (Contemporary Mathematics and Its Applications), Vol. 30, Algebra, 2005.  相似文献   
70.
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