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   590851篇
  免费   6931篇
  国内免费   1811篇
化学   318499篇
晶体学   8644篇
力学   25402篇
综合类   19篇
数学   70941篇
物理学   176088篇
  2021年   4935篇
  2020年   5551篇
  2019年   6039篇
  2018年   7937篇
  2017年   7768篇
  2016年   11574篇
  2015年   7232篇
  2014年   11139篇
  2013年   26839篇
  2012年   20450篇
  2011年   25140篇
  2010年   17788篇
  2009年   17473篇
  2008年   23238篇
  2007年   23267篇
  2006年   21655篇
  2005年   19527篇
  2004年   17854篇
  2003年   15819篇
  2002年   15637篇
  2001年   17172篇
  2000年   13297篇
  1999年   10292篇
  1998年   8652篇
  1997年   8447篇
  1996年   8170篇
  1995年   7171篇
  1994年   7162篇
  1993年   7062篇
  1992年   7729篇
  1991年   7854篇
  1990年   7458篇
  1989年   7280篇
  1988年   7315篇
  1987年   7153篇
  1986年   6788篇
  1985年   8844篇
  1984年   9098篇
  1983年   7224篇
  1982年   7531篇
  1981年   7392篇
  1980年   6895篇
  1979年   7440篇
  1978年   7720篇
  1977年   7561篇
  1976年   7503篇
  1975年   6992篇
  1974年   6969篇
  1973年   7070篇
  1972年   4908篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
The integral characteristics of magnetization switching in amorphous gadolinium-cobalt films with perpendicular anisotropy are studied by visualizing the domain structure and measuring magnetooptic hysteresis loops. The films have a radial gradient of magnetic properties that is due to a spatially nonuniform thermal field. Magnetization switching in those film areas where the domain wall motion depends only on the coercive force is simulated in simple terms. In a first approximation, local events of magnetization switching are shown to take place independently of each other and the net hysteresis loop can be represented as a sum of the local loops.  相似文献   
962.
An analytical expression for the concentration profile of a low-soluble diffusant in a sample is derived for a high-capacity diffusion source. The model is checked by determining the diffusion coefficient of yttrium in beryllium.  相似文献   
963.
The establishment of the steady-state dopant profile in a medium with a time-variable diffusion coefficient is considered within the approach proposed previously for estimating mass-and heat-transfer time characteristics. It is shown that the time it takes for the equilibrium concentration to set in may be increased or decreased by appropriately choosing the law of variation of the diffusion coefficient.  相似文献   
964.
Technical Physics - An analytical expression for the generatrix of the shape of a nonlinearly vibrating charged drop of a perfect incompressible conducting fluid immersed in an ideal incompressible...  相似文献   
965.
A theory of a planar disk-shaped RF plasma source under anomalous skin effect conditions is developed. In the absence of an external magnetic field, such conditions are satisfied for transverse electromagnetic waves with phase velocities below the electron thermal velocity, and, in the presence of this field, they are satisfied for electron cyclotron waves with frequencies corresponding to the resonant absorption line. For each of these cases, the RF field power deposited in a plasma with given parameters is determined and the equivalent plasma resistance is calculated.  相似文献   
966.
The mass spectrum of a coupled state is analytically determined. The mechanism of production of a constituent mass of particles forming a coupled state is explained. The change of the coupled state and constituent particle component masses attendant to changes of the coupling constant is analyzed. The mass spectrum of a two-gluon glueball is determined with allowance for spin-orbital and spin-spin interactions.__________Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 33–41, December, 2004.  相似文献   
967.
968.
969.
970.
Sensitivity-enhanced 2D IPAP experiments using the accordion principle for measuring one-bond 13C'-13Calpha and 1Halpha-13Calpha dipolar couplings in proteins are presented. The resolution of the resulting spectra is identical to that of the decoupled HSQC spectra and the sensitivity of the corresponding 1D acquisitions are only slightly lower than those obtained with 3D HNCO and 3D HN(COCA)HA pulse sequences due to an additional delay 2Delta. For cases of limited resolution in the 2D 15N-1HN HSQC spectrum the current pulse sequences can easily be modified into 3D versions by introducing a poorly digitized third dimension, if so desired. The experiments described here are a valuable addition to the suites available for determination of residual dipolar couplings in biological systems.  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