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   7050篇
  免费   184篇
  国内免费   30篇
化学   3292篇
晶体学   134篇
力学   262篇
数学   822篇
物理学   1687篇
无线电   1067篇
  2022年   109篇
  2021年   143篇
  2020年   144篇
  2019年   159篇
  2018年   143篇
  2017年   125篇
  2016年   198篇
  2015年   156篇
  2014年   213篇
  2013年   478篇
  2012年   345篇
  2011年   358篇
  2010年   240篇
  2009年   226篇
  2008年   282篇
  2007年   309篇
  2006年   259篇
  2005年   247篇
  2004年   194篇
  2003年   150篇
  2002年   153篇
  2001年   85篇
  2000年   83篇
  1999年   78篇
  1998年   68篇
  1997年   58篇
  1996年   67篇
  1995年   63篇
  1994年   78篇
  1993年   89篇
  1992年   86篇
  1991年   64篇
  1990年   77篇
  1989年   64篇
  1988年   77篇
  1987年   70篇
  1986年   51篇
  1985年   125篇
  1984年   133篇
  1983年   87篇
  1982年   81篇
  1981年   82篇
  1980年   82篇
  1979年   88篇
  1978年   81篇
  1977年   85篇
  1976年   70篇
  1975年   54篇
  1974年   61篇
  1973年   85篇
排序方式: 共有7264条查询结果,搜索用时 46 毫秒
941.
942.
G P Gupta  K C Mathur 《Pramana》1981,17(1):81-91
The rotational excitation of the H2 and N2 molecules from (J→J+2,J=0) and (J→J+2,J=1) states by electron impact is studied, in the framework of the regional-plane-wave approximation. The empirical cut-off parameterρ, involved in these calculations, is varied to give the best fit to the experimental data of Srivastava and co-workers.  相似文献   
943.
High resolution gamma-ray spectra have been measured from the27Al (p,γ)28Si reaction for the resonances atE p=2·482, 2·511 and 2·735 MeV at ϑ pγ=0°, 30°, 55° and 90° using a Ge (Li) gamma spectrometer. From the spectra and the angular distributions the properties of the resonance states have been obtained. These states are the isobaric analogues of the levels at 4·69, 4·75 and 4·93MeV levels respectively in the parent nucleus A28l.  相似文献   
944.
This paper investigates the mathematical model of a system composed of (m + 1) non-identical units—one functioning and m standbys. Each unit of the system has four possible states—normal, partial failure, total failure and repair facility—the last one meaning that the totally failed unit is being attended to at the repair facility where it might be either repaired or eventually rejected and replaced. The normal and partial failure states are up states while the other two are down states. The system breaks down when the (m + 1)th unit after total failure is finally rejected and no standby remains to replace it. Several reliability characteristics of interest to system designers as well as operations managers have been computed. Results obtained earlier are verified as particular cases.  相似文献   
945.
This paper deals with the study of some irreversible processes like slow heating of a thermodynamic system or of inhomogeneity, i.e. spatially local equilibrium in it, based on the principle of maximum entropy estimation, in a stochastic model.  相似文献   
946.
The present paper describes the polarographic behaviour of Mn(II) in various supporting electrolytes in aqueous and aqueous-alcoholic mixtures. The reduction has been found to be a quasi reversible one. The values of α,E 3 2/r , andk s have been calculated by the method developed byMatsuda andAyabe 4.  相似文献   
947.
In photographic emulsions, grains have been reported to be clustered. A model for the observed optical density in the presence of grain clustering has been developed.  相似文献   
948.
949.
The effect of jammer power on the performance of adaptive arrays is studied. It is shown that the output signal-to-interference-plus-noise ratio (SINR) of an adaptive array is a function of jammer power. In the presence of a wide-band jammer, the output SINR of the array decreases with an increase in jammer power and eventually goes to zero. Unlike continuous wave (CW) jammers, a wide-band jammer does not go through power inversion. Instead, as the jammer power is increased, the interference-to-noise ratio (INR) at the array output shows oscillations. For large jammer power, the output INR increases with an increase in jammer power.  相似文献   
950.
A band structure study reveals that in contrast to the pure rare earth metal, the Fermi level of the dihydride falls near the bottom of the 5d band, in a region of low density of states; consequences on Fermi surface geometry, magnetic properties and resistivity are suggested. Below the metal d states lie two overlapping metal-hydrogen bands, in agreement with Weaver's photoemission data and Switendick's result on YH2.  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