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   204796篇
  免费   2030篇
  国内免费   502篇
化学   112234篇
晶体学   3668篇
力学   8037篇
综合类   11篇
数学   19383篇
物理学   63995篇
  2020年   1799篇
  2019年   1997篇
  2018年   2295篇
  2017年   2403篇
  2016年   3607篇
  2015年   2250篇
  2014年   3641篇
  2013年   9238篇
  2012年   6670篇
  2011年   8226篇
  2010年   5819篇
  2009年   5755篇
  2008年   7321篇
  2007年   7200篇
  2006年   6814篇
  2005年   6142篇
  2004年   5593篇
  2003年   5152篇
  2002年   4913篇
  2001年   6175篇
  2000年   4660篇
  1999年   3544篇
  1998年   2766篇
  1997年   2711篇
  1996年   2617篇
  1995年   2460篇
  1994年   2354篇
  1993年   2192篇
  1992年   2848篇
  1991年   2750篇
  1990年   2679篇
  1989年   2704篇
  1988年   2728篇
  1987年   2735篇
  1986年   2604篇
  1985年   3316篇
  1984年   3327篇
  1983年   2608篇
  1982年   2718篇
  1981年   2778篇
  1980年   2548篇
  1979年   2890篇
  1978年   2867篇
  1977年   2988篇
  1976年   2822篇
  1975年   2564篇
  1974年   2513篇
  1973年   2473篇
  1972年   1706篇
  1968年   1704篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Flowing and static gas-phase samples of HNO3 in O2 and N2 were analyzed by long-path ultraviolet/visible (UV/VIS) spectroscopy to reveal the presence of both NO2 and NO3, the concentrations of which were calculated using differential absorption cross sections. NO2 is produced predominantly by the heterogeneous decomposition of HNO3, whereas NO3 is generated in the gas phase by the thermal decomposition of N2O5, a product of the self-disproportionation of liquid HNO3. © 1993 John Wiley & Sons, Inc.  相似文献   
42.
43.
44.
To describe the long time asymptotic behaviour of weakly nonlinear plasma waves propagating in a strongly magnetized plasmafilled cylindrical waveguide the usual KDV equation which is first order in wave amplitude is extended to second order including the effects of finite temperature, mobile ions and giving a proper treatment to the radial co-ordinate for all possible modes of propagation. The second-order effects on the first-order solitary wave profile, phase speed and first order correction to the wavelength are all determined and discussed.  相似文献   
45.
The statistical characteristics of conditional time before ruin of an insurance company, including the distribution function of conditional time and its moments are examined.  相似文献   
46.
47.
In recent years there has emerged significant interest in low pressure radio frequency (rf) glow discharges which are used widely particulary in IC fabrication. Various parameters of the rf glow discharge have been found to be useful for its electrical characterization; however, there is no uniformity and agreement. Extensive experimental investigations on various discharge systems have shown, that the self-bias on the rf driven electrode, the complex conductivity and the breakdown characteristic are preferable parameters of rf discharges. Advantageously the self-bias and the complex conductivity should be presented in dependence on the pressure and the applied rf voltage. The discharge current cannot be measured quite accurately due to currents via leaky capacitors and the deviations from a sinusoidal form of the current due to nonlinearities.  相似文献   
48.
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   
49.
50.
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