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   372721篇
  免费   3088篇
  国内免费   902篇
化学   197554篇
晶体学   6365篇
力学   17301篇
综合类   19篇
数学   39459篇
物理学   116013篇
  2021年   3094篇
  2020年   3385篇
  2019年   4092篇
  2018年   5348篇
  2017年   5427篇
  2016年   7562篇
  2015年   4161篇
  2014年   7215篇
  2013年   16369篇
  2012年   12314篇
  2011年   14763篇
  2010年   11126篇
  2009年   11264篇
  2008年   13518篇
  2007年   13432篇
  2006年   12231篇
  2005年   10904篇
  2004年   10189篇
  2003年   9374篇
  2002年   9205篇
  2001年   10686篇
  2000年   8056篇
  1999年   6125篇
  1998年   5051篇
  1997年   5076篇
  1996年   4756篇
  1995年   4310篇
  1994年   4331篇
  1993年   4076篇
  1992年   4943篇
  1991年   4939篇
  1990年   4822篇
  1989年   4861篇
  1988年   4822篇
  1987年   4830篇
  1986年   4530篇
  1985年   5819篇
  1984年   5921篇
  1983年   4786篇
  1982年   4899篇
  1981年   4911篇
  1980年   4502篇
  1979年   5149篇
  1978年   5133篇
  1977年   5375篇
  1976年   5238篇
  1975年   4820篇
  1974年   4721篇
  1973年   4781篇
  1972年   3502篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
72.
73.
Specific features of the initiated oxidation of polyethylene and its low-molecular-weight analogue tridecane, associated with the occurrence of the process in the short-chain mode, were studied.  相似文献   
74.
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   
75.
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   
76.
The luminescence and scintillation properties of poly(methyl methacrylate) containing 1,1,3-trimethyl-3-phenylindan were studied.  相似文献   
77.
78.
79.
The structural change in the depth direction of a polyimide (UPILEX‐S) film treated in alkaline solution, which was a representative surface treatment used to form a seed layer for plating and to improve the adhesive strength, was analyzed by means of micro Fourier transform infrared attenuated total reflection (FTIR‐ATR) line analysis with gradient shaving preparation. The polyimide film was treated with KOH. The imide ring opened through the alkaline treatment, and the amide structure and carboxylic acid salt were formed. The attainment depth of this structural change was almost proportional to the treatment time, and it reached about 8 μm after a 30‐min treatment. The degree of structural change through the alkaline treatment was almost constant after it reached a considerably degraded stage, and the chemically changed region penetrated into the inner part of the film from the surface. An intermediate layer before the final degraded stage appeared in the treated layer, and its thickness increased with the treatment time. The region that was changed chemically by the alkaline treatment progressed to the inner part simultaneously and continuously as the treatment time increased. The combined use of gradient shaving preparation and micro FTIR‐ATR line analysis was found to be extremely effective for the depth profiling of organic materials. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2071–2078, 2003  相似文献   
80.
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