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   205107篇
  免费   3473篇
  国内免费   447篇
化学   118150篇
晶体学   2386篇
力学   7594篇
综合类   7篇
数学   23761篇
物理学   57129篇
  2022年   1436篇
  2021年   1883篇
  2020年   1998篇
  2019年   2087篇
  2018年   2623篇
  2017年   2470篇
  2016年   4413篇
  2015年   3175篇
  2014年   4060篇
  2013年   9795篇
  2012年   8486篇
  2011年   9941篇
  2010年   6455篇
  2009年   6191篇
  2008年   8850篇
  2007年   8907篇
  2006年   8195篇
  2005年   7514篇
  2004年   6558篇
  2003年   5542篇
  2002年   5395篇
  2001年   5309篇
  2000年   4177篇
  1999年   3227篇
  1998年   2754篇
  1997年   2614篇
  1996年   2579篇
  1995年   2306篇
  1994年   2320篇
  1993年   2173篇
  1992年   2403篇
  1991年   2452篇
  1990年   2229篇
  1989年   2206篇
  1988年   2120篇
  1987年   2004篇
  1986年   1942篇
  1985年   2555篇
  1984年   2671篇
  1983年   2133篇
  1982年   2323篇
  1981年   2219篇
  1980年   2106篇
  1979年   2238篇
  1978年   2395篇
  1977年   2254篇
  1976年   2273篇
  1975年   2179篇
  1974年   2183篇
  1973年   2209篇
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
61.
We present the results of an experimental investigation of a RF splitting of57Fe hyperfine lines in the regime of NMR and Mössbauer double resonance. The experiments have been performed as a function of RF field intensity and static magnetic field magnitude. The intensity of the RF components and the separation between them are extremely sensitive to the frequency and amplitude of the RF magnetic field. The RF splitting of hyperfine lines is inversely proportional to the strength of the static magnetic field.  相似文献   
62.
Surface relief formation at holographic recording on amorphous selenium films was demonstrated and investigated. The presence of this optical phase modulation component is essential for ensuring significant, stable and erasable optical recording in a-Se films at 290–320 K temperatures, where conventional photodarkening was known as insignificant and unstable. Photocrystallization can only be observed in super-exposed a-Se films at the given experimental conditions of hologram recording. Erasing behavior of surface relief gratings under heat treatment was also investigated in order to reveal further details of the mechanism. Photoinduced structural transformations within the amorphous phase, connected to local ordering under the condition of light-induced fluidity, are proposed as an explanation for the relief formation and erasing. The observed reversible optical recording process may be useful for the various optoelectronic applications of photoconductive a-Se layers. Received: 12 June 2000 / Accepted: 6 June 2001 / Published online: 30 August 2001  相似文献   
63.
64.
Physics and Mathematics Division with Computational Center of the Bashkir Branch of the USSR Academy of Sciences. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 80, No. 3, pp. 470–473, September, 1989.  相似文献   
65.
Electrochemical separation of lead-silver alloys into the constituents by thin-layer electrolysis in molten electrolytes, with bismuth as metal separator, is studied. It is proposed to determine the extent of component recovery by potentiometry.  相似文献   
66.
In this paper, a two-dimensional finite volume unstructured mesh method (FVUM) based on a triangular background interpolation mesh is developed for analysing the evolution of the saltwater intrusion into single and multiple coastal aquifer systems. The model formulation consists of a ground-water flow equation and a salt transport equation. These coupled and non-linear partial differential equations are transformed by FVUM into a system of differential/algebraic equations, which is solved using backward differentiation formulas of order one through five. Simulation results are compared with previously published solutions where good agreement is observed.  相似文献   
67.
In this paper a new state called odd-excited binomial state (OEBS) is introduced. It interpolates between the odd number state and the odd-excited coherent state. We discuss some statistical properties, such as the Glauber second-order correlation function and squeezing phenomenon (normal and amplitude-squared squeezing) for this state. The quasiprobability distribution functions (Husimi Q-function and Wigner W-function) are also examined.  相似文献   
68.
The versatile behavior of a trihydrazidophosphoradamantane allowing the synthesis of a variety of neutral, mono- or di-cationic water-soluble molecules of potential interest for biphasic catalysis is reported.  相似文献   
69.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 6, pp. 970–975, June, 1991.  相似文献   
70.
In a twisted nematic liquid crystal cell we report and study the self-transparency effect induced by the creation of an isotropic droplet. A simple theoretical model is presented and good agreement with experimental data is found. In a two beams configuration transistor-like behavior is observed and theoretically discussed.  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