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   299941篇
  免费   2386篇
  国内免费   526篇
化学   143916篇
晶体学   4257篇
力学   14857篇
综合类   11篇
数学   43536篇
物理学   96276篇
  2020年   1804篇
  2019年   1994篇
  2018年   10928篇
  2017年   11788篇
  2016年   7570篇
  2015年   3135篇
  2014年   3798篇
  2013年   9397篇
  2012年   11028篇
  2011年   20556篇
  2010年   12803篇
  2009年   12892篇
  2008年   17681篇
  2007年   21154篇
  2006年   7021篇
  2005年   12877篇
  2004年   8972篇
  2003年   8507篇
  2002年   6320篇
  2001年   6330篇
  2000年   4968篇
  1999年   3586篇
  1998年   2809篇
  1997年   2752篇
  1996年   2790篇
  1995年   2558篇
  1994年   2468篇
  1993年   2288篇
  1992年   2952篇
  1991年   2744篇
  1990年   2710篇
  1989年   2710篇
  1988年   2746篇
  1987年   2747篇
  1986年   2596篇
  1985年   3339篇
  1984年   3359篇
  1983年   2638篇
  1982年   2743篇
  1981年   2808篇
  1980年   2587篇
  1979年   2942篇
  1978年   2950篇
  1977年   2996篇
  1976年   2858篇
  1975年   2591篇
  1974年   2544篇
  1973年   2541篇
  1972年   1721篇
  1968年   1803篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
The construction of non-Abelian affine Toda models is discussed in terms of its underlying Lie algebraic structure. It is shown that a subclass of such non-conformal two-dimensional integrable models naturally leads to the construction of a pair of actions, which share the same spectra and are related by canonical transformations.  相似文献   
994.
Imaging of latent fingerprints using time-resolved (TR) method offers a broader platform to eliminate the unwanted background emission. In this paper, a novel TR imaging technique is demonstrated and implemented, which facilitates the detection of latent fingerprints with nanosecond resolution. Simulated experiments were carried out with two overlapping fingerprints treated with two fluorescent powders having different lifetimes in nanosecond range. The dependence of the fluorescence emission intensity in nanosecond resolution of TR imaging is also revealed.  相似文献   
995.
The theory and experiment of spatially and temporally partially coherent speckle shearing interferometry is reported in this rapid communication for the first time. The general requirements for the surface roughness and coherence area of a diffuse object surface in spatially and temporally partially coherent speckle shearing interferometry are discussed. An experimental verification is presented and the results of theory and experiment are in good agreement.  相似文献   
996.
997.
The IR absorption spectrum of polycrystalline 4-amyloxy-4′-cyanobiphenyl (5OCB) is measured in a KBr pellet over the range 400–4000 cm?1. The structure of the molecule and the frequencies and intensities of the bands in the spectrum are calculated in the approximation of the B3LYP hybrid density functional with the 6-31G(d) and 6-31+G(d) basis sets. With the method of linear scaling of frequencies, 39 bands of the experimental IR spectrum are assigned. On the basis of calculations for related compounds, the vibrations belonging to the substituents and the biphenyl fragment are ascertained. It is shown that the IR absorption spectra of polycrystalline 4-hydroxypropyl-4′-cyanobiphenyl and 5OCB are almost identical and differ by the occurrence of three bands associated with vibrations localized on the oxyamyl radical.  相似文献   
998.
999.
JET (Joint European Torus) is the largest tokamak in the world and the only fusion facility able to operate with Tritium, the fusion fuel, and Beryllium, the ITER first wall material. JET also features the most complete remote handling equipment for invessel maintenance. As a multinational research center, JET provides logistic experience in preparing for operation of the global facility, tokamak ITER.Experiments on JET are focused on ITER-relevant studies, in particular on detailing the operational scenarios (EL My H-modes and advanced regimes), on enhancing the heating systems, on developing diagnostics for burning plasmas etc. Pioneering real-time control techniques have been implemented that maximize performance and minimize internal disturbances of JET plasmas. In helium plasmas, ion cyclotron heating (ICRH) created fast α-particles, mimicking their populations in future burning plasmas. The recent successful Trace Tritium campaign provided important new data on fuel transport. Current enhancements on JET include a new ITER-like ELM-resilient high power ICRH antenna (7 MW) and over twenty new diagnostics that will further extend the JET scientific capabilities and push the facility even closer to the ITER parameters.A special mention is given to the involvement of the fusion experts from Association EURATOM-IPP.CR, who have been actively participating in the collective use of JET facility for more than three years.  相似文献   
1000.
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