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   16033篇
  免费   421篇
  国内免费   330篇
化学   10014篇
晶体学   104篇
力学   497篇
综合类   30篇
数学   2097篇
物理学   4042篇
  2022年   186篇
  2021年   221篇
  2020年   185篇
  2019年   188篇
  2018年   191篇
  2017年   155篇
  2016年   356篇
  2015年   328篇
  2014年   401篇
  2013年   833篇
  2012年   699篇
  2011年   799篇
  2010年   570篇
  2009年   548篇
  2008年   735篇
  2007年   780篇
  2006年   633篇
  2005年   651篇
  2004年   636篇
  2003年   643篇
  2002年   675篇
  2001年   457篇
  2000年   419篇
  1999年   322篇
  1998年   239篇
  1997年   212篇
  1996年   244篇
  1995年   251篇
  1994年   244篇
  1993年   191篇
  1992年   178篇
  1991年   187篇
  1990年   199篇
  1989年   160篇
  1988年   144篇
  1987年   146篇
  1986年   130篇
  1985年   227篇
  1984年   249篇
  1983年   171篇
  1982年   199篇
  1981年   164篇
  1980年   155篇
  1979年   152篇
  1978年   125篇
  1977年   174篇
  1976年   152篇
  1975年   126篇
  1974年   119篇
  1973年   117篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
32.
Reduction of the representation of infrared spectra from coal samples by osculating polynomials of degree nine is discussed. The reduced representation contains polynomial coefficients of order zero to four. Mathematical models of the original spectra are obtained by linear combination of the coefficients. These compressed models are statistically correlated to coal properties, namely, volatile matter, fixed carbon, ash content, heating value, hydrogen, carbon, sulphur, nitrogen, and maximum vitrinite reflectance, and the results are compared with those previously obtained from second derivatives of the same spectra. The use of compressed data, while giving slightly better correlations for some of the properties, has the advantage of requiring less computational time.  相似文献   
33.
A diagnostic study q (energy transfer processes in a He-N2 flowing discharge and afterglow has been performed in a radiofrequency-produced plasma cooled in a liquid nitrogen hath. Optical emission spectroscopy in the visible and infrared spectral range as well as Langrnuir probe diagnostics were used. The vibrational kinetics of CO injected in such an afterglow has been examined. It shows a slow cooling of the electrons in the afterglow regime. The electron kinetics responsible joy CO vibrahonal excitation is turned off when N2 is added to the He discharge, while that for vibrationally excited N2 molecules is turned on. The results are discussed on the basis of previous theorerical calculations and experiments on the He-N2 system.  相似文献   
34.
35.
Dopo aver dato una definizione di parte convessa di un gruppo topologico, si stabilisce una condizione affinchè il condominio di una misura sia convesso.  相似文献   
36.
37.
We demonstrate the surprising integrability of the classical Hamiltonian associated to a spin 1/2 system under periodic external fields. The one-qubit rotations generated by the dynamical evolution is, on the one hand, close to that of the rotating wave approximation (RWA), on the other hand to two different “average” systems, according to whether a certain parameter is small or large. Of particular independent interest is the fact that both the RWA and the averaging theorem are seen to hold well beyond their expected region of validity. Finally, we determine conditions for the realization of the quantum NOT operation by means of classical stroboscopic maps.  相似文献   
38.
文章讨论无界区域上GBBM方程的Cauchy问题,对方程的解进行了先验估计,并证明了在H1弱拓扑中整体吸引子的存在性.  相似文献   
39.
40.
Brouwer and Wilbrink [3] showed the nonexistence of regular near octagons whose parameters s, t2, t3 and t satisfy s ≥ 2, t2 ≥ 2 and t3t2(t2+1). Later an arithmetical error was discovered in the proof. Because of this error, the existence problem was still open for the near octagons corresponding with certain values of s, t2 and t3. In the present paper, we will also show the nonexistence of these remaining regular near octagons. MSC2000 05B25, 05E30, 51E12 Postdoctoral Fellow of the Research Foundation - Flanders  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