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   44835篇
  免费   6609篇
  国内免费   5110篇
化学   32443篇
晶体学   530篇
力学   2397篇
综合类   336篇
数学   5315篇
物理学   15533篇
  2024年   85篇
  2023年   804篇
  2022年   869篇
  2021年   1343篇
  2020年   1590篇
  2019年   1578篇
  2018年   1382篇
  2017年   1296篇
  2016年   1914篇
  2015年   1909篇
  2014年   2273篇
  2013年   3080篇
  2012年   3774篇
  2011年   3920篇
  2010年   2759篇
  2009年   2646篇
  2008年   2977篇
  2007年   2732篇
  2006年   2484篇
  2005年   2209篇
  2004年   1692篇
  2003年   1393篇
  2002年   1373篇
  2001年   1119篇
  2000年   964篇
  1999年   994篇
  1998年   842篇
  1997年   767篇
  1996年   777篇
  1995年   654篇
  1994年   587篇
  1993年   535篇
  1992年   467篇
  1991年   406篇
  1990年   376篇
  1989年   295篇
  1988年   239篇
  1987年   180篇
  1986年   199篇
  1985年   211篇
  1984年   128篇
  1983年   93篇
  1982年   101篇
  1981年   72篇
  1980年   62篇
  1979年   60篇
  1978年   40篇
  1976年   37篇
  1974年   40篇
  1973年   46篇
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
991.
992.
993.
The dilepton spectra from open charm decay inp+A reactions at $\sqrt s = 200$ AGeV are proposed to constrain gluon shadowing in nuclei. We show that the required measurements are feasible at RHIC.  相似文献   
994.
Velocity distributions and production cross sections of evaporation residues have been measured in the reaction20Ne+208Pb at projectile energies of 8.6, 11.4, 14.9 A.MeV. Essential deviations from statistical model of deexcitation have been observed. Monte Carlo simulations involving emission of non-equilibrium particles have been used in order to reproduce experimental velocity, charge and mass distributions of evaporation residues and to estimate indirectly multiplicities of pre-equilibrium particles. Communicated by V. Metag  相似文献   
995.
996.
We derive the exact Bahadur slopes of studentized score tests for a simple null hypothesis in a one-parameter family of distributions. The Student's t-test is included as a special case for which a recent result of Rukhin (1993, Sankhy Ser. A, 55, 159–163) was improved upon. It is shown that locally optimal Bahadur efficiency for one-sample location models with a known or estimated scale parameter is attained within the class of studentized score tests. The studentized test has an asymptotic null distribution free of the scale parameter, and the optimality of likelihood scores does not depend on the existence of a moment generating function. We also consider the influence function and breakdown point of such tests as part of our robustness investigation. The influence of any studentized score test is bounded from above, indicating certain degree of robustness of validity, but a bounded score function is needed to cap the influence from below and to ensure a high power breakdown point. We find that the standard Huber-type score tests are not only locally minimax in Bahadur efficiency, but also very competitive in global efficiency at a variety of location models.  相似文献   
997.
Exact solutions for Belousov-Zhabotinskii reaction-diffusion system   总被引:1,自引:0,他引:1  
Abstract. We consider the following simplified model for the Belousou-Zhabotinskii(B-Z)reaction:  相似文献   
998.
Denote bymi(G) the number of maximal independent sets ofG. This paper studies the setS(k) of all graphsG withmi(G) = k and without isolated vertices (exceptG K 1) or duplicated vertices. We determineS(1), S(2), andS(3) and prove that |V(G)| 2 k–1 +k – 2 for anyG inS(k) andk 2; consequently,S(k) is finite for anyk. Supported in part by the National Science Council under grant NSC 83-0208-M009-050  相似文献   
999.
Let be a bounded smooth domain in , and a function with compact support in . Moser's inequality states that there is a constant , depending only on the dimension , such that

where is the Lebesgue measure of , and the surface area of the unit ball in . We prove in this paper that there are extremal functions for this inequality. In other words, we show that the

is attained. Earlier results include Carleson-Chang (1986, is a ball in any dimension) and Flucher (1992, is any domain in 2-dimensions).

  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