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   1195篇
  免费   56篇
  国内免费   103篇
化学   87篇
力学   16篇
综合类   24篇
数学   1092篇
物理学   135篇
  2024年   1篇
  2023年   11篇
  2022年   19篇
  2021年   14篇
  2020年   30篇
  2019年   22篇
  2018年   21篇
  2017年   25篇
  2016年   32篇
  2015年   13篇
  2014年   49篇
  2013年   121篇
  2012年   30篇
  2011年   60篇
  2010年   42篇
  2009年   77篇
  2008年   89篇
  2007年   94篇
  2006年   74篇
  2005年   56篇
  2004年   57篇
  2003年   45篇
  2002年   54篇
  2001年   41篇
  2000年   38篇
  1999年   38篇
  1998年   41篇
  1997年   25篇
  1996年   20篇
  1995年   13篇
  1994年   15篇
  1993年   12篇
  1992年   10篇
  1991年   6篇
  1990年   9篇
  1989年   3篇
  1988年   3篇
  1987年   2篇
  1985年   3篇
  1984年   9篇
  1983年   5篇
  1982年   3篇
  1981年   2篇
  1980年   2篇
  1979年   6篇
  1978年   4篇
  1977年   4篇
  1971年   1篇
  1970年   2篇
  1959年   1篇
排序方式: 共有1354条查询结果,搜索用时 15 毫秒
41.
关于两两NQD列的若干极限性质   总被引:32,自引:0,他引:32  
本文讨论了两两NQD列的Marcinkiewicz型弱大数律及Jamison型加权和的强稳定性,指出了两两NQD列与独立列的一个本质性区别,从而提出了解决两两NQD旬几乎处处收敛和完全收敛的一种方式。  相似文献   
42.
43.
The partial order on monomials that corresponds to domination when evaluated at positive Newton sequences is fully understood. Here we take up the corresponding partial order on linear combinations of monomials. In part using analysis based upon the cone structure of the exponents in p-Newton sequences, an array of conditions is given for this new partial order. It appears that a characterization in general will be difficult. Within the case in which all coefficients are 1, the situation in which, for general sequence length, there are two monomials, each of length two and nonnegative integer exponents, the partial order is fully characterized. The characterization is combinatorial, in terms of indices in the monomials, and, already here there is much more than term-wise domination.  相似文献   
44.
We consider β-expansions of formal Laurent series over finite fields. If the base β is a Pisot or Salem series, we prove that the β-expansion of a Laurent series α is automatic if and only if α is algebraic.  相似文献   
45.
In the present work, we deal with the quadratic decomposition of symmetric semi-classical polynomial sequences of even class. An example from class 2 is settled. We give an integral representation of the considered symmetric form.  相似文献   
46.
47.
兰冲锋  吴群英 《数学杂志》2015,35(3):665-671
本文研究了扩展负相依(END)样本最近邻密度估计的强相合性问题.利用END序列的Bernstein型不等式和截尾的方法,获得了END样本最近邻密度估计的强相合速度,推广了NA样本和ND样本最近邻密度估计的相应结果.  相似文献   
48.
Quinoline based aromatic amide foldamers are known to adopt stable folded conformations. We have developed a synthetic approach to produce similar oligomers where all amide bonds, or part of them, have been replaced by an isosteric vinylene group. The results of solution and solid state structural studies show that oligomers exclusively containing vinylene linkages are not well folded, and adopt predominantly flat conformations. In contrast, a vinylene segment flanked by helical oligoamides also folds in a helix, albeit with a slightly lower curvature. The presence of vinylene functions also result in an extension of π-conjugation across the oligomer that may change charge transport properties. Altogether, these results pave the way to foldamers in which both structural control and specific electronic properties may be engineered.  相似文献   
49.
This paper presents the theoretical analysis of adaptive multiuser RAKE receiver scheme in frequency selective fading channel for direct-sequence code division multiple access (DS-CDMA) system. Least mean square (LMS) algorithm is used to estimate the channel coefficients. Chaotic sequences are used as spreading sequence and corresponding bit error rate (BER) in closed form is derived for imperfect channel estimation conditions. Performances of chaotic sequences are compared with pseudorandom noise (PN) sequences. Under perfect synchronization assumption, various simulation results are shown to investigate the performance of the proposed system.  相似文献   
50.
Let X n1 * , ... X nn * be a sequence of n independent random variables which have a geometric distribution with the parameter p n = 1/n, and M n * = \max\{X n1 * , ... X nn * }. Let Z 1, Z2, Z3, ... be a sequence of independent random variables with the uniform distribution over the set N n = {1, 2, ... n}. For each j N n let us denote X nj = min{k : Zk = j}, M n = max{Xn1, ... Xnn}, and let S n be the 2nd largest among X n1, Xn2, ... Xnn. Using the methodology of verifying D(un) and D'(un) mixing conditions we prove herein that the maximum M n has the same type I limiting distribution as the maximum M n * and estimate the rate of convergence. The limiting bivariate distribution of (Sn, Mn) is also obtained. Let n, n Nn, , and T n = min{M(An), M(Bn)}. We determine herein the limiting distribution of random variable T n in the case n , n/n > 0, as n .  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