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   20621篇
  免费   2249篇
  国内免费   2056篇
化学   2279篇
晶体学   30篇
力学   1801篇
综合类   512篇
数学   14074篇
物理学   6230篇
  2024年   25篇
  2023年   168篇
  2022年   320篇
  2021年   349篇
  2020年   421篇
  2019年   430篇
  2018年   452篇
  2017年   592篇
  2016年   664篇
  2015年   511篇
  2014年   1041篇
  2013年   1354篇
  2012年   1060篇
  2011年   1280篇
  2010年   1148篇
  2009年   1425篇
  2008年   1396篇
  2007年   1484篇
  2006年   1335篇
  2005年   1244篇
  2004年   1025篇
  2003年   944篇
  2002年   799篇
  2001年   737篇
  2000年   684篇
  1999年   587篇
  1998年   535篇
  1997年   488篇
  1996年   357篇
  1995年   295篇
  1994年   242篇
  1993年   181篇
  1992年   158篇
  1991年   134篇
  1990年   141篇
  1989年   95篇
  1988年   93篇
  1987年   78篇
  1986年   69篇
  1985年   85篇
  1984年   69篇
  1983年   50篇
  1982年   70篇
  1981年   62篇
  1980年   40篇
  1979年   35篇
  1978年   31篇
  1977年   28篇
  1976年   31篇
  1973年   24篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
131.
Abnormalities in the cochlear function usually cause broadening of the auditory filters which reduces the speech intelligibility. An attempt to apply a spectral enhancement algorithm has been undertaken to improve the identification of Polish vowels by subjects with cochlear-based hearing-impairment. The identification scores of natural (unprocessed) vowels and spectrally enhanced (processed) vowels has been measured for hearing-impaired subjects. It has been found that spectral enhancement improves vowel scores by about 10% for those subjects, however, a wide variation in individual performance among subjects has been observed. The overall vowels identification scores obtained were 85% for natural vowels and 96% for spectrally enhanced vowels.  相似文献   
132.
A horizontal translation of a function is the focus of this study. We examine the explanations provided by secondary school students and secondary school teachers to a translation of a function, focusing on the example of the parabola y=(x−3)2 and its relationship to y=x2. The participants’ explanations focused on attending to patterns, locating the zero of the function, and the point-wise calculation of function values. The results confirm that the horizontal shift of the parabola is, at least initially, inconsistent with expectations and counterintuitive to most participants. We articulate possible sources of this perceived inconsistency and describe a pedagogical approach aimed at resolving it.  相似文献   
133.
In this paper, based on the Lame function and Jacobi elliptic function, the perturbation method is appliedto some nonlinear evolution equations to derive their multi-order solutions.  相似文献   
134.
设{Xni:1≤i≤n,n≥1}为行间独立的B值r.v.阵列,g(z)是指数为1/p的正则变化函数,r>0,{ani 1≤t≤n,n≥1}为实数阵列,本文得到了使(?)成立的条件,推广并改进了Stout及Sung等的著名结论.  相似文献   
135.
Janssen  K. 《Potential Analysis》2003,19(3):289-299
We show that functions which are invariant for suitable product semigroups (one of which is a quasi-Poisson semigroup on a general state space) decompose into a singular eigen-function and a mixture of products of minimal eigen-functions.  相似文献   
136.
Let Um be an m×m Haar unitary matrix and U[m,n] be its n×n truncation. In this paper the large deviation is proven for the empirical eigenvalue density of U[m,n] as m/nλ and n→∞. The rate function and the limit distribution are given explicitly. U[m,n] is the random matrix model of quq, where u is a Haar unitary in a finite von Neumann algebra, q is a certain projection and they are free. The limit distribution coincides with the Brown measure of the operator quq.  相似文献   
137.
138.
We prove that all invariant distances on the universal Teichmuller space agree and are determined by the Grunsky coefficients of the naturally related conformal maps. This fact yields various important consequences; in particular, we obtain solutions of certain well-known geometric problems in complex analysis and related fields.  相似文献   
139.
140.
More recently, sixteen families of Jacobian elliptic function solutions of mKdV equation have been foundby using our extended Jacobian elliptic function expansion method. In this paper, we continue to improve our methodby using another eight pairs of the closed Jacobian elliptic functions. The mKdV equation is chosen to illustrate theimproved method such that another eight families of new Jacobian elliptic function solutions are obtained again. Thenew method can be more powerful to be applied to other nonlinear differential equations.  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