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   7314篇
  免费   460篇
  国内免费   859篇
化学   169篇
力学   248篇
综合类   105篇
数学   6695篇
物理学   1416篇
  2024年   11篇
  2023年   67篇
  2022年   82篇
  2021年   125篇
  2020年   137篇
  2019年   204篇
  2018年   206篇
  2017年   225篇
  2016年   200篇
  2015年   154篇
  2014年   259篇
  2013年   1196篇
  2012年   228篇
  2011年   314篇
  2010年   296篇
  2009年   414篇
  2008年   508篇
  2007年   474篇
  2006年   437篇
  2005年   382篇
  2004年   370篇
  2003年   373篇
  2002年   355篇
  2001年   248篇
  2000年   267篇
  1999年   198篇
  1998年   209篇
  1997年   213篇
  1996年   108篇
  1995年   74篇
  1994年   53篇
  1993年   47篇
  1992年   32篇
  1991年   27篇
  1990年   14篇
  1989年   19篇
  1988年   16篇
  1987年   9篇
  1986年   14篇
  1985年   15篇
  1984年   13篇
  1983年   6篇
  1982年   6篇
  1981年   2篇
  1980年   4篇
  1979年   4篇
  1977年   4篇
  1976年   2篇
  1974年   3篇
  1936年   6篇
排序方式: 共有8633条查询结果,搜索用时 140 毫秒
151.
在电力体制改革的大背景下,合理评估零售电价套餐适应性,对控制电网经营风险和推进售电侧改革有重要意义。针对我国电力市场以及一般工商业的特点,首先从竞争、用户以及市场环境角度出发建立了一般工商业零售电价套餐评估指标体系;其次将层次分析法和改进的灰色白化权函数相结合,对电价套餐进行适应性评估;最后针对该评估方法建立了基于蚁群算法的优化模型,以最小成本得到提高电价套餐适应性等级的优化方案,并验证了该方法具有良好的鲁棒性,具有一定的参考意义。  相似文献   
152.
We devote to the calculation of Batalin–Vilkovisky algebra structures on the Hochschild cohomology of skew Calabi–Yau generalized Weyl algebras. We first establish a Van den Bergh duality at the level of complex. Then based on the results of Solotar et al., we apply Kowalzig and Krähmer's method to the Hochschild homology of generalized Weyl algebras, and translate the homological information into cohomological one by virtue of the Van den Bergh duality, obtaining the desired Batalin–Vilkovisky algebra structures. Finally, we apply our results to quantum weighted projective lines and Podleś quantum spheres, and the Batalin–Vilkovisky algebra structures for them are described completely.  相似文献   
153.
作为Hom-Leibniz代数胚的代数类比, 本文引入Hom-Leibniz-Rinehart代数的概念. 证明了分裂的正则Hom-Leibniz-Rinehart代数$L$写成$L=U+\sum_{\gamma}I_\gamma$, 其中$U$为极大交换子代数$H$的子空间和$I_\gamma$为$L$的理想, 若$[\gamma]\neq[d]$, 满足$[I_\gamma, I_d]=0$. 随后分别发展了分裂Hom-Leibniz-Rinehart代数的根和权的连通技术.最后研究了紧致的正则Hom-Leibniz-Rinehart代数的结构.  相似文献   
154.
155.
The vector -algorithm is obtained from the scalar -algorithm by taking the pseudo-inverse of a vector instead of the inverse of a scalar. Thus the vector -algorithm is known only through its rules contrarily to the scalar -algorithm and some other extrapolation algorithms.The aim of this paper is to provide an algebraic approach to the vector -algorithm.  相似文献   
156.
We show that a primeness criterion for enveloping algebras of Lie superalgebras discovered by Bell is applicable to the Cartan type Lie superalgebras , even. Other algebras are considered but there are no definitive answers in these cases.

  相似文献   

157.
One-parameter semigroups occurring in operator-limit distributions are investigated. The topological-algebraic background of the relevant monoids is discussed and Lie semigroup theory is applied to the Urbanik Decomposability Semigroup.  相似文献   
158.
Let (W, S) be a Coxeter group associated to a Coxeter graph which has no multiple bonds. Let H be the corresponding Hecke Algebra. We define a certain quotient \-H of H and show that it has a basis parametrized by a certain subset W cof the Coxeter group W. Specifically, W cconsists of those elements of W all of whose reduced expressions avoid substrings of the form sts where s and t are noncommuting generators in S. We determine which Coxeter groups have finite W cand compute the cardinality of W cwhen W is a Weyl group. Finally, we give a combinatorial application (which is related to the number of reduced expressions for w W cof an exponential formula of Lusztig which utilizes a specialization of a subalgebra of \-H.  相似文献   
159.
Whitehead test modules   总被引:4,自引:0,他引:4  
A (right -) module is said to be a Whitehead test module for projectivity (shortly: a p-test module) provided for each module , implies is projective. Dually, i-test modules are defined. For example, is a p-test abelian group iff each Whitehead group is free. Our first main result says that if is a right hereditary non-right perfect ring, then the existence of p-test modules is independent of ZFC + GCH. On the other hand, for any ring , there is a proper class of i-test modules. Dually, there is a proper class of p-test modules over any right perfect ring.

A non-semisimple ring is said to be fully saturated (-saturated) provided that all non-projective (-generated non-projective) modules are i-test. We show that classification of saturated rings can be reduced to the indecomposable ones. Indecomposable 1-saturated rings fall into two classes: type I, where all simple modules are isomorphic, and type II, the others. Our second main result gives a complete characterization of rings of type II as certain generalized upper triangular matrix rings, . The four parameters involved here are skew-fields and , and natural numbers . For rings of type I, we have several partial results: e.g. using a generalization of Bongartz Lemma, we show that it is consistent that each fully saturated ring of type I is a full matrix ring over a local quasi-Frobenius ring. In several recent papers, our results have been applied to Tilting Theory and to the Theory of -modules.

  相似文献   

160.
In this paper we introduce an algebraic concept of the product of Ockham algebras called the Braided product. We show that ifL i MS(i=1, 2, ,n) then the Braided product ofL i(i=1, 2, ,n) exists if and only ifL 1, ,L n have isomorphic skeletons.  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