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   11482篇
  免费   828篇
  国内免费   1548篇
化学   3435篇
晶体学   47篇
力学   369篇
综合类   190篇
数学   8181篇
物理学   1636篇
  2024年   14篇
  2023年   130篇
  2022年   159篇
  2021年   257篇
  2020年   275篇
  2019年   327篇
  2018年   313篇
  2017年   355篇
  2016年   265篇
  2015年   251篇
  2014年   408篇
  2013年   1138篇
  2012年   388篇
  2011年   521篇
  2010年   459篇
  2009年   639篇
  2008年   715篇
  2007年   888篇
  2006年   705篇
  2005年   680篇
  2004年   560篇
  2003年   612篇
  2002年   549篇
  2001年   443篇
  2000年   439篇
  1999年   407篇
  1998年   371篇
  1997年   345篇
  1996年   245篇
  1995年   133篇
  1994年   155篇
  1993年   95篇
  1992年   85篇
  1991年   67篇
  1990年   51篇
  1989年   51篇
  1988年   51篇
  1987年   46篇
  1986年   28篇
  1985年   51篇
  1984年   37篇
  1983年   21篇
  1982年   26篇
  1981年   24篇
  1980年   17篇
  1979年   11篇
  1978年   14篇
  1977年   14篇
  1976年   6篇
  1974年   5篇
排序方式: 共有10000条查询结果,搜索用时 343 毫秒
271.
Two Kleinian groups and are said to be topologically conjugate when there is a homeomorphism such that . It is conjectured that if two Kleinian groups and are topologically conjugate, one is a quasi-conformal deformation of the other. In this paper generalizing Minsky's result, we shall prove that this conjecture is true when is finitely generated and freely indecomposable, and the injectivity radii of all points of and are bounded below by a positive constant.

  相似文献   

272.
We demonstrate a one to one correspondence between the irreducible projective representations of an affine Kac-Moody group and those of the related loop group, which leads to the results that every non-trivial representation of an affine Kac-Moody group must have its degree greater than or equal to the rank of the group and that the equivalence appears if and only if the group is of type for some . Moreover the characteristics of the base fields for the non-trivial representations are found being always zero.

  相似文献   

273.
Let be a log surface with at worst log canonical singularities and reduced boundary such that is nef and big. We shall prove that either has finite fundamental group or is affine-ruled. Moreover, and the structure of are determined in some sense when .

  相似文献   

274.
The observation that the quotient orbifold of an orientation- reversing involution on a 3-dimensional handlebody has the structure of a compression body leads to a strong classification theorem, and general structure theorems. The structure theorems decompose the action along invariant discs into actions on handlebodies which preserve the -fibers of some -bundle structure. As applications, various results of R. Nelson are proved without restrictive hypotheses.

  相似文献   

275.
Letf:XX be a selfmap of a compact connected polyhedron, andA a nonempty closed subset ofX. In this paper, we shall deal with the question whether or not there is a mapg:XX homotopic tof such that the fixed point set Fixg ofg equalsA. We introduce a necessary condition for the existence of such a mapg. It is shown that this condition is easy to check, and hence some sufficient conditions are obtained.Partially supported by the Natural Science Foundation of Liaoning University.  相似文献   
276.
The reactions of three aromatic hydrocarbons, benzene, toluene, and styrene, with oxygen in a radiofrequency (r) plasma were investigated. Benzene was oxidized to yield phenol as a single volatile organic product. Similarly, toluene gave the ring oxidation products, cresols, as well as considerable amounts of methyl oxidation products, consisting mainly of benzaldehyde and benzyl alcohol. In contrast, the oxidation of styrene took place predominantly on the olefinic double bond to produce styrene oxide On basis of the products and effects of reaction variables, r power and flow rates of hydrocarbons and oxygen, on the reaction rate, the oxidation mechanism was discussed, particularly focusing on the intermediate species responsible for the formation of major products.  相似文献   
277.
Derivative of the exponential mapping for infinite dimensional lie groups   总被引:1,自引:1,他引:0  
It is proved that for infinite dimensional Lie groups in the sense of the differential calculus of Frölicher and Kriegl the derivative of the exponential mappings is given by the formula d(exp)(X)Y=dexp(X)(e) 0 1 Adexp(–tX) Y dt, where stands for the left translation ande is the neutral element.This work was supported by the Alexander von Humboldt-Stiftung.  相似文献   
278.
Jean Barge 《K-Theory》1993,7(1):9-16
In this paper we construct a canonical 2-cocycle on the groupP SL(2,k) with values in the Witt groupW(k) of the fieldk. This allows us to produce anatural homomorphism :H 2(SL(2,k); Z)I 2(k), whereI 2(k) is the square of the fundamental ideal. We prove that this homomorphism is in fact a lift of Milnor's symbol.
  相似文献   
279.
The paper addresses a part of the problem of classifying all 2-arc transitive graphs: namely, that of finding all groups acting 2-arc transitively on finite connected graphs such that there exists a minimal normal subgroup that is nonabelian and regular on vertices. A construction is given for such groups, together with the associated graphs, in terms of the following ingredients: a nonabelian simple group T, a permutation group P acting 2-transitively on a set , and a map F : Tsuch that x = x –1 for all x F() and such that Tis generated by F(). Conversely we show that all such groups and graphs arise in this way. Necessary and sufficient conditions are found for the construction to yield groups that are permutation equivalent in their action on the vertices of the associated graphs (which are consequently isomorphic). The different types of groups arising are discussed and various examples given.  相似文献   
280.
We obtain a resolution of the identity operator, for functions on a latticeZ d, which is derived from the block renormalization group. We use eigenfunctions of the terms of the decomposition to form a basis forl 2(Zd) and show how the basis is generated from lattice wavelets. The lattice spacing is taken to zero and continuum wavelets are obtained.  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