全文获取类型
收费全文 | 144819篇 |
免费 | 12945篇 |
国内免费 | 7623篇 |
专业分类
化学 | 71518篇 |
晶体学 | 1352篇 |
力学 | 10931篇 |
综合类 | 311篇 |
数学 | 39386篇 |
物理学 | 41889篇 |
出版年
2024年 | 76篇 |
2023年 | 1547篇 |
2022年 | 1603篇 |
2021年 | 2380篇 |
2020年 | 3075篇 |
2019年 | 2847篇 |
2018年 | 12225篇 |
2017年 | 11886篇 |
2016年 | 9138篇 |
2015年 | 4124篇 |
2014年 | 4254篇 |
2013年 | 5456篇 |
2012年 | 10183篇 |
2011年 | 16770篇 |
2010年 | 9879篇 |
2009年 | 10017篇 |
2008年 | 10912篇 |
2007年 | 12567篇 |
2006年 | 3983篇 |
2005年 | 4390篇 |
2004年 | 3902篇 |
2003年 | 3829篇 |
2002年 | 2659篇 |
2001年 | 1656篇 |
2000年 | 1576篇 |
1999年 | 1640篇 |
1998年 | 1464篇 |
1997年 | 1395篇 |
1996年 | 1449篇 |
1995年 | 1153篇 |
1994年 | 992篇 |
1993年 | 853篇 |
1992年 | 721篇 |
1991年 | 639篇 |
1990年 | 550篇 |
1989年 | 439篇 |
1988年 | 390篇 |
1987年 | 329篇 |
1986年 | 306篇 |
1985年 | 250篇 |
1984年 | 185篇 |
1983年 | 138篇 |
1982年 | 120篇 |
1981年 | 105篇 |
1980年 | 111篇 |
1979年 | 76篇 |
1978年 | 64篇 |
1977年 | 58篇 |
1976年 | 46篇 |
1973年 | 53篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
991.
Joshua Maglione 《Archiv der Mathematik》2017,108(3):225-232
Let f(p, n) be the number of pairwise nonisomorphic p-groups of order \(p^n\), and let g(p, n) be the number of groups of order \(p^n\) whose automorphism group is a p-group. We prove that the limit, as p grows to infinity, of the ratio g(p, n) / f(p, n) equals 1/3 for \(n=6,7\). 相似文献
992.
Tomasz Beberok 《Archiv der Mathematik》2017,108(4):341-350
Let \({\mathcal {S}}\) denote the set of positive integers that may appear as the strong symmetric genus of a finite abelian group. We obtain a set of (simple) necessary and sufficient conditions for an integer g to belong to \({\mathcal {S}}\). We also prove that the set \({\mathcal {S}}\) has an asymptotic density and approximate its value. 相似文献
993.
Suppose that G is a finite group and let H be a proper subgroup of G. Then the restriction map from the characters of G to the characters of H is never injective. 相似文献
994.
This is a survey on recent progress concerning maximal regularity of non-autonomous equations governed by time-dependent forms on a Hilbert space. It also contains two new results showing the limits of the theory. 相似文献
995.
A manifold is locally k-fold symmetric if for any point and any k-dimensional vector subspace tangent to this point, there exists a local isometry such that this point is a fixed point and the differential of the isometry restricted to that k-dimensional vector subspace is minus the identity. We show that for \(k \ge 2\), Riemannian, pseudoriemannian, and Finslerian locally k-fold symmetric manifolds are locally symmetric. 相似文献
996.
The aim of this paper is to show some rigidity results for complete Riemannian manifolds with parallel Cotton tensor. In particular, we prove that any compact manifold of dimension \(n\ge 3\) with parallel Cotton tensor and positive constant scalar curvature is isometric to a finite quotient of \({\mathbb {S}}^n\) under a pointwise or integral pinching condition. Moreover, a rigidity theorem for stochastically complete manifolds with parallel Cotton tensor is also given. The proofs rely mainly on curvature elliptic estimates and the weak maximum principle. 相似文献
997.
Kirby A. Baker 《Algebra Universalis》2017,77(1):1-28
Normal categories are pointed categorical counterparts of 0-regular varieties, i.e., varieties where each congruence is uniquely determined by the equivalence class of a fixed constant 0. In this paper, we give a new axiomatic approach to normal categories, which uses self-dual axioms on a functor defined using subobjects of objects in the category. We also show that a similar approach can be developed for 0-regular varieties, if we replace subobjects with subsets of algebras containing 0. 相似文献
998.
999.
Let B be an Archimedean reduced f-ring. A positive element \({\omega}\) in B is said to satisfy the property \({(\ast)}\) if for every f-ring A with identity e and every \({\ell}\)-group homomorphism \({\gamma : A \rightarrow B}\) with \({\gamma(e) = \omega}\), there exists a unique \({\ell}\)-ring homomorphism \({\rho: B \rightarrow B}\) such that \({\gamma = \omega \rho}\) and \({\rho(e)^{\perp \perp} = \omega^{\perp \perp}}\). Boulabiar and Hager proved that any (positive) von Neumann regular element in B satisfies the property \({(\ast)}\) and proved that the converse holds in the C(X)-case. In this regard, they asked about this converse in the general case. Our main purpose in this note is to prove, via a counter-example, that the converse in question fails in general. In addition, we shall take the opportunity to extend the direct result obtained by Boulabiar and Hager, and to get the C(X)-case we were talking about in an easier way. 相似文献
1000.
Generalizing the obvious representation of a subspace \({Y \subseteq X}\) as a sublocale in Ω(X) by the congruence \({\{(U, V ) | U\cap Y = V \cap Y\}}\), one obtains the congruence \({\{(a, b) |\mathfrak{o}(a) \cap S = \mathfrak{o}(b) \cap S\}}\), first with sublocales S of a frame L, which (as it is well known) produces back the sublocale S itself, and then with general subsets \({S\subseteq L}\). The relation of such S with the sublocale produced is studied (the result is not always the sublocale generated by S). Further, we discuss in general the associated adjunctions, in particular that between relations on L and subsets of L and view the aforementioned phenomena in this perspective. 相似文献