全文获取类型
收费全文 | 14842篇 |
免费 | 293篇 |
国内免费 | 206篇 |
专业分类
化学 | 1350篇 |
晶体学 | 68篇 |
力学 | 152篇 |
综合类 | 32篇 |
数学 | 12423篇 |
物理学 | 1316篇 |
出版年
2023年 | 34篇 |
2022年 | 93篇 |
2021年 | 56篇 |
2020年 | 73篇 |
2019年 | 316篇 |
2018年 | 369篇 |
2017年 | 198篇 |
2016年 | 156篇 |
2015年 | 176篇 |
2014年 | 388篇 |
2013年 | 824篇 |
2012年 | 507篇 |
2011年 | 948篇 |
2010年 | 699篇 |
2009年 | 947篇 |
2008年 | 1027篇 |
2007年 | 1099篇 |
2006年 | 828篇 |
2005年 | 606篇 |
2004年 | 456篇 |
2003年 | 437篇 |
2002年 | 339篇 |
2001年 | 337篇 |
2000年 | 336篇 |
1999年 | 390篇 |
1998年 | 336篇 |
1997年 | 269篇 |
1996年 | 319篇 |
1995年 | 373篇 |
1994年 | 323篇 |
1993年 | 284篇 |
1992年 | 237篇 |
1991年 | 149篇 |
1990年 | 179篇 |
1989年 | 156篇 |
1988年 | 100篇 |
1987年 | 102篇 |
1986年 | 76篇 |
1985年 | 128篇 |
1984年 | 101篇 |
1983年 | 64篇 |
1982年 | 104篇 |
1981年 | 88篇 |
1980年 | 72篇 |
1979年 | 38篇 |
1978年 | 59篇 |
1977年 | 57篇 |
1976年 | 42篇 |
1975年 | 17篇 |
1973年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Chris Good 《Topology and its Applications》2007,154(3):734-740
One possible natural monotone version of countable paracompactness, MCP, turns out to have some interesting properties. We investigate various other possible monotone versions of countable paracompactness and how they are related. 相似文献
2.
Any system that approximates an infinite lattice by a family of finite clusters (with periodic boundary conditions) passes through an intermediate region with enlarged (hidden) symmetry as the system size is increased. The hidden symmetry allows for extra degeneracies and level crossings and has application to exact-diagonalization studies, Monte Carlo simulations, lattice gauge theories, and renormalization group calculations. 相似文献
3.
J. I. Hall 《Combinatorica》1987,7(1):77-85
Within the Johnson schemeI(m, d) we find the graphK(m, d) ofd-subsets of anm-set, two such adjacent when disjoint. Among all connected graphs,K(m, d) is characterized by the isomorphism type of its vertex neighborhoods providedm is sufficiently large compared tod.
Partial support provided by NSF (USA), SERC (UK), ZWO (NL). 相似文献
4.
Feng-Yu Wang 《Probability Theory and Related Fields》1994,98(3):299-306
Summary By using coupling methods, some lower bounds are obtained for the first Neumann eigenvalue on Riemannian manifolds. This method is new and the results improve some known estimates. An example shows that our estimates can be sharp.Research supported in part by the Foundation of Beijing Normal University 相似文献
5.
B. Abramovitz 《Acta Appl Math》1994,36(3):211-226
In this work, we consider the regularization method for linear ill-posed problems. For operators and approximating subspaces satisfying certain conditions and for a specific form of the regularization parameter, upper and lower bounds are given for the condition number of the corresponding discrete problem. 相似文献
6.
The TiO2(110) surfaces were observed by a Scanning Tunneling Microscope (STM). We found two types of bright p(1×1)-type rows on the p(1×2) surface. One p(1×1)-type formed independently and corresponds to the bridging oxygen rows. The second p(1×1)-type appeared in a bright grouping, forming narrow rows, and corresponds to the five-fold titanium rows. The above results suggest the following two conclusions. First, the density of state (DOS) on the bridging oxygen rows becomes higher than that on the five-fold titanium atom rows when a bridging oxygen row exists independently on the p(1×2) surface. Second, the bright rows on a TiO2(110)-p(1×1) surface correspond to the five-fold titanium atom rows. The results further show the validity of DOS calculations on the TiO2(110)-p(1×1) surface by Diebold et al. [Phys. Rev. Lett. 77 (1996) 1322]. The difference of width for Ti2O3 unit rows on the p(1×2) and p(1×3) surfaces in STM images are also discussed. 相似文献
7.
All the symmetries and conservation laws of Navier-Stokes equations are calculated. 相似文献
8.
An element σ of An, the Alternating group of degree n, is extendible in Sn, the Symmetric group of degree n, if there exists a subgroup H of Sn but not An whose intersection with An is the cyclic group generated by σ. A simple number-theoretic criterion, in terms of the cycle-decomposition, for an element of An to be extendible in Sn is given here. 相似文献
9.
Yu. P. Goncharov 《Letters in Mathematical Physics》1990,19(1):73-81
The possibility is discussed of generalizing the Polyakov approach to strings on membranes and the connection of such a generalization with Thurston's classification of three-dimensional geometries. The important ingredients for computing a membrane path integral are the determinants of scalar Laplacians acting in real line bundles over three-dimensional closed manifolds. In the closed bosonic membrane case, such determinants are evaluated for a class of closed 3-manifolds of the H
3/ form with a discrete subgroup of isometries of the three-dimensional Lobachevsky space H
3 and they are expressed in terms of the Selberg zeta function. Some further possible implications of the results obtained are also discussed. 相似文献
10.
We derive a lower bound on the number of points of a partial linear space of girth 5. As an application, certain strongly regular graphs with=2 are ruled out by observing that the first subconstituents are partial linear spaces. 相似文献