全文获取类型
收费全文 | 52875篇 |
免费 | 732篇 |
国内免费 | 408篇 |
专业分类
化学 | 26920篇 |
晶体学 | 381篇 |
力学 | 1951篇 |
综合类 | 12篇 |
数学 | 13203篇 |
物理学 | 11548篇 |
出版年
2021年 | 280篇 |
2020年 | 319篇 |
2019年 | 333篇 |
2018年 | 1416篇 |
2017年 | 1629篇 |
2016年 | 1173篇 |
2015年 | 985篇 |
2014年 | 935篇 |
2013年 | 1945篇 |
2012年 | 4209篇 |
2011年 | 3698篇 |
2010年 | 2500篇 |
2009年 | 2219篇 |
2008年 | 1788篇 |
2007年 | 1864篇 |
2006年 | 1822篇 |
2005年 | 5583篇 |
2004年 | 4905篇 |
2003年 | 3188篇 |
2002年 | 1290篇 |
2001年 | 636篇 |
2000年 | 379篇 |
1999年 | 428篇 |
1998年 | 386篇 |
1997年 | 375篇 |
1996年 | 402篇 |
1995年 | 286篇 |
1994年 | 329篇 |
1993年 | 294篇 |
1992年 | 417篇 |
1991年 | 400篇 |
1990年 | 332篇 |
1989年 | 346篇 |
1988年 | 338篇 |
1987年 | 262篇 |
1986年 | 241篇 |
1985年 | 334篇 |
1984年 | 375篇 |
1983年 | 251篇 |
1982年 | 392篇 |
1981年 | 357篇 |
1980年 | 333篇 |
1979年 | 353篇 |
1978年 | 350篇 |
1977年 | 318篇 |
1976年 | 361篇 |
1975年 | 289篇 |
1974年 | 291篇 |
1973年 | 288篇 |
1972年 | 169篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
Girard V Farrenq R Sorokin E Sorokina IT Guelachvili G Picqué N 《Chemical physics letters》2006,419(4-6):584-588
The spectral dynamics of a mid-infrared multimode Cr(2+):ZnSe laser located in a vacuum sealed chamber containing acetylene at low pressure is analyzed by a stepping-mode high-resolution time-resolved Fourier transform interferometer. Doppler-limited absorption spectra of C(2)H(2) in natural isotopic abundance are recorded around 4000 cm(-1) with kilometric absorption path lengths and sensitivities better than 3 10(-8) cm(-1). Two cold bands are newly identified and assigned to the ν(1)+ν(4) (1) and ν(3)+ν(5) (1) transitions of (12)C(13)CH(2). The ν(1)+ν(5) (1) band of (12)C(2)HD and fourteen (12)C(2)H(2) bands are observed, among which for the first time ν(2)+2ν(4) (2)+ν(5) (-1). 相似文献
73.
Piotr Ko?cielniak 《Topology and its Applications》2007,154(9):1951-1955
Let M be a compact manifold with dimM?2. We prove that some iteration of the generic homeomorphism on M is semiconjugated to the shift map and has infinite topological entropy (Theorem 1.1). 相似文献
74.
Covering numbers of precompact symmetric convex subsets of Hilbert spaces are investigated. Lower bounds are derived for sets containing orthogonal subsets with norms of their elements converging to zero sufficiently slowly. When these sets are convex hulls of sets with power-type covering numbers, the bounds are tight. The arguments exploit properties of generalized Hadamard matrices. The results are illustrated by examples from machine learning, neurocomputing, and nonlinear approximation. 相似文献
75.
We give counterexamples to the following conjecture of Auslander: given a finitely generated module M over an Artin algebra Λ, there exists a positive integer nM such that for all finitely generated Λ-modules N, if ExtΛi(M,N)=0 for all i?0, then ExtΛi(M,N)=0 for all i?nM. Some of our examples moreover yield homologically defined classes of commutative local rings strictly between the class of local complete intersections and the class of local Gorenstein rings. 相似文献
76.
Franck D'Agosto Marie‐Thrse Charreyre Christian Pichot Robert G. Gilbert 《Journal of polymer science. Part A, Polymer chemistry》2003,41(9):1188-1195
A method is described for synthesizing latex particles with anchored hairs by the grafting of hydrophilic chains, synthesized by reversible addition–fragmentation chain transfer, onto functionalized latex particles. These have the potential to bind biologically active species. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1188–1195, 2003 相似文献
77.
It can be conjectured that the colored Jones function of a knot can be computed in terms of counting paths on the graph of
a planar projection of a knot. On the combinatorial level, the colored Jones function can be replaced by its weight system.
We give two curious formulas for the weight system of a colored Jones function: one in terms of the permanent of a matrix
associated to a chord diagram, and another in terms of counting paths of intersecting chords.
Electronic supplementary material to this article is available at and is accessible to authorized users.
* S. G. was partially supported by an NSF and by an Israel-US BSF grant.
† M. L. was partly supported by GAUK 158 grant and by the Project LN00A056 of the Czech Ministry of Education. 相似文献
78.
79.
We study a class of shape optimization problems for semi-linear elliptic equations with Dirichlet boundary conditions in smooth
domains in ℝ2. A part of the boundary of the domain is variable as the graph of a smooth function. The problem is equivalently reformulated
on a fixed domain. Continuity of the solution to the state equation with respect to domain variations is shown. This is used
to obtain differentiability in the general case, and moreover a useful formula for the gradient of the cost functional in
the case where the principal part of the differential operator is the Laplacian.
Online publication 23 January 2004. 相似文献
80.