全文获取类型
收费全文 | 19956篇 |
免费 | 483篇 |
国内免费 | 437篇 |
专业分类
化学 | 3908篇 |
晶体学 | 933篇 |
力学 | 385篇 |
综合类 | 44篇 |
数学 | 11938篇 |
物理学 | 3668篇 |
出版年
2023年 | 55篇 |
2022年 | 144篇 |
2021年 | 149篇 |
2020年 | 159篇 |
2019年 | 369篇 |
2018年 | 393篇 |
2017年 | 268篇 |
2016年 | 327篇 |
2015年 | 323篇 |
2014年 | 597篇 |
2013年 | 1358篇 |
2012年 | 525篇 |
2011年 | 1578篇 |
2010年 | 1388篇 |
2009年 | 1279篇 |
2008年 | 1376篇 |
2007年 | 1355篇 |
2006年 | 1018篇 |
2005年 | 891篇 |
2004年 | 785篇 |
2003年 | 600篇 |
2002年 | 619篇 |
2001年 | 416篇 |
2000年 | 397篇 |
1999年 | 370篇 |
1998年 | 382篇 |
1997年 | 292篇 |
1996年 | 334篇 |
1995年 | 336篇 |
1994年 | 318篇 |
1993年 | 244篇 |
1992年 | 248篇 |
1991年 | 173篇 |
1990年 | 183篇 |
1989年 | 171篇 |
1988年 | 106篇 |
1987年 | 124篇 |
1986年 | 89篇 |
1985年 | 158篇 |
1984年 | 114篇 |
1983年 | 68篇 |
1982年 | 91篇 |
1981年 | 121篇 |
1980年 | 106篇 |
1979年 | 61篇 |
1978年 | 108篇 |
1977年 | 91篇 |
1976年 | 90篇 |
1975年 | 39篇 |
1974年 | 44篇 |
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
181.
Haitao Zhang Shuxin Ouyang Zhaosheng Li Lifei Liu Tao Yu Jinhua Ye Zhigang Zou 《Journal of Physics and Chemistry of Solids》2006,67(12):2501-2505
Bi2O3/SrTiO3 composite powders have been prepared and their photocatalytic activities were investigated by photooxidation of methanol. These powders were characterized by UV-Visible diffuse reflectance spectra, SEM and X-ray diffraction (XRD). The results revealed that all the Bi2O3/SrTiO3 composite powders exhibited higher photocatalytic activity than pure SrTiO3, Bi2O3 and TiO2 (P25) under visible light irradiation (λ>440 nm). The effects of the Bi2O3 contents on the photocatalytic activities of the composite powders were examined, the photocatalytic activities increased with the content of Bi2O3 increasing to a maximum of 83% and then decreased under visible light irradiation. The effects of the calcination temperatures on the photocatalytic activities of the composite powders were also investigated. 相似文献
182.
Under some general continuous and compact conditions, the existence problems of fiked points andd coupled fixed points for increasing operators are studied. an application, we utilize the results obtained to study the existence of solutions for differential inclusions in Banach spaces. 相似文献
183.
184.
The algebra dual to Woronowicz's deformation of the two-dimensional Euclidean group is constructed. The same algebra is obtained from SU
q
(2) via contraction on both the group and algebra levels. 相似文献
185.
Claire Cates Haulk John Drew Charles R. Johnson J. Hunter Tart 《Linear and Multilinear Algebra》1997,43(1):35-51
For a given n-by-n matrix A, we consider the set of matrices which commute with A and all of whose principal submatrices commute with the corresponding principal submatrices of A. The properties of this set are examined, with particular attention to its dimension. 相似文献
186.
Zbigniew Lonc 《Order》1994,11(2):149-158
We show that in an ordered setP of width 3 there always exists a fibre (i.e., a subset intersecting each maximal nontrivial antichain) of size at most 11/18|P|. This improves previously known results.Research supported by Polish KBN Grant 2 2037 92 03. 相似文献
187.
Scott McCullough 《Integral Equations and Operator Theory》1992,15(1):43-71
Kernels over the unit disk for which a version of Carathéodory interpolation is true are characterized in a simple computationally verifiable manner. 相似文献
188.
We show that it is a NP-complete problem to decide whether a finite poset arises as the (Birkhoff) dual of the Frattini sublattice of some finite distributive lattice.This work was supported in part by Swiss NSF grant 20-32644.91. 相似文献
189.
Erik Woldt 《Journal of Physics and Chemistry of Solids》2002,63(4):699-704
The paper investigates whether a change from a homogeneous to an inhomogeneous dislocation distribution, assumed to be caused by a slight additional deformation, can lead to an increase of the recrystallization temperature of a deformed metal. In this case, the higher temperature would indicate a more stable deformation structure despite the increase of stored energy. The recrystallization temperature is related to the growth rate. Hence, the steady state velocity of a recrystallization front moving either parallel or vertically to the stripes of a simplified two-dimensional heterogeneous dislocation distribution of parallel sections of higher and lower dislocation densities is calculated. The results show that if a front growths through the high and low density sections in series an overall slower rate despite higher mean dislocation density is, indeed, possible. However, growing in the parallel arrangement always leads to a higher growth rate compared with the homogeneous case of slightly less stored energy. Since in a real structure the faster growth is likely to succeed, the recrystallization temperature observed will be lowered with additional deformation in accordance with experimental experience. 相似文献
190.
Motivated by the work of Crapo and Rota [6] on the lifting of a projective complex, we introduce a class of invariant operations associated to integral-weighted graphs, which we call graphical operations. Such operations generalize the sixth harmonic of a quadranguler set on a projective line. We determine the expansion of the graphical operations in terms of multi-linear bracket polynomials in a Grassmann-Cayley algebra. Reducibility and compositions of such invariant operations are also investigated with a number of examples.Supported by Courant Instructorship, New York University. 相似文献