全文获取类型
收费全文 | 27523篇 |
免费 | 629篇 |
国内免费 | 129篇 |
专业分类
化学 | 17397篇 |
晶体学 | 255篇 |
力学 | 786篇 |
数学 | 4005篇 |
物理学 | 5838篇 |
出版年
2022年 | 176篇 |
2021年 | 271篇 |
2020年 | 338篇 |
2019年 | 321篇 |
2018年 | 281篇 |
2017年 | 247篇 |
2016年 | 511篇 |
2015年 | 493篇 |
2014年 | 545篇 |
2013年 | 1266篇 |
2012年 | 1260篇 |
2011年 | 1573篇 |
2010年 | 903篇 |
2009年 | 764篇 |
2008年 | 1417篇 |
2007年 | 1364篇 |
2006年 | 1430篇 |
2005年 | 1354篇 |
2004年 | 1254篇 |
2003年 | 1029篇 |
2002年 | 1010篇 |
2001年 | 493篇 |
2000年 | 443篇 |
1999年 | 354篇 |
1998年 | 344篇 |
1997年 | 369篇 |
1996年 | 434篇 |
1995年 | 331篇 |
1994年 | 334篇 |
1993年 | 370篇 |
1992年 | 360篇 |
1991年 | 335篇 |
1990年 | 266篇 |
1989年 | 240篇 |
1988年 | 275篇 |
1987年 | 309篇 |
1986年 | 266篇 |
1985年 | 364篇 |
1984年 | 350篇 |
1983年 | 284篇 |
1982年 | 309篇 |
1981年 | 327篇 |
1980年 | 314篇 |
1979年 | 298篇 |
1978年 | 278篇 |
1977年 | 271篇 |
1976年 | 242篇 |
1975年 | 245篇 |
1974年 | 209篇 |
1973年 | 204篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
161.
162.
163.
164.
For a real Enriques surface Y we prove that every homology class in H1(Y (R), Z/2) can be represented by a real algebraic curve if and only if all connected components of Y(R) are orientable. Furthermore, we give a characterization of real Enriques surfaces which are Galois-Maximal and/or Z-Galois-Maximal and we determine the Brauer group of any real Enriques surface Y. 相似文献
165.
166.
Mark Levi 《Communications in Mathematical Physics》1991,143(1):43-83
It is shown that for a large class of potentials on the line with superquadratic growth at infinity and with the additional time-periodic dependence all possible motions under the influence of such potentials are bounded for all time and that most (in a precise sense) motions are in fact quasiperiodic. The class of potentials includes, as very particular examples, the exponential, polynomial and much more. This extends earlier results and gives an answer to a problem posed by Littlewood in the mid 1960's. Along the way machinery is developed for estimating the action-angle transformation directly in terms of the potential and also some apparently new identities involving singular integrals are derived. 相似文献
167.
A line bundle on a complex projective manifold is said to be lef if one of its powers is globally generated and defines a semismall map in the sense of Goresky-MacPherson. As in the case of ample bundles the first Chern class of lef line bundles satisfies the Hard Lefschetz Theorem and the Hodge-Riemann Bilinear Relations. As a consequence, we prove a generalization of the Grauert contractibility criterion: the Hodge Index Theorem for semismall maps, Theorem 2.4.1. For these maps the Decomposition Theorem of Beilinson, Bernstein and Deligne is equivalent to the non-degeneracy of certain intersection forms associated with a stratification. This observation, joint with the Hodge Index Theorem for semismall maps gives a new proof of the Decomposition Theorem for the direct image of the constant sheaf. A new feature uncovered by our proof is that the intersection forms involved are definite. 相似文献
168.
Tetsuya Okuyama Masaru Nakayama Yoshitsugu Tomokiyo Omer Van Der Biest 《Microscopy and microanalysis》2002,8(1):11-15
Lattice strains around a platelet oxygen precipitate in Si wafer is studied by energy filtering convergent-beam electron diffraction (CBED) and calculations based on the finite element method (FEM). Local lattice strains are measured from CBD patterns obtained with a probe size less than 2 nm in a specimen thicker than 450 nm. Strains measured are compressive along a direction normal to a plate of the precipitation and tensile along a direction parallel to the plate. Two-dimensional stress fields near the precipitate are obtained with FEM computer analyses by fitting the measured strains. It appears that shear stresses are concentrated at the end of the precipitate edge and the maximum shear stress at an interface between the precipitate and the Si-matrix is 1.9 GPa. It is demonstrated that a combination of the energy filtering CBED and FEM is very useful for the study of local strains near interfaces in semiconductor devices, in particular for the study of stress fields that are too steep for application of the conventional CBED technique. 相似文献
169.
Supported by a Heisenberg-scholarship of the DFG 相似文献
170.
Digraph games are cooperative TU-games associated to digraph competitions: domination structures that can be modeled by directed
graphs. Examples come from sports competitions or from simple majority win digraphs corresponding to preference profiles for
a group of individuals within the framework of social choice theory. Brink and Gilles (2000) defined theβ-measure of a digraph competition as the Shapley value of the corresponding digraph game. This paper provides a new characterization
of theβ-measure. 相似文献