全文获取类型
收费全文 | 13359篇 |
免费 | 1187篇 |
国内免费 | 1593篇 |
专业分类
化学 | 1012篇 |
晶体学 | 17篇 |
力学 | 918篇 |
综合类 | 373篇 |
数学 | 11341篇 |
物理学 | 2478篇 |
出版年
2024年 | 18篇 |
2023年 | 131篇 |
2022年 | 145篇 |
2021年 | 210篇 |
2020年 | 262篇 |
2019年 | 291篇 |
2018年 | 280篇 |
2017年 | 334篇 |
2016年 | 390篇 |
2015年 | 289篇 |
2014年 | 582篇 |
2013年 | 870篇 |
2012年 | 581篇 |
2011年 | 804篇 |
2010年 | 743篇 |
2009年 | 949篇 |
2008年 | 1027篇 |
2007年 | 1091篇 |
2006年 | 895篇 |
2005年 | 808篇 |
2004年 | 621篇 |
2003年 | 692篇 |
2002年 | 573篇 |
2001年 | 486篇 |
2000年 | 507篇 |
1999年 | 469篇 |
1998年 | 453篇 |
1997年 | 356篇 |
1996年 | 262篇 |
1995年 | 149篇 |
1994年 | 160篇 |
1993年 | 104篇 |
1992年 | 89篇 |
1991年 | 65篇 |
1990年 | 50篇 |
1989年 | 38篇 |
1988年 | 40篇 |
1987年 | 22篇 |
1986年 | 23篇 |
1985年 | 45篇 |
1984年 | 41篇 |
1983年 | 21篇 |
1982年 | 37篇 |
1981年 | 22篇 |
1980年 | 28篇 |
1979年 | 20篇 |
1978年 | 14篇 |
1977年 | 14篇 |
1976年 | 8篇 |
1936年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
31.
曾六川 《数学物理学报(A辑)》2002,22(3):336-341
设犈是一致凸Banach空间,满足Opial条件或具有Frechet可微范数,犆是犈的非空闭凸子集,且犜:犆→犆是非扩张映象.又设对任何初始数据狓1 ∈犆,序列{狓狀}由下列修改了的Ishikawa迭代程序生成:狓狀+1 =狋狀犜狀(狊狀犜狀狓狀+ (1-狊狀)狓狀)+ (1-狋狀)狓狀, 狀≥1, (I)其中,数列{狋狀}与{狊狀}满足下列条件(i)和(ii)之一:(i)狋狀∈ [犪,犫]且狊狀∈ [0,犫];(ii)狋狀∈ [犪,1]且狊狀∈ [犪,犫],这里,常数犪,犫满足0<犪≤犫<1.作者证明了,犜有不动点的充要条件是,{狓狀}
弱收敛且{‖狓狀-犜狓狀‖}收敛到0.而且,由此即知,若犜有不动点,则{狓狀}弱收敛到犜的一个不动点. 相似文献
32.
Electron beam induced quantitative X-ray mapping has become a very useful characterisation tool for determining the elemental
distribution in materials, whether using energy dispersive spectroscopy or wavelength dispersive spectroscopy. The X-ray intensity
distributions of the elements from an X-ray map allow us to generate two dimensional and ternary scatter diagrams thus converting
spatial information into concentration dimensions, which is an important tool for displaying the spatial relationships of
elements or correlated elements (phases) in materials. To best understand how to use this tool, we need to understand the
production and features of the scatter diagram. The type of clustering observed in the scatter diagram, whether oval, linear
or spherical, can give the major and trace element distributions within phases as well as qualitative and quantitative phase
information. This paper demonstrates the generation of scatter diagrams, properties of scatter diagrams, interpretation of
scatter diagrams and the advantages of scatter diagrams through the use of examples. 相似文献
33.
Suppose μ is a Radon measure on ℝ
d
, which may be non doubling. The only condition assumed on μ is a growth condition, namely, there is a constant C0>0 such that for all x∈supp(μ) and r>0, μ(B(x, r))⪯C0rn, where 0<n⪯d. We prove T1 theorem for non doubling measures with weak kernel conditions. Our approach yields new results
for kernels satisfying weakened regularity conditions, while recovering previously known Tolsa’s results. We also prove T1
theorem for Besov spaces on nonhomogeneous spaces with weak kernel conditions given in [7]. 相似文献
34.
Shinji Takesue 《Journal of statistical physics》1989,56(3-4):371-402
This is the first part of a series devoted to the study of thermodynamic behavior of large dynamical systems with the use of a family of fully-discrete and conservative models named elementary reversible cellular automata (ERCAs). In this paper, basic properties such as conservation laws and phase space structure are investigated in preparation for the later studies. ERCAs are a family of one-dimensional reversible cellular automata having two Boolean variables on each site. Reflection and Boolean conjugation symmetries divide them into 88 equivalence classes. For each rule, additive conserved quantities written in a certain form are regarded as a kind of energy, if they exist. By the aid of the discreteness of the variables, every ERCA satisfies the Liouville theorem or the preservation of phase space volume. Thus, if an energy exists in the above sense, statistical mechanics of the model can formally be constructed. If a locally defined quantity is conserved, however, it prevents the realization of statistical mechanics. The existence of such a quantity is examined for each class and a number of rules which have at least one energy but no local conservation laws are selected as hopeful candidates for the realization of thermodynamic behavior. In addition, the phase space structure of ERCAs is analyzed by enumerating cycles exactly in the phase space for systems of comparatively small sizes. As a result, it is revealed that a finite ERCA is not ergodic, that is, a large number of orbits coexist on an energy surface. It is argued that this fact does not necessarily mean the failure of thermodynamic behavior on the basis of an analogy with the ergodic nature of infinite systems. 相似文献
35.
Continuity is obtained of some multilinear operators related to certain integral operators for the weighted Herz spaces with extreme exponents. The operators include the Littlewood–Paley and Marcinkiewicz operators. 相似文献
36.
本文考察了包括平面上的各种广义 Cantor集 ,Sierpinski集和包括某些连续不可微曲线在内的广义 Sierpinski集 .由相似变换 ,导出了它们的级数表达式 ,并利用它和字符串空间的对应关系 ,计算出它们的Hausdorff维数 相似文献
37.
Michael T. Jury David W. Kribs 《Proceedings of the American Mathematical Society》2005,133(1):213-222
Given a row contraction of operators on a Hilbert space and a family of projections on the space that stabilizes the operators, we show there is a unique minimal joint dilation to a row contraction of partial isometries that satisfy natural relations. For a fixed row contraction the set of all dilations forms a partially ordered set with a largest and smallest element. A key technical device in our analysis is a connection with directed graphs. We use a Wold decomposition for partial isometries to describe the models for these dilations, and we discuss how the basic properties of a dilation depend on the row contraction.
38.
In the present paper, some new almost fixed point theorems and fixed point theorems for lower semicontinuous type multivalued mappings are obtained in metrizable H-spaces. 相似文献
39.
40.
Richard Brown 《Geometriae Dedicata》2003,97(1):129-150
In this note, we show that given a closed, orientable genus-g surface S
g
, any hyperbolic toral automorphism has a positive power which induces a quadratic, orientable pseudo-Anosov homeomorphism on S
g
. To show this, we lift Anosov toral automorphisms through a ramified topological covering and present the lifted homeomorphism via a standard set of Lickorish twists. This construction provides a general method of producing pseudo-Anosov maps of closed surfaces with predetermined orientable foliations and quadratic dilatation. Since these lifted automorphisms have orientable foliations, this construction is a sort of converse to that of Franks and Rykken [Trans. Amer. Math. Soc. 1999], who established that one can associate to a quadratic pseudo-Anosov homeomorphism with oriented unstable foliation a hyperbolic toral automorphism. 相似文献