全文获取类型
收费全文 | 2744篇 |
免费 | 126篇 |
国内免费 | 286篇 |
专业分类
化学 | 211篇 |
晶体学 | 6篇 |
力学 | 118篇 |
综合类 | 23篇 |
数学 | 2550篇 |
物理学 | 248篇 |
出版年
2024年 | 4篇 |
2023年 | 30篇 |
2022年 | 32篇 |
2021年 | 30篇 |
2020年 | 66篇 |
2019年 | 72篇 |
2018年 | 66篇 |
2017年 | 49篇 |
2016年 | 58篇 |
2015年 | 61篇 |
2014年 | 140篇 |
2013年 | 277篇 |
2012年 | 136篇 |
2011年 | 161篇 |
2010年 | 157篇 |
2009年 | 223篇 |
2008年 | 186篇 |
2007年 | 197篇 |
2006年 | 192篇 |
2005年 | 121篇 |
2004年 | 116篇 |
2003年 | 118篇 |
2002年 | 84篇 |
2001年 | 67篇 |
2000年 | 79篇 |
1999年 | 65篇 |
1998年 | 76篇 |
1997年 | 53篇 |
1996年 | 45篇 |
1995年 | 24篇 |
1994年 | 28篇 |
1993年 | 12篇 |
1992年 | 12篇 |
1991年 | 15篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 10篇 |
1984年 | 12篇 |
1983年 | 5篇 |
1982年 | 9篇 |
1981年 | 13篇 |
1980年 | 6篇 |
1979年 | 7篇 |
1978年 | 8篇 |
1977年 | 8篇 |
1975年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有3156条查询结果,搜索用时 15 毫秒
81.
The Geodesics of Metric Connections with Vectorial Torsion 总被引:1,自引:0,他引:1
The present note deals with the dynamics of metric connections with vectorial torsion, as already described by E. Cartan in 1925. We show that the geodesics of metric connections with vectorial torsion defined by gradient vector fields coincide with the Levi-Civita geodesics of a conformally equivalent metric. By pullback, this yields a systematic way of constructing invariants of motion for such connections from isometries of the conformally equivalent metric, and we explain in as much this result generalizes the Mercator projection which maps sphere loxodromes to straight lines in the plane. An example shows that Beltrami's theorem fails for this class of connections. We then study the system of differential equations describing geodesics in the plane for vector fields which are not gradients, and show among others that the Hopf–Rinow theorem does also not hold in general. 相似文献
82.
与A-调和方程有关的两个结果 总被引:2,自引:0,他引:2
给出两个与A 调和方程有关的结果 .第一个结果是一类A 调和方程的很弱解可由调和函数逼近 .另一个是变分积分弱极值的充分必要条件 相似文献
83.
The potential distribution on the scalp produced by current sources in the brain can be measured by an EEG recorder. The relationship between these sources and the scalp potential distribution may be described by a well-known mathematical model where some simplifications are usually introduced. The head is modeled as a multicompartment nested set and the conductivity of the different tissues is approximated by a positive piecewise constant function. This simplified model is used to solve the forward problem (FP), i.e., to calculate the scalp potential for a current source configuration. In this work, we prove that the weak solutions of the FP are continuous with respect to the conductivity values, that is, the difference between the scalp potentials is small if the conductivity values are closed enough. We present numerical examples that illustrates this property. 相似文献
84.
丘维敦 《数学的实践与认识》2005,(3)
完美非线性映射在原差分攻击中起着重要作用 .对任意素数 p,任意偶数 n,任意正整数m m n2 ,构造了一批 Znp 到 Zmp 的完美非线性映射 . 相似文献
85.
P. Mun F. C. Fonseca R. Muccillo R. F. Jardim 《Physica C: Superconductivity and its Applications》2003,390(4):363-373
A systematic study of the magnetic hysteresis in transport properties of polycrystalline YBa2Cu3O7−δ–Ag compounds has been made based on two kinds of measurements at 77 K and under applied magnetic fields up to 30 mT: critical current density Jc(Ba) and magnetoresistance R(Ba). The R(Ba) curves show a minimum in their decreasing branch occurring at B=Bmin which was found to be both the excitation current Iex and the maximum applied magnetic field Bam dependent. In addition, for a certain value of Bam>5 mT, we have observed that Bmin increases with increasing Iex and reaches a saturation value. The Jc(Ba) curves show a maximum in decreasing applied magnetic fields occurring at B=Bmax. We have also found that Bmax increases with increasing Bam and reaches a saturation value. The minimum in the R(Ba) and the maximum in Jc(Ba) curves were found to be related to the trapped flux within the grains. All the experimental results are discussed within the context of the flux dynamics and transport mechanisms in these high-Tc materials. 相似文献
86.
Rachid Tribak 《代数通讯》2013,41(8):3190-3206
We introduce and study the notion of wd-Rickart modules (i.e. modules M such that for every nonzero endomorphism ? of M, the image of ? contains a nonzero direct summand of M). We show that the class of rings R for which every right R-module is wd-Rickart is exactly that of right semi-artinian right V-rings. We prove that a module M is dual Baer if and only if M is wd-Rickart and M has the strong summand sum property. Several structure results for some classes of wd-Rickart modules and dual Baer modules are provided. Some relevant counterexamples are indicated. 相似文献
87.
In this paper, a new iterative scheme by hybrid method is constructed. Strong convergence of the scheme to a common element of the set of common fixed points of finite family of relatively quasi-nonexpansive mappings and set of common solutions of a system of equilibrium problems in a uniformly convex and uniformly smooth real Banach space is proved using the properties of generalized f-projection operator. Our results extend important recent results. 相似文献
88.
Siwaporn Saewan Poom Kumam 《Applied mathematics and computation》2011,218(7):3522-3538
We introduce a modified block hybrid projection algorithm for finding a common element of the set of common fixed points of an infinite family of closed and uniformly quasi-?-asymptotically nonexpansive mappings, the set of the variational inequality for an α-inverse-strongly monotone operator, the set of solutions of the mixed equilibrium problems. Then, we obtain strong convergence theorems for the sequences generated by this process in a 2-uniformly convex and uniformly smooth Banach space. Our results extend and improve ones from several earlier works. 相似文献
89.
90.
W. Götze 《Journal of statistical physics》1996,83(5-6):1183-1197