全文获取类型
收费全文 | 3625篇 |
免费 | 190篇 |
国内免费 | 254篇 |
专业分类
化学 | 706篇 |
晶体学 | 28篇 |
力学 | 262篇 |
综合类 | 21篇 |
数学 | 1546篇 |
物理学 | 1506篇 |
出版年
2024年 | 6篇 |
2023年 | 39篇 |
2022年 | 53篇 |
2021年 | 82篇 |
2020年 | 81篇 |
2019年 | 68篇 |
2018年 | 60篇 |
2017年 | 126篇 |
2016年 | 100篇 |
2015年 | 131篇 |
2014年 | 153篇 |
2013年 | 260篇 |
2012年 | 128篇 |
2011年 | 205篇 |
2010年 | 150篇 |
2009年 | 210篇 |
2008年 | 237篇 |
2007年 | 281篇 |
2006年 | 218篇 |
2005年 | 180篇 |
2004年 | 168篇 |
2003年 | 152篇 |
2002年 | 146篇 |
2001年 | 116篇 |
2000年 | 103篇 |
1999年 | 126篇 |
1998年 | 119篇 |
1997年 | 92篇 |
1996年 | 54篇 |
1995年 | 38篇 |
1994年 | 33篇 |
1993年 | 21篇 |
1992年 | 37篇 |
1991年 | 19篇 |
1990年 | 12篇 |
1989年 | 12篇 |
1988年 | 9篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 7篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1969年 | 2篇 |
排序方式: 共有4069条查询结果,搜索用时 0 毫秒
21.
For the purpose of testing the spherical uniformity based on i.i.d. directional data (unit vectors) zi, i=1,…,n, Anderson and Stephens (Biometrika 59 (1972) 613–621) proposed testing procedures based on the statistics Smax=maxu S(u) and Smin=minu S(u), where u is a unit vector and nS(u) is the sum of squares of u′zi's. In this paper, we also consider another test statistic Srange=Smax−Smin. We provide formulas for the P-values of Smax, Smin, Srange by approximating tail probabilities of the limiting null distributions by means of the tube method, an integral-geometric approach for evaluating tail probability of the maximum of a Gaussian random field. Monte Carlo simulations for examining the accuracy of the approximation and for the power comparison of the statistics are given. 相似文献
22.
Siaw-Lynn Ng 《Designs, Codes and Cryptography》2003,30(1):5-19
Deciding whether a matroid is secret sharing or not is a well-known open problem. In Ng and Walker [6] it was shown that a matroid decomposes into uniform matroids under strong connectivity. The question then becomes as follows: when is a matroid m with N uniform components secret sharing? When N = 1, m corresponds to a uniform matroid and hence is secret sharing. In this paper we show, by constructing a representation using projective geometry, that all connected matroids with two uniform components are secret sharing 相似文献
23.
We prove that simply connected open manifolds of bounded geometry, linear growth and sublinear filling growth (e.g. finite filling area) are simply connected at infinity. 相似文献
24.
Awatif A. Hendi 《Journal of Quantitative Spectroscopy & Radiative Transfer》2004,84(3):339-347
The neutron transport equation for a slab geometry with the extremely anisotropic scattering kernel is considered. The albedo and transmission factors are calculated using the variation method. The effect of the extremely anisotropic parameter on the variation of the slab albedo and transmission factor is calculated. The obtained results are compared with the published data. 相似文献
25.
Hopf Modules and Noncommutative Differential Geometry 总被引:1,自引:0,他引:1
We define a new algebra of noncommutative differential forms for any Hopf algebra with an invertible antipode. We prove that there is a one-to-one correspondence between anti-Yetter–Drinfeld modules, which serve as coefficients for the Hopf cyclic (co)homology, and modules which admit a flat connection with respect to our differential calculus. Thus, we show that these coefficient modules can be regarded as “flat bundles” in the sense of Connes’ noncommutative differential geometry. 相似文献
26.
Axel Kohnert 《Discrete Applied Mathematics》2007,155(11):1451-1457
We construct new linear two-weight codes over the finite field with q elements. To do so we solve the equivalent problem of finding point sets in the projective geometry with certain intersection properties. These point sets are in bijection to solutions of a Diophantine linear system of equations. To reduce the size of the system of equations we restrict the search for solutions to solutions with special symmetries.Two-weight codes can be used to define strongly regular graphs. We give tables of the two-weight codes and the corresponding strongly regular graphs. In some cases we find new distance-optimal two-weight codes and also new strongly regular graphs. 相似文献
27.
The fourth-order ordinary differential equation that defines the self-similar solutions of the Kaup—Kupershmidt and Sawada—Kotera
equations is studied. This equation belongs to the class of fourth-order analogues of the Painlevé equations. All the power
and non-power asymptotic forms and expansions near points z = 0, z = ∞ and near an arbitrary point z = z
0 are found by means of power geometry methods. The exponential additions to the solutions of the studied equation are also
determined.
相似文献
28.
29.
Hanna Sandler 《Geometriae Dedicata》1998,69(3):317-327
In this paper it is shown that one can choose an arbitrarily large number of inconjugate elements of the group Z/2Z*Z/2Z*Z/2Z which have the property that, under all representations of the group in SU(2,1) as a discrete complex hyperbolic ideal triangle group, the elements are hyperbolic and correspond to closed geodesics of equal length on the associated complex hyperbolic surface. This is an analogue of the geometric fact that the multiplicity of the length spectrum of a Riemann surface is never bounded or the equivalent algebraic phenomenon that an arbitrarily large number of conjugacy classes in a free group can have the same trace under all representations in SL(2,R ). 相似文献
30.
We compute the cyclic homology of the coordinate ring A(SLq(2)) of the quantum algebraic group SL
q
(2). We observe a degeneration of the noncommutative de Rham complex. The results are also verified from the point of view of Connes' noncommutative differential geometry. 相似文献