全文获取类型
收费全文 | 1752篇 |
免费 | 297篇 |
国内免费 | 283篇 |
学科分类
数理化 | 2332篇 |
出版年
2024年 | 21篇 |
2023年 | 43篇 |
2022年 | 59篇 |
2021年 | 61篇 |
2020年 | 85篇 |
2019年 | 68篇 |
2018年 | 67篇 |
2017年 | 66篇 |
2016年 | 86篇 |
2015年 | 63篇 |
2014年 | 62篇 |
2013年 | 129篇 |
2012年 | 79篇 |
2011年 | 93篇 |
2010年 | 66篇 |
2009年 | 80篇 |
2008年 | 88篇 |
2007年 | 121篇 |
2006年 | 97篇 |
2005年 | 107篇 |
2004年 | 85篇 |
2003年 | 83篇 |
2002年 | 82篇 |
2001年 | 58篇 |
2000年 | 71篇 |
1999年 | 75篇 |
1998年 | 67篇 |
1997年 | 44篇 |
1996年 | 42篇 |
1995年 | 20篇 |
1994年 | 23篇 |
1993年 | 21篇 |
1992年 | 15篇 |
1991年 | 13篇 |
1990年 | 8篇 |
1989年 | 5篇 |
1988年 | 10篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 17篇 |
1984年 | 11篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 5篇 |
1980年 | 7篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1974年 | 2篇 |
1959年 | 1篇 |
排序方式: 共有2332条查询结果,搜索用时 15 毫秒
991.
Using a scheme given by Marco, we prove that partially hyperbolic tori along resonant surfaces of near-integrable Hamiltonian systems possess the obstruction property in Arnold's terminology. The proof is based on a specific lambda lemma for these tori. 相似文献
992.
Let f, g: (Rn, 0) (Rp, 0) be two C map-germs. Then f and gare C0-equivalent if there exist homeomorphism-germs h and lof (Rn, 0) and (Rp, 0) respectively such that g = l f h1.Let k be a positive integer. A germ f is k-C0-determined ifevery germ g with jk g(0) = jk f(0) is C0-equivalent to f. Moreover,we say that f is finitely topologically determined if f is k-C0-determinedfor some finite k. We prove a theorem giving a sufficient conditionfor a germ to be finitely topologically determined. We explainthis condition below. Let N and P be two C manifolds. Consider the jet bundle Jk(N,P) with fiber Jk(n, p). Let z in Jk(n, p) and let f be suchthat z = jkf(0). Define
Whether (f) < k depends only on z, not on f. We can thereforedefine the set
Let Wk(N, P) be the subbundle of Jk(N, P) with fiber Wk(n, p).Mather has constructed a finite Whitney (b)-regular stratificationSk(n, p) of Jk(n, p) Wk(n, p) such that all strata aresemialgebraic and K-invariant, having the property that if Sk(N,P) denotes the corresponding stratification of Jk(N, P) Wk(N, P) and f C(N, P) is a C map such that jkf is multitransverseto Sk(N, P), jkf(N) Wk(N, P) = and N is compact (or f is proper),then f is topologically stable. For a map-germ f: (Rn, 0) (Rp, 0), we define a certain ojasiewiczinequality. The inequality implies that there exists a representativef: U Rp such that jkf(U 0) Wk (Rn, Rp = and suchthat jkf is multitransverse to Sk (Rn, Rp) at any finite setof points S U 0. Moreover, the inequality controlsthe rate jkf becomes non-transverse as we approach 0. We showthat if f satisfies this inequality, then f is finitely topologicallydetermined. 1991 Mathematics Subject Classification: 58C27. 相似文献
993.
Summary Capacitance-voltage measurements have been carried out onp-type ɛ-GaSe single crystal ∥c in the temperature range 300 to 360 K, with applied voltages of -1, 0 and +1 V. TheC-V measurements in this temperature range have shown a shift in capacitanceC and conductanceG to the higher values with an increase in temperature. The depletion layer widthW, the Debye length LD and the doping densityN
α
have been worked out and plots ofN
α
vs. W have shown a decrease inW with an increase in temperature. The plots of LD
vs. N
α
vary as 1/Nα1/2, which gives NαLD ⋍ 3.3 × 1011 charges/m2 for doping density of 1016m−3. The values ofG at different temperatures have been used to obtain the activation energies, which are found to be ΔE ⋍ 0.11 eV for -1 and
+1 V applied voltages, and ΔE ⋍ 0.06 eV for zero volt.
The authors of this paper have agreed to not receive the proofs for correction. 相似文献
994.
Jerzy Kakol 《Rendiconti del Circolo Matematico di Palermo》1993,42(3):453-458
Developing ideas found in a recent paper of Gilsdorf to arbitrary topological vector spaces (tvs) one shows that a Hausdorff (LB)
tv
-spaceE is regular provided every null-sequence inE has a series convergent subsequence inE.
Received by the editors 1980Mathematics Subject Classification (1985 Revision) 46A12. 相似文献
995.
We pursue the study of the multiscale spaces Sν introduced by Jaffard in the context of multifractal analysis. We give the necessary and sufficient condition for Sν to be locally p-convex, and exhibit a sequence of p-norms that defines its natural topology. The strong topological dual of Sν is identified to another sequence space depending on ν, endowed with an inductive limit topology. As a particular case, we describe the dual of a countable intersection of Besov spaces. 相似文献
996.
997.
Our systematic study has shown that the gap in doped CeNiSn Kondo insulator is very sensitive to the degree of hybridization V between the f-electron and conduction electron states. In the system CeNi1−xRhxSn, the carrier concentration diminishes upon Rh substitution for Ni. The transition from Kondo-insulator region to a metallic region is discussed as a function of variable valence electron number induced by substitution of Rh for Ni and of the accompanying effect of the change hybridization energy V. 相似文献
998.
By using topological current theory, this paper studies the inner
topological structure of disclinations during the melting of
two-dimensional systems. From two-dimensional elasticity theory, it
finds that there are topological currents for topological defects in
homogeneous equation. The evolution of disclinations is studied, and
the branch conditions for generating, annihilating, crossing,
splitting and merging of disclinations are given. 相似文献
999.
By making use of Duan--Ge's decomposition theory of gauge potential
and the topological current theory proposed by Prof. Duan
Yi-Shi, we study a two-component superfluid Bose condensed system,
which is supposed to be realized in the interior of neutron stars in
the form of the coexistence of a neutron superfluid and a protonic
superconductor. We propose that this system possesses vortex lines.
The topological charges of the vortex lines are characterized by the
Hopf indices and the Brower degrees of φ-mapping. 相似文献
1000.
通过对Willmore区域外,特别是中等及较小约化体积下的形状及其演化进行深入细致的研究,发现在这一区域的形状要远比原有的猜测丰富,亏格g=2的膜泡会展现出比已有结果更多迷人的形状并出现新的膜泡相变分支.同时,数值计算的结果更加期待实验验证,从而为曲率模型的正确性提供有力支持. 相似文献