全文获取类型
收费全文 | 6155篇 |
免费 | 153篇 |
国内免费 | 38篇 |
专业分类
化学 | 216篇 |
晶体学 | 3篇 |
力学 | 28篇 |
综合类 | 4篇 |
数学 | 5664篇 |
物理学 | 431篇 |
出版年
2022年 | 14篇 |
2021年 | 12篇 |
2020年 | 21篇 |
2019年 | 154篇 |
2018年 | 149篇 |
2017年 | 72篇 |
2016年 | 57篇 |
2015年 | 66篇 |
2014年 | 164篇 |
2013年 | 341篇 |
2012年 | 203篇 |
2011年 | 376篇 |
2010年 | 332篇 |
2009年 | 461篇 |
2008年 | 495篇 |
2007年 | 490篇 |
2006年 | 385篇 |
2005年 | 277篇 |
2004年 | 215篇 |
2003年 | 178篇 |
2002年 | 134篇 |
2001年 | 122篇 |
2000年 | 133篇 |
1999年 | 153篇 |
1998年 | 129篇 |
1997年 | 99篇 |
1996年 | 148篇 |
1995年 | 138篇 |
1994年 | 127篇 |
1993年 | 94篇 |
1992年 | 80篇 |
1991年 | 40篇 |
1990年 | 39篇 |
1989年 | 42篇 |
1988年 | 31篇 |
1987年 | 35篇 |
1986年 | 29篇 |
1985年 | 57篇 |
1984年 | 36篇 |
1983年 | 24篇 |
1982年 | 42篇 |
1981年 | 33篇 |
1980年 | 15篇 |
1979年 | 26篇 |
1978年 | 18篇 |
1977年 | 19篇 |
1976年 | 22篇 |
1975年 | 5篇 |
1974年 | 5篇 |
1949年 | 2篇 |
排序方式: 共有6346条查询结果,搜索用时 10 毫秒
101.
Oscillatory properties of a weak convergent sequence of functions bounded inL
p
, 1 ≤p ≤ ∞, may be summarized by the parametrized measure it generates. When such a measure is generated by the gradients of a sequence
of functions bounded inH
1,p
, it must have special properties. The purpose of this paper is to characterize such parametrized measures as the ones that
obey Jensen’s inequality for all quasiconvex functions with the appropriate growth at infinity. We have found subtle differences
between the casesp < ∞ andp = ∞. A consequence is that any measure determined by biting convergence is in fact generated by a sequence convergent in
a stronger sense. We also give a few applications.
Research groupTransitions and Defects in Ordered Materials, funded by the NSF, the AFOSR, and the ARO. The work of the second author is also supported by DGICYT (Spain) through “Programa
de Perfeccionamiento y Movilidad del Personal Investigador” and through Grant PB90-0245. 相似文献
102.
A. Dönni P. Fischer B. Roessli H. Kitazawa 《Zeitschrift für Physik B Condensed Matter》1994,93(4):449-454
Nuclear and magnetic structures of an annealed polycrystalline sample of the heavy-fermion compound CePd2Al3 prepared by arc-melting were investigated by neutron powder diffraction. The chemical structure corresponds well to the ordered hexagonal PrNi2Al3-type structure. The antiferromagnetic structure of CePd2Al3 with an ordered magnetic moment
Ce=0.47(2)
B at saturation is remarkably similar to that in the heavy fermion superconductor UPd2Al3. The additional incommensurate magnetic structures reported previously both for UPd2Al3 and CePd2Al3 are not observed in the present sample of CePd2Al3. At 1.4 K the magnetoresistivity of CePd2Al3 measured up to 14 T indicates only one field-induced phase transition at 3.0 T. 相似文献
103.
The possibility of lasing without inversion on the 1079.8 nm line of a HeNe laser is investigated. It is shown that a modified double- scheme can be realized by use of the 877.9 nm line for introducing Zeeman coherence. It is shown experimentally that Zeeman coherence can enforce laser action, even if the inversion is below threshold. A different choice of the polarization of the driving beam can result in suppression of laser action above threshold. The underlying mechanisms are examined. On the 611.8 nm line, laser action below threshold inversion is obtained with the driving beam tuned to 824.9 nm (up-conversion). 相似文献
104.
We consider a period map from Teichmüller space to
, which is a real vector bundle over the Siegel upper half space. This map lifts the Torelli map. We study the action of the mapping class group on this period map. We show that the period map from Teichmüller space modulo the Johnson kernel is generically injective. We derive relations that the quadratic periods must satisfy. These identities are generalizations of the symmetry of the Riemann period matrix. Using these higher bilinear relations, we show that the period map factors through a translation of the subbundle
and is completely determined by the purely holomorphic quadratic periods. We apply this result to strengthen some theorems in the literature. One application is that the quadratic periods, along with the abelian periods, determine a generic marked compact Riemann surface up to an element of the kernel of Johnson's homomorphism. Another application is that we compute the cocycle that exhibits the mapping class group modulo the Johnson kernel as an extension of the group SP
g
() by the group
. 相似文献
105.
We study the topological structure of all 3-manifolds obtained by surgery along principal fibers of a closed orientable
-manifold. As a consequence, we give alternative proofs of some classical results due to W. Heil and L. Moser. Moreover, we completely specify the Seifert invariants for the considered manifolds. Finally we classify the manifolds obtained by surgery along certain Seifert links and determine geometric presentations of their fundamental groups.Work performed under the auspices of C.N.R. (National Research Council) of Italy and partially supported by Ministero della Ricerca Scientifica e Tecnologica within the projects Geometria Reale e Complessa and Topologia. 相似文献
106.
Dariusz Zagrodny 《Set-Valued Analysis》1996,4(4):301-314
In the paper we deal with the problem when the graph of the subdifferential operator of a convex lower semicontinuous function has a common point with the product of two convex nonempty weak and weak* compact sets, i.e. when graph (Q × Q
*) 0. The results obtained partially solve the problem posed by Simons as well as generalize the Rockafellar Maximal Monotonicity Theorem. 相似文献
107.
C. Luppi 《Archive for Mathematical Logic》1996,35(3):173-189
LetL be one of the intuitionistic modal logics considered in [7] (or one of its extensions) and letM
L be the algebraic semantics ofL. In this paper we will extend toL the equivalence, proved in the classical case (see [6]), among he weak Craig interpolation theorem, the Robinson theorem and the amalgamation property of varietyM
L. We will also prove the equivalence between the Craig interpolation theorem and the super-amalgamation property of varietyM
L. Then we obtain the Craig interpolation theorem and Robinson theorem for two intuitionistic modal logics, one ofS
4-type and the other one ofS
5-type, showing the super-amalgamation property of the corresponding algebraic semantics. 相似文献
108.
We describe an algorithm for selecting the n-th largest element (where 0<<1), from a totally ordered set ofn elements, using at most (1+(1+o(1))H())·n comparisons whereH() is the binary entropy function and theo(1) stands for a function that tends to 0 as tends to 0. For small values of this is almost the best possible as there is a lower bound of about (1+H())·n comparisons. The algorithm obtained beats the global 3n upper bound of Schönhage, Paterson and Pippenger for <1/3. 相似文献
109.
For everyt>1 and positiven we construct explicit examples of graphsG with |V (G)|=n, |E(G)|c
t
·n
2–1/t
which do not contain a complete bipartite graghK
t,t
!+1 This establishes the exact order of magnitude of the Turán numbers ex (n, K
t,s
) for any fixedt and allst!+1, improving over the previous probabilistic lower bounds for such pairs (t, s). The construction relies on elementary facts from commutative algebra.Research supported in part by NSF Grants DMS-8707320 and DMS-9102866.Research supported in part by Hungarian National Foundation for Scientific Research Grant 相似文献
110.
Ryszard Rudnicki 《Integral Equations and Operator Theory》1996,24(3):320-327
A class of Markov operators appearing in biomathematics is investigated. It is proved that these operators are asymptotic stable inL
1, i.e. lim
n
P
n f=0 forfL
1 and f(x) dx=0. 相似文献