全文获取类型
收费全文 | 41481篇 |
免费 | 1351篇 |
国内免费 | 15篇 |
专业分类
化学 | 23918篇 |
晶体学 | 177篇 |
力学 | 811篇 |
数学 | 6837篇 |
物理学 | 11104篇 |
出版年
2021年 | 308篇 |
2020年 | 498篇 |
2019年 | 333篇 |
2018年 | 440篇 |
2017年 | 428篇 |
2016年 | 1020篇 |
2015年 | 867篇 |
2014年 | 976篇 |
2013年 | 2166篇 |
2012年 | 1665篇 |
2011年 | 2014篇 |
2010年 | 1047篇 |
2009年 | 880篇 |
2008年 | 1925篇 |
2007年 | 1918篇 |
2006年 | 1712篇 |
2005年 | 1526篇 |
2004年 | 1232篇 |
2003年 | 1040篇 |
2002年 | 994篇 |
2001年 | 818篇 |
2000年 | 718篇 |
1999年 | 512篇 |
1998年 | 481篇 |
1997年 | 488篇 |
1996年 | 597篇 |
1995年 | 543篇 |
1994年 | 562篇 |
1993年 | 638篇 |
1992年 | 542篇 |
1991年 | 414篇 |
1990年 | 462篇 |
1989年 | 401篇 |
1988年 | 400篇 |
1987年 | 415篇 |
1986年 | 412篇 |
1985年 | 588篇 |
1984年 | 546篇 |
1983年 | 501篇 |
1982年 | 507篇 |
1981年 | 509篇 |
1980年 | 494篇 |
1979年 | 421篇 |
1978年 | 492篇 |
1977年 | 467篇 |
1976年 | 402篇 |
1975年 | 361篇 |
1974年 | 366篇 |
1973年 | 372篇 |
1970年 | 219篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
Montgomery and Vaughan improved a theorem of Erd?s and Fuchs for an arbitrary sequence. Sárközy extended this theorem of Erd?s and Fuchs for two arbitrary sequences which are "near" in a certain sense. Using the idea of Jurkat (differentiation of the generating function), we will extend similarly the result of Montgomery and Vaughan for "sufficiently near" sequences. 相似文献
93.
94.
György Maróti 《ZDM》2003,35(2):63-68
This paper continues the discussion of teaching nondeterminism (see [6]) where we presented a didactic approach introducing the notion of nondeterministic automata. Although in this paper we use the same methodology we have to face up to new didactic challenges. Namely, teaching the subset construction requires answers to the question how can CAS be used in teaching the different phases of mathematical problem solving so that we can reach higher cognitive efficiency. 相似文献
95.
B. Sun Yu. A. Litvinov P. M. Walker K. Beckert P. Beller F. Bosch D. Boutin C. Brandau L. Chen C. Dimopoulou H. Geissel R. Knöbel C. Kozhuharov J. Kurcewicz S. A. Litvinov M. Mazzocco J. Meng C. Nociforo F. Nolden W. R. Plass C. Scheidenberger M. Steck H. Weick M. Winkler 《The European Physical Journal A - Hadrons and Nuclei》2007,31(3):393-394
A new long-lived isomeric state in the near proton dripline nucleus 125Ce has been identified with Schottky mass spectrometry at GSI. The excitation energy E
* = 103(12)keV and the decay time of 193(1)s have been obtained from a single stored fully ionized 125m
Ce58+ ion. The data implies an E3 transition and a 1/2+ assignment for the spin of the isomer. 相似文献
96.
Gerhard Starke 《Numerische Mathematik》1997,78(1):103-117
Summary. The convergence rate of Krylov subspace methods for the solution of nonsymmetric systems of linear equations, such as GMRES
or FOM, is studied. Bounds on the convergence rate are presented which are based on the smallest real part of the field of
values of the coefficient matrix and of its inverse. Estimates for these quantities are available during the iteration from
the underlying Arnoldi process. It is shown how these bounds can be used to study the convergence properties, in particular,
the dependence on the mesh-size and on the size of the skew-symmetric part, for preconditioners for finite element discretizations
of nonsymmetric elliptic boundary value problems. This is illustrated for the hierarchical basis and multilevel preconditioners
which constitute popular preconditioning strategies for such problems.
Received May 3, 1996 相似文献
97.
98.
The change of the superstructure of different polyethylenes during uniaxial deformation is investigated. The method used is small-angle scattering with synchrotron radiation. For branched polyethylene (Lupolen 1840D) the whole deformation range is analyzed. Beginning with superstructure of the lamellar cluster type, the superstructure partly disappears on a time scale of a few minutes and the fibrillar structure is built up. The degree of destruction and rebuilding depends on the drawing temperature. For very high molecular weight polyethylene (GUR) a reversible change of the superstructure at higher deformation ratios and at different temperatures is observed. The superstructure of (ethylene—hexene) copolymers (TIPELIN) at high draw ratios depends on the drawing temperature and is almost independent of the side group content. Interfibrillar microcracks parallel to the draw direction are produced in samples with a low side group content for draw ratios λ ≥ 1.5. 相似文献
99.
Let E\subset \Bbb R
s
be compact and let d
n
E
denote the dimension of the space of polynomials of degree at most n in s variables restricted to E . We introduce the notion of an asymptotic interpolation measure (AIM). Such a measure, if it exists , describes the asymptotic behavior of any scheme τ
n
={ \bf x
k,n
}
k=1
dnE
, n=1,2,\ldots , of nodes for multivariate polynomial interpolation for which the norms of the corresponding interpolation operators do
not grow geometrically large with n . We demonstrate the existence of AIMs for the finite union of compact subsets of certain algebraic curves in R
2
. It turns out that the theory of logarithmic potentials with external fields plays a useful role in the investigation. Furthermore,
for the sets mentioned above, we give a computationally simple construction for ``good' interpolation schemes.
November 9, 2000. Date revised: August 4, 2001. Date accepted: September 14, 2001. 相似文献
100.