全文获取类型
收费全文 | 10248篇 |
免费 | 1485篇 |
国内免费 | 1086篇 |
专业分类
化学 | 3763篇 |
晶体学 | 94篇 |
力学 | 735篇 |
综合类 | 137篇 |
数学 | 3400篇 |
物理学 | 4690篇 |
出版年
2024年 | 18篇 |
2023年 | 77篇 |
2022年 | 177篇 |
2021年 | 164篇 |
2020年 | 247篇 |
2019年 | 270篇 |
2018年 | 258篇 |
2017年 | 361篇 |
2016年 | 400篇 |
2015年 | 315篇 |
2014年 | 612篇 |
2013年 | 1042篇 |
2012年 | 612篇 |
2011年 | 701篇 |
2010年 | 556篇 |
2009年 | 688篇 |
2008年 | 773篇 |
2007年 | 755篇 |
2006年 | 693篇 |
2005年 | 583篇 |
2004年 | 548篇 |
2003年 | 473篇 |
2002年 | 455篇 |
2001年 | 278篇 |
2000年 | 287篇 |
1999年 | 228篇 |
1998年 | 208篇 |
1997年 | 201篇 |
1996年 | 144篇 |
1995年 | 115篇 |
1994年 | 99篇 |
1993年 | 69篇 |
1992年 | 56篇 |
1991年 | 43篇 |
1990年 | 38篇 |
1989年 | 45篇 |
1988年 | 49篇 |
1987年 | 29篇 |
1986年 | 19篇 |
1985年 | 22篇 |
1984年 | 16篇 |
1983年 | 10篇 |
1982年 | 18篇 |
1981年 | 23篇 |
1980年 | 11篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 8篇 |
1976年 | 6篇 |
1957年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
111.
刘永民 《数学物理学报(A辑)》2004,24(3):375-380
讨论了 C\+n 中有界对称域的加权Bergman空间上符号属于 L\+2\-a(Ω, dV\-λ) 的小Hankel算子, 利用符号 Φ 的某种积分变换,给出了小Hankel算子 h\-Φ 属于Schatten理想 S\-p 的特征. 相似文献
112.
Josef Obermaier 《Journal of Approximation Theory》2003,125(2):303-312
Let
be compact with #S=∞ and let C(S) be the set of all real continuous functions on S. We ask for an algebraic polynomial sequence (Pn)n=0∞ with deg Pn=n such that every fC(S) has a unique representation f=∑i=0∞ αiPi and call such a basis Faber basis. In the special case of
, 0<q<1, we prove the existence of such a basis. A special orthonormal Faber basis is given by the so-called little q-Legendre polynomials. Moreover, these polynomials state an example with A(Sq)≠U(Sq)=C(Sq), where A(Sq) is the so-called Wiener algebra and U(Sq) is the set of all fC(Sq) which are uniquely represented by its Fourier series. 相似文献
113.
114.
U. Goginava 《分析论及其应用》2007,23(3):255-265
In this paper we prove that iff ∈ C([-π,π]2) and the function f is bounded partial p-variation for some p ∈ [1, ∞), then the double trigonometric Fourier series of a function f is uniformly (C;-α,-β) summable (α β< 1/p,α,β> 0) in the sense of Pringsheim. If α β≥ 1/p, then there exists a continuous function f0 of bounded partial double trigonometric Fourier series of fo diverge over cubes. 相似文献
115.
提出了一种新结构的X波段五腔渡越管振荡器,进行了理论和实验研究。根据场分布进行了一维非线性分析,结果表明该结构可以产生高功率微波,并判断了工作模式,为TM01模的3π/5模。采用粒子模拟验证了一维非线性分析的结论,并优化设计出五腔渡越管振荡器,优化结果为:输出功率约1 GW, 工作频率9.3 GHz,束波转换效率约22%。实验中,通过参数调节,得到频率约9.25 GHz,峰值功率约780 MW,脉宽(半高宽)21 ns的输出微波,束波转换效率约为16%。实验结果与模拟结果基本符合。 相似文献
116.
117.
Modelling a complex geometry, such as ice roughness, plays a key role for the computational flow analysis over rough surfaces. This paper presents two enhancement ideas in modelling roughness geometry for local flow analysis over an aerodynamic surface. The first enhancement is use of the leading‐edge region of an airfoil as a perturbation to the parabola surface. The reasons for using a parabola as the base geometry are: it resembles the airfoil leading edge in the vicinity of its apex and it allows the use of a lower apparent Reynolds number. The second enhancement makes use of the Fourier analysis for modelling complex ice roughness on the leading edge of airfoils. This method of modelling provides an analytical expression, which describes the roughness geometry and the corresponding derivatives. The factors affecting the performance of the Fourier analysis were also investigated. It was shown that the number of sine–cosine terms and the number of control points are of importance. Finally, these enhancements are incorporated into an automated grid generation method over the airfoil ice accretion surface. The validations for both enhancements demonstrate that they can improve the current capability of grid generation and computational flow field analysis around airfoils with ice roughness. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
118.
119.
Veli B. Shakhmurov 《Journal of Mathematical Analysis and Applications》2004,292(2):605-620
This study focuses on nonlocal boundary value problems (BVP) for degenerate elliptic differential-operator equations (DOE), that are defined in Banach-valued function spaces, where boundary conditions contain a degenerate function and a principal part of the equation possess varying coefficients. Several conditions obtained, that guarantee the maximal Lp regularity and Fredholmness. These results are also applied to nonlocal BVP for regular degenerate partial differential equations on cylindrical domain to obtain the algebraic conditions that ensure the same properties. 相似文献
120.
We solve the problem of describing compatible nonlocal Poisson brackets of hydrodynamic type. We prove that for nonsingular pairs of compatible nonlocal Poisson brackets of hydrodynamic type, there exist special local coordinates such that the metrics and the Weingarten operators of both brackets are diagonal. The nonlinear evolution equations describing all nonsingular pairs of compatible nonlocal Poisson brackets of hydrodynamic type are derived in these special coordinates, and the integrability of these equations is proved using the inverse scattering transform. The Lax pairs with a spectral parameter for these equations are found. We construct various classes of integrable reductions of the derived equations. These classes of reductions are of an independent differential-geometric and applied interest. In particular, if one of the compatible Poisson brackets is local, we obtain integrable reductions of the classical Lamé equations describing all orthogonal curvilinear coordinate systems in a flat space; if one of the compatible brackets is generated by a constant-curvature metric, the corresponding equations describe integrable reductions of the equations for orthogonal curvilinear coordinate systems in a space of constant curvature. 相似文献