全文获取类型
收费全文 | 22211篇 |
免费 | 1751篇 |
国内免费 | 1099篇 |
专业分类
化学 | 5540篇 |
晶体学 | 235篇 |
力学 | 910篇 |
综合类 | 112篇 |
数学 | 8776篇 |
物理学 | 9488篇 |
出版年
2024年 | 47篇 |
2023年 | 235篇 |
2022年 | 420篇 |
2021年 | 442篇 |
2020年 | 576篇 |
2019年 | 612篇 |
2018年 | 564篇 |
2017年 | 574篇 |
2016年 | 575篇 |
2015年 | 573篇 |
2014年 | 995篇 |
2013年 | 1383篇 |
2012年 | 814篇 |
2011年 | 1874篇 |
2010年 | 1385篇 |
2009年 | 1702篇 |
2008年 | 1766篇 |
2007年 | 1550篇 |
2006年 | 1206篇 |
2005年 | 1032篇 |
2004年 | 945篇 |
2003年 | 737篇 |
2002年 | 744篇 |
2001年 | 425篇 |
2000年 | 410篇 |
1999年 | 445篇 |
1998年 | 328篇 |
1997年 | 293篇 |
1996年 | 299篇 |
1995年 | 260篇 |
1994年 | 266篇 |
1993年 | 242篇 |
1992年 | 205篇 |
1991年 | 157篇 |
1990年 | 120篇 |
1989年 | 113篇 |
1988年 | 82篇 |
1987年 | 73篇 |
1986年 | 68篇 |
1985年 | 88篇 |
1984年 | 82篇 |
1983年 | 46篇 |
1982年 | 65篇 |
1981年 | 51篇 |
1980年 | 47篇 |
1979年 | 29篇 |
1978年 | 37篇 |
1977年 | 22篇 |
1976年 | 23篇 |
1974年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Joseph Majdalani Sjoerd W. Rienstra 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2007,58(2):289-308
The bidirectional vortex refers to the bipolar, coaxial swirling motion that can be triggered, for example, in cyclone separators
and some liquid rocket engines with tangential aft-end injectors. In this study, we present an exact solution to describe
the corresponding bulk motion in spherical coordinates. To do so, we examine both linear and nonlinear solutions of the momentum
and vorticity transport equations in spherical coordinates. The assumption will be that of steady, incompressible, inviscid,
rotational, and axisymmetric flow. We further relate the vorticity to some power of the stream function. At the outset, three
possible types of similarity solutions are shown to fulfill the momentum equation. While the first type is incapable of satisfying
the conditions for the bidirectional vortex, it can be used to accommodate other physical settings such as Hill’s vortex.
This case is illustrated in the context of inviscid flow over a sphere. The second leads to a closed-form analytical expression
that satisfies the boundary conditions for the bidirectional vortex in a straight cylinder. The third type is more general
and provides multiple solutions. The spherical bidirectional vortex is derived using separation of variables and the method
of variation of parameters. The three-pronged analysis presented here increases our repertoire of general mean flow solutions
that rarely appear in spherical geometry. It is hoped that these special forms will permit extending the current approach
to other complex fluid motions that are easier to capture using spherical coordinates. 相似文献
62.
A subgroup H of a finite group G is said to have the semi cover-avoiding property in G if there is a normal series of G such that H covers or avoids every normal factor of the series. In this paper, some new results are obtained based on the assumption that some subgroups have the semi cover-avoiding property in the group. 相似文献
63.
64.
Michèle Audin 《manuscripta mathematica》2007,124(4):533-550
In this paper, we investigate symplectic manifolds endowed with a Morse–Bott function with only two critical submanifolds,
one of which is Lagrangian while the other one is symplectic. 相似文献
65.
By exploiting the construction of charged field algebras as canonical extensions of CCR current algebras in 1+1 dimensions and nonregular representations of extended algebras, we provide an algebraic construction of local Fermi fields as ultrastrong limits of bosonic variables in all representations which are locally Fock with respect to the ground-state representation of the massless scalar field. 相似文献
66.
Keka Chakraborty S K Paranjpe V Siruguri O D Jayakumar S K Kulshreshtha 《Pramana》1997,48(6):1115-1122
Neutron diffraction and M?ssbauer measurements have been carried out on the cubic Laves phase intermetallic TbMnFe. The magnetic
moment on the transition metal atom is found to be low, 0.2μ
B, at room temperature. This moment is temperature independent down to 10 K. Magnetic moment on the rare earth atom varies
from 2.5μ
B at 296 K to 7.27μ
B at 10 K. M?ssbauer spectra recorded at 298 K and 78 K have magnetic character but there is a large distribution of hyperfine
field values. Both these features arise due to magnetic frustration created in the sample due to the competing ferro and antiferromagnetic
interactions between the transition metal atoms. 相似文献
67.
关于非齐次m阶马氏信源的渐近均分割性 总被引:4,自引:0,他引:4
本文研究非齐次m阶马氏信源的渐近均分割性,首先我们得到关于此种信源m 1元函数的一类强极限定理,作为推论,得到关于任意非齐次m阶马氏信源状态和熵密度的几个极限定理,最后得到一类非齐次m阶马氏信源的渐近均分割性。 相似文献
68.
Yuri Borovskikh 《Acta Appl Math》1994,35(3):213-298
U-statistics in Banach spaces are considered and thoroughly investigated. The martingale structure, estimates of moments, the law of large numbers, the central limit theorem, the invariance principle, estimates of the rate of convergence, and large deviations are established 相似文献
69.
Abakumov G. A. Druzhkov N. O. Kurskii Yu. A. Shavyrin A. S. 《Russian Chemical Bulletin》2003,52(3):712-717
Products of thermal transformation of substituted N-aryl-o-quinoneimines were studied using NMR spectroscopy. The formation of 4aH-phenoxazine, which was further dimerized by the Diels—Alder reaction, was established. 相似文献
70.
We study the tangent space at a monomial point M in the Hilbert scheme that parameterizes all ideals with the same Hilbert function as M over an exterior algebra. 相似文献