全文获取类型
收费全文 | 12046篇 |
免费 | 621篇 |
国内免费 | 3篇 |
专业分类
化学 | 8912篇 |
晶体学 | 69篇 |
力学 | 202篇 |
数学 | 1695篇 |
物理学 | 1792篇 |
出版年
2023年 | 116篇 |
2022年 | 61篇 |
2021年 | 113篇 |
2020年 | 193篇 |
2019年 | 204篇 |
2018年 | 124篇 |
2017年 | 124篇 |
2016年 | 423篇 |
2015年 | 440篇 |
2014年 | 467篇 |
2013年 | 882篇 |
2012年 | 987篇 |
2011年 | 881篇 |
2010年 | 532篇 |
2009年 | 402篇 |
2008年 | 830篇 |
2007年 | 788篇 |
2006年 | 790篇 |
2005年 | 717篇 |
2004年 | 573篇 |
2003年 | 491篇 |
2002年 | 431篇 |
2001年 | 175篇 |
2000年 | 174篇 |
1999年 | 101篇 |
1998年 | 77篇 |
1997年 | 78篇 |
1996年 | 113篇 |
1995年 | 75篇 |
1994年 | 68篇 |
1993年 | 84篇 |
1992年 | 71篇 |
1991年 | 50篇 |
1990年 | 50篇 |
1989年 | 41篇 |
1988年 | 39篇 |
1987年 | 39篇 |
1986年 | 60篇 |
1985年 | 84篇 |
1984年 | 67篇 |
1983年 | 37篇 |
1982年 | 56篇 |
1981年 | 57篇 |
1980年 | 62篇 |
1979年 | 48篇 |
1978年 | 52篇 |
1977年 | 39篇 |
1976年 | 48篇 |
1975年 | 28篇 |
1974年 | 28篇 |
排序方式: 共有10000条查询结果,搜索用时 797 毫秒
51.
There is a general interest in ranking schemes applied to complex entities described by multiple attributes. Published rankings
for universities are in great demand but are also highly controversial. We compare two classification and ranking schemes
involving universities; one from a published report, ‘Top American Research Universities’ by the University of Florida's TheCenter and the other using DEA. Both approaches use the same data and model. We compare the two methods and discover important equivalences.
We conclude that the critical aspect in classification and ranking is the model. This suggests that DEA is a suitable tool
for these types of studies. 相似文献
52.
53.
We prove the vanishing of the Koszul homology group H
μ(Kos(M)μ), where μ is the minimal number of generators of M. We give a counterexample that the Koszul complex of a module is not always
acyclic and show its relationship with the homology of commutative rings. 相似文献
54.
Designing a majorization scheme for the recourse function in two-stage stochastic linear programming
José H. Dulá 《Computational Optimization and Applications》1993,1(4):399-414
We discuss issues pertaining to the domination from above of the second-stage recourse function of a stochastic linear program and we present a scheme to majorize this function using a simpler sublinear function. This majorization is constructed using special geometrical attributes of the recourse function. The result is a proper, simplicial function with a simple characterization which is well-suited for calculations of its expectation as required in the computation of stochastic programs. Experiments indicate that the majorizing function is well-behaved and stable. 相似文献
55.
José M. Figueroa-O'Farrill 《Communications in Mathematical Physics》1990,127(1):181-186
The recent identification of classical BRST cohomology with the vertical cohomology of a certain fibration is used to compute it in terms of the classical observables and the topology of the gauge orbits. When the gauge orbits are compact and orientable, a duality theorem is exhibited. 相似文献
56.
57.
58.
José A. Ferrari 《General Relativity and Gravitation》1990,22(1):19-32
In this paper we investigate the (static) solution of the Kaluza-Klein equations for a cylindrically symmetric current distribution. Specifically, we are interested in the fields generated by a long, cylindrical solenoid. We shall examine in some detail the concept of effective mass of a charged test particle. We shall show that, for a certain charge-to(rest)mass ratio of the test particle, the effective mass becomes imaginary at a certain distance from the axis of our solenoid. 相似文献
59.
Summary Bhattacharya, Chernoff and Yang (1983) proposed a nonparametric estimate for the slope of a regression lineY =
o
X + V subjected to the truncationYy
0. The estimate corresponds to the zero-crossing of a random functionS
n
(). In this paper an estimate for the asymptotic variance of the estimate of the slope is proposed and the rate of convergence is given. The proofs rest heavily on the local behavior ofS
n
() in the neighborhood of the true value o. 相似文献
60.
A critical review of known results about the permanence conditions for the null character of the solutions to the (vacuum) Maxwell equations, is presented. Concomitants of the electromagnetic field and the metric tensor are constructed, which give the principal directions of the field in covariant form. The known permanence conditions are generalized in order to includeall the (local) null fields; the above concomitants allow these conditions to be explicitly formulated in terms of the electromagnetic field.Supported in part by Conselleria de Cultura, Educació i Ciència de la Generalitat Valenciana. 相似文献