全文获取类型
收费全文 | 15065篇 |
免费 | 673篇 |
国内免费 | 7篇 |
专业分类
化学 | 11073篇 |
晶体学 | 93篇 |
力学 | 287篇 |
数学 | 2086篇 |
物理学 | 2206篇 |
出版年
2023年 | 118篇 |
2022年 | 93篇 |
2021年 | 145篇 |
2020年 | 223篇 |
2019年 | 248篇 |
2018年 | 223篇 |
2017年 | 235篇 |
2016年 | 522篇 |
2015年 | 477篇 |
2014年 | 510篇 |
2013年 | 969篇 |
2012年 | 1171篇 |
2011年 | 1263篇 |
2010年 | 678篇 |
2009年 | 533篇 |
2008年 | 1100篇 |
2007年 | 1072篇 |
2006年 | 963篇 |
2005年 | 913篇 |
2004年 | 752篇 |
2003年 | 609篇 |
2002年 | 536篇 |
2001年 | 202篇 |
2000年 | 184篇 |
1999年 | 117篇 |
1998年 | 93篇 |
1997年 | 85篇 |
1996年 | 136篇 |
1995年 | 90篇 |
1994年 | 72篇 |
1993年 | 89篇 |
1992年 | 75篇 |
1991年 | 61篇 |
1990年 | 51篇 |
1989年 | 45篇 |
1988年 | 47篇 |
1987年 | 44篇 |
1986年 | 65篇 |
1985年 | 91篇 |
1984年 | 74篇 |
1983年 | 45篇 |
1982年 | 71篇 |
1981年 | 69篇 |
1980年 | 71篇 |
1979年 | 56篇 |
1978年 | 55篇 |
1977年 | 44篇 |
1976年 | 50篇 |
1975年 | 28篇 |
1974年 | 33篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
53.
We focus on continuous Markov chains as a model to describe the evolution of credit ratings. In this work it is checked whether a simple, tridiagonal type of generator provides a good approximation to a general one. Three different tridiagonal approximations are proposed and their performance is checked against two generators, corresponding to a volatile and a stable period, respectively. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
54.
Berry Frank J. Ren Xiaolin Gancedo J. Ramón Marco José F. 《Hyperfine Interactions》2004,156(1-4):335-340
Hyperfine Interactions - Perovskite-related phases of the type LaFe1?x Co x O3 (x=0 and 0.5) have been synthesised by milling techniques. The materials are of smaller particle size and more... 相似文献
55.
José Natário 《General Relativity and Gravitation》2006,38(3):475-484
We find a class of warp drive spacetimes possessing Newtonian limits, which we then determine. The same method is used to
compute Newtonian limits of the Schwarzschild solution and spatially flat Friedmann-Robertson-Walker cosmological models.
This work was partially supported by FCT/POCTI/FEDER. 相似文献
56.
This article explores the use of geometric algebra in linear and multilinear algebra, and in affine, projective and conformal geometries. Our principal objective is to show how the rich algebraic tools of geometric algebra are fully compatible with and augment the more traditional tools of matrix algebra. The novel concept of an h-twistor makes possible a simple new proof of the striking relationship between conformal transformations in a pseudo-Euclidean space to isometries in a pseudo-Euclidean space of two higher dimensions. The utility of the h-twistor concept, which is a generalization of the idea of a Penrose twistor to a pseudo-Euclidean space of arbitrary signature, is amply demonstrated in a new treatment of the Schwarzian derivative. 相似文献
57.
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
58.
59.
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
60.
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