全文获取类型
收费全文 | 14891篇 |
免费 | 3607篇 |
国内免费 | 1872篇 |
专业分类
化学 | 8546篇 |
晶体学 | 259篇 |
力学 | 1093篇 |
综合类 | 123篇 |
数学 | 1187篇 |
物理学 | 9162篇 |
出版年
2024年 | 27篇 |
2023年 | 174篇 |
2022年 | 493篇 |
2021年 | 535篇 |
2020年 | 740篇 |
2019年 | 615篇 |
2018年 | 615篇 |
2017年 | 681篇 |
2016年 | 770篇 |
2015年 | 663篇 |
2014年 | 827篇 |
2013年 | 1286篇 |
2012年 | 1090篇 |
2011年 | 1138篇 |
2010年 | 975篇 |
2009年 | 1000篇 |
2008年 | 945篇 |
2007年 | 1008篇 |
2006年 | 901篇 |
2005年 | 793篇 |
2004年 | 712篇 |
2003年 | 650篇 |
2002年 | 678篇 |
2001年 | 508篇 |
2000年 | 432篇 |
1999年 | 317篇 |
1998年 | 303篇 |
1997年 | 223篇 |
1996年 | 203篇 |
1995年 | 162篇 |
1994年 | 142篇 |
1993年 | 97篇 |
1992年 | 109篇 |
1991年 | 81篇 |
1990年 | 60篇 |
1989年 | 61篇 |
1988年 | 48篇 |
1987年 | 34篇 |
1986年 | 43篇 |
1985年 | 44篇 |
1984年 | 43篇 |
1983年 | 17篇 |
1982年 | 31篇 |
1981年 | 13篇 |
1980年 | 15篇 |
1979年 | 7篇 |
1978年 | 16篇 |
1977年 | 7篇 |
1976年 | 8篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
51.
52.
Kurt M. Anstreicher 《Mathematical Programming》1997,76(1):245-263
We consider the construction of small step path following algorithms using volumetric, and mixed volumetric-logarithmic, barriers.
We establish quadratic convergence of a volumetric centering measure using pure Newton steps, enabling us to use relatively
standard proof techniques for several subsequently needed results. Using a mixed volumetric-logarithmic barrier we obtain
an O(n
1/4
m
1/4
L) iteration algorithm for linear programs withn variables andm inequality constraints, providing an alternative derivation for results first obtained by Vaidya and Atkinson. In addition,
we show that the same iteration complexity can be attained while holding the work per iteration to O(n
2
m), as opposed to O(nm
2), operations, by avoiding use of the true Hessian of the volumetric barrier. Our analysis also provides a simplified proof
of self-concordancy of the volumetric and mixed volumetric-logarithmic barriers, originally due to Nesterov and Nemirovskii.
This paper was first presented at the 1994 Faculty Research Seminar “Optimization in Theory and Practice”, at the University
of Iowa Center for Advanced Studies. 相似文献
53.
Magnetic Properties of the Cobaltates Na6CoS4, Na6CoSe4, and K6CoS4 The alkali metal cobalt chalcogenides Na6CoS4, Na6CoSe4, and K6CoS4 crystallize in the space group P63mc with Z = 4. The structure is characterized by isolated [CoX4]-tetrahedra. The magnetic susceptibilities show Curie-Weiss behaviour. The deviations at low temperatures are caused by antiferromagnetic interactions. The magnetic moments are discussed with regard to ligand-field parameters. 相似文献
54.
Th. Gerrits H. A. M. van den Berg J. Hohlfeld O. Gielkens L. Br Th. Rasing 《Journal of magnetism and magnetic materials》2002,240(1-3):283-286
We have measured the response of a 20×10 μm, 8 nm thin NiFe (80:20) permalloy film due to excitation by short in-plane magnetic field pulses. We will show that using a two-pulse-technique a complete control of the precessional motion of the magnetisation can be achieved on picosecond timescales. Furthermore, we will present numerical calculations which show that a complete suppression of magnetisation ringing after switching can only be realised by a cascade of short field pulses. 相似文献
55.
56.
57.
A simple model has been developed to describe the Zeeman patterns of far-infrared laser magnetic resonance spectra of the monobromomethyl radical CH2Br observed at 447.3 and 671.1μm. A satisfactory agreement between the experimental spectra of the radical and their simulation with this simple model has been achieved. This approach can be used to gain further information about the structure and the spectrum of this interesting radical. 相似文献
59.
Recently extremal double circulant self-dual codes have been classified for lengths n ≤ 62. In this paper, a complete classification
of extremal double circulant self-dual codes of lengths 64 to 72 is presented. Almost all of the extremal double circulant
singly-even codes given have weight enumerators for which extremal codes were not previously known to exist. 相似文献
60.
Based on the effective-field theory with self-spin correlations and the differential operator technique,physical properties of the spin-2 system with biaxial crystal field on the simple cubic, body-centered cubic, as well as faced-centered lattice have been studied. The influences of the external longitudinal magnetic field on the magnetization,internal energy, specific heat, and susceptibility have been discussed in detail. The phenomenon that the magnetization in the ground state shows quantum effects produced by the biaxial transverse crystal field has been found. 相似文献