全文获取类型
收费全文 | 86000篇 |
免费 | 897篇 |
国内免费 | 421篇 |
专业分类
化学 | 30152篇 |
晶体学 | 832篇 |
力学 | 6908篇 |
综合类 | 1篇 |
数学 | 33403篇 |
物理学 | 16022篇 |
出版年
2022年 | 61篇 |
2021年 | 88篇 |
2020年 | 89篇 |
2019年 | 147篇 |
2018年 | 10501篇 |
2017年 | 10331篇 |
2016年 | 6291篇 |
2015年 | 1103篇 |
2014年 | 548篇 |
2013年 | 800篇 |
2012年 | 4126篇 |
2011年 | 10883篇 |
2010年 | 5939篇 |
2009年 | 6355篇 |
2008年 | 6984篇 |
2007年 | 9073篇 |
2006年 | 568篇 |
2005年 | 1614篇 |
2004年 | 1884篇 |
2003年 | 2258篇 |
2002年 | 1341篇 |
2001年 | 405篇 |
2000年 | 457篇 |
1999年 | 248篇 |
1998年 | 276篇 |
1997年 | 239篇 |
1996年 | 329篇 |
1995年 | 191篇 |
1994年 | 177篇 |
1993年 | 185篇 |
1992年 | 146篇 |
1991年 | 124篇 |
1990年 | 121篇 |
1989年 | 126篇 |
1988年 | 119篇 |
1987年 | 114篇 |
1986年 | 113篇 |
1985年 | 129篇 |
1984年 | 141篇 |
1983年 | 120篇 |
1982年 | 141篇 |
1981年 | 139篇 |
1980年 | 152篇 |
1979年 | 152篇 |
1978年 | 143篇 |
1977年 | 131篇 |
1976年 | 113篇 |
1975年 | 118篇 |
1974年 | 120篇 |
1973年 | 105篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
Philippe Jean 《Applied Acoustics》2004,65(9):861-882
A numerical model of sound transmission inside dwellings has been developed. It is based on a decoupled method mixing integral, modal and geometric approaches. Kropp's formulation has been adapted to take balconies into account. Architectural effects such as projected roofs or nearby buildings have been analysed. Sound transmission is strongly affected by the angle of incidence of incoming waves. The proposed approach makes use of velocity fields on windows either computed or measured with a laser vibrometer. Comparisons between computations and measurements are reported. 相似文献
102.
C Guéret N Jussien O Lhomme C Pavageau C Prins 《The Journal of the Operational Research Society》2003,54(5):458-465
In this paper, we describe an aircraft loading problem submitted by the French military agency (DGA) as part of a more general military airlift planning problem. It can be viewed as a kind of bi-dimensional bin-packing problem, with heterogeneous bins and several additional constraints. We introduce two-phase methods for solving this NP-hard problem. The first phase consists in building good initial solutions, thanks to two fast algorithms: a list-based heuristic and a loading pattern generation method. Both algorithms call a constraint-based subroutine, able to determine quickly if the items already loaded can be reshuffled to accommodate a new object. The second phase improves these preliminary solutions using local search techniques. Results obtained on real data sets are presented. 相似文献
103.
YaoKui ChenZhixiang 《分析论及其应用》2003,19(2):115-120
This paper gives the weighted Lp convergence rate estimations of the Gruenwald interpolatory polynomials based on the zeros of Chebyshev polymomials of the first kind,and proves that the order of the estimations is optimal for p≥1. 相似文献
104.
Howard Robinson 《Acta Analytica》2005,20(3):7-10
Nicholas Nathan tries to resist the current version of the causal argument for sense-data in two ways. First he suggests that,
on what he considers to be the correct re-construction of the argument, it equivocates on the sense of proximate cause. Second
he defends a form of disjunctivism, by claiming that there might be an extra mechanism involved in producing veridical hallucination,
that is not present in perception. I argue that Nathan’s reconstruction of the argument is not the appropriate one, and that,
properly interpreted, the argument does not equivocate on proximate cause. Furthermore, I claim that his postulation of a
modified mechanism for hallucinations is implausibly ad hoc. 相似文献
105.
Chris Pollett 《Archive for Mathematical Logic》2003,42(5):469-488
The paper establishes lower bounds on the provability of 𝒟=NP and the MRDP theorem in weak fragments of arithmetic. The
theory I
5
E
1
is shown to be unable to prove 𝒟=NP. This non-provability result is used to show that I
5
E
1
cannot prove the MRDP theorem. On the other hand it is shown that I
1
E
1
proves 𝒟 contains all predicates of the form (∀i≤|b|)P(i,x)^Q(i,x) where ^ is =, <, or ≤, and I
0
E
1
proves 𝒟 contains all predicates of the form (∀i≤b)P(i,x)=Q(i,x). Here P and Q are polynomials. A conjecture is made that 𝒟 contains NLOGTIME. However, it is shown that this conjecture would not be sufficient
to imply 𝒟=N P. Weak reductions to equality are then considered as a way of showing 𝒟=NP. It is shown that the bit-wise less than predicate,
≤2, and equality are both co-NLOGTIME complete under FDLOGTIME reductions. This is used to show that if the FDLOGTIME functions
are definable in 𝒟 then 𝒟=N P.
Received: 13 July 2001 / Revised version: 9 April 2002 /
Published online: 19 December 2002
Key words or phrases: Bounded Arithmetic – Bounded Diophantine Complexity 相似文献
106.
107.
Grégory Duby 《Archive for Mathematical Logic》2003,42(5):435-447
This paper generalizes results of F. K?rner from [4] where she established the existence of maximal automorphisms (i.e. automorphisms
moving all non-algebraic elements). An ω-maximal automorphism is an automorphism whose powers are maximal automorphisms. We
prove that any structure has an elementary extension with an ω-maximal automorphism. We also show the existence of ω-maximal
automorphisms in all countable arithmetically saturated structures. Further we describe the pairs of tuples (ˉa,ˉb) for which there is an ω-maximal automorphism mapping ˉa to ˉb.
Received: 12 December 2001 /
Published online: 10 October 2002
Supported by the ``Fonds pour la Formation à la Recherche dans l'Industrie et dans l'Agriculture'
Mathematics Subject Classification (2000): Primary: 03C50; Secondary: 03C57
Key words or phrases: Automorphism – Recursively saturated structure 相似文献
108.
An Application of Branch and Cut to Open Pit Mine Scheduling 总被引:5,自引:0,他引:5
The economic viability of the modern day mine is highly dependent upon careful planning and management. Declining trends in average ore grades, increasing mining costs and environmental considerations will ensure that this situation will remain in the foreseeable future. The operation and management of a large open pit mine having a life of several years is an enormous and complex task. Though a number of optimization techniques have been successfully applied to resolve some important problems, the problem of determining an optimal production schedule over the life of the deposit is still very much unresolved. In this paper we will critically examine the techniques that are being used in the mining industry for production scheduling indicating their limitations. In addition, we present a mixed integer linear programming model for the scheduling problems along with a Branch and Cut solution strategy. Computational results for practical sized problems are discussed. 相似文献
109.
This paper analyzes the compromise social choice correspondence derived from the τ-value of digraph games. Monotonicity of
this correspondence is shown. A connection between several properties of social choice correspondences based on game theoretical
solutions and game theoretical properties of the underlying solutions is given. Applications to several game theoretic solutions
are provided. 相似文献
110.