全文获取类型
收费全文 | 11452篇 |
免费 | 1728篇 |
国内免费 | 779篇 |
专业分类
化学 | 4535篇 |
晶体学 | 118篇 |
力学 | 1108篇 |
综合类 | 227篇 |
数学 | 3342篇 |
物理学 | 4629篇 |
出版年
2024年 | 15篇 |
2023年 | 132篇 |
2022年 | 333篇 |
2021年 | 382篇 |
2020年 | 483篇 |
2019年 | 348篇 |
2018年 | 320篇 |
2017年 | 421篇 |
2016年 | 500篇 |
2015年 | 435篇 |
2014年 | 627篇 |
2013年 | 747篇 |
2012年 | 652篇 |
2011年 | 619篇 |
2010年 | 564篇 |
2009年 | 713篇 |
2008年 | 664篇 |
2007年 | 691篇 |
2006年 | 638篇 |
2005年 | 571篇 |
2004年 | 498篇 |
2003年 | 454篇 |
2002年 | 446篇 |
2001年 | 342篇 |
2000年 | 341篇 |
1999年 | 298篇 |
1998年 | 292篇 |
1997年 | 214篇 |
1996年 | 160篇 |
1995年 | 170篇 |
1994年 | 141篇 |
1993年 | 110篇 |
1992年 | 96篇 |
1991年 | 67篇 |
1990年 | 52篇 |
1989年 | 50篇 |
1988年 | 42篇 |
1987年 | 41篇 |
1986年 | 45篇 |
1985年 | 56篇 |
1984年 | 33篇 |
1983年 | 14篇 |
1982年 | 28篇 |
1981年 | 15篇 |
1980年 | 12篇 |
1979年 | 22篇 |
1978年 | 15篇 |
1977年 | 17篇 |
1976年 | 17篇 |
1972年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
We examine the problem of building or fortifying a network to defend against enemy attacks in various scenarios. In particular,
we examine the case in which an enemy can destroy any portion of any arc that a designer constructs on the network, subject
to some interdiction budget. This problem takes the form of a three-level, two-player game, in which the designer acts first
to construct a network and transmit an initial set of flows through the network. The enemy acts next to destroy a set of constructed
arcs in the designer’s network, and the designer acts last to transmit a final set of flows in the network. Most studies of
this nature assume that the enemy will act optimally; however, in real-world scenarios one cannot necessarily assume rationality
on the part of the enemy. Hence, we prescribe optimal network design algorithms for three different profiles of enemy action:
an enemy destroying arcs based on capacities, based on initial flows, or acting optimally to minimize our maximum profits
obtained from transmitting flows. 相似文献
92.
93.
This paper introduced the concept of L-fuzzy sub lattice implication algebra and discussed its properties. Proved that the intersection set of a family of L-fuzzy sub lattice implication algebras is a L-fuzzy sub lattice implication algebra, that a L-fuzzy sub set of a lattice implication algebra is a L-fuzzy sub lattice implication algebra if and only if its every cut set is a sub lattice implication algebra, and that the image and original image of a L-fuzzy sub lattice implication algebra under a lattice implication homomorphism are both L-fuzzy sub lattice implication algebras. 相似文献
94.
95.
A mistake concerning the ultra LI-ideal of a lattice implication algebra is pointed out, and some new sufficient and necessary conditions for an LI-ideal to be an ultra LI-ideal are given. Moreover, the notion of an LI-ideal is extended to MTL-algebras, the notions of a (prime, ultra, obstinate, Boolean) LI-ideal and an ILI-ideal of an MTL-algebra are introduced, some important examples are given, and the following notions are proved to be equivalent in MTL-algebra: (1) prime proper LI-ideal and Boolean LI-ideal, (2) prime proper LI-ideal and ILI-ideal, (3) proper obstinate LI-ideal, (4) ultra LI-ideal.
This work was supported by the Zhejiang Provincial Natural Science Foundation of China (Grant No. Y605389) and K. C. Wong
Magna Fund in Ningbo University. 相似文献
96.
It was argued by Schramm and Smirnov that the critical site percolation exploration path on the triangular lattice converges
in distribution to the trace of chordal SLE
6. We provide here a detailed proof, which relies on Smirnov’s theorem that crossing probabilities have a conformally invariant
scaling limit (given by Cardy’s formula). The version of convergence to SLE
6 that we prove suffices for the Smirnov–Werner derivation of certain critical percolation crossing exponents and for our analysis
of the critical percolation full scaling limit as a process of continuum nonsimple loops.
Research of Charles M.Newman was partially supported by the US NSF under grants DMS-01-04278 and DMS-06-06696. 相似文献
97.
Masaaki Harada 《Designs, Codes and Cryptography》2006,38(1):5-16
In this paper, we show that the code generated by the rows of a block-point incidence matrix of a self-orthogonal 3-(56,12,65)
design is a doubly-even self-dual code of length 56. As a consequence, it is shown that an extremal doubly-even self-dual
code of length 56 is generated by the codewords of minimum weight. We also demonstrate that there are more than one thousand
inequivalent extremal doubly-even self-dual [56,28,12] codes. This result shows that there are more than one thousand non-isomorphic
self-orthogonal 3-(56,12,65) designs.
AMS Classification: 94B05, 05B05 相似文献
98.
99.
详细介绍用等效折射率概念设计短波通滤光片的原理和计算方法。根据原理和方法,选择二氧化钛(TiO2)作为高折射率材料、二氧化硅(SiO2)作为低折射率材料。首先从理论上计算出用这2种材料设计的波长λ=950~1150nm的短波通滤光片所需要的周期数,然后给出短波通滤光片的主膜系和光谱曲线。由于据此周期数设计出的膜系光谱曲线在750~810nm处的透过率不符合要求,因此对该膜系进行了改进。依照改进的设计进行多次制备,最终制备出了符合要求的短波通滤光片,找到了最佳制备工艺和方法。最后,对制备出来的短波通滤光片薄膜进行了各种环境实验。实验结果表明,膜层的各项指标符合设计要求。 相似文献
100.
Parking Capacity and Pricing in Park'n Ride Trips: A Continuous Equilibrium Network Design Problem 总被引:2,自引:0,他引:2
In this paper we consider the problem of designing parking facilities for park'n ride trips. We present a new continuous equilibrium network design problem to decide the capacity and fare of these parking lots at a tactical level. We assume that the parking facilities have already been located and other topological decisions have already been taken.The modeling approach proposed is mathematical programming with equilibrium constraints. In the outer optimization problem, a central Authority evaluates the performance of the transport network for each network design decision. In the inner problem a multimodal traffic assignment with combined modes, formulated as a variational inequality problem, generates the share demand for modes of transportation, and for parking facilities as a function of the design variables of the parking lots. The objective is to make optimal parking investment and pricing decisions in order to minimize the total travel cost in a subnetwork of the multimodal transportation system.We present a new development in model formulation based on the use of generalized parking link cost as a design variable.The bilevel model is solved by a simulated annealing algorithm applied to the continuous and non-negative design decision variables. Numerical tests are reported in order to illustrate the use of the model, and the ability of the approach to solve applications of moderate size. 相似文献