全文获取类型
收费全文 | 1325篇 |
免费 | 332篇 |
国内免费 | 26篇 |
专业分类
化学 | 163篇 |
力学 | 61篇 |
综合类 | 53篇 |
数学 | 927篇 |
物理学 | 479篇 |
出版年
2023年 | 11篇 |
2022年 | 34篇 |
2021年 | 51篇 |
2020年 | 28篇 |
2019年 | 39篇 |
2018年 | 37篇 |
2017年 | 55篇 |
2016年 | 62篇 |
2015年 | 43篇 |
2014年 | 106篇 |
2013年 | 123篇 |
2012年 | 93篇 |
2011年 | 111篇 |
2010年 | 91篇 |
2009年 | 121篇 |
2008年 | 100篇 |
2007年 | 94篇 |
2006年 | 79篇 |
2005年 | 56篇 |
2004年 | 42篇 |
2003年 | 43篇 |
2002年 | 43篇 |
2001年 | 29篇 |
2000年 | 23篇 |
1999年 | 24篇 |
1998年 | 22篇 |
1997年 | 20篇 |
1996年 | 7篇 |
1995年 | 14篇 |
1994年 | 16篇 |
1993年 | 9篇 |
1992年 | 8篇 |
1991年 | 7篇 |
1990年 | 11篇 |
1989年 | 2篇 |
1988年 | 7篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1979年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有1683条查询结果,搜索用时 328 毫秒
981.
路见可 《应用数学和力学(英文版)》1983,4(5):751-763
In this paper,the problem of an infinite plane with acircular hole welded by a nearly circular plate with a crackof different material is considered.The problem is tran-sformed into solving a certain boundary value problem ofanalytic functions and then reduced to solving a singularintegral equation along the crack.The formulas and somenumerical results of the factors of stress intensityfor the cases Mode Ⅰ and Mode Ⅱ are obtained at the endof this paper. 相似文献
982.
We study an asymmetric cyclic polling model with general mixtures of exhaustive and gated service, and with zero switch-over
times, in heavy traffic. We derive closed-form expressions for all moments of the steady-state delay at each of the queues,
under standard heavy-traffic scalings. The expressions obtained provide new and useful insights into the behavior of polling
systems under heavy-load conditions.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
983.
为研究交通流相变过程问题,对一维交通流进行元胞自动机模拟,进行截面车流率数据提取,并将数据经过离散的傅里叶变换进行能量谱分析.研究结果发现:在阻塞相,系统周期即为因采用周期边界条件而形成的交通激波周期;在高密度区所对应的同步交通流状态中,系统中仍然存在着周期性波动,该周期明显异于交通激波周期,因而其形成原因不能简单归结为周期边界条件的影响;在低密度区对应的自由流状态下,没有此类波动存在. 相似文献
984.
Diffusion approximations for multiclass queueing networks under preemptive priority service discipline 总被引:1,自引:0,他引:1
戴万阳 《应用数学和力学(英文版)》2007,28(10):1331-1342
We prove a heavy traffic limit theorem to justify diffusion approximations for multiclass queueing networks under preemptive priority service discipline and provide effective stochastic dynamical models for the systems.Such queueing networks appear typically in high-speed integrated services packet networks about telecommunication sys- tem.In the network,there is a number of packet traffic types.Each type needs a number of job classes(stages)of processing and each type of jobs is assigned the same priority rank at every station where it possibly receives service.Moreover,there is no inter-routing among different traffic types throughout the entire network. 相似文献
985.
In order to exhibit the meta-stable states, several slow-to-start rules have been investigated as modification to Nagel-Schreckenberg (NS) model. These models can reproduce some realistic phenomena which are absent in the original NS model. But in these models, the size of cluster is still not considered as a useful parameter. In real traffic, the slow-to-start motion of a standing vehicle often depends on the degree of congestion which can be measured by the clusters' size. According to this idea, we propose a cluster-size dependent slow-to-start model based on the speed- dependent slow-to-start rule (VDR) model. It gives expected results through simulations. Comparing with the VDR model, our new model has a better traffic efficiency and shows richer complex characters.[第一段] 相似文献
986.
In this paper, the speed gradient (SG) model is extended to describe
the traffic flow on two-lane freeways. Terms related to lane change
are added into the continuity equations and velocity dynamic
equations. The empirically observed two-lane phenomena, such as lane
usage inversion and lane change rate versus density, are reproduced
by extended SG model. The local cluster effect is also investigated
by numerical simulations. 相似文献
987.
We restudy the master-equation approach to aggregation in
freeway traffic based on the theory of birth--death
process, in which the clustering behaviour in one-lane freeway
traffic model is investigated.
The transition probabilities for the jump processes
are reconstructed by using Greenshields' model, and the equation of
the mean size of the cluster at any time t is derived from the
birth--death equation. Numerical experiments show the clustering
behaviours varying with time very well. 相似文献
988.
A type of multiple “look-ahead” car-following models is studied
by nonlinear analysis. The mKdV equation to describe density wave
of traffic jamming is derived. The result indicates that the behavior of
multiple “look-ahead” is in favor of stability enhancement of traffic flow.
Furthermore, the traffic flow can reach the most stable case
via adjustment of the parameter of weight functions m=3. 相似文献
989.
双极室联合处理啤酒废水的微生物燃料电池 总被引:1,自引:0,他引:1
构建了双极室连续流联合处理废水的微生物燃料电池(MFC), 该MFC阳极室的出水直接用于阴极室的进水, 利用阴极室的好氧微生物进一步降解有机物. 以啤酒废水作底物, 研究了该MFC的产电性能和废水处理效果. 结果表明, 采用双极室连续流MFC可以大大提高废水的处理效果, 对啤酒废水化学需氧量(COD)的总去除率可达92.2%~95.1%, 其中阳极室中COD去除率为47.6%~56.5%. MFC的开路电压为0.451 V, 最大输出功率为2.89 W/m3. 实验中抑制MFC性能的主要因素是阴极的极化损失, 通过降低进入阴极室溶液的COD浓度、采用优质的阴极材料和加大阴极室内的曝气量等方法进一步优化电池的性能. 相似文献
990.
Establishment of effective traffic models to reveal fundamental traffic characteristics is an essential requirement in the design, planning and operation of transportation systems. In 1992 Nagel and Schreckenberg presented a cellular automaton model describing traffic flow of N cars on a single lane and applied it in the famous project TRANSIMS on transportation simulation. In this paper, the author proposes a new model for the same problem and gives a comparison of simulation results with the former ones. The comparison shows that the new model works better under the condition of high traffic density. 相似文献