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351.
Mechanical testing of ultra-high temperature alloys 总被引:1,自引:0,他引:1
Specially designed facilities for tensile testing of ultra-high temperature alloys are presented. Ohmic heating is chosen
for easy access to the sample, fast attainable heating and cooling rates, simplicity in design and operation. Strain is measured
with a video extensometer by means of the software SuperCreep. The algorithm for the strain measurements is described. Stability
and accuracy of the test system were determined by testing an oxide dispersion strengthened Pt alloy. Performance of the video
extensometer was checked by thermal expansion tests on pure Pt. Tensile tests of the oxide dispersion strengthened alloy Pt-10
wt% Rh DPH at 1600°C have proven the reliability of the equipment. 相似文献
352.
353.
354.
In this paper we address the biobjective problem of locating a semiobnoxious facility, that must provide service to a given set of demand points and, at the same time, has some negative effect on given regions in the plane. In the model considered, the location of the new facility is selected in such a way that it gives answer to these contradicting aims: minimize the service cost (given by a quite general function of the distances to the demand points) and maximize the distance to the nearest affected region, in order to reduce the negative impact. Instead of addressing the problem following the traditional trend in the literature (i.e., by aggregation of the two objectives into a single one), we will focus our attention in the construction of a finite -dominating set, that is, a finite feasible subset that approximates the Pareto-optimal outcome for the biobjective problem. This approach involves the resolution of univariate d.c. optimization problems, for each of which we show that a d.c. decomposition of its objective can be obtained, allowing us to use standard d.c. optimization techniques. 相似文献
355.
应急设施选址受应急物资需求量的影响。为优化应急设施选址布局,提高突发事件应急处置能力,以化工园区突发事件为研究背景,对化工园区突发事故下应急设施选址进行研究。考虑到化工园区突发事件的随机性和复杂性、突发事件应急物资需求的不确定性等特点,以应急设施选址安全性最大、经济性和服务效益最好为目标,基于传统确定性应急设施选址模型,构建了不确定需求条件下化工园区应急设施选址区间规划数学模型。模型中应急物资需求量是一个区间值,通过引入区间规划理论和模糊理论对模型进行求解,不仅避免了不确定参数随机概率分布的波动率,而且也降低了模型求解过程中的不确定性。最后,以园区各企业潜在事故为工程背景进行实例分析,得到园区应急设施的布局方案。结果表明,模型的求解效果较好,可为园区应急设施选址决策提供参考依据。 相似文献
356.
能源系统(PCS)为固体激光装置片状放大系统提供匹配的电脉冲泵浦能量,涉及到高压、大电流的充放电过程,在这个过程中可能发生电容器短路、高低压母排短路等灾难性故障。针对上述情况,建立了能源系统及其三种主要故障的数学模型;通过仿真计算分析了氙灯负载非线性特性对系统模型的影响,提出了加入补偿参数的修正模型,并通过实验验证了其有效性;分析了故障情况下关键元件(阻尼电感、调波电感、储能电容)的耐受能力以及保护措施。 相似文献
357.
This paper considers the mobile facility routing and scheduling problem with stochastic demand (MFRSPSD). The MFRSPSD simultaneously determines the route and schedule of a fleet of mobile facilities which serve customers with uncertain demand to minimize the total cost generated during the planning horizon. The problem is formulated as a two-stage stochastic programming model, in which the first stage decision deals with the temporal and spatial movement of MFs and the second stage handles how MFs serve customer demands. An algorithm based on the multicut version of the L-shaped method is proposed in which several lower bound inequalities are developed and incorporated into the master program. The computational results show that the algorithm yields a tighter lower bound and converges faster to the optimal solution. The result of a sensitivity analysis further indicates that in dealing with stochastic demand the two-stage stochastic programming approach has a distinctive advantage over the model considering only the average demand in terms of cost reduction. 相似文献
358.
叙述了曙光一号装置(SG-1FEL)继1991年首轮实验后安排的第二轮实验,由于注入器设计和新的天鹅绒阴极材料的使用,使电子束亮度有较大提高,在数值模拟基础上,省去了长9m的束流调制区,而改用2m束流传输段。实验表明,自发辐射放大(ASE)的输出功率接近100kW,指数增益系数约20dB/m,在相互作用区自由电子激光功率呈良好的指数增长;磁场失谐曲线与数值模拟基本一致,摇摆器内通过的电流基本保持在600A左右,从而验证了双向聚焦的摇摆器设计达到了预期目标。 相似文献
359.
Competitive facility location problem with attractiveness adjustment of the follower: A bilevel programming model and its solution 总被引:1,自引:0,他引:1
We are concerned with a problem in which a firm or franchise enters a market by locating new facilities where there are existing facilities belonging to a competitor. The firm aims at finding the location and attractiveness of each facility to be opened so as to maximize its profit. The competitor, on the other hand, can react by adjusting the attractiveness of its existing facilities with the objective of maximizing its own profit. The demand is assumed to be aggregated at certain points in the plane and the facilities of the firm can be located at predetermined candidate sites. We employ Huff’s gravity-based rule in modeling the behavior of the customers where the fraction of customers at a demand point that visit a certain facility is proportional to the facility attractiveness and inversely proportional to the distance between the facility site and demand point. We formulate a bilevel mixed-integer nonlinear programming model where the firm entering the market is the leader and the competitor is the follower. In order to find the optimal solution of this model, we convert it into an equivalent one-level mixed-integer nonlinear program so that it can be solved by global optimization methods. Apart from reporting computational results obtained on a set of randomly generated instances, we also compute the benefit the leader firm derives from anticipating the competitor’s reaction of adjusting the attractiveness levels of its facilities. The results on the test instances indicate that the benefit is 58.33% on the average. 相似文献
360.
The attractiveness of retail facilities is an essential component of models analyzing competition among retail facilities. In this paper we introduce an innovative method for inferring retail facility attractiveness. Readily available data from secondary sources about customers' buying power and sales volumes obtained by competing retail facilities are used. The gravity-based competitive facility location model is used to predict sales. The attractiveness of the retail facilities are inferred from these data.The procedure is used to confirm the gravity competitive facility location model. Inferred attractiveness results based on empirical data from Orange County, California, were compared with an independent survey with excellent match. 相似文献