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151.
Matthew S. Goldberg 《海军后勤学研究》1987,34(4):535-545
If material failures follow a Poisson distribution, then the expected number of failures is exactly proportional to flight hours. However, this article demonstrates that proportionality will not be revealed by simple correlation or regression analysis between monthly flight hours and the number of monthly failures. To test for proportionality, one must instead test the underlying hypothesis that the data follow a Poisson distribution. This article presents three simple tests that may be used for this purpose. The Poisson distribution requires that the mean and variance of the number of failures be equal. This article suggests several alternative models that may be used for samples in which the variance exceeds the mean. First, the mean of the Poisson distribution may itself be randomly distributed across the observational units according to a gamma distribution. If so, the number of failures will have a negative binomial distribution. Second, the mean of the Poisson distribution may depend systematically upon a set of observable explanatory variables. In this case, the Poisson regression model is appropriate. Finally, the mean of the Poisson distribution may contain both a systematic component that depends upon observable variables and a random component. This situation yields a generalized Poisson regression model. 相似文献
152.
本文给出了具有四个圆形柔性铰链的平行弹性平台的研究结果,并运用材料力学和有限元分析进行了理论仿真,利用线切割加工工艺制造了几个整体式的平台。颈缩截面的厚度为20—100um。对这些结构的刚度进行了精密测量并与理论值进行了比较。这使得能够定性的分析在电加工中产生的在微米级范围内不能忽略的粗糙度和其它表面变形的影响。通过这些实验得到的结果对其它具有几个自由度的复杂柔性机构非常有用。 相似文献
153.
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155.
In this paper, we develop efficient interactive methods for the solution of bicriteria nonlinear programming problems. The methods do not require trade-off information from the decision maker, pose less cognitive burden and converge to the “best compromise solution” fast. Two methods, called the paired comparison method and comparative trade-off method, are presented with examples. A real application of the interactive method to a bicriteria problem that arose in the planning of the cardiovascular disease control program in the U.S. Air Force is also presented. 相似文献
156.
Kyung S. Park 《海军后勤学研究》1983,30(3):397-400
This article presents another inventory model for situations in which, during the stockout period, a fraction b of the demand is backordered and the remaining fraction 1 ? b is lost. By defining a time-proportional backorder cost and a fixed penalty cost per unit lost, a unimodal objective function representing the average annual cost of operating the inventory system is obtained. The optimal operating policy variables are calculated directly. 相似文献
157.
In this article we extend our previous work on the continuous single-module design problem to the multiple-module case. It is assumed that there is a fixed cost associated with each additional module used. The Kuhn–Tucker conditions characterize local optima among which there is a global optimum. Modules are associated with partitions and a special class, guillotine partitions, are characterized. Branch-and-bound, partial enumeration, and heuristic procedures for finding optimum or good guillotine partitions are discussed and illustrated with examples. 相似文献
158.
This paper is a state-of-the-art review of the literature related to optimal maintenance models of systems subject to failure. The emphasis is on work appearing since the 1976 survey, “A Survey of Maintenance Models: The Control and Surveillance of Deteriorating Systems,” by W.P. Pierskalla and J.A. Voelker, published in this journal. 相似文献
159.
The extreme spread, or greatest distance between all pairs of impact points on a target, is often used as a rapid measure of dispersion or precision of shot groups on a target. It is therefore desirable to know its statistical properties. Since the exact theoretical distribution has not yet been worked out, this paper examines the accuracy of several approximations which are checked against large sample monte carlo values. We find in particular that for the sample sizes considered the extreme spread can be approximated well by a Chi variate. 相似文献
160.
Lower confidence limits are derived for the impact probability within a circle of fixed radius. The bivariate normal distribution with zero means, unequal variances, and zero correlation is the probability model for impacts. A new representation of the impact probability function is offered. This presentation is valid also for the dependent case, where the eigenvalues of the covariance matrix replace the variances. When the ratio of variances is known the lower confidence limits are uniformly most accurate (UMA). A few alternative approaches are compared by simulation when the ratio of variances is unknown. 相似文献