全文获取类型
收费全文 | 1097篇 |
免费 | 327篇 |
国内免费 | 34篇 |
出版年
2024年 | 2篇 |
2023年 | 5篇 |
2022年 | 10篇 |
2021年 | 53篇 |
2020年 | 18篇 |
2019年 | 7篇 |
2018年 | 12篇 |
2017年 | 34篇 |
2016年 | 10篇 |
2015年 | 40篇 |
2014年 | 43篇 |
2013年 | 64篇 |
2012年 | 48篇 |
2011年 | 43篇 |
2010年 | 70篇 |
2009年 | 89篇 |
2008年 | 81篇 |
2007年 | 100篇 |
2006年 | 43篇 |
2005年 | 59篇 |
2004年 | 24篇 |
2003年 | 17篇 |
2002年 | 18篇 |
2001年 | 30篇 |
2000年 | 21篇 |
1999年 | 105篇 |
1998年 | 59篇 |
1997年 | 64篇 |
1996年 | 41篇 |
1995年 | 40篇 |
1994年 | 33篇 |
1993年 | 37篇 |
1992年 | 35篇 |
1991年 | 26篇 |
1990年 | 26篇 |
1989年 | 11篇 |
1988年 | 13篇 |
1987年 | 10篇 |
1986年 | 7篇 |
1985年 | 5篇 |
1983年 | 3篇 |
1982年 | 2篇 |
排序方式: 共有1458条查询结果,搜索用时 15 毫秒
131.
李红梅 《武警工程学院学报》2010,(2):54-58
《钢结构设计规范》(GB50017—2003)认为单轴对称的T型钢轴心压杆绕对称轴的稳定性是弯扭失稳问题。本次试验发现,剖分T型钢轴压杆有必要做弯扭屈曲验算,计算方法采用换算长系比法。 相似文献
132.
曹利 《武警工程学院学报》2010,(2):89-91
针对网络化数字化环境下图书馆参考咨询的特征,阐述由于图书馆总体业务格局的变化和工作重心的转移,参考咨询成为图书馆工作的核心,并对图书馆参考咨询专业化发展提出了建议。 相似文献
133.
This article studies a min‐max path cover problem, which is to determine a set of paths for k capacitated vehicles to service all the customers in a given weighted graph so that the largest path cost is minimized. The problem has wide applications in vehicle routing, especially when the minimization of the latest service completion time is a critical performance measure. We have analyzed four typical variants of this problem, where the vehicles have either unlimited or limited capacities, and they start from either a given depot or any depot of a given depot set. We have developed approximation algorithms for these four variants, which achieve approximation ratios of max{3 ‐ 2/k,2}, 5, max{5 ‐ 2/k,4}, and 7, respectively. We have also analyzed the approximation hardness of these variants by showing that, unless P = NP , it is impossible for them to achieve approximation ratios less than 4/3, 3/2, 3/2, and 2, respectively. We have further extended the techniques and results developed for this problem to other min‐max vehicle routing problems.© 2010 Wiley Periodicals, Inc. Naval Research Logistics, 2010 相似文献
134.
对大流量气体减压器工作过程中的振动故障进行分析,建立了减压器系统动态数学模型,进行了故障数值仿真,找到了简单有效的提高减压器输出响应稳定性的方法--减小控制腔入口面积,并得到试验验证.仿真结果还表明,大流量气体减压器的振动问题不仅和减压器本身设计参数有关,还和下游管路容积有关. 相似文献
135.
We study the supplier relationship choice for a buyer that invests in transferable capacity operated by a supplier. With a long‐term relationship, the buyer commits to source from a supplier over a long period of time. With a short‐term relationship, the buyer leaves open the option of switching to a new supplier in the future. The buyer has incomplete information about a supplies efficiency, and thus uses auctions to select suppliers and determine the contracts. In addition, the buyer faces uncertain demand for the product. A long‐term relationship may be beneficial for the buyer because it motivates more aggressive bidding at the beginning, resulting a lower initial price. A short‐term relationship may be advantageous because it allows switching, with capacity transfer at some cost, to a more efficient supplier in the future. We find that there exists a critical level of the switching cost above which a long‐term relationship is better for the buyer than a short‐term relationship. In addition, this critical switching cost decreases with demand uncertainty, implying a long‐term relationship is more favorable for a buyer facing volatile demand. Finally, we find that in a long‐term relationship, capacity can be either higher or lower than in a short‐term relationship. © 2009 Wiley Periodicals, Inc. Naval Research Logistics 2009 相似文献
136.
使用数值模拟方法对比分析了环型通道与齿轮型通道两种内旁路构型的燃烧性能,固体燃料为丁羟,燃烧采用总包反应,反应速率由涡团耗散模型计算.研究发现,环型通道在补燃室头部产生突扩回流区,仍为扩散燃烧;齿轮型通道在补燃室头部产生对称的涡结构,能够增强未燃烧燃料与旁路空气的掺混效果,且总压损失与环型相当,综合燃烧性能较好. 相似文献
137.
Environmentally friendly energy resources open a new opportunity to tackle the problem of energy security and climate change arising from wide use of fossil fuels. This paper focuses on optimizing the allocation of the energy generated by the renewable energy system to minimize the total electricity cost for sustainable manufacturing systems under time‐of‐use tariff by clipping the peak demand. A rolling horizon approach is adopted to handle the uncertainty caused by the weather change. A nonlinear mathematical programming model is established for each decision epoch based on the predicted energy generation and the probability distribution of power demand in the manufacturing plant. The objective function of the model is shown to be convex, Lipchitz‐continuous, and subdifferentiable. A generalized benders decomposition method based on the primal‐dual subgradient descent algorithm is proposed to solve the model. A series of numerical experiments is conducted to show the effectiveness of the solution approach and the significant benefits of using the renewable energy resources. 相似文献
138.
In this paper, we derive new families of facet‐defining inequalities for the finite group problem and extreme inequalities for the infinite group problem using approximate lifting. The new valid inequalities for the finite group problem include two‐ and three‐slope facet‐defining inequalities as well as the first family of four‐slope facet‐defining inequalities. The new valid inequalities for the infinite group problem include families of two‐ and three‐slope extreme inequalities. These new inequalities not only illustrate the diversity of strong inequalities for the finite and infinite group problems, but also provide a large variety of new cutting planes for solving integer and mixed‐integer programming problems. © 2008 Wiley Periodicals, Inc. Naval Research Logistics, 2008 相似文献
139.
140.
以冲压增程弹为应用背景进行了进气道设计.结合增程弹的特点,讨论了轴对称进气道中心锥参数、喉道参数、外罩参数的选择.特别对进气道唇口处参数、扩张段角度设计方法进行了分析.设计了单锥混压式、单锥外压式以及双锥混压式三种进气道,并进行了数值模拟.分析了进气道主要设计参数对其性能的影响.数值结果表明,就增程弹的性能要求而言,双锥混压式进气道的性能较高. 相似文献