全文获取类型
收费全文 | 406篇 |
免费 | 47篇 |
专业分类
财政金融 | 17篇 |
工业经济 | 69篇 |
计划管理 | 165篇 |
经济学 | 46篇 |
综合类 | 80篇 |
运输经济 | 3篇 |
旅游经济 | 5篇 |
贸易经济 | 11篇 |
农业经济 | 38篇 |
经济概况 | 19篇 |
出版年
2024年 | 3篇 |
2023年 | 13篇 |
2022年 | 6篇 |
2021年 | 7篇 |
2020年 | 16篇 |
2019年 | 6篇 |
2018年 | 9篇 |
2017年 | 9篇 |
2016年 | 12篇 |
2015年 | 14篇 |
2014年 | 49篇 |
2013年 | 27篇 |
2012年 | 36篇 |
2011年 | 56篇 |
2010年 | 48篇 |
2009年 | 32篇 |
2008年 | 20篇 |
2007年 | 14篇 |
2006年 | 19篇 |
2005年 | 13篇 |
2004年 | 10篇 |
2003年 | 9篇 |
2002年 | 3篇 |
2001年 | 6篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1993年 | 1篇 |
排序方式: 共有453条查询结果,搜索用时 31 毫秒
1.
2.
为了研究骨料形态对再生混凝土材料力学性能的影响,基于势能原理的基面力元法,利用图像处理技术和MATLAB软件,建立了再生混凝土真实骨料细观模型。应用FORTRAN分析软件对再生混凝土试件进行单轴拉伸试验的数值模拟,研究了真实骨料细观模型再生混凝土宏观应力-应变曲线变化规律和试件的破坏形态。结果显示,真实骨料模型得到的宏观应力-应变曲线和试验曲线吻合度较高,骨料形状对试件的破坏形态影响较小。模型可真实地模拟再生混凝土在单轴拉伸作用下的损伤破坏过程,准确地反映试件的实际骨料形态。 相似文献
3.
Elisa Calliari 《Journal of Risk Research》2018,21(6):725-747
The years-long negotiations on loss and damage (L&D) associated with climate change impacts reached a milestone with the adoption of the Paris Agreement, sanctioning the permanence of the Warsaw International Mechanism (WIM) created in 2013. The WIM aims at advancing knowledge gathering, coordination and support to address L&D associated with extreme and slow onset events in vulnerable developing countries (Decision 2/CP.19). Despite being among the most controversial issues to be recently treated in climate change negotiation, L&D has attracted little attention in the field of international relations. This paper aims at addressing this gap by reconstructing the emergence and evolution of the negotiating positions on L&D of developing and developed countries. It employs a critical discourse analytical approach and builds on Fairclough’s three-dimensional framework for critical discourse analysis, taking decision 2/CP.19 as the core communicative event. Consistently, the decision is analysed at three different levels: as a text (micro-scale); as a discursive practice (meso-scale); and as a social practice (macro-scale). The analysis makes use of a wide range of materials including previous decisions, High Level Segment statements and Parties submissions. It reconstructs Parties’ conflicting views on the positioning of L&D vis-à-vis the adaptation space (L&D as a part of, or as beyond adaptation) and the scientific, ethical and legal arguments employed to support these standpoints. It highlights, in particular, the strategic importance which the ‘compensation argument’ had in determining developing countries’ capacity to influence the UNFCCC process up to the inclusion of a specific article on L&D in the Paris Agreement. While calls for compensation might have lost momentum as a result of the Warsaw and Paris talks, the paper argues that their potential is far from exhausted. They in fact imply a more general request for climate justice which the UNFCCC has not yet addressed. 相似文献
4.
为了研究网架结构的损伤检测方法,根据应变能密度理论,提出采用单元模态应变能密度差值作为网架结构损伤识别指标的方法,以损伤单元模态应变能密度差值的大小初步确定单元的损伤程度。分析了5种具有代表性的损伤工况,并在数值计算结果中引入了白噪声。结果显示,在一阶模态下,针对单损伤、多损伤和轻微损伤、严重损伤等不同损伤工况,损伤杆件的模态应变能密度差值均为高值。因此,该方法可以有效识别出网架结构的损伤位置,根据损伤单元的模态应变能密度差值大小初步确定单元的损伤程度,且在一定的噪声水平下具有较强的鲁棒性,对网架结构损伤识别具有参考价值。 相似文献
5.
现有的板锚极限抗拔力计算方法只考虑了常规形状锚板的情况,不适用于特殊形状的锚板。为了更好地指导工程实践,在总结已有研究的基础上,研究了圆形、方形、正三角形和风筝形锚板,假定锚板的破坏面从锚板的侧面以膨胀角向上延伸,形成与锚板自身具有相同横截面形状的棱台,结合数学和力学理论分析,提出了一种可以考虑形状效应的浅埋板锚极限抗拔承载力计算方法,并将简化方法计算所得承载力和公开试验结果进行对比。结果表明,简化计算方法适用于埋深与板宽之比小于5的浅埋情况,且具有较高的精度,可以在初步工程设计中加以应用。研究结果为多种形态的浅埋锚板极限抗拔力计算提供了新的方法,可为类似工程项目的设计提供参考,具有一定的工程借鉴价值。 相似文献
6.
7.
采用TAW-2000D微机控制电液伺服岩石三轴试验机和SDAES型数字声发射仪组成的动态测试系统,对云南大红山铜矿白云岩进行了单轴压缩条件下的声发射试验,研究岩石在峰值应力前后声发射特性。试验结果表明:加载早期就有声发射活动,岩样在试验接近峰值强度时单位时间内的应力增长速度减小、声发射事件率出现明显下降,即出现相对平静期,峰值强度后的声发射现象仍然明显。 相似文献
8.
There is now a growing consensus that ratifying International Environmental Agreements (IEAs) is the most effective way to tackle transboundary pollution problems. While the social benefit function (SBF) critically affects emission choices as well as decisions to ratify IEAs, the related economic literature has mainly concentrated on scenarios where the marginal SBF is linear. Using climatic data, I find that the linear marginal SBF case does not match data and isoelastic SBFs fit data better. In the more realistic, but not yet explored, context of isoelastic SBFs, I reconsider incentives to ratify IEAs. My analysis gives rise to novel conclusions. For instance, changes in the scale of damages do not affect the level of cooperation. When the scale of damages is small, variations of the SBF parameter reveal that large coalitions including the coalition of all countries are stable, but only when the potential gain from cooperation is sufficiently high. 相似文献
9.
Xingliang Ma Melinda Smale David J. Spielman Patricia Zambrano Hina Nazli Fatima Zaidi 《Journal of Agricultural Economics》2017,68(2):366-385
Bt cotton remains one of the most widely grown biotech crops among smallholder farmers in lower income countries, and numerous studies attest to its advantages. However, the effectiveness of Bt toxin, which depends on many technical constraints, is heterogeneous. In Pakistan, the diffusion of Bt cotton occurred despite a weak regulatory system and without seed quality control; whether or not many varieties sold as Bt are in fact Bt is also questionable. We utilise nationally representative sample data to test the effects of Bt cotton use on productivity. Unlike previous studies, we invoke several indicators of Bt identity: variety name, official approval status, farmer belief, laboratory tests of Bt presence in plant tissue, and biophysical assays measuring Bt effectiveness. Only farmer belief affects cotton productivity in the standard production model, which does not treat Bt appropriately as damage‐abating. In the damage control framework, all Bt indicators reduce damage from pests. Biophysical indicators have the largest effect and official approval has the weakest. Findings have implications for impact measurement. For policy‐makers, they suggest the need, on ethical and productivity grounds, to improve variety information and monitor variety integrity closer to point of sale. 相似文献
10.
本文介绍了一起由于平整土地过程中挖掘机与导线之间的电气距离不够造成的线路跳闸故障,从管理角度出发,提出了具体的防范措施,为降低该类故障总结了经验。 相似文献