全文获取类型
收费全文 | 1276篇 |
免费 | 24篇 |
出版年
2024年 | 11篇 |
2023年 | 12篇 |
2022年 | 15篇 |
2021年 | 16篇 |
2020年 | 41篇 |
2019年 | 28篇 |
2018年 | 27篇 |
2017年 | 31篇 |
2016年 | 52篇 |
2015年 | 28篇 |
2014年 | 29篇 |
2013年 | 100篇 |
2012年 | 62篇 |
2011年 | 86篇 |
2010年 | 73篇 |
2009年 | 78篇 |
2008年 | 73篇 |
2007年 | 91篇 |
2006年 | 89篇 |
2005年 | 68篇 |
2004年 | 51篇 |
2003年 | 59篇 |
2002年 | 51篇 |
2001年 | 38篇 |
2000年 | 27篇 |
1999年 | 15篇 |
1998年 | 10篇 |
1997年 | 2篇 |
1996年 | 8篇 |
1995年 | 8篇 |
1994年 | 6篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1983年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有1300条查询结果,搜索用时 15 毫秒
1.
This paper contributes to a critical methodological discussion that has direct ramifications for policy studies: how computational methods can be concretely incorporated into existing processes of textual analysis and interpretation without compromising scientific integrity. We focus on the computational method of topic modeling and investigate how it interacts with two larger families of qualitative methods: content and classification methods characterized by interest in words as communication units and discourse and representation methods characterized by interest in the meaning of communicative acts. Based on analysis of recent academic publications that have used topic modeling for textual analysis, our findings show that different mixed‐method research designs are appropriate when combining topic modeling with the two groups of methods. Our main concluding argument is that topic modeling enables scholars to apply policy theories and concepts to much larger sets of data. That said, the use of computational methods requires genuine understanding of these techniques to obtain substantially meaningful results. We encourage policy scholars to reflect carefully on methodological issues, and offer a simple heuristic to help identify and address critical points when designing a study using topic modeling. 相似文献
2.
Knowledge about the Inca measurement system is based on information from the colonial chronicles and modern studies of the 16th-century Quechua dictionaries. Based on those texts, we can presume that the Incas used an anthropometric system of measurement adopted from the proportions of the human body. Using cosine quantogram analysis and statistical verification, it is possible to verify the existence of the measurement system used by the Inca architects. For this purpose, a measurement series of architectural and water infrastructure elements were collected from 3D point cloud of the Chachabamba and Machu Picchu settlements in Machupicchu National Archaeological Park. 相似文献
3.
4.
5.
Daniel Gabaldón-Estevan Liney Manjarrés-Henríquez F. Xavier Molina-Morales 《European Planning Studies》2018,26(5):895-914
In this work, we apply a systemic approach to the analysis of a particular geographic territory, the industrial district. We are particularly interested in analysing the interaction between the productive-technological environment and the scientific environment by an examination of research contracts and patents. Our analysis shows that R&D activity in the Spanish ceramic tile District Innovation System was mainly conducted by suppliers. Final producers’ innovation efforts were related to non-technological aspects and differentiation. 相似文献
6.
New industrial innovation policies like smart specialization aim at boosting economic growth by diversification towards more complex and higher value economic activities. This paper proposes a conceptual and analytical framework to support the design and implementation of such policies considering place-specific preconditions, particularly the differentiation of the regional system of innovation and entrepreneurship and the degree of current industrial diversification. The paper expands on the links between these preconditions and the barriers and opportunities for industrial diversification. Consequently, it proposes an archetypical place-based policy framework covering overall policy objectives as well as measures at the level of actors, networks, and the institutional and organizational support structures. 相似文献
7.
许多出土饱水木质文物因其降解严重、含水率较高,容易在脱水过程中出现不可逆的收缩变形以及开裂现象,从而遭到严重破坏。因此,饱水木质文物脱水方法的研究是文物保护工作中的重要课题。为探究风冷冷冻法对饱水木质文物脱水的效果,以一批无法复原的出土饱水木质文物为研究对象,在对其材种、含水率、基本密度及化学成分进行了测定和分析后,使用一台风冷电冰箱在-18℃条件下对样品进行了风冷干燥脱水处理,记录脱水时间和脱水效果,并分析了该方法的传质传热特点,证明了风冷干燥法用于饱水木质文物的脱水干燥能够取得良好效果,并且具有对文物干预小、适用性广、操作简便、成本低廉等优点,为饱水木质文物的脱水处理提供了一种新的思路。 相似文献
8.
John Hutchinson 《Nations & Nationalism》2018,24(1):6-21
This article argues that warfare has been marginalised in theories of nationalism but that in conjunction with nationalism is vital for understanding the rise of nation‐states, the formation of nations and the nature of the international system. It offers a critique of statist approaches, suggests mechanisms through which warfare may sacralise nations and explores different patterns of nation‐state formation as they affect the interstate system. In particular, it emphasises tensions between state and nation‐formation as activated by the fortunes of war and the destabilising effects of waves of imperial dissolution, which are accompanied by patterns of re‐imperialization. It suggests that it is simplistic both to claim that war has led to a transition from empires to nation‐states and that contemporary practices of war‐making have led to a postnational era. 相似文献
9.
K. Su J.‐P. Latham D. Pavlidis J. Xiang F. Fang P. Mostaghimi J. R. Percival C. C. Pain M. D. Jackson 《Geofluids》2015,15(4):592-607
Accurate simulation of multiphase flow in fractured porous media remains a challenge. An important problem is the representation of the discontinuous or near discontinuous behaviour of saturation in real geological formations. In the classical continuum approach, a refined mesh is required at the interface between fracture and porous media to capture the steep gradients in saturation and saturation‐dependent transport properties. This dramatically increases the computational load when large numbers of fractures are present in the numerical model. A discontinuous finite element method is reported here to model flow in fractured porous media. The governing multiphase porous media flow equations are solved in the adaptive mesh computational fluid dynamics code IC‐FERST on unstructured meshes. The method is based on a mixed control volume – discontinuous finite element formulation. This is combined with the PN+1DG‐PNDG element pair, which has discontinuous (order N+1) representation for velocity and discontinuous (order N) representation for pressure. A number of test cases are used to evaluate the method's ability to model fracture flow. The first is used to verify the performance of the element pair on structured and unstructured meshes of different resolution. Multiphase flow is then modelled in a range of idealised and simple fracture patterns. Solutions with sharp saturation fronts and computational economy in terms of mesh size are illustrated. 相似文献
10.
Stavros K. Kourkoulis Ermioni D. Pasiou 《International Journal of Architectural Heritage》2015,9(3):177-194
The restoration of destroyed connections of epistyles joined together by means of metallic connectors is among the most difficult problems encountered by scientists working for the conservation/restoration of monuments made of marble. The complexity of the geometry and the interaction of three completely different materials (metal-filling material-marble) constituting the connection render the study (either experimental or analytic) extremely complicated. In this direction a numerical analysis is presented here in order to deeply understand the response of a typical ancient connection subjected to axial loads as well as to quantify the influence of some geometric parameters on its response. The parameters studied include the length of the connector, the width of its flanges, the depth of the groove (mortise), the existence or not of relieving space and the filling material’s volume. The numerical model was calibrated and validated according to the results of an earlier experimental study realized on the worksite of the Parthenon Temple. It was concluded that the interventions required to relieve the stress field by changing the size of the connector are disproportional to the respective positive effect on the response of the connection. Moreover it was proved that the most beneficial parameter is the relieving space. 相似文献