首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   3018篇
  免费   99篇
  2024年   2篇
  2023年   32篇
  2022年   40篇
  2021年   53篇
  2020年   117篇
  2019年   117篇
  2018年   117篇
  2017年   147篇
  2016年   155篇
  2015年   79篇
  2014年   85篇
  2013年   391篇
  2012年   197篇
  2011年   140篇
  2010年   120篇
  2009年   138篇
  2008年   166篇
  2007年   142篇
  2006年   154篇
  2005年   117篇
  2004年   88篇
  2003年   93篇
  2002年   75篇
  2001年   91篇
  2000年   69篇
  1999年   39篇
  1998年   13篇
  1997年   21篇
  1996年   18篇
  1995年   13篇
  1994年   14篇
  1993年   2篇
  1992年   19篇
  1991年   12篇
  1990年   1篇
  1989年   5篇
  1988年   5篇
  1987年   7篇
  1986年   5篇
  1985年   5篇
  1984年   10篇
  1982年   1篇
  1981年   1篇
  1980年   1篇
排序方式: 共有3117条查询结果,搜索用时 15 毫秒
61.
In the Iberian Peninsula, the copper metallurgy from the Chalcolithic to the Middle Bronze Age (MBA) was mostly characterized by low arsenic contents. A collection of 53 MBA artefacts from southern Portugal was analysed by micro‐EDXRF, optical microscopy, SEM–EDS and Vickers to investigate the metal composition and manufacture. No technological distinction was found between artefacts from domestic and funerary contexts, which were radiocarbon‐dated to 2000–1500 cal bc . The arsenic contents of almost 100 MBA artefacts from this region, including the above‐mentioned set, have a Gaussian distribution with a high average (3.9 wt% As). Possible explanations are discussed for this distinctive metallurgy at the south‐western end of the Iberian Peninsula.  相似文献   
62.
Metallurgical analyses and chemical characterizations were carried out on historical cannonballs from the Fortress of San Juan de Ulúa, Veracruz, México. Cannonballs dating from the 18th and 19th centuries share metallurgical characteristics similar to those of material coming from a shipment of ammunition found in the wreck of a sunken French ship from the battle of Trafalgar. The analyses show that the base material is grey cast iron with a carbon equivalent of 4.94 and a ferritic–perlitic matrix, in which the high phosphorus content has led to the formation of iron phosphide compounds in conjunction with a homogeneous distribution of carbon graphite flakes of Type C. In addition, corrosion products from samples revealed the presence of various crystalline iron compounds (X‐ray diffraction), mostly highly chlorinated iron compounds identified as akaganeite. X‐ray fluorescence identified various characteristics of the corrosion products as a function of the sampling depth. FT–IR spectroscopy revealed that the main difference between the corrosion products (internal and external) is determined by the number of organic species. Differential scanning calorimetry corroborated that these corrosion products are thermally stable compounds at elevated temperatures.  相似文献   
63.
This introduction to the translation of Henri Lefebvre's 1956 essay “The theory of ground rent and rural Sociology” moves through three stages. First, it suggests that Anglophone appropriations of Lefebvre have tended to focus too much on his urban writings, at the expense of understanding his early work on rural sociology, and failing to recognise how his urban focus emerged as a result of his interest in rural–urban transformation. Second, it provides a summary of his wider work on rural questions, including his unfinished work on a major treatise of rural sociology; and outlines the key themes of the present essay in relation to these other projects. Third, it connects Lefebvre's issues to wider debates in political economy and geography about aspects of the rural, land and ground rent, not least including the work of Antonio Gramsci and José Carlos Mariátegui.  相似文献   
64.
民国《贵州通志·艺文志》著录黄彭年撰《尔雅集韵》一书。而追索《艺文志》著录的史源,并取其他史料相印证,推寻其致误的原因,证明黄彭年曾批校《尔雅》《集韵》二书,但并未撰《尔雅集韵》一书。此外,又据各家书目题跋,梳理了黄彭年批校《集韵》的经过及其批校本流传情况。  相似文献   
65.
This article discusses how land-use planning and management can combine the aim of local development with the protection of mountain areas. The basis for this double approach comprises protected areas and the land-use element of the Municipal Master Plan according to the Nature Diversity Act and the Planning and Building Act (PBA), respectively. Case studies performed in six mountain municipalities show that the planning processes in general are performed by a combination of rationalistic and communicative rationality based on consensus and with little awareness of power structures. Today's two-part system is dominated by the interests backing protection, not only in the protected areas, but also in the buffer-zones. Though the conflicts are rather few, they nevertheless often seem deep-set and rooted in national–local power relations. We argue that a more agonistic and decentralized approach where the protection-area management is transferred to the PBA will, to a larger extent, be able to combine both use and protection and to stimulate local development in mountain municipalities.  相似文献   
66.
This paper explores the effectiveness of policies ‘in’ attracting the foreign research and development (R&D) of multinational enterprises (MNEs) to specific countries in Europe. We develop a macroeconomic investigation covering 29 European countries during the period between 1990 and 2012 in order to address: (a) whether the provision of direct financial support for business R&D is effective for the attraction of foreign R&D; (b) whether direct support is more effective than indirect support for this purpose and (c) whether the link between direct financial support for business R&D and the foreign R&D of MNEs is conditioned by the context within which the support is provided. The results of the analysis show that, first, the provision of direct financial support is generally effective for the attraction of foreign R&D by MNEs. Second, direct support for business R&D is more effective for this purpose than indirect support. Third, the provision of direct financial support for business R&D yields greater returns in contexts that are more socio-economically suitable for knowledge-intensive, innovative activity.  相似文献   
67.
This paper discusses three normative standpoints on conflict in strategic spatial planning: no conflict, conflict for consensus and conflict for meta-consensus on the validity of dispute. These views apply to the questions of whether and why projects, as a major source of conflict, should be identified in the process of strategic planning. In their approaches to these questions, the performance school advocates the production of general guidelines to avoid conflict, the collaborative perspective supports the identification of projects in strategic planning in order to utilize their potential in a conflict-to-consensus journey and the conflict-oriented perspective favours the identification of projects in strategic planning in order to arrive at meta-consensus on the immediate disputability of robust agreements. Reflecting on the collaborative perspective, this paper tests a hypothetical model of how conflicts created in the face of project identification can feed in making consensual strategies. Findings in the North West region of England support the model and suggest some difficulties with reviewing such consensus around which a resistance network forms. The paper puts forward some recommendations for overcoming the review challenge.  相似文献   
68.
This article discusses the role of non-governmental organizations (NGOs) as a cultural and political force in shaping the gendered and classed subjectivities of young women growing up in ‘red-light areas’ in Kolkata, India. It foregrounds the flexible deployment of NGO gender narratives by ‘subjects’ of NGO development to improve their everyday lives. Drawing on debates of NGOization, post-colonial urban Indian femininities and intersectionality, it demonstrates how several young women who grew up as ‘subjects’ of NGO development mobilize, reject and improvise contested NGO-inspired femininities for their everyday gain. At the same time, it illustrates how NGO gender narratives that are useful to some young women in their renegotiation of gender norms are deemed ineffective, if not obstructive, by other young women, particularly those whose lives remain entangled in multiple marginalities.  相似文献   
69.
About half of children age under five worldwide who are classified as undernourished (84 million out of 151 million) or overweight or obese (17.5 million out of 38 million) live in Asia. Tackling malnutrition in Asia is however fairly complex since the nutritional transition, a consequence of rapid economic development and globalisation, made many Asian nations undergo the simultaneous burdens of under- and over-nutrition. The dual burden of malnutrition is characterised by a concurrence of undernutrition along with overweight and obesity within the same individual, household, community, region and/or country. Providing that household food security is closely linked to malnutrition, this raises questions about the implications of climate change on the dual burden of malnutrition. That climate change affects food availability, access, utilisation and stability is evident. Accordingly, households facing food insecurity due to climatic shocks may allocate food differentially. Adult members may receive low-cost high-calorie food inducing obesity, whilst children receive nutrient-poor foods leading to undernutrition. Little is known about the climate impacts on the double burden of malnutrition and how this affects population subgroups differentially. This Editorial discusses the potential impacts of climate change on the double burden of malnutrition and concludes with the recommendation of strategies to tackle the issue.  相似文献   
70.
In 2004, a controversy arose in Aotearoa New Zealand's coal mining sector that involved Powelliphanta augusta, a species of land snail. This paper considers that controversy in terms of emergent assemblages involving the snail, the mining industry, the Department of Conservation, political action by environmental non‐government organisations, and public expressions of environmental and other values. Three sets of relations embedded in those assemblages are examined—those related to positioning and organising nature; values, politics, and power relations; and human and non‐human materialities. Those relations illuminate how a protracted controversy and its objects form a “social test bed” for contested views in legislation and guidelines dealing with economy, conservation, and restoration. To assess the dynamics, complexities, and contingencies of such relations, attention is paid to the controversy's detailed time line and legal framing, as well as to ontological shifts of snail and habitat and snail metrics. This analytical focus highlights the shifting quality of ideas about how the snail and its habitat are understood as entangled in fraught and mutating strategies of translocation that are played out in a particular regulatory setting. It also provides insights into international geographical efforts to re‐shape environmental governance and management.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号