全文获取类型
收费全文 | 719篇 |
免费 | 91篇 |
国内免费 | 62篇 |
出版年
2024年 | 3篇 |
2023年 | 20篇 |
2022年 | 18篇 |
2021年 | 29篇 |
2020年 | 35篇 |
2019年 | 56篇 |
2018年 | 53篇 |
2017年 | 47篇 |
2016年 | 45篇 |
2015年 | 55篇 |
2014年 | 37篇 |
2013年 | 92篇 |
2012年 | 32篇 |
2011年 | 28篇 |
2010年 | 29篇 |
2009年 | 35篇 |
2008年 | 30篇 |
2007年 | 35篇 |
2006年 | 31篇 |
2005年 | 20篇 |
2004年 | 11篇 |
2003年 | 15篇 |
2002年 | 14篇 |
2001年 | 14篇 |
2000年 | 7篇 |
1999年 | 13篇 |
1998年 | 16篇 |
1997年 | 11篇 |
1996年 | 8篇 |
1995年 | 3篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1981年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有872条查询结果,搜索用时 62 毫秒
741.
Monika Piotrowska 《Bioethics》2021,35(1):98-104
New discoveries are improving the odds of human cells surviving in host animals, prompting regulatory and funding agencies to issue calls for additional layers of ethical oversight for certain types of human–animal chimeras. Of interest are research proposals involving chimeric animals with humanized brains. But what is motivating the demand for additional oversight? I locate two, not obviously compatible, motivations, each of which provides the justificatory basis for paying special attention to different sets of human–animal chimeras. Surprisingly, the sets of animals that actually get flagged for special scrutiny by research and funding guidelines do not correlate with either of the sets of animals that arise when we think about what is motivating additional oversight. What this shows is that existing research policies and funding guidelines are disconnected from their motivation: the rationale for flagging certain types of human–animal chimeras as requiring special oversight is ignored in execution. 相似文献
742.
743.
Advocates of land-titling programs in developing countries posit that these programs lead to a multitude of benefits, including health improvements. This paper presents the results of a child health survey of several Lima communities after various time exposures to Peru's urban land-titling program. The results provide suggestive evidence that improved property rights increase children's weight but not their height, which is consistent with previous work on the topic. However, titles also appear to raise children's risk of being overweight or obese, implying that the observed weight gain is not necessarily an improvement in nutritional status. 相似文献
744.
Mohammad Firdaus Bin Abdul Aziz Michael Morrison Jane Kaye 《New genetics and society》2018,37(1):2-20
Many “rising powers” such as India, China, Argentina, Singapore, and Brazil are investing in stem cell technology, joining the traditional leaders in the field, such as the UK, Germany, USA, and Japan. Malaysia is also entering this sector because of the potential medical and economic benefits that the use of stem cell technologies could provide. Like other countries, Malaysia faces the challenge of how to encourage scientific progress and innovation in an ethical manner while at the same time ensuring a safe and accessible market for regenerative therapies. This paper reports on the research findings of semi-structured interviews with local stakeholders to investigate how they perceived and evaluated the current regulatory framework for human stem cell research in Malaysia, and what might be at stake if the state continues with its current regulatory approach. 相似文献
745.
David Rejeski 《Journal of Industrial Ecology》1997,1(4):13-18
Although industrial ecology represents a captivating metaphor and rich repertoire of analytical tools, its impact on environmental policy has been marginal at best. This article examines the insights provided by the studies of three common materials in the US. economy-lead, arsenic, and silver-and the abilrty of such studies to illuminate some larger and looming challenges for future environmental policy. Three specific challenges are explored: the flow of materials across national borders, the increasing embodiment of emissions in products, and the dangers of unchallenged assumptions about the drivers of material flows. The article argues that industrial ecology can inform public policy but that it is time for the practitioners of industrial ecology, an applied science, to apply it in the often messy world of environmental policymaking. 相似文献
746.
Regulatory Influences on Environmental Protection: Why Shipping Companies Comply and When They Don't
Ngwatung Akamangwa 《Ocean Development & International Law》2017,48(2):158-180
This article reports the findings of an empirical study on the regulation of ship-source pollution at one United Kingdom-based global ship management company. In examining the corporate response of the case-study company, particular attention is given to the regulatory influences promoting such compliance as expressed in the views of company executives. The findings show that both legal regulatory pressures and customer demands are important factors in encouraging the company to comply with environmental requirements. However, the study also revealed that compliance with environmental requirements ultimately depends on the way in which individual companies adapt to different national regulatory and enforcement regimes. 相似文献
747.
We investigated perceptions of wildlife policy and issues through questionnaires (n = 148) administered to policy makers, conservation scientists, individuals representing non-government organizations (NGOs), and field officials, who implemented government policies and enforced laws. We found significant differences among attitudes of stakeholders identifying major threats to wildlife, the use of science, the role of poaching in conservation, and the composition of species illegally traded. Policy makers and field officials differed in their views with NGOs and scientists on community response to wildlife policies and the varying threat perceptions to different species due to poaching and illegal trade. We noted ambiguity among stakeholders about sustainable use principles in India. Policies must be more effective in conservation and the process of making policy must be broad-based and participatory if wildlife conservation is to advance on the subcontinent. © 2011 The Wildlife Society. 相似文献
748.
Kieran Campbell-Johnston Erik Roos Lindgreen Giovanni Mondello Teresa Maria Gulotta Walter J. V. Vermeulen Roberta Salomone 《Journal of Industrial Ecology》2023,27(2):508-521
The strategic relevance of extracting raw materials from waste from electrical and electronic equipment (WEEE) in the EU is increasing due to value chain risks caused by geopolitical instability, accessibility of specific minerals, and decreasing reserves due to growing extraction rates. This article examines the quantities of so-called critical raw materials (CRMs) originating within WEEE streams from a depletion perspective. Presently, current recycling targets are based solely on mass collection and recycling rates. We examine the potential limitations of this approach using an exergy-based indicator named thermodynamic rarity. This indicator represents the exergy costs needed for producing materials from the bare rock to market. The case of Italy is used to explore the application of the indicator at the macro (national) and micro (company) level for the product categories “small electronics” and “screens and monitors.” Our estimations show significant differences between the mass and rarity of materials within Italian WEEE streams. While iron accounts for more than 70% of the weight of the product categories analyzed, it accounts for less than 15% of the rarity. Similarly, several CRMs with a small mass have a higher rarity value, for example, tungsten with less than 0.1% of the mass and over 6% of the rarity. The policy context is reflected upon, where it is argued that thermodynamic rarity can provide novel insights to support end-of-life WEEE decision-making processes, for example, target development and recycling standards setting to help prioritize material monitoring and recovery options. 相似文献
749.
David C. Natcher 《Human ecology: an interdisciplinary journal》2004,32(4):421-441
Through a process of participatory mapping, this research assessed the impacts of the 1984 change in Alaska fire policy from one of exclusion to one of management on Native land use in the Yukon Flats National Wildlife Refuge. Findings suggest that while the change in policy has had little measurable effect on community land use the continued suppression of fire on Native owned lands is having a direct impact on the current availability of wildlife resources to the point of necessitating territorial expansion among Native resource users. However, given the complexity of human nature, the impacts associated with the 1984 policy change should not be reduced to a simplistic cause-and-effect relationship. Rather this analysis demonstrates the interaction as well as the contradiction that occur between policy, culture, and ecology as these factors together have come to influence Native land use. 相似文献
750.
A J. KROLL 《The Journal of wildlife management》2007,71(1):226-230
Abstract: Recent articles have called for enhanced quantitative proficiency in wildlife students, arguing that such training will increase scientific rigor and produce wildlife researchers and managers who are better able to remedy current problems and to address future challenges in wildlife management. The idea that better, or more rigorous, science is the panacea for controversial natural resource problems is a cavalier and common presumption in many applied professions and one to which wildlife science and management is not immune. However, science and management are distinct processes and although scientific rigor is important, dialogue between the 2 processes is more critical for successful interaction. Integrated training that exposes students to nontraditional coursework and develops essential professional skills, such as planning, consensus-building, and communication, can help produce graduates to bridge the science—management gap and promote the conservation of natural resources. Changes in the structure and coursework of university wildlife departments can help to develop more effective wildlife professionals. 相似文献