全文获取类型
收费全文 | 299篇 |
免费 | 29篇 |
国内免费 | 56篇 |
出版年
2023年 | 41篇 |
2022年 | 10篇 |
2021年 | 11篇 |
2020年 | 16篇 |
2019年 | 24篇 |
2018年 | 16篇 |
2017年 | 13篇 |
2016年 | 9篇 |
2015年 | 13篇 |
2014年 | 9篇 |
2013年 | 29篇 |
2012年 | 12篇 |
2011年 | 19篇 |
2010年 | 10篇 |
2009年 | 15篇 |
2008年 | 6篇 |
2007年 | 19篇 |
2006年 | 7篇 |
2005年 | 7篇 |
2004年 | 11篇 |
2003年 | 11篇 |
2002年 | 6篇 |
2001年 | 4篇 |
2000年 | 5篇 |
1999年 | 2篇 |
1998年 | 8篇 |
1997年 | 6篇 |
1996年 | 5篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 5篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有384条查询结果,搜索用时 15 毫秒
91.
M. J. S. Hodge 《Journal of the history of biology》2009,42(3):399-416
When socio-economic contexts are sought for Darwin’s science, it is customary to turn to the Industrial Revolution. However,
important issues about the long run of England’s capitalisms can only be recognised by taking a wider view than Industrial
Revolution historiographies tend to engage. The role of land and finance capitalisms in the development of the empire is one
such issue. If we historians of Darwin’s science allow ourselves a distinction between land and finance capitalisms on the
one hand and industrial capitalism on the other; and if we ask with which side of this divide were Darwin and his theory of
branching descent by natural selection aligned, then reflection on leading features of that theory, including its Malthusian
elements, suggests that the answer is often and largely, though not exclusively: on the land side. The case of Wallace, socialist
opponent of land capitalism, may not be as anomalous for this suggestion as one might at first think. Social and economic
historians have reached no settled consensuses on the long-run of England’s capitalisms. We historians of Darwin’s science
would do well to import some of these unsettled states of discussion into our own work over the years to come. 相似文献
92.
ABSTRACT Even faced with overwhelming evidence that tobacco threatens human health, along with economic developments undermining their status as independent producers, North Carolina tobacco farmers view tobacco production in ways congruent with a moral economy. A shift from independent to contract production of tobacco and the dismantling of government price supports have challenged this moral economy, converting tobacco producers into a quasi–working class dependent on tobacco companies while leading to fewer tobacco farms and an increase in the average tobacco farm's size. These changes signal a shift away from a moral economy of tobacco, although moral-economic dimensions remain. Producers today emphasize different moral dimensions of economic behavior, such as producing quality human beings, than during earlier eras, when moral-economic actors pressed for state intervention in economic crises. Moral-economic principles are not restricted to either non-Western or historical peoples but, rather, influence economic production and ideology in advanced capitalist settings today. 相似文献
93.
Integrating dark and light bio-hydrogen production strategies: towards the hydrogen economy 总被引:1,自引:0,他引:1
Mark D. Redwood Marion Paterson-Beedle Lynne E. Macaskie 《Reviews in Environmental Science and Biotechnology》2009,8(2):149-185
Biological methods of hydrogen production are preferable to chemical methods because of the possibility to use sunlight, CO2 and organic wastes as substrates for environmentally benign conversions, under moderate conditions. By combining different
microorganisms with different capabilities, the individual strengths of each may be exploited and their weaknesses overcome.
Mechanisms of bio-hydrogen production are described and strategies for their integration are discussed. Dual systems can be
divided broadly into wholly light-driven systems (with microalgae/cyanobacteria as the 1st stage) and partially light-driven
systems (with a dark, fermentative initial reaction). Review and evaluation of published data suggests that the latter type
of system holds greater promise for industrial application. This is because the calculated land area required for a wholly
light-driven dual system would be too large for either centralised (macro-) or decentralised (micro-) energy generation. The
potential contribution to the hydrogen economy of partially light-driven dual systems is overviewed alongside that of other
bio-fuels such as bio-methane and bio-ethanol. 相似文献
94.
利用灰色系统理论与时间序列分析,提出了带灰色项的时间序列模型,对这类模型进行了分析,给出了建模与预报方法,并将其应用于我国农业产值问题的预报与研究之中,模型的正确性得到了检验. 相似文献
95.
Suites of plant traits in species from different stages of a Mediterranean secondary succession 总被引:1,自引:0,他引:1
M.-L. Navas C. Roumet A. Bellmann G. Laurent & E. Garnier 《Plant biology (Stuttgart, Germany)》2010,12(1):183-196
The aim of this study was to detect suites of traits related to whole plant and seed morphology, phenology and resource use – including water – in species differing in successional status. Twenty traits were measured on 55 species representative of 5 successional stages in Mediterranean southern France, including eight pertaining to phenology and five to water economy. Suites of traits that changed along succession in agreement with the acquisition/conservation trade-off were completed by continuous changes in phenology. Early successional species had leaves with a high specific leaf area that were produced and lost continuously through the growing season. Late-successional species were taller with long-lived, high δ13 C leaves produced during short periods, most of them persisting during summer, and produced large seeds requiring a long ripening period. Replacement of species occurred with change in strategies of drought survival: early successional species escaped drought by dying before summer; later herbaceous species maintained favourable water status in relation to leaf shedding during summer; late successional trees with a large body allowing access to a large pool of resources, produced dense leaves that could tolerate desiccation. These changes occurred concomitantly with a shift in CSR strategies, using traits related to resource use, plant size and flowering phenology: ruderal herbs were replaced by more stress-tolerant herbs and shrubs throughout the succession, with competitive trees dominating the latest successional stage. These results suggest that the breadth of functional variability found in natura is not predicted by the CSR framework, and calls for a more integrated view of whole plant functioning. 相似文献
96.
This review provides a contemporary account of knowledge on aspects of introductions of non‐native fish species and includes issues associated with introduction pathways, ecological and economic impacts, risk assessments, management options and impact of climate change. It offers guidance to reconcile the increasing demands of certain stakeholders to diversify their activities using non‐native fishes with the long‐term sustainability of native aquatic biodiversity. The rate at which non‐native freshwater fishes have been introduced worldwide has doubled in the space of 30 years, with the principal motives being aquaculture (39%) and improvement of wild stocks (17%). Economic activity is the principal driver of human‐mediated non‐native fish introductions, including the globalization of fish culture, whereby the production of the African cichlid tilapia is seven times higher in Asia than in most areas of Africa, and Chile is responsible for c. 30% of the world's farmed salmon, all based on introduced species. Consequently, these economic benefits need balancing against the detrimental environmental, social and economic effects of introduced non‐native fishes. There are several major ecological effects associated with non‐native fish introductions, including predation, habitat degradation, increased competition for resources, hybridization and disease transmission. Consideration of these aspects in isolation, however, is rarely sufficient to adequately characterize the overall ecological effect of an introduced species. Regarding the management of introduced non‐native fish, pre‐introduction screening tools, such as the fish invasiveness scoring kit (FISK), can be used to ensure that species are not introduced, which may develop invasive populations. Following the introduction of non‐native fish that do develop invasive populations, management responses are typified by either a remediation or a mitigation response, although these are often difficult and expensive to implement, and may have limited effectiveness. 相似文献
97.
Steudel-Numbers KL 《Journal of human evolution》2003,44(2):255-262
A wide range of selective pressures have been advanced as possible causes for the adoption of bipedalism in the hominin lineage. One suggestion has been that because modern human walking is relatively efficient compared to that of a typical quadruped, the ancestral quadruped may have reaped an energetic advantage when it walked on two legs. While it has become clear that human walking is relatively efficient and human running inefficient compared to "generalized endotherms", workers differ in their opinion of how the cost of human bipedal locomotion compares to that of a generalized primate walking quadrupedally. One view is that human walking is particularly efficient in comparison to other primates. The present study addresses this by comparing the cost of human walking and running to that of the eight primate species for which data are available and by comparing cost in primates to that of a "generalized endotherm". There is no evidence that primate locomotion is more costly than that of a generalized endotherm, although more data on adult Old World monkeys and apes would be useful. Further, human locomotion does not appear to be particularly efficient relative to that of other primates. 相似文献
98.
This article is the first of a two-part series that describes and compares the essential features of nine existing "physical economy" approaches for quantifying the material demands of the human economy upon the natural environment. A range of material flow analysis (MFA) and related techniques is assessed and compared in terms of several major dimensions. These include the system boundary identification for material flow sources, extents, and the key socioinstitutional entities containing relevant driving forces, as well as the nature and detailing of system components and flow interconnections, and the comprehensiveness and types of flows and materials covered.
Shared conceptual themes of a new wave of physical economy approaches are described with a brief overview of the potential applications of this broad family of methodologies. The evolving and somewhat controversial nature of the characteristics and role that define MFA is examined. This review suggests the need to specify whether MFA is a general metabolic flow measurement procedure that can be applied from micro to macrolevels of economic activity, or a more specific methodology aimed primarily at economy-wide analyses that "map" the material relations between society and nature. Some alternative options for classifying MFA are introduced for discussion before a more detailed comparative summary of the key methodological features of each approach in the second part of this two-part article.
The review is presented (1) as a reference and resource for the increasing number of policy makers and practitioners involved in industrial ecology and the evaluation of the material basis of economies and the formulation of eco-efficiency strategies, and (2) to provoke discussion and ongoing dialogue to clarify the many existing areas of discordance in environmental accounting related to material flows, and help consolidate the methodological basis and application of MFA. 相似文献
Shared conceptual themes of a new wave of physical economy approaches are described with a brief overview of the potential applications of this broad family of methodologies. The evolving and somewhat controversial nature of the characteristics and role that define MFA is examined. This review suggests the need to specify whether MFA is a general metabolic flow measurement procedure that can be applied from micro to macrolevels of economic activity, or a more specific methodology aimed primarily at economy-wide analyses that "map" the material relations between society and nature. Some alternative options for classifying MFA are introduced for discussion before a more detailed comparative summary of the key methodological features of each approach in the second part of this two-part article.
The review is presented (1) as a reference and resource for the increasing number of policy makers and practitioners involved in industrial ecology and the evaluation of the material basis of economies and the formulation of eco-efficiency strategies, and (2) to provoke discussion and ongoing dialogue to clarify the many existing areas of discordance in environmental accounting related to material flows, and help consolidate the methodological basis and application of MFA. 相似文献
99.
在分析毛乌素沙地自然、社会经济、人文等条件与现状的基础上,诊断高效生态经济复合系统运行的限制因素及有利条件。运用线性规划的理论与方法进行系统的优化设计。当降水量分别在80%保证率的280mm、中等雨量350mm、较强雨量400mm时,径流园林区中种植作物覆盖度分别为65%、82.5%、95%;高效农牧区的种植覆盖度分别为75%、92%、100%。但在毛乌素沙地降水达到400mm的保证率很低,350mm的降水保证率也较低,为保证高效生态经济复合系统的持续发展,降水量以280mm计算为宜,也即径流园林区的种植覆盖度可达到65%;高效农牧区的种植覆盖度可达到75%,最大不超过80%。同时表明在毛乌素沙地高效生态经济复合系统持续发展的限制因子主要是水分。 相似文献
100.
Kunle Ibukun Olatayo Paul T. Mativenga Annlizé L. Marnewick 《Journal of Industrial Ecology》2023,27(2):601-623
Despite the promotion of plastic recycling to sustainably manage plastic waste and advance the circular economy, existing plastic recycling systems globally are largely experiencing low performance and growth. To transition to world-class plastic material recycling and circularity, defining the metrics that impact the performance of a plastic recycling system is crucial. Bringing together existing literature, this study developed a conceptual framework, comprised of eight key performance metrics, for benchmarking recycling success or assessing the degree to which the performance of any plastic recycling system is optimal. Through a value chain approach, the specific performance metrics relevant to each stage of the plastic recycling system, their objectives, and the actors characterizing the system were analyzed in detail. Also, specific maturity models were developed to measure the performance of any plastic recycling system. This framework provides essential knowledge for related stakeholders to inform further development of plastic recycling and a circular economy. 相似文献