全文获取类型
收费全文 | 1010篇 |
免费 | 151篇 |
国内免费 | 315篇 |
出版年
2024年 | 6篇 |
2023年 | 50篇 |
2022年 | 48篇 |
2021年 | 58篇 |
2020年 | 70篇 |
2019年 | 98篇 |
2018年 | 54篇 |
2017年 | 86篇 |
2016年 | 80篇 |
2015年 | 68篇 |
2014年 | 70篇 |
2013年 | 83篇 |
2012年 | 56篇 |
2011年 | 60篇 |
2010年 | 49篇 |
2009年 | 60篇 |
2008年 | 56篇 |
2007年 | 52篇 |
2006年 | 40篇 |
2005年 | 51篇 |
2004年 | 31篇 |
2003年 | 39篇 |
2002年 | 24篇 |
2001年 | 41篇 |
2000年 | 31篇 |
1999年 | 21篇 |
1998年 | 11篇 |
1997年 | 19篇 |
1996年 | 11篇 |
1995年 | 10篇 |
1994年 | 4篇 |
1993年 | 7篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 5篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 4篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有1476条查询结果,搜索用时 15 毫秒
11.
Liping Jiang Jie Yu Shanyun Wang Xiaomin Wang Lorenz Schwark Guibing Zhu 《Global Change Biology》2023,29(7):1984-1997
The contribution of agriculture to the sustainable development goals requires climate-smart and profitable farm innovations. Increasing the ammonia fertilizer applications to meet the global food demands results in high agricultural costs, environmental quality deterioration, and global warming, without a significant increase in crop yield. Here, we reported that a third microbial ammonia oxidation process, complete ammonia oxidation (comammox), is contributing to a significant ammonia fertilizer loss (41.9 ± 4.8%) at the rate of 3.53 ± 0.55 mg N kg−1 day−1 in agricultural soils around the world. The contribution of comammox to ammonia fertilizer loss, occurring mainly in surface agricultural soil profiles (0–0.2 m), was equivalent to that of bacterial ammonia oxidation (48.6 ± 4.5%); both processes were significantly more important than archaeal ammonia oxidation (9.5 ± 3.6%). In contrast, comammox produced less N2O (0.98 ± 0.44 μg N kg−1 day−1, 11.7 ± 3.1%), comparable to that produced by archaeal ammonia oxidation (16.4 ± 4.4%) but significantly lower than that of bacterial ammonia oxidation (72.0 ± 5.1%). The efficiency of ammonia conversion to N2O by comammox (0.02 ± 0.01%) was evidently lower than that of bacterial (0.24 ± 0.06%) and archaeal (0.16 ± 0.04%) ammonia oxidation. The comammox rate increased with increasing soil pH values, which is the only physicochemical characteristic that significantly influenced both comammox bacterial abundance and rates. Ammonia fertilizer loss, dominated by comammox and bacterial ammonia oxidation, was more intense in soils with pH >6.5 than in soils with pH <6.5. Our results revealed that comammox plays a vital role in ammonia fertilizer loss and sustainable development in agroecosystems that have been previously overlooked for a long term. 相似文献
12.
Maja Wiprächtiger Melanie Haupt Andreas Froemelt Magdalena Klotz Claudio Beretta Dominik Osterwalder Vanessa Burg Stefanie Hellweg 《Journal of Industrial Ecology》2023,27(1):254-271
Industrial ecology (IE) methodologies, such as input/output or material flow analysis and life cycle assessment (LCA), are often used for the environmental evaluation of circular economy strategies. Up to now, an approach that utilizes these methods in a systematic, integrated framework for a holistic assessment of a geographic region's sustainable circular economy potential has been lacking. The approach developed in this study (IE4CE approach) combines IE methodologies to determine the environmental impact mitigation potential of circular economy strategies for a defined geographic region. The approach foresees five steps. First, input/output analysis helps identify sectors with high environmental impacts. Second, a refined analysis is conducted using material flow and LCA. In step 3, circular strategies are used for scenario design and evaluated in step 4. In step 5, the assessment results are compiled and compared across sectors. The approach was applied to a case study of Switzerland, analyzing 8 sectors and more than 30 scenarios in depth. Carbon capture and storage (CCS) from waste incineration, biogas and cement production, food waste prevention in households, hospitality and production, and the increased recycling of plastics had the highest mitigation potential. Most of the scenarios do not influence each other. One exception is the CCS scenarios: waste avoidance scenarios decrease the reduction potential of CCS. A combination of scenarios from different sectors, including their impact on the CCS scenario potential, led to an environmental impact mitigation potential of 11.9 Mt CO2-eq for 2050, which equals 14% of Switzerland's current consumption-based impacts. 相似文献
13.
14.
Despite efforts on ecosystem restoration and management, biodiversity loss remains one of the major environmental concerns of our time. Beyond the focus on threatened species, animals that indicate regional biodiversity hotspots and population trends, such as brood parasites, should also be targeted by conservation actions. We studied how reed habitat quality and management influence brood parasitism rate and offspring survival in Common Cuckoos Cuculus canorus parasitizing nests of Great Reed Warblers Acrocephalus arundinaceus in six reed habitats in an intensive agricultural landscape. Data collected from 45 sites over 13 years showed that the brood parasitism rate was highest on large canals and was positively influenced by the availability of potential perches (Cuckoo vantage points) and the height where host nests were built. Cuckoo chick survival decreased with water depth and was not affected by other factors. Our results suggest that the habitat-dependent detectability of host nests was central in brood parasitism rate and that water level was central in Cuckoo chick survival. Our study shows that a maintenance of intermediate water levels is the most optimal for maintaining Cuckoo populations in intensive agricultural landscapes. Because brood parasites are excellent bioindicators as their presence predicts regional hotspots of taxonomic and functional diversity as well as population trends in bird communities, knowledge on their habitat requirements is relevant in management targeting diverse bird communities. 相似文献
15.
Research data management (RDM) requires standards, policies, and guidelines. Findable, accessible, interoperable, and reusable (FAIR) data management is critical for sustainable research. Therefore, collaborative approaches for managing FAIR-structured data are becoming increasingly important for long-term, sustainable RDM. However, they are rather hesitantly applied in bioengineering. One of the reasons may be found in the interdisciplinary character of the research field. In addition, bioengineering as application of principles of biology and tools of process engineering, often have to meet different criteria. In consequence, RDM is complicated by the fact that researchers from different scientific institutions must meet the criteria of their home institution, which can lead to additional conflicts. Therefore, centrally provided general repositories implementing a collaborative approach that enables data storage from the outset In a biotechnology research network with over 20 tandem projects, it was demonstrated how FAIR-RDM can be implemented through a collaborative approach and the use of a data structure. In addition, the importance of a structure within a repository was demonstrated to keep biotechnology research data available throughout the entire data lifecycle. Furthermore, the biotechnology research network highlighted the importance of a structure within a repository to keep research data available throughout the entire data lifecycle. 相似文献
16.
Using an Australian focus to explore theoretical and policy issues of wider concern, this article examines linkages between public policy and the science of ecology. This is done within the broader framework of sustainability, emphasizing the problem of decision making in the face of uncertainty. Insights from the ecological, risk, sustainability and policy literatures are used. The sustainability-uncertainty problem is characterized, and the adequacy of existing policy support techniques and approaches noted, particularly the precautionary principle. The problem is further defined using the notion of ignorance. The treatment of ignorance and uncertainty in ecology is discussed. We suggest that the science of ecology has had a limited influence on policy formulation and discuss the basis of this using biodiversity conservation and ecosystem management as examples. We conclude by considering challenges for handling risk, uncertainty and ignorance in ecological science for policy formulation. We emphasize the need for improved communication between the science and policy communities, greater recognition of the limits of quantitative techniques in addressing uncertainty, and contingency planning. 相似文献
17.
Bruce Aylward Katie Allen Jaime Echeverría Joseph Tosi 《Biodiversity and Conservation》1996,5(3):315-343
The paper discusses the sustainability of the Monteverde Cloud Forest Preserve in the context of Costa Rican ecotourism. While the history of the Preserve is somewhat unique, the analysis of visitation, financial, ecological and economic factors provides a convincing case that tourism at the Preserve is sustainable. The experience of the Preserve is also put in the context of Costa Rican ecotourism, particularly to the national parks. The paper concludes that the Preserve has played a very important role in the development of Costa Rica as an ecotourism destination. Nonetheless, the failure of experience at the Preserve to inform recent changes in national park pricing policy reveal that Costa Rica has yet to fully capitalize on the experience gained and lessons learned at the Preserve. 相似文献
18.
Ricardo Godoy Nicholas Brokaw David Wilkie 《Human ecology: an interdisciplinary journal》1995,23(1):29-52
We use microeconomic theory to frame hypotheses about the effects of income on the use of non-timber rain forest products. We hypothesize that an increase in income: (a) encourages foraging specialization, resulting in the extraction of fewer goods; (b) increases the share of household income from occupations besides foraging; (c) produces a yearly value from the extraction of nontimber forest goods of about $50 per hectare; and (d) produces depletion of forest goods entering commercial channels and sustainable extraction of goods facing cheaper industrial substitutes. To examine these hypotheses we present worldwide ethnographic information and preliminary findings from field work carried out among the Sumu Indians of Nicaragua. Field work suggests that higher income produces: (a) foraging specialization with animals rather than with plants; (b) a decline in the economic importance of forest goods in household income; (c) and a rise in the value of non-timber goods removed from the forest to about $35/ha/year. We did not have time to test hypothesis d. 相似文献
19.
Ivette Perfecto John Vandermeer Paul Hanson Victor Cartín 《Biodiversity and Conservation》1997,6(7):935-945
The coffee (Coffea arabica) agro-ecosystem in the Central Valley of Costa Rica was formerly characterized by a high vegetational diversity. This complex system has been undergoing a major transformation to capital-intensive monocultural plantations where all shade trees are eliminated. In this study we examined the pattern of arthropod biodiversity loss associated with this transformation. Canopy arthropods were sampled in three coffee farms: a traditional plantation with many species of shade trees, a moderately shaded plantation with only Erythrina poeppigeana and coffee, and a coffee monoculture. An insecticidal fogging technique was used to sample both canopy and coffee arthropods. Data are presented on three major taxonomic groups: Coleoptera, non-formicid Hymenoptera, and Formicidae. Data demonstrate that the transformation of the coffee agro-ecosystem results in a significant loss of biological diversity of both canopy arthropods as well as arthropods living in coffee bushes. Percentage of species overlap was very small for all comparisons. Furthermore, species' richness on a per tree basis was found to be within the same order of magnitude as that reported for trees in tropical forests. If results presented here are generalizable, this means that conservation efforts to preserve biological diversity should also include traditional agro-ecosystems as conservation units. 相似文献
20.
L. Jiménez M.J. de la Torre F. Maestre J.L. Ferrer I. Pérez 《Bioresource technology》1997,60(3):199-205
A central composite design was used to investigate the influence of the cooking conditions (time, temperature and phenol concentration) for wheat straw with phenol-water mixtures on the properties of the pulp obtained (yield and holocellulose, -cellulose, lignin and ethanol-benzene extractable contents) and the pH of the resulting wastewater. A second-order polynomial model consisting of three independent process variables was found to accurately describe the organosolv pulping of wheat straw. The equations derived predict the yield, the holocellulose, -cellulose, lignin and ethanol-benzene extractable contents of the pulp, and the pH of the wastewater with multiple-R, R2 and adjusted-R2 high values. The process variables must be set at low variables in order to ensure a high yield and pH. Conversely, if high holocellulose and -cellulose contents, and low lignin and ethanol-benzene extractable contents are desired, then a high temperature (200°C), long cooking time (120 min), and intermediate phenol concentration (65%) must be used. 相似文献