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   1189篇
  免费   437篇
  国内免费   5篇
安全科学   3篇
环保管理   4篇
综合类   37篇
基础理论   1555篇
污染及防治   15篇
评价与监测   4篇
社会与环境   11篇
灾害及防治   2篇
  2023年   90篇
  2022年   84篇
  2021年   113篇
  2020年   114篇
  2019年   105篇
  2018年   89篇
  2017年   117篇
  2016年   107篇
  2015年   129篇
  2014年   137篇
  2013年   119篇
  2012年   86篇
  2011年   95篇
  2010年   117篇
  2009年   25篇
  2008年   48篇
  2007年   3篇
  2006年   6篇
  2005年   4篇
  2004年   3篇
  2003年   6篇
  2002年   6篇
  2001年   4篇
  2000年   2篇
  1999年   2篇
  1998年   1篇
  1997年   2篇
  1995年   1篇
  1993年   2篇
  1992年   1篇
  1990年   4篇
  1989年   1篇
  1987年   2篇
  1986年   1篇
  1984年   1篇
  1983年   1篇
  1982年   2篇
  1975年   1篇
排序方式: 共有1631条查询结果,搜索用时 15 毫秒
991.
利用微生物除臭技术研究与应用   总被引:19,自引:2,他引:19  
简述了微生物在降解生产和生活中臭气方面的研究与应用,特别着重介绍了EM复合菌群在除臭方面的卓越效果,表明了生物除臭与物理、化学方法除臭相比具有彻底性、实用性与经济性的特点,在环境保护与资源的重复利用方面有着巨大的应用潜力。  相似文献   
992.
Hybridization poses a major challenge for species conservation because it threatens both genetic integrity and adaptive potential. Yet, hybridization can occasionally offer unprecedented opportunity for species recovery if the genome of an extinct taxon is present among living hybrids such that selective breeding could recapture it. We explored the design elements for establishing a captive-breeding program for Galapagos tortoises (Chelonoidis spp.) built around individuals with admixed ancestry involving an extinct species. The target individuals were hybrids between the extinct species from Floreana Island, C. niger, and an extant species, C. becki, which were recently found in the endemic range of C. becki, from Wolf Volcano on Isabela Island. We combined genotypic data from 35 tortoises with high ancestry from C. niger with forward-in-time simulations to explore captive breeding strategies that maximized overall genetic diversity and ancestry from C. niger while accommodating resource constraints, species biology, and the urgency to return tortoises to Floreana Island for facilitating ecosystem restoration. Overall genetic diversity was maximized when in the simulation tortoises were organized in relatively small breeding groups. Substantial amounts of the C. niger genome were captured despite limited resources available for selectively breeding tortoises in captivity. Genetic diversity was maximized when captive-bred offspring were released to the wild rather than being used as additional breeders. Our results provide genetic-based and practical guidance on the inclusion of hybrids with genomic representation from extinct taxa into species restoration programs and informs the ongoing debate on the value of hybrids in biodiversity conservation.  相似文献   
993.
Conservation conflicts are increasing on a global scale and instruments for reconciling competing interests are urgently needed. Multicriteria decision analysis (MCDA) is a structured, decision‐support process that can facilitate dialogue between groups with differing interests and incorporate human and environmental dimensions of conflict. MCDA is a structured and transparent method of breaking down complex problems and incorporating multiple objectives. The value of this process for addressing major challenges in conservation conflict management is that MCDA helps in setting realistic goals; entails a transparent decision‐making process; and addresses mistrust, differing world views, cross‐scale issues, patchy or contested information, and inflexible legislative tools. Overall we believe MCDA provides a valuable decision‐support tool, particularly for increasing awareness of the effects of particular values and choices for working toward negotiated compromise, although an awareness of the effect of methodological choices and the limitations of the method is vital before applying it in conflict situations. Uso de Análisis de Decisiones Multicriterio para Abordar Conflictos de Conservación  相似文献   
994.
The Convention on Biological Diversity (CBD) expects forestry plantations to contribute to biodiversity conservation. A well‐developed understory in forestry plantations might serve as a surrogate habitat for native species and mitigate the negative effect of plantations on species richness. We experimentally tested this hypothesis by removing the understory in Monterey pine (Pinus radiata) plantations in central Chile and assessing changes in species richness and abundance of medium‐sized mammals. Frequency of occurrence of mammals, including kodkods (Leopardus guigna), culpeo foxes (Pseudalopex culpaeus), lesser grisons (Conepatus chinga), and Southern pudu deer (Pudu puda), was low in forest stands with little to no understory relative to stands with well‐developed undergrowth vegetation. After removing the understory, their frequency of occurrence decreased significantly, whereas in control stands, where understory was not removed, their frequency did not change. This result strongly supports the idea that facilitating the development of undergrowth vegetation may turn forestry stands into secondary habitats as opposed to their containing no habitat for native mammals. This forestry practice could contribute to conservation of biological diversity as it pertains to CBD targets. Proporcionando Hábitat para Mamíferos Nativos Mediante el Mejoramiento del Sotobosque en Plantaciones Forestales  相似文献   
995.
Terrestrial biodiversity loss and climate change, driven mainly by loss of habitat to agriculture and fossil fuel (FF) use, respectively, are considered among the world's greatest environmental threats. However, FF-dependent technologies are currently essential for manufacturing synthetic nitrogen fertilizers (SNFs) and synthetic pesticides (SPs) critical to increasing agricultural productivity, which reduces habitat loss. Fossil fuel use increases CO2 levels, further enhancing agricultural productivity. Based on estimates of global increases in yields from SNFs, SPs, and atmospheric CO2 fertilization, I estimated that FF-dependent technologies are responsible for at least 62.5% of current global food production (GFP) from cropland. Thus, if FF use is eschewed in the future, maintaining current GFP means croplands would have to increase from 12.2% of global land area (GLA) excluding Antarctica to 32.7%. The additional 20.4% of GLA needed exceeds habitat lost currently to cropland (12.2% of GLA) and cumulative conservation areas globally (14.6% of GLA). Thus, although eliminating FF use could reduce climate change, its unintended consequences may be to significantly exacerbate biodiversity loss and indirectly increase food costs, reducing food security which, moreover, disproportionately affects the poor. Although it may be possible to replace SNFs and SPs with FF-free technologies, such substitutes have not yet been demonstrated to be sufficiently economical or efficient. In the interim, meeting global food demand and keeping food prices affordable would increase habitat conversion and food prices. These trade-offs should be considered in analyses of climate change policies.  相似文献   
996.
Leading societies toward a more sustainable, equitably shared, and environmentally just future requires elevating and strengthening conversations on the nonmaterial and perhaps unquantifiable values of nonhuman nature to humanity. Debates among conservationists relating to the appropriateness of valuing ecosystems in terms of their human utility have eclipsed the more important and impactful task of expressing conservation concerns in terms that are meaningful to diverse stakeholders. We considered the wide global diversity of perspectives on the biosocial complex—the relationships and interactions between all living species on Earth—and argue that humanity's best chance for effective conservation is to take a pluralistic approach that engages seriously with the worldviews of all stakeholders. Many worldviews—particularly those in indigenous cultures—place a higher value on the spiritual and nonmaterial aspects than what is often represented by the discourse surrounding Western conservation policy. Alternative framings of the biosocial complex that recognize nature's intrinsic value can be powerful motivators for social change and for local-scale conservation efforts. At a national and international level, changing ethical framings of human relationships with nature have started influencing conceptions of human rights relating to the environment and of the rights of nature itself. This change has led to an increased role of the judiciary in promoting environmental sustainability and promoting justice for groups who are most often affected by environmental harms. We hope our essay will motivate the scientific community to change its own perception of what a sound and sustainable relationship between humanity and other species should be and will help citizens become active environmental subjects, connected to the ecosystems around them.  相似文献   
997.
Abstract: The nonuse (or passive) value of nature is important but time‐consuming and costly to quantify with direct surveys. In the absence of estimates of these values, there will likely be less investment in conservation actions that generate substantial nonuse benefits, such as conservation of native species. To help overcome decisions about the allocation of conservation dollars that reflect the lack of estimates of nonuse values, these values can be estimated indirectly by environmental value transfer (EVT). EVT uses existing data or information from a study site such that the estimated monetary value of an environmental good is transferred to another location or policy site. A major challenge in the use of EVT is the uncertainty about the sign and size of the error (i.e., the percentage by which transferred value exceeds the actual value) that results from transferring direct estimates of nonuse values from a study to a policy site, the site where the value is transferred. An EVT is most useful if the decision‐making framework does not require highly accurate information and when the conservation decision is constrained by time and financial resources. To account for uncertainty in the decision‐making process, a decision heuristic that guides the decision process and illustrates the possible decision branches, can be followed. To account for the uncertainty associated with the transfer of values from one site to another, we developed a risk and simulation approach that uses Monte Carlo simulations to evaluate the net benefits of conservation investments and takes into account different possible distributions of transfer error. This method does not reduce transfer error, but it provides a way to account for the effect of transfer error in conservation decision making. Our risk and simulation approach and decision‐based framework on when to use EVT offer better‐informed decision making in conservation.  相似文献   
998.
Effective population size, a central concept in conservation biology, is now routinely estimated from genetic surveys and can also be theoretically predicted from demographic, life‐history, and mating‐system data. By evaluating the consistency of theoretical predictions with empirically estimated effective size, insights can be gained regarding life‐history characteristics and the relative impact of different life‐history traits on genetic drift. These insights can be used to design and inform management strategies aimed at increasing effective population size. We demonstrated this approach by addressing the conservation of a reintroduced population of Asiatic wild ass (Equus hemionus). We estimated the variance effective size (Nev) from genetic data () and formulated predictions for the impacts on Nev of demography, polygyny, female variance in lifetime reproductive success (RS), and heritability of female RS. By contrasting the genetic estimation with theoretical predictions, we found that polygyny was the strongest factor affecting genetic drift because only when accounting for polygyny were predictions consistent with the genetically measured Nev. The comparison of effective‐size estimation and predictions indicated that 10.6% of the males mated per generation when heritability of female RS was unaccounted for (polygyny responsible for 81% decrease in Nev) and 19.5% mated when female RS was accounted for (polygyny responsible for 67% decrease in Nev). Heritability of female RS also affected Nev; (heritability responsible for 41% decrease in Nev). The low effective size is of concern, and we suggest that management actions focus on factors identified as strongly affecting , namely, increasing the availability of artificial water sources to increase number of dominant males contributing to the gene pool. This approach, evaluating life‐history hypotheses in light of their impact on effective population size, and contrasting predictions with genetic measurements, is a general, applicable strategy that can be used to inform conservation practice.  相似文献   
999.
To determine the distribution and causes of extinction threat across functional groups of terrestrial vertebrates, we assembled an ecological trait data set for 18,016 species of terrestrial vertebrates and utilized phylogenetic comparative methods to test which categories of habitat association, mode of locomotion, and feeding mode best predicted extinction risk. We also examined the individual categories of the International Union for Conservation of Nature Red List extinction drivers (e.g., agriculture and logging) threatening each species and determined the greatest threats for each of the four terrestrial vertebrate groups. We then quantified the sum of extinction drivers threatening each species to provide a multistressor perspective on threat. Cave dwelling amphibians (p < 0.01), arboreal quadrupedal mammals (all of which are primates) (p < 0.01), aerial and scavenging birds (p < 0.01), and pedal (i.e., walking) squamates (p < 0.01) were all disproportionately threatened with extinction in comparison with the other assessed ecological traits. Across all threatened vertebrate species in the study, the most common risk factors were agriculture, threatening 4491 species, followed by logging, threatening 3187 species, and then invasive species and disease, threatening 2053 species. Species at higher risk of extinction were simultaneously at risk from a greater number of threat types. If left unabated, the disproportionate loss of species with certain functional traits and increasing anthropogenic pressures are likely to disrupt ecosystem functions globally. A shift in focus from species- to trait-centric conservation practices will allow for protection of at-risk functional diversity from regional to global scales.  相似文献   
1000.
We describe a female fetus with a de novo X chromosome rearrangement detected prenatally in both chorion villi and a pleural effusion. Chromosome painting showed the chromosome to be composed entirely of X chromosome material, while G-banding indicated a duplication of X short arms, four copies of the proximal long arm, and deletion of the distal long arm of the X. C-banding showed the presence of one active and two inactive centromeres and X-inactivation studies demonstrated the tricentric chromosome to be late replicating in all cells examined. The origin of this complex de novo rearrangement appears to have involved two separate breakage events, the first leading to the production of a dicentric X chromosome and the second generating the tricentric X.  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