全文获取类型
收费全文 | 5878篇 |
免费 | 46篇 |
国内免费 | 27篇 |
专业分类
安全科学 | 91篇 |
废物处理 | 352篇 |
环保管理 | 466篇 |
综合类 | 871篇 |
基础理论 | 1149篇 |
环境理论 | 6篇 |
污染及防治 | 2076篇 |
评价与监测 | 542篇 |
社会与环境 | 382篇 |
灾害及防治 | 16篇 |
出版年
2023年 | 64篇 |
2022年 | 165篇 |
2021年 | 170篇 |
2020年 | 72篇 |
2019年 | 73篇 |
2018年 | 185篇 |
2017年 | 167篇 |
2016年 | 288篇 |
2015年 | 167篇 |
2014年 | 314篇 |
2013年 | 552篇 |
2012年 | 369篇 |
2011年 | 392篇 |
2010年 | 268篇 |
2009年 | 230篇 |
2008年 | 355篇 |
2007年 | 332篇 |
2006年 | 313篇 |
2005年 | 225篇 |
2004年 | 192篇 |
2003年 | 164篇 |
2002年 | 160篇 |
2001年 | 91篇 |
2000年 | 59篇 |
1999年 | 45篇 |
1998年 | 26篇 |
1997年 | 22篇 |
1996年 | 26篇 |
1995年 | 36篇 |
1994年 | 33篇 |
1993年 | 18篇 |
1992年 | 14篇 |
1991年 | 12篇 |
1990年 | 17篇 |
1989年 | 12篇 |
1982年 | 8篇 |
1967年 | 7篇 |
1966年 | 12篇 |
1965年 | 18篇 |
1964年 | 29篇 |
1963年 | 12篇 |
1962年 | 17篇 |
1961年 | 11篇 |
1960年 | 9篇 |
1959年 | 26篇 |
1958年 | 27篇 |
1957年 | 17篇 |
1956年 | 14篇 |
1955年 | 18篇 |
1954年 | 8篇 |
排序方式: 共有5951条查询结果,搜索用时 15 毫秒
951.
Andrés González Frank C. Schroeder Athula B. Attygalle Aleš Svatoš Jerrold Meinwald Thomas Eisner 《Chemoecology》1999,9(3):105-112
Summary. Female Photuris fireflies sequester defensive steroidal pyrones (lucibufagins) from male fireflies of the genus Photinus. Lucibufagin analyses of Photuris females and Photinus ignitus males show that the lucibufagin mixtures of predator and prey differ in their composition. Analyses of whole body extracts
showed that P. ignitus males contain a mixture of eight non-glycosylated lucibufagins, composed mostly of compounds with two oxygenated positions
in the steroidal A-ring (C-3, C-5). After feeding on P. ignitus males, Photuris females contain six major lucibufagins. Three of these compounds are not present in the prey, including the novel lucibufagin
glycoside 5β,11α-dihydroxy-12-oxo-3β-O-β-D-xylopyranosylbufalin, and two other lucibufagins with a trioxygenated A-ring (C-2,
C-3, C-5). These results indicate that Photuris females transform the sequestered lucibufagins both by glycosylation and oxidation, which could affect the systemic transportability
of these compounds due to an increase in their polarity.
Received 18 February 1999; accepted 19 April 1999. 相似文献
952.
Summary. Female Photuris fireflies contain defensive chemicals of two types. They sequester steroidal pyrones (lucibufagins) from male fireflies of
the genus Photinus that they eat, and themselves produce the defensive betaine N-methylquinolinium 2-carboxylate. Chemical analyses of Photuris eggs showed that females that fed on Photinus males endow their eggs with both lucibufagin and the betaine, while those that did not feed on Photinus lay eggs that contain betaine, but virtually no lucibufagin. Photuris females collected in the field during the Photinus flight season laid eggs that invariably contained betaine, but lucibufagin only at times. Predation experiments showed that
Photuris eggs are essentially unacceptable to larvae of a coccinellid beetle (Harmonia axyridis) and an ant (Leptothorax longispinosus), but moderately acceptable to an earwig (Forficula auricularia). When applied experimentally to palatable insect eggs, lucibufagin proved deterrent to these three predators, while the
betaine proved deterrent to the ant and coccinellid larva only. Both types of defensive compound decreased egg predation in
the field. By endowing their eggs with both exogenous and endogenous chemicals, Photuris females are essentially “maximizing their options”– when feeding on Photinus, their eggs are doubly protected, but they are not entirely defenseless when the females are unable to procure lucibufagin.
Received 12 August 1999; accepted 27 August 1999 相似文献
953.
Université de Perpignan 《生态毒理学报》1999,21(4):45-54
珊瑚礁在全世界,尤其两个热带区域和三大洋中都有发育.它们在海水温度高于20℃的沿岸表面附近扩展.它们占据约100万平方公里,是世界上最重要的、由活生物建造的建筑物.珊瑚(约800种)是这些巨大的碳酸钙物体的主要建造者.活珊瑚就落在数以亿万计的祖先骨骼之上.珊瑚之所以有这样一种碳酸钙骨骼的能力,是由于它们与它们在其软组织上繁殖的藻类的共生关系.一平方米的一个珊瑚群落每年能钙化多达10kg碳酸盐.在印度-太平洋地区,石灰藻作为建造者也是重要的. 相似文献
954.
Jared D. Margulies Francesca R. Moorman Bárbara Goettsch Jan C. Axmacher Amy Hinsley 《Conservation biology》2023,37(3):e14030
Although illegal wildlife trade (IWT) represents a serious threat to biodiversity, research into the prevalence of illegal plant collection and trade remains scarce. Because cacti and succulents are heavily threatened by overcollection for often illegal, international ornamental trade, we surveyed 441 members of the cacti and succulent hobbyist collector community with a mixed quantitative and qualitative approach. We sought to understand collector perspectives on the Convention on the International Trade in Endangered Species of Wild Flora and Fauna (CITES) and on the threats IWT poses to cactus and succulent conservation. Most respondents (74% of 401 respondents) stated that illegal collection in cacti and succulents represents a “very serious problem” and that the problem of wild plant collection is increasing (72% of 319 respondents). Most forms of illegal collection and trade were seen as very unacceptable by respondents. Self-reported noncompliance with CITES rules was uncommon (11.2% of 418 respondents); it remains a persistent problem in parts of the cacti and succulent hobbyist community. People engaging in rule breaking, such as transporting plants without required CITES documents, generally did so knowingly. Although 60.6% of 381 respondents regarded CITES as a very important tool for conservation, sentiment toward CITES and its efficacy in helping species conservation was mixed. Collectors in our survey saw themselves as potentially playing important roles in cactus and succulent conservation, but this potential resource remains largely untapped. Our results suggest the need for enhanced consultation with stakeholders in CITES decision-making. For challenging subjects like IWT, developing evidence-based responses demands deep interdisciplinary engagement, including assessing the conservation impact of species listings on CITES appendices. 相似文献
955.
Alexandrine Daniel Paul Savary Jean-Christophe Foltête Aurélie Khimoun Bruno Faivre Anthony Ollivier Cyril Éraud Hervé Moal Gilles Vuidel Stéphane Garnier 《Conservation biology》2023,37(3):e14047
Habitat connectivity is a key objective of current conservation policies and is commonly modeled by landscape graphs (i.e., sets of habitat patches [nodes] connected by potential dispersal paths [links]). These graphs are often built based on expert opinion or species distribution models (SDMs) and therefore lack empirical validation from data more closely reflecting functional connectivity. Accordingly, we tested whether landscape graphs reflect how habitat connectivity influences gene flow, which is one of the main ecoevolutionary processes. To that purpose, we modeled the habitat network of a forest bird (plumbeous warbler [Setophaga plumbea]) on Guadeloupe with graphs based on expert opinion, Jacobs’ specialization indices, and an SDM. We used genetic data (712 birds from 27 populations) to compute local genetic indices and pairwise genetic distances. Finally, we assessed the relationships between genetic distances or indices and cost distances or connectivity metrics with maximum-likelihood population-effects distance models and Spearman correlations between metrics. Overall, the landscape graphs reliably reflected the influence of connectivity on population genetic structure; validation R2 was up to 0.30 and correlation coefficients were up to 0.71. Yet, the relationship among graph ecological relevance, data requirements, and construction and analysis methods was not straightforward because the graph based on the most complex construction method (species distribution modeling) sometimes had less ecological relevance than the others. Cross-validation methods and sensitivity analyzes allowed us to make the advantages and limitations of each construction method spatially explicit. We confirmed the relevance of landscape graphs for conservation modeling but recommend a case-specific consideration of the cost-effectiveness of their construction methods. We hope the replication of independent validation approaches across species and landscapes will strengthen the ecological relevance of connectivity models. 相似文献
956.
Spatial Relationships of Levees and Wetland Systems within Floodplains of the Wabash Basin,USA
下载免费PDF全文
![点击此处可从《Journal of the American Water Resources Association》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Ryan R. Morrison Erin Bray Fernando Nardi Antonio Annis Quan Dong 《Journal of the American Water Resources Association》2018,54(4):934-948
Given the unique biogeochemical, physical, and hydrologic services provided by floodplain wetlands, proper management of river systems should include an understanding of how floodplain modifications influence wetland ecosystems. The construction of levees can reduce river–floodplain connectivity, yet it is unclear how levees affect wetlands within floodplains, let alone the cumulative impacts within an entire watershed. This paper explores spatial relationships between levee and floodplain wetland systems in the Wabash Basin, United States. We used a hydrogeomorphic floodplain delineation technique to map floodplain extents and identify wetlands that may be hydrologically connected to river networks. We then spatially examined the relationship between levee presence, wetland area, and other river network attributes within discrete subbasins. Our results show that cumulative wetland area is relatively constant in subbasins that contain levees, regardless of maximum stream order within the subbasin. In subbasins that do not contain levees, cumulative wetland area increases with maximum stream order. However, we found that wetland distributions around levees can be complex, and further studies on the influence of levees on wetland habitat may need to consider finer resolution spatial scales. 相似文献
957.
Růžičková Jana Raclavská Helena Juchelková Dagmar Šafář Michal Kucbel Marek Švédová Barbora Slamová Karolina Grobelak Anna 《Environmental science and pollution research international》2023,30(4):8582-8600
Environmental Science and Pollution Research - The utilisation of waste wood from furniture production brings new problems connected with an incomplete thermochemical decomposition of additives... 相似文献
958.
Pironti Concetta Ricciardi Maria Motta Oriana Venier Marta Faggiano Antonio Cucciniello Raffaele Proto Antonio 《Environmental science and pollution research international》2023,30(2):3112-3120
Environmental Science and Pollution Research - Thermo-mineral springs are widely spread over the volcanic areas of Salerno, a city in southern Italy. Although the water of thermal structures... 相似文献
959.
Sousa Vitor Bogas José Alexandre Real Sofia Meireles Inês 《Environmental science and pollution research international》2023,30(4):8778-8789
Environmental Science and Pollution Research - The urge to reduce greenhouse gas emissions, in particular carbon dioxide, is a global problem, not only in spatial terms but also in terms of the... 相似文献
960.
Rolim Silvia Beatriz Alves Veettil Bijeesh Kozhikkodan Vieiro Antonio Pedro Kessler Anita Baldissera Gonzatti Clóvis 《Environmental science and pollution research international》2023,30(8):19602-19616
Environmental Science and Pollution Research - A large number of freshwater lakes around the world show recurring harmful algal blooms, particularly cyanobacterial blooms, that affect public health... 相似文献