全文获取类型
收费全文 | 39370篇 |
免费 | 392篇 |
国内免费 | 477篇 |
专业分类
安全科学 | 890篇 |
废物处理 | 1991篇 |
环保管理 | 5237篇 |
综合类 | 6898篇 |
基础理论 | 10265篇 |
环境理论 | 13篇 |
污染及防治 | 9372篇 |
评价与监测 | 2747篇 |
社会与环境 | 2659篇 |
灾害及防治 | 167篇 |
出版年
2022年 | 266篇 |
2021年 | 267篇 |
2020年 | 240篇 |
2019年 | 239篇 |
2018年 | 1824篇 |
2017年 | 1703篇 |
2016年 | 1750篇 |
2015年 | 637篇 |
2014年 | 741篇 |
2013年 | 2308篇 |
2012年 | 1367篇 |
2011年 | 2582篇 |
2010年 | 1673篇 |
2009年 | 1703篇 |
2008年 | 2122篇 |
2007年 | 2484篇 |
2006年 | 1190篇 |
2005年 | 1026篇 |
2004年 | 1058篇 |
2003年 | 1029篇 |
2002年 | 1011篇 |
2001年 | 1159篇 |
2000年 | 828篇 |
1999年 | 551篇 |
1998年 | 360篇 |
1997年 | 401篇 |
1996年 | 412篇 |
1995年 | 460篇 |
1994年 | 404篇 |
1993年 | 385篇 |
1992年 | 345篇 |
1991年 | 369篇 |
1990年 | 344篇 |
1989年 | 314篇 |
1988年 | 301篇 |
1987年 | 266篇 |
1986年 | 273篇 |
1985年 | 270篇 |
1984年 | 341篇 |
1983年 | 296篇 |
1982年 | 315篇 |
1981年 | 282篇 |
1980年 | 236篇 |
1979年 | 252篇 |
1978年 | 212篇 |
1977年 | 199篇 |
1976年 | 167篇 |
1975年 | 183篇 |
1974年 | 192篇 |
1972年 | 170篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
271.
M. Böhm U. Hentschel A. Friedrich L. Fieseler R. Steffen V. Gamulin I. Müller W. Müller 《Marine Biology》2001,139(6):1037-1045
The aim of this study was the documentation of the molecular immune response of Suberites domuncula upon bacterial infection. Additionally, the bacteria that are naturally present in the sponge after prolonged aquarium maintenance were characterized. After 6 months of maintenance of S. domuncula in seawater aquaria, only one bacterial 16S rDNA sequence could be recovered, which belongs to the genus Pseudomonas. Concomitantly, morphologically uniform bacteria were found encapsulated in bacteriocytes. These findings indicate that certain bacteria, possibly of the genus Pseudomonas, are able to persist for long periods in host bacteriocytes. Subsequent to performing a previously established infection assay with S. domuncula, a potentially pathogenic Vibrio sp. was isolated from the tissues. Furthermore, the host tissue disintegrated and asexual propagation bodies (gemmules) were formed. In order to gain insights into the molecular events occurring after bacterial infection, the stress-response kinases, p38 protein kinase and JNK protein kinase, were analyzed. It is demonstrated that these two kinases are activated (phosphorylated) upon incubation of the tissue with the bacterial endotoxin lipopolysaccharide (LPS). Moreover, LPS strongly inhibits protein synthesis. It is concluded that there are many functionally different interactions between S. domuncula and bacteria and that the animal possesses mechanisms to differentiate between bacteria and to respond accordingly. 相似文献
272.
We determined the nuclear 18S rRNA sequences for 41 species of octocorals and used these to address the validity of the historical
ordinal divisions and the current subordinal divisions within the subclass Octocorallia. We also explored the phylogenetic
affinities of the species Dendrobrachia paucispina, which was originally classified in the order Antipatharia (subclass Ceriantipatharia) although polyp structure indicates
it belongs in the subclass Octocorallia. Trees constructed using maximum likelihood techniques are incongruent with the current
and historical taxonomy of the Octocorallia. There appeared to be three major clades of octocorals. The first clade included
most, but not all, pennatulaceans as a monophyletic group. The second clade contained 21 species, representing all major octocoral
groups other than pennatulaceans. The third clade contained members from three suborders of the Alcyonacea and one member
of the Pennatulacea. These data could not be used to distinguish the branching order of the three major clades. The species
D. paucispina had a close affinity with the genera Corallium and Paragorgia (Alcyonacea: Scleraxonia), although its morphology suggests it is more similar to the genus Chrysogorgia (Alcyonacea: Calcaxonia). The morphological character of dimorphism (the presence of both autozooids and siphonozooids within
a single colony) corresponded loosely with the topology of the most likely trees, and a single origin of dimorphism could
not be rejected. Despite sampling from the majority of families within the Octocorallia, many of the relationships within
this group remain ambiguous.
Received: 16 June 2000 / Accepted: 14 September 2000 相似文献
273.
A Systematic Test of an Enterprise Strategy for Community-Based Biodiversity Conservation 总被引:6,自引:0,他引:6
N. Salafsky H. Cauley G. Balachander B. Cordes J. Parks C. Margoluis S. Bhatt C. Encarnacion D. Russell R. Margoluis 《Conservation biology》2001,15(6):1585-1595
Abstract: A commonly held belief is that if people can benefit financially from enterprises that depend on nearby forests, reefs, and other natural habitats, then they will take action to conserve and sustainably use them. The Biodiversity Conservation Network brought together conservation and development organizations and local communities to systematically test this hypothesis across 39 conservation project sites in Asia and the Pacific. Each project implemented one or more community-based enterprises such as setting up an ecotourism lodge, distilling essential oils from wild plant roots, producing jams and jellies from forest fruits, harvesting timber, or collecting marine samples to test for pharmaceutical compounds. Each project team collected the biological, enterprise, and social data necessary to test the network's hypothesis. We present the results of this test. We found that a community-based enterprise strategy can lead to conservation, but only under limited conditions and never on its own. We summarize the specific conditions under which an enterprise strategy will and will not work in a decision chart that can be used by project managers to determine whether this strategy might make sense at their site. We also found that an enterprise strategy can be subsidized and still create a net gain that pays for conservation. Based on our experiences, we recommend developing "learning portfolios" that combine action and research to test other conservation strategies. 相似文献
274.
Jutta M. Schneider Melissa L. Thomas Mark A. Elgar 《Behavioral ecology and sociobiology》2001,49(5):410-415
Male genitalia may facilitate sperm protection by acting as a plug that prevents or hinders future matings. The pedipalps (intromittant organs) of males of the orb-web spider, Nephila plumipes, have a conductor with a peculiarly curved ending and a triangular process near the terminal end. The tip of the conductor, including the process, breaks during most matings and remains inside the female genital tract. We explored the possible function of the conductor as a mating plug using the double-mating sterile-male technique. Our data are not consistent with a plug function because males use only one pedipalp in each mating, thus leaving an unobstructed insemination duct available for future matings; conductors of males mating with virgin females are not more likely to break than those of males mating with mated females, and second males show no preference for used or unused spermathecae. In addition, males that inserted their palp in the insemination duct that contained a tip of the conductor from a previous male obtained a share in the paternity of the female's clutch of eggs. Interestingly, the conductor is more likely to break if it is inserted in an unused spermatheca. We argue that several lines of evidence suggest that the conductor breaks as a result of intersexual conflict over the duration of copulation. 相似文献
275.
Chemosensory discrimination of familiar and unfamiliar conspecifics by lizards: implications of field spatial relationships between males 总被引:2,自引:2,他引:0
The ability of territorial lizards to discriminate between scents of neighbors and non-neighbors might contribute to decreasing the costs of aggressive interactions. To test this hypothesis, we conducted a field study to analyze the spatial relationships between male Iberian rock-lizards, Lacerta monticola. We then used the same individuals in a laboratory experiment to test whether male lizards can use chemical cues to discriminate between familiar conspecific males (those whose home ranges overlapped) and unfamiliar conspecific males (those whose home ranges did not overlap, and whose home range centers were at least 50 m apart). Differences in tongue-flick rates in the presence of chemical cues suggested that male L. monticola discriminated between odors of familiar and unfamiliar males. The behavioral responses were also dependent on relative differences in body size between the responding male and the unfamiliar male that donated the scent: There was a significant negative correlation between tongue-flick rates emitted in cages of unfamiliar males and the body size differences between males. In contrast, when the donor of the scent was a familiar male, the tongue-flick rate was not dependent on body size differences. These results are compatible with individual discrimination through chemical cues in male L. monticola. 相似文献
276.
277.
Bryce A. Mihalevich Jeffery S. Horsburgh Anthony A. Melcher 《Environmental monitoring and assessment》2017,189(11):593
Stormwater runoff in urban areas can contribute high concentrations of dissolved organic matter (DOM) to receiving waters, potentially causing impairment to the aquatic ecosystem of urban streams and downstream water bodies. Compositional changes in DOM due to storm events in forested, agricultural, and urban landscapes have been well studied, but in situ sensors have not been widely applied to monitor stormwater contributions in urbanized areas, leaving the spatial and temporal characteristics of DOM within these systems poorly understood. We deployed fluorescent DOM (FDOM) sensors at upstream and downstream locations within a study reach to characterize the spatial and temporal changes in DOM quantity and sources within an urban water conveyance that receives stormwater runoff. Baseflow FDOM decreased over the summer season as seasonal flows upstream transported less DOM. FDOM fluctuated diurnally, the amplitude of which also declined as the summer season progressed. During storms, FDOM concentrations were rapidly elevated to values orders of magnitude greater than baseflow measurements, with greater concentrations at the downstream monitoring site, revealing high contributions from stormwater outfalls between the two locations. Observations from custom, in situ fluorometers resembled results obtained using laboratory methods for identifying DOM source material and indicated that DOM transitioned to a more microbially derived composition as the summer season progressed, while stormwater contributions contributed DOM from terrestrial sources. Deployment of a mobile sensing platform during varying flow conditions captured spatial changes in DOM concentration and composition and revealed contributions of DOM from outfalls during stormflows that would have otherwise been unobserved. 相似文献
278.
A new method for municipal solid waste incinerator (MSWI) fly ash inertization, based on colloidal silica 总被引:1,自引:0,他引:1
Bontempi E Zacco A Borgese L Gianoncelli A Ardesi R Depero LE 《Journal of environmental monitoring : JEM》2010,12(11):2093-2099
Municipal solid waste incineration (MSWI) is a straightforward way to manage waste, however the disposal of process byproducts, mainly bottom and fly ash, is still a problem, because of their hazardous contents. Fly ash is a byproduct of many other processes that involve combustion to produce energy. In this paper we present and discuss a new method for MSWI fly ash inertization, mainly based on the use of colloidal silica as a stabilization agent for metals. In the patented procedure, fly ash of different provenance can be used to produce an inert and non-hazardous material, that can be reused. In fact to make the recovery process more efficient, landfilling should be totally avoided. For this reason, to enhance the possibility of reuse, a washing process, for salts recovery, is proposed as a final step of the inertization procedure. The obtained inert material is called COSMOS (COlloidal Silica Medium to Obtain Safe inert), and it is composed of calcium carbonate, calcium sulfate, silicon oxide and a wide quantity of non-soluble amorphous compounds. COSMOS does not contain any corrosive salts. This makes it extremely interesting for cement industry applications with several other advantages, and environmental benefits. The new proposed inertization procedure appears very promising, because it allows MSWI fly ash to be considered a valuable resource. Thanks to the obtained results, a demonstration project, in the frame of LIFE+, has been funded by the European Commission (LIFE+ 2008 project ENV/IT/000434, ). 相似文献
279.
Karadag A 《Environmental monitoring and assessment》2012,184(3):1617-1632
This paper is a summary of a project changed into a book named by “Changing Environment, City and Identity in Soma with the
Geographical Evaluations” issued on May 2005. In this research, Soma, which is one of the most remarkable districts in Manisa
in the West Anatolia from the point of economical figures, is assessed with its physical environment potential, improving
economical activities and changing socio-economical structure. Owing to the open coal basins in the northeast and southwest
of the district where lignite is produced and the impact of the thermic power plant near the city centre, Soma has changed
on a large scale. This change has introduced some environmental problems into the district such as the devastation of the
forestry land; the infertility of farming land; and soil, water and air pollution. Even though the change under discussion
has led to many problems to deal with, it has also influenced its socio-economical structure to a large extent and revealed
new type of inhabitants having different life expectations and aims. In conclusion, in this article, changing environment
and city structure after lignite processing and thermic station establishment in Soma are discussed through the effective
geographical factors. The new city profile formed by the local dynamics in question is evaluated according to the data obtained
by the studies made in the neighbourhood. 相似文献
280.
Laura Eichelberger 《Environmental science and pollution research international》2018,25(33):32938-32951
Using a relational approach, I examine several cultural dimensions involved in household water access and use in Newtok, Alaska. I describe the patterns that emerge around domestic water access and use, as well as the subjective lived experiences of water insecurity including risk perceptions, and the daily work and hydro-social relationships involved in accessing water from various sources. I found that Newtok residents haul water in limited amounts from a multitude of sources, both treated and untreated, throughout the year. Household water access is tied to hydro-social relationships predicated on sharing and reciprocity, particularly when the primary treated water access point is unavailable. Older boys and young men are primarily responsible for hauling water, and this role appears to be important to male Yupik identity. Many interviewees described preferring to drink untreated water, a practice that appears related to cultural constructions of natural water sources as pure and self-purifying, as well as concerns about the safety of treated water. Concerns related to the health consequences of low water access appear to differ by gender and age, with women and elders expressing greater concern than men. These preliminary results point to the importance of understanding the cultural dimensions involved in household water access and use. I argue that institutional responses to water insecurity need to incorporate such cultural dimensions into solutions aimed at increasing household access to and use of water. 相似文献