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801.

Background

The vertical migration of phytoplankton was investigated in natural waters using in situ fluorescence profiling, chlorophyll a concentrations and life counts at two study sites differing in coloured dissolved organic matter (cDOM) concentrations. The data from the corresponding water depths (50-cm intervals down to 10 m) and times (hourly, before dawn to sunset, several days) were related to the highly resolved (2 nm) underwater ultraviolet radiation (UVR)/photosynthetic active radiation (PAR) transparency (290 to 700 nm).

Results

Chlorophyll a maxima of mainly motile dinoflagellates were observed in situ at all days and at both study sites (open marine, brackish waters), independent on prevailing weather conditions or cDOM concentrations. Phytoplankton migration was triggered solely by irradiance in the 400- to 700-nm wavelength range (PAR) at the particular water depth, irrespective of PAR/UVR ratios and surface UVR (290 to 400 nm), after an illumination period of about 40 min. Interestingly, the PAR tolerance levels of the phytoplankton, which have been lower in cDOM-rich waters, matched their light acclimation values determined by parallel PAM measurements.

Conclusions

The response of the phytoplankton to PAR is not a sufficient protection strategy versus increasing UVR levels, which might have wide ecological implications beyond the level of primary producers to impact important ecosystem functions such as the delicate trophic interactions.  相似文献   
802.
This report provides a brief review of the fourth joint meeting of the German Language Branch of Society of Environmental Toxicology and Chemistry (SETAC GLB) and the Working Group "Environmental Chemistry and Ecotoxicology" of the German Chemical Society (GDCh) held from 6th to 9th of September 2010 at the Federal Environment Agency (UBA) in Dessau-Rosslau (Germany). For the first time a governmental institution was responsible for the local organization, a novelty that was expressed in the meeting's main theme "From insight to decision (making)". 366 participants discussed 105 oral and 125 poster presentations and three invited key speakers from government, academia and industry. The best oral and poster presentations of the meeting were awarded. Moreover, the annual young scientist award of SETAC GLB for the best diploma and doctoral thesis and the best publication award of the GDCh-Working Group "Environmental Chemistry and Ecotoxicology" were officially handed over. The reader of the meeting (mostly in German language) including the meeting program and all abstracts is for free available via: http://www.setac-glb.de  相似文献   
803.
Contemporary coral reefs are forced to survive through and recover from disturbances at a variety of spatial and temporal scales. Understanding disturbances in the context of ecological processes may lead to accurate predictive models of population trajectories. Most coral-reef studies and monitoring programs examine state variables, which include the percentage coverage of major benthic organisms, but few studies examine the key ecological processes that drive the state variables. Here we outline a sampling strategy that captures both state and process variables, at a spatial scale of tens of kilometers. Specifically, we are interested in (1) examining spatial and temporal patterns in coral population size-frequency distributions, (2) determining major population processes, including rates of recruitment and mortality, and (3) examining relationships between processes and state variables. Our effective sampling units are randomly selected 75 × 25 m stations, spaced approximately 250?C500 m apart, representing a 103 m spatial scale. Stations are nested within sites, spaced approximately 2 km apart, representing a 104 m spatial scale. Three randomly selected 16 m2 quadrats placed in each station and marked for relocation are used to assess processes across time, while random belt-transects, re-randomized at each sampling event, are used to sample state variables. Both quadrats and belt-transects are effectively sub-samples from which we will derive estimates of means for each station at each sampling event. This nested sampling strategy allows us to determine critical stages in populations, examine population performance, and compare processes through disturbance events and across regions.  相似文献   
804.
Recent evidence shows that the frequently proclaimed collapse of the traditional career model is actually not supported by job tenure data. This paper argues that the observed stability of job tenure might be explained by an increasing number of shamrock organizations. This organizational form has three types of workers: core employees, professional freelancers, and routine workers. In such an organization, two very different career models coexist. The organization largely determines the career of the core employee, whereas the individual essentially shapes that of the professional freelancer. This paper studies extensively the career of this second group: the professional freelancer, a growing phenomenon in many developed countries but not yet the focus of many career studies. We develop a freelance career success model on basis of the intelligent career framework augmented by insights from literature on entrepreneurship. Data are from a web survey with responses from about 1600 independent professionals in the Netherlands, in combination with 51 in‐depth interviews. We provide two main contributions. First, we report findings from the first large‐scale quantitative study into freelance career success. Second, this study enhances our understanding of the success of the modern career by building bridges between career and entrepreneurship literatures. We conclude that the external environment in which an individual freelancer operates is the most important factor determining career success. The study therefore suggests that more work needs to be performed on the relationship between the environment and individual career success. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   
805.
In Ethiopia, climate change and associated risks are expected to have serious consequences for agriculture and food security. This in turn will seriously impact on the welfare of the people, particularly the rural farmers whose main livelihood depends on rain-fed agriculture. The level of impacts will mainly depend on the awareness and the level of adaptation in response to the changing climate. It is thus important to understand the role of the different factors that influence farmers’ adaptation to ensure the development of appropriate policy measures and the design of successful development projects. This study examines farmers’ perception of change in climatic attributes and the factors that influence farmers’ choice of adaptation measures to climate change and variability. The estimated results from the climate change adaptation models indicate that level of education, age and wealth of the head of the household; access to credit and agricultural services; information on climate, and temperature all influence farmers’ choices of adaptation. Moreover, lack of information on adaptation measures and lack of finance are seen as the main factors inhibiting adaptation to climate change. These conclusions were obtained with a Multinomial logit model, employing the results from a survey of 400 smallholder farmers in three districts in Tigray, northern Ethiopian.  相似文献   
806.
Animal welfare scientific literature has accumulated rapidly in recent years, but bias may exist which influences understanding of progress in the field. We conducted a survey of articles related to animal welfare or well being from an electronic database. From 8,541 articles on this topic, we randomly selected 115 articles for detailed review in four funding categories: government; charity and/or scientific association; industry; and educational organization. Ninety articles were evaluated after unsuitable articles were rejected. The welfare states of animals in new treatments, conventional treatments or control groups with no treatment were classified as high, medium or low according to one or more. More articles were published in which the welfare of animals in new treatments was better than that of animals in the conventional or no treatment groups, demonstrating a positive result bias. Failure to publish studies with negative or inconclusive results may lead to other scientists unnecessarily repeating the research. The authors’ assessments of the welfare state of the groups were similarly rated high, medium or low, and it was found that new treatments were rated lower if the research was funded by industry, and higher when funded by charities, with government funding agencies intermediate. These differences were not evident in the Five Freedoms assessment, demonstrating an authors’ assessment bias that appeared to support the funding agencies’ interests. North American funded publications rated the welfare of animals in New treatments higher and those in a Conventional or No Treatment lower, compared with European-funded publications. It is concluded that preliminary evidence was provided of several forms of publication bias in animal welfare science.  相似文献   
807.
Moving towards a more sustainable adaptation process requires closer integration of policies related to the environment. An important actor in this is the local government. This paper examines to what extend adaptation is currently being integrated into Dutch local policies, and what the role is of a municipality's size, risk and experience in the encountered manifestations of adaptation. First, it was determined that adaptations taking place only anticipate currently perceivable weather extremes – mostly increasing precipitation. Second, it was determined that the realisation of further adaptations is hindered by a strongly sectoral divided reality. Adaptation is now heavily dominated by the water department, while spatial planning and the environment are only limitedly involved. Finally, it was observed that the contextual factor size proved to most important for horizontal policy integration, whereas the contextual factor extreme-weather experience was the most definite for the realisation of adaptations. We conclude that a more sustainable adaptation should first tackle the sectoral divides which requires administrative efforts, for example, professional training. These would preferably be initiated from a vertical direction.  相似文献   
808.
We draw attention to a number of key factors in the evaluation of major projects, such as smelters, which are highly capital- and energy-intensive as well as export-orientated. The practice of justifying such projects by upvaluing foreign exchange is considered, as is the cost of distortion. Export efficiency is introduced as the key criterion: the efficiency of some recent smelter proposals in Oceania was between 36 and 50 cents in the dollar. A correct power price is essential: hydropower (in contrast with hydroenergy) should be priced as a depletable resource.  相似文献   
809.
810.
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