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641.
Strike propensities refer to the extent to which union members are willing to engage in strikes. The present paper identifies four motivational explanations for individual propensity to strike: social exchange relationships between member and union, and member and company, economic circumstances, and social status. These four models complement each other, and together permit substantial integration of previous literature as well as suggesting new antecedents of strike propensities. We evaluated each model using survey data from 2548 unionized retail employees. While the economic model explained the most variance in strike propensity, each model accounted for a significant amount of unique variation in the members' strike propensities. Our organizational framework of the motivational explanations of strike propensity into four distinct but complementary motivational models and our addition of new predictor variables represent our study's major contributions. Implications for strike research and union member–union relations are discussed. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   
642.
ABSTRACT: We tracked vegetation succession on a debris‐flow deposit in Oregon's Coast Range to examine factors influencing the development of riparian plant communities following disturbance. Plots were stratified across five areas of the deposit (bank slump, seep, upper and lower sediment wedge, log jam) the first growing season after debris flow. At six times during the next ten years we estimated cover of vascular plants and tallied density of woody plants. Plant colonization occurred within two years. Total cover increased two‐to seven‐fold on the five areas within three years. Red alder and salmonberry were the dominant species, although weedy herbs persisted where woody species were lacking. Ordination of cover data showed that the five areas remained floristically distinct over time, while undergoing similar shifts related to the increasing dominance of alder and salmonberry. Rapid height growth of alder allowed it to outcompete salmonberry and effectively capture most areas by the tenth year, even where sprouts from transported rhizomes gave salmonberry an early advantage. Our results suggest that successional patterns were influenced by substrate variability, species composition of initial colonizers, propagule sources and their distribution, and species life‐history traits such as growth rate, competitive ability, and shade tolerance.  相似文献   
643.
ABSTRACT: The ability of regulators, resource managers, and consultants to assess accurately wetland hydrology is crucial when identifying and delineating wetlands. In this study, simple linear regression and long‐term (ten year) New Jersey Pinelands stream gaging and pitch pine lowland water‐level data sets were used to estimate long‐term hydroperiods at lowland test sites with short‐term (two year) records. Separate regression equations were developed for each test site using reference site data and stream gaging data, and two sets of equations for selected test sites were produced using two different short‐term periods of record. Test sites had long‐term records ranging from four to ten years, allowing validation of the regression models. Measured and predicted test site growing season water levels were similar regardless of which short‐term period of record was used. The results based on the stream gaging site data were similar, although the difference between measured and estimated growing season water levels was greater when this approach was used. Excellent agreement was found between measured and estimated frequencies of near‐surface saturation at test sites for each growing season month, and these relationships improved when cumulative, seasonal frequencies were considered. The reference wetland approach used in this study may have its greatest value in regions with both high development pressures and problem wetlands and may provide an effective way of resolving costly wetland delineation disputes.  相似文献   
644.
645.
Three types of concern for animal welfare are widelyheld: Animals should feel well, they should function well, andthey should lead natural lives. The paper deals with a well-knownanswer to the question of why such concerns are morallyappropriate: Human beings have direct duties towards animals,because animals are beings that can flourish, the flourishing ofanimals is intrinsically or inherently valuable, and that whichis conducive to their flourishing is a legitimate object of moralconcern. Looking for a tenable conception of direct dutiestowards animals, the following questions are discussed: Whatshould we take it to mean that ``animal flourishing isintrinsically or inherently valuable?'' Under what conditions doesa living being's ability to flourish create direct duties towardsthis being? Is awareness or sentience required for there to bedirect duties towards a living being? Does such a requirementimply that moral concerns for animals would be limited to theirfeeling well, or does it also give way to having moral concernsfor their functioning well and leading natural lives? Can onetake into account considered judgements that claim that towardsdifferent animals we have moral duties that differ in kind and/orstrength? If environmental ethics cannot be based on theconception of direct duties here discussed, should one draw adistinction between duties towards ourselves, our fellow humanbeings, or animals, and duties regarding plants, or collectiveentities such as populations, species, and ecosystems?  相似文献   
646.
This paper describes an application of the long termdynamic model, MAGIC, on a monthly timestep, enablingincorporation of the seasonal dynamics associated with abroad understanding of the ecosystem N cycle. The modelhas been applied to the Dargall Lane catchment in theGalloway region of Scotland where marked seasonal Ndynamics are apparent. Mean monthly proportions ofrainfall, runoff, deposition fluxes and net retention ofN are utilised to drive the model on a monthly timestep.Calibration of the model has successfully reproduced thepresent day observed seasonal variation in streamNO3 and ANC. Prediction of recovery at the siteunder the second sulphur protocol indicates that,although mean annual ANC increases, mean monthly ANC doesnot rise above zero for all months of the year until2010.  相似文献   
647.
ABSTRACT: Simulated daily precipitation, temperature, and runoff time series were compared in three mountainous basins in the United States: (1) the Animas River basin in Colorado, (2) the East Fork of the Carson River basin in Nevada and California, and (3) the Cle Elum River basin in Washington State. Two methods of climate scenario generation were compared: delta change and statistical downscaling. The delta change method uses differences between simulated current and future climate conditions from the Hadley Centre for Climate Prediction and Research (HadCM2) General Circulation Model (GCM) added to observed time series of climate variables. A statistical downscaling (SDS) model was developed for each basin using station data and output from the National Center for Environmental Prediction/National Center for Atmospheric Research (NCEPINCAR) reanalysis regridded to the scale of HadCM2. The SDS model was then used to simulate local climate variables using HadCM2 output for current and future conditions. Surface climate variables from each scenario were used in a precipitation‐runoff model. Results from this study show that, in the basins tested, a precipitation‐runoff model can simulate realistic runoff series for current conditions using statistically down‐scaled NCEP output. But, use of downscaled HadCM2 output for current or future climate assessments are questionable because the GCM does not produce accurate estimates of the surface variables needed for runoff in these regions. Given the uncertainties in the GCMs ability to simulate current conditions based on either the delta change or downscaling approaches, future climate assessments based on either of these approaches must be treated with caution.  相似文献   
648.
A survey was conducted in the United Statesin 1998 and 1999 to determine what members of theNational Association of State Universities and LandGrant Colleges (NASULGC) and of the AmericanAssociation of State Colleges and Universities (AASCU)offered agricultural ethics as an undergraduatecourse. Of the 59 responses, the survey found 15 USuniversities that have a course on agricultural ethicsor one that includes the topic. This paper willdiscuss the survey's findings and offer six reasonsthat explain why so few universities includeagricultural ethics in their curriculum. The sixreasons are: 1) lack of education in ethics andphilosophy on the part of agricultural scientists; 2)lack of institutional or disciplinary incentives foragricultural scientists to reflect on their work andits effects; 3) lack of administrative leadership incolleges of agriculture due to their failure tounderstand the benefits of agricultural ethics; 4)continuance of the prevailing assumption thatagriculture is inherently ethically correct; 5) thefelt necessity by agricultural scientists to defendthemselves against what are perceived to be unjust andinaccurate criticisms of agriculture; and 6) areluctance to engage in ethical reflection because itmay raise more problems than it solves. The paper'scentral question is why ethics is not taught in morecolleges of agriculture. Those who teach know thattheir students are tomorrow's farmers, businesspeople, professors, and policy makers. If we who nowteach and administer fail to include true ethicalstudy in our student's education, our students willstill be defensive when confronted with an ethicalissue and unable to respond except with assertionsbased on the production paradigm, the correctness ofwhich, although unexamined, we taught them. If theagricultural faculty does not recognize theopportunity and the obligation to participate in theshaping of values, then the values of agriculture willbe shaped elsewhere in the institution and insociety.  相似文献   
649.
The slope and aspect of a vegetated surface strongly affects the amount of solar radiation intercepted by that surface. Solar radiation is the dominant component of the surface energy balance and influences ecologically critical factors of microclimate, including near-surface temperatures, evaporative demand and soil moisture content. It also determines the exposure of vegetation to photosynthetically active and ultra-violet wavelengths. Spatial variation in slope and aspect is therefore a key determinant of vegetation pattern, species distribution and ecosystem processes in many environments. Slope and aspect angle may vary considerably over distances of a few metres, and fine-scale species’ distribution patterns frequently follow these topographic patterns. The availability of suitable microclimate at such scales may be critical for the response of species distributions to climatic change at much larger spatial scales. However, quantifying the relevant microclimatic gradients is not straightforward, as the potential variation in solar radiation flux under clear-sky conditions is modified by local and regional variations in cloud cover, and interacts with long-wave radiation exchange, local meteorology and surface characteristics.  相似文献   
650.
Ecological network analysis (ENA) is a modeling approach increasingly being used to evaluate food webs and provide an ecosystem-based approach to resource management. Unfortunately, validation of ENA output is rarely performed. This study represents part of a larger effort to critically evaluate ENA. Here we validate ENA output using stable isotope analysis (SIA), and where validation is not met, determine the effects of modifying trophic networks to reflect validation.  相似文献   
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