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411.
Recovery of Faunal Communities During Tropical Forest Regeneration   总被引:14,自引:0,他引:14  
Abstract:  As mature tropical forests are cleared, secondary forests may play an important role in the conservation of animal species, depending on how fast animal communities recover during forest regeneration. I reviewed published studies on the recovery of animal species richness and composition during tropical forest regeneration. In 38 of the 39 data sets I examined, conversion of forest to agriculture or pasture substantially reduced species richness. Given suitable conditions for forest recovery, the species richness of the animal taxa considered can be predicted to resemble that of mature forests roughly 20–40 years after land abandonment. At least for ants and birds, however, recovery of species composition appears to take substantially longer than recovery of species richness. Because species richness for many taxa appears to recover relatively rapidly in secondary forests, conservation of secondary forests may be an effective investment in future diversity. The slower recovery of species composition indicates, however, that some species will require stands of mature forest to persist.  相似文献   
412.
413.
应用5种多样性指数对祁连山圆柏群落的物种多样性进行了研究,并采用相邻格子样方法测定了乔木种群及其各立木级的分布格局.结果表明,灌木层的物种多样性偏低,而草本层多样性较高,群落总的物种多样性(以丰富度表示)较高.群落总的物种多样性较高是由于较低的灌木层多样性与较高的草本层多样性综合作用的结果,与放牧影响、阳坡的干燥环境有关,可能是林草交错区固有的特点.乔木种群的分布格局呈现出集群分布,但在其发育过程中显示了动态变化的特征,即在幼苗和小树阶段为集群分布,到了大树阶段转变为随机分布或均匀分布.表6参32  相似文献   
414.
Reproductive Investment of a Lacertid Lizard in Fragmented Habitat   总被引:3,自引:0,他引:3  
Abstract:  We studied the effect of habitat fragmentation on female reproductive investment in a widespread lacertid lizard (  Psammodromus algirus ) in a mixed-forest archipelago of deciduous and evergreen oak woods in northern Spain. We captured gravid females in fragments (≤10 ha) and forests (≥ 200 ha) and brought them to the laboratory, where they laid their eggs. We incubated the eggs and released the first cohort of juveniles into the wild to monitor their survival. Females from fragments produced a smaller clutch mass and laid fewer eggs (relative to mean egg mass) than females of similar body size from forests. Lizards did not trade larger clutches for larger offspring, however, because females from fragments did not lay larger eggs (relative to their number) than females from forests. Among the first cohort of juveniles, larger egg mass and body size increased the probability of recapture the next year. Thus, fragmentation decreased the relative fecundity of lizards without increasing the quality of their offspring. Reduced energy availability, increased predation risk, and demographic stochasticity could decrease the fitness of lizards in fragmented habitats, which could contribute to the regional scarcity of this species in agricultural areas sprinkled with small patches of otherwise suitable forest. Our results show that predictable reduction of reproductive output with decreasing size of habitat patches can be added to the already known processes that cause inverse density dependence at low population numbers.  相似文献   
415.
Abstract

Contaminated food chain is a serious contender for arsenic (As) uptake around the globe. In Nadia, West Bengal, we trace possible means of transfer of As from multiple sources reaching different trophic levels, and associated seasonal variability leading to chronic As uptake. This work considers possible sources-pathways of As transfer through food chain in rural community. Arsenic concentration in groundwater, soil, rice, and vegetable-samples collected detected in different harvest seasons of 2014 and 2016. Arsenic level in shallow groundwater samples ranged from 0.1 to 354?µg/L, with 75% of the sites above the prescribed limit by WHO (10?µg/L) during the boro harvest season. High soil As content (~20.6?mg/kg), resulted in accumulation of As in food crops. A positive correlation in As conc. with increase over period in all sites indicating gradual As accumulation in topsoil. Unpolished rice samples showed high As content (~1.75?mg/kg), polishing reduced 80% of As. Among vegetables, the plant family Poaceae with high irrigation requirements and Solanaceae retaining high moisture, have the highest levels of As. Contaminated animal fodder (Poaceae) and turf water for cattle are shown to contaminate milk (0.06 to 0.24?µg/L) and behoves strategies, practices to minimize As exposure.  相似文献   
416.
职业卫生安全管理体系(OHSMS)标准倡导好的管理的共同原理,将OHSMS融入组织总的管理体系,与我国组织职业卫生安全(OHS)管理的经验相容,对我国组织在市场经济体制下建立自主安全管理机制有极重要的意义。实施OHSMS标准不存在经济实力的前提,且OHS投入与组织的经济效益是一致的。这种标准化适应了我国经济体制转变时期政府安全管理职能和管理方式的变化,还与我国OHS管理体制的改革方向相吻合。我国基本具备实施OHSMS标准的法律基础。为有效实施OHSMS标准化,应加强OHS法规建设,在监察体系上实行第三方机构的认证/注册制度  相似文献   
417.
ABSTRACT: Forest land managers are concerned about the effects of logging on soil erosion, streamflow, and water quality and are promoting the use of Best Management Practices (BMPs) to control impacts. To compare the effects of BMP implementation on streamwater quality, two of three small watersheds in Kentucky were harvested in 1983 and 1984, one with BMPs, the other without BMPs. There was no effect of clearcutting on stream temperatures. Streamflow increased by 17.8 cm (123 percent) on the BMP watershed during the first 17 months after cutting and by 20.6 cm (138 percent) on the Non-BMP watershed. Water yields remained significantly elevated compared to the uncut watershed 8 years after harvesting. Suspended sediment flux was 14 and 30 times higher on the BMP and Non-BMP Watersheds, respectively, than on the uncut watershed during treatment, and 4 and 6.5 times higher in the 17 months after treatment was complete. Clearcutting resulted in increased concentrations of nitrate, and other nutrients compared to the uncut watershed, and concentrations were highest on the non-BMP watershed. Recovery of biotic control over nutrient losses occurred within three years of clearcutting. The streamside buffer strip was effective in reducing the impact of clearcutting on water yield and sediment flux.  相似文献   
418.
ABSTRACT. Estimates of peak flows, with specified return periods, are needed in practice for the design of works that affect streams in forested areas. In the province of British Columbia (B.C.), Canada, the new Forest Practices Code specifies the 100-year instantaneous peak flow (Q100) for the design of bridges and culverts for stream crossings under forest roads; and many practitioners are engaged in making such estimates. The state of the art is still quite primitive, very similar to the state of urban hydrology 30 years ago, when popular estimating techniques were used with little consideration given to their applicability. Urban hydrology then evolved on a much more scientific basis, such that within about a 10-year period, standard approaches to design were developed. Forest hydrology should follow the same pattern, at least as far as estimating design flows is concerned. Popular present day design procedures include the rational method and other empirical approaches based on rainfall data, as use of the standard flood frequency approach is limited by the paucity of relevant flow data. Estimating procedures based on peak streamflow measurements and statistics are likely to evolve, and these will include distinctions for rain, snowmelt, and rain on snow floods. Guidelines will also be developed for selecting and applying appropriate procedures for particular areas.  相似文献   
419.
ABSTRACT: This paper explores a range of forest hydrology issues and identifies my concepts of the field's most pressing research needs. I extend the topic to include teaching and education in the broader sense because current teaching is usually part of the researcher's portfolio and because education involves that of both the research scientist and a broader audience. I consider the primary research, education, and service roles of the forest hydrologist also within a range of domains or, as I prefer to identify them, scales: (1) the molecular or pore level; (2) hydrological process; (3) watershed function; (4) global considerations, and (5) the human dimension which, while not actually a scale itself, embraces, is important to, and is affected by the first four. All are topics screaming for attention by researchers, educators, and practitioners. I shall here focus on the middle three.  相似文献   
420.
森林影响河川径流的流域因素   总被引:7,自引:1,他引:7  
国内外所进行的小区或小流域试验表明,砍伐森林径流量增加,增加森林植被覆盖则径流量减少。但是,在大流域,砍伐森林并不一定能增加河川径流量。小面积试验得出的结论不适于推而广之到大的流域。其主要原因是流域因素——所处的自然气候地带、地质地貌特别是水文地质条件的不同。大面积种树种草或砍伐森林,对一个较大流域总水量的影响是比较复杂的。在什么样的条件下水量减少、增加或者变化不大,要对整个流域进行详细地调查和观测,只进行简单的小流域试验是不可能得出正确结论的。  相似文献   
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