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991.
Current Trends in Plant and Animal Population Monitoring   总被引:3,自引:0,他引:3  
Abstract:  Animal and plant population monitoring programs are critical for identifying species at risk, evaluating the effects of management or harvest, and tracking invasive and pest species. Nevertheless, monitoring activities are highly decentralized, which makes it difficult for researchers or conservation planners to get a good general picture of what real-world monitoring programs actually entail. We used a Web-based survey to collect information on population monitoring programs. The survey focused on basic questions about each program, including motivations for monitoring, types of data being collected, spatiotemporal design of the program, and reasons for choosing that design. We received responses from 311 people involved in monitoring of various species and used these responses to summarize ongoing monitoring efforts. We also used responses to determine whether monitoring strategies have changed over time and whether they differed among monitoring agencies. Most commonly, monitoring entailed collection of count data at multiple sites with the primary goal of detecting trends. But we also found that goals and strategies for monitoring appeared to be diversifying, that area-occupied and presence–absence approaches appeared to be gaining in popularity, and that several other promising approaches (monitoring to reduce parameter uncertainty, risk-based monitoring, and directly linking monitoring data to management decisions) have yet to become widely established. We suggest that improved communication between researchers studying monitoring designs and those who are charged with putting these designs into practice could further improve monitoring programs and better match sampling designs to the objectives of monitoring programs.  相似文献   
992.
为研究甜椒根际土壤中氮的行为,与既报同样的方法进行研究,即,利用15NH4+,15NO3-双标记的硝胺(NH,4>15NO3,15NH4NO3),在温室里对甜椒进行6周的根箱栽培.收割后,对土壤全氮,NO3-N,水溶性NH4-N,KCl抽出NH4-N和其各自的15N atom%进行测定.结果表明,土壤全氮从非根际到根际逐渐增加,与栽培前相比,土壤全氮在非根际中减少,却在根际中增大.土壤NO3-N浓度朝根际增加到离根际2 mm处,然后激减到根际.NO3-N的来自施给NO3-N的比例靠近根际逐渐升高,在根际达到了69%,反而,来自施给NH4-N的比例靠近根际逐渐降低,在根际将至7%左右.水溶性NH4-N和KCl抽出NH4-N浓度靠近根际逐渐降低,而且,从非根际到根际,二者匀保持3∶10的比例.KCl抽出NH4-N的来自施给NO3-N的比例靠近根际逐渐升高,但在根际仍低于3%,反而,其来自施给NH4-N的比例在非根际约为47%~55%,在根际降到41%.在整个根箱里,施用NO3-N的有機率达到62%,但其值在根际比非根圈要低.相反,施用NH4-N的有機率仅11%左右,但其值在根际比非根际要高.以上结果表明,在甜椒根际土壤中氮的无机化-有机化活性与水稻相比显著低.  相似文献   
993.
为研究结伴行为以及障碍物对疏散过程的影响,建立考虑2人结伴行为的双出口元胞自动机疏散模型.模型在静态场中引入危险度模拟行人路径选择,设置个体和2人结伴疏散人群,研究不同行人密度下二者的疏散过程,比较疏散效率;分析相同密度下不同结伴比例的行人疏散过程,得到最优比例;设置横向、竖向和横竖3种障碍物排列方式,模拟个体疏散和结...  相似文献   
994.
水资源配置大致存在完全政府配置、完全市场配置和准市场配置3种模式。中国正处于水权制度改革的过程中,水资源配置制度有从完全政府配置转向依靠市场配置的趋势。新制度经济学的交易成本理论和租值消散理论可以为新的水权制度的设计和选择提供依据。水资源的不同配置制度对应着相应的交易成本,相对较好的制度应该能在扣除交易成本之后获得较多的社会净租值。目前我国水资源管理的当务之急是根据经济理性,科学地界定好水资源的公有和私有权利,并由完全政府管制向市场体制转型。  相似文献   
995.
为明确主动避让行为对养老场所人员疏散的影响,建立考虑主动避让弱势群体行为的元胞自动机模型,模型分别考虑避让弱势群体前方行走区域、斜前方行走区域、前方和斜前方行走区域对人员疏散的影响;分析不同避让方式下弱势群体比例、行人密度、弱势群体位置分布对整体疏散结果的影响.结果 表明:主动避让弱势群体行为能够降低疏散时间,增加疏散...  相似文献   
996.
Many prey assess predation risk through predator chemical cues. Numerous studies have shown that (1) prey sometimes respond to chemical cues produced by heterospecifics and (2) that many species are capable of associative learning. This study extends this research by focusing on predation risk assessment and antipredator behavior in environments containing chemical cues produced by multiple prey species. The results show that green frog (Rana clamitans) tadpoles (1) assess risk from the chemical cue produced during predation by a heterospecific (gray tree frog, Hyla versicolor, tadpoles) and (2) can exhibit similarly strong behavioral responses to a mix of conspecific and heterospecific cues compared to conspecific cue alone, depending on their conditioning environment. I then discuss how the prey choice of the predators and the relative abundances of the prey species should influence the informational value of heterospecific cues.  相似文献   
997.
The regulation of protein collection through pollen foraging plays an important role in pollination and in the life of bee colonies that adjust their foraging to natural variation in pollen protein quality and temporal availability. Bumble bees occupy a wide range of habitats from the Nearctic to the Tropics in which they play an important role as pollinators. However, little is known about how a bumble bee colony regulates pollen collection. We manipulated protein quality and colony pollen stores in lab-reared colonies of the native North American bumble bee, Bombus impatiens. We debut evidence that bumble bee colony foraging levels and pollen storage behavior are tuned to the protein quality (range tested: 17–30% protein by dry mass) of pollen collected by foragers and to the amount of stored pollen inside the colony. Pollen foraging levels (number of bees exiting the nest) significantly increased by 55%, and the frequency with which foragers stored pollen in pots significantly increased by 233% for pollen with higher compared to lower protein quality. The number of foragers exiting the nest significantly decreased (by 28%) when we added one pollen load equivalent each 5 min to already high intranidal pollen stores. In addition, pollen odor pumped into the nest is sufficient to increase the number of exiting foragers by 27%. Foragers directly inspected pollen pots at a constant rate over 24 h, presumably to assess pollen levels. Thus, pollen stores can act as an information center regulating colony-level foraging according to pollen protein quality and colony need. An erratum to this article can be found at  相似文献   
998.
A Quantitative Method for Estimating Probable Public Costs of Hurricanes   总被引:2,自引:0,他引:2  
/ A method is presented for estimating probable public costs resulting from damage caused by hurricanes, measured as local government expenditures approved for reimbursement under the Stafford Act Section 406 Public Assistance Program. The method employs a multivariate model developed through multiple regression analysis of an array of independent variables that measure meteorological, socioeconomic, and physical conditions related to the landfall of hurricanes within a local government jurisdiction. From the regression analysis we chose a log-log (base 10) model that explains 74% of the variance in the expenditure data using population and wind speed as predictors. We illustrate application of the method for a local jurisdiction-Lee County, Florida, USA. The results show that potential public costs range from $4.7 million for a category 1 hurricane with winds of 137 kilometers per hour (85 miles per hour) to $130 million for a category 5 hurricane with winds of 265 kilometers per hour (165 miles per hour). Based on these figures, we estimate expected annual public costs of $2.3 million. These cost estimates: (1) provide useful guidance for anticipating the magnitude of the federal, state, and local expenditures that would be required for the array of possible hurricanes that could affect that jurisdiction; (2) allow policy makers to assess the implications of alternative federal and state policies for providing public assistance to jurisdictions that experience hurricane damage; and (3) provide information needed to develop a contingency fund or other financial mechanism for assuring that the community has sufficient funds available to meet its obligations. KEY WORDS: Hurricane; Public costs; Local government; Disaster recovery; Disaster response; Florida; Stafford Act  相似文献   
999.
绿色行政体系中识别环境因素的意义及标准   总被引:2,自引:1,他引:1  
简要介绍了“绿色行政体系”的定义和建设意义,着重介绍了将环境因素引入体系建设的意义以及在体系中识别环境因素的标准。  相似文献   
1000.
应用气相色谱法对对二氯苯(p-DCB)在雪与水中残留动态进行测定,探讨了不同气候下水中p-DCB的挥发污染行为.结果表明,雪与水中p-DCB的挥发速率都相当迅速,并服从一级反应动力学.在自然条件下,雪与水中p-DCB半减期分别为2.32~3.25d和0.76~1.20d.雪与水中p-DCB在投加浓度分别为0.1~100.0μg/g,0.1~100.0μg/mL范围时,投加浓度越高挥发速率越快,挥发半减期越短.  相似文献   
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