全文获取类型
收费全文 | 1901篇 |
免费 | 51篇 |
国内免费 | 20篇 |
专业分类
安全科学 | 129篇 |
废物处理 | 82篇 |
环保管理 | 446篇 |
综合类 | 210篇 |
基础理论 | 490篇 |
环境理论 | 2篇 |
污染及防治 | 385篇 |
评价与监测 | 124篇 |
社会与环境 | 72篇 |
灾害及防治 | 32篇 |
出版年
2023年 | 14篇 |
2022年 | 24篇 |
2021年 | 22篇 |
2020年 | 26篇 |
2019年 | 24篇 |
2018年 | 47篇 |
2017年 | 61篇 |
2016年 | 68篇 |
2015年 | 64篇 |
2014年 | 60篇 |
2013年 | 131篇 |
2012年 | 86篇 |
2011年 | 155篇 |
2010年 | 100篇 |
2009年 | 88篇 |
2008年 | 114篇 |
2007年 | 125篇 |
2006年 | 120篇 |
2005年 | 72篇 |
2004年 | 71篇 |
2003年 | 71篇 |
2002年 | 59篇 |
2001年 | 40篇 |
2000年 | 28篇 |
1999年 | 30篇 |
1998年 | 28篇 |
1997年 | 15篇 |
1996年 | 25篇 |
1995年 | 16篇 |
1994年 | 20篇 |
1993年 | 17篇 |
1992年 | 17篇 |
1991年 | 9篇 |
1990年 | 11篇 |
1989年 | 5篇 |
1988年 | 10篇 |
1987年 | 15篇 |
1986年 | 10篇 |
1985年 | 5篇 |
1984年 | 9篇 |
1983年 | 6篇 |
1982年 | 10篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1969年 | 3篇 |
1937年 | 2篇 |
1936年 | 2篇 |
1935年 | 3篇 |
1926年 | 2篇 |
排序方式: 共有1972条查询结果,搜索用时 210 毫秒
711.
Salinity is an insidious soil conservation issue. Its expression can be greatly removed in time and space from its causes, so a focus on prevention is preferred. To avoid over or under-investment, a communication strategy for salinity needs to be a staged approach, the risks defined and the assets at risk identified. This paper describes a risk assessment schema and associated information base designed to support community investment in preventative actions. It describes a new approach to salinity risk similar to the concepts of diagnosis and staging used by physicians for diseases such as cancer. It outlines the diagnostic tools now being developed to define the timeframes of salinity development, the biophysical features of the landscape within which salinity develops and the riskiness of current and alternative management systems and matches this with a complementary community process designed to build knowledge and intervention. A GIS/database system captures the concepts of salinity risk and a large array of diagnostic information in a form designed for the development of salinity knowledge in the community and to guide investment in salinity prevention. The communication strategy and the salinity risk system are being applied in the Fitzroy Basin, Australia, an area of approximately 150,000 km2 straddling the Tropic of Capricorn. 相似文献
712.
Janet K. Kern David A. Geier Françoise Ayzac James B. Adams Jyutika A. Mehta Mark R. Geier 《毒物与环境化学》2013,95(2):396-405
The purpose of this blinded study was to evaluate potential environmental toxicity in a cohort of neurotypical children (n = 28) living in a suburban area of north-central Texas in the United States (US) with a comparable age- and gender-matched cohort of neurotypical children (n = 28) living in a suburban area of southeastern France using urinary porphyrin testing: uroporphyrin (uP), heptacarboxyporphyrin (7cxP), hexacarboxyporphyrin (6cxP), pentacarboxyporphyrin (5cxP), precoproporphyrin (prcP), and coproporphyrin (cP). Results showed significantly elevated 6cxP, prcP (an atypical, mercury-specific porphyrin), and cP levels, and increasing trends in 5cxP levels, among neurotypical children in the USA compared to children in France. Data suggest that in US neurotypical children, there is a significantly increased body-burden of mercury (Hg) compared to the body-burden of Hg in the matched neurotypical children in France. The presence of lead contributing to the higher levels of cP also needs to be considered. Further, other factors including genetics can not be completely ruled out. 相似文献
713.
The processes underlying the development of new populations are important for understanding how species colonize new territory and form viable long-term populations. Life-history-mediated processes such as Allee effects and dispersal capability may interact with climate variability and site-specific factors to govern population success and failure over extended time frames. We studied four disjunct populations of ponderosa pine in the Bighorn Basin of north-central Wyoming to examine population growth spanning more than five centuries. The study populations are separated from continuous ponderosa pine forest by distances ranging from 15 to >100 km. Strong evidence indicates that the initial colonizing individuals are still present, yielding a nearly complete record of population history. All trees in each population were aged using dendroecological techniques. The populations were all founded between 1530 and 1655 cal yr CE. All show logistic growth patterns, with initial exponential growth followed by a slowing during the mid to late 20th century. Initial population growth was slower than expectations from a logistic regression model at all four populations, but increased during the mid-18th century. Initial lags in population growth may have been due to strong Allee effects. A combination of overcoming Allee effects and a transition to favorable climate conditions may have facilitated a mid-18th century pulse in population growth rate. 相似文献
714.
The prevalence of older drivers’ engagement in distracting activities while driving is largely unexplored. Face-to-face interviews were conducted in the city of Braunschweig, Germany, comparing a sample of older drivers (n = 205) to a group of middle-aged drivers (n = 209). The drivers were interviewed on their engagement in distracting activities during the last half an hour of their driving trip, including the frequency and duration of these activities, their perception of the risk associated with these distracting activities and the role of these activities in at-fault crashes. Middle-aged drivers were significantly more likely to engage in certain distracting activities than older drivers. With regard to the duration of interactions with the passengers older drivers were significantly more talkative than middle-aged drivers. Middle-aged drivers rated most of the distracting activities as significantly less dangerous than older drivers. Distraction-related crashes are not a special problem of older drivers but seem to be very comparable to the middle-aged drivers. It is concluded that older drivers’ reluctance to engage in distracting tasks while driving is either a process of self-regulation or their age-related prudence. The study is the first to gather knowledge about distraction in German older drivers. Although older drivers are not currently overrepresented in distraction-related crashes, it is important to note that future cohorts of older drivers might differ in the way they engage with vehicles and technologies, which in turn may influence their driving patterns and willingness to engage in potentially distracting activities. 相似文献
715.
716.
717.
Fish migrate to spawn, feed, seek refuge from predators, and escape harmful environmental conditions. The success of upstream migration is limited by the presence of barriers that can impede the passage of fish. We used a spatially explicit modeling strategy to examine the effects of barriers on passage for 21 native and non-native migratory fish species and the amount of suitable habitat blocked for each species. Spatially derived physical parameter estimates and literature based fish capabilities and tolerances were used to predict fish passage success and habitat suitability. Both the fish passage and the habitat suitability models accurately predicted fish presence above barriers for most common, non-stocked species. The fish passage model predicted that barriers greater than or equal to 6 m block all migratory species. Chinook salmon (Oncorhynchus tshawytscha) was expected to be blocked the least. The habitat suitability model predicted that low gradient streams with intact habitat quality were likely to support the highest number of fish species. The fish passage and habitat suitability models were intended to be used by environmental managers as strategy development tools to prioritize candidate dams for field assessment and make decisions regarding the management of migratory fish populations. 相似文献
718.
Predicting national sustainability: The convergence of energetic,economic and environmental realities 总被引:2,自引:0,他引:2
The “constraint space” dictated by energetic, economic and environmental realities on scenarios for future organization of humanity and nature is explored from the perspective of the energy and resources driving economies. Net energy of energy sources is presented as an index (Emergy Yield Ratio; EYR) that must be evaluated for energy sources to better understand their potential contributions to society, but more important, as an indicator of the changes needed in the future if lower net yielding sources are to be relied upon. An aggregate EYR was calculated for the USA economy and shown to have decreased by 38% since 1950, from 11/1 to 6.8/1. Several measures of efficiency at the scale of national economies are explored and the data suggest that the most efficient economies are also the most energetically intense (as measured by empower intensity). An index of environmental loading is suggested as a measure to evaluate environmental efficacy. An obvious outcome is that the smallest most energetically intense countries have the highest environmental loads, and those with large land area and/or continental shelves have the lowest ratios. An Emergy Sustainability Index (EmSI) is defined, computed for countries, and proposed as a multi-dimensional measure of long-term sustainability. The most sustainable economies are those with the highest EYR and lowest environmental loads. 相似文献
719.
Stefan Krause Lutz Mattner Richard James Tristan Guttridge Mark J. Corcoran Samuel H. Gruber Jens Krause 《Behavioral ecology and sociobiology》2009,63(7):1089-1096
Analyses of animal social networks derived from group-based associations often rely on randomisation methods developed in
ecology (Manly, Ecology 76:1109–1115, 1995) and made available to the animal behaviour community through implementation of a pair-wise swapping algorithm by Bejder
et al. (Anim Behav 56:719–725, 1998). We report a correctable flaw in this method and point the reader to a wider literature on the subject of null models in
the ecology literature. We illustrate the importance of correcting the method using a toy network and use it to make a preliminary
analysis of a network of associations among eagle rays.
相似文献
Stefan KrauseEmail: |
720.
Cathryn L. Abbott Rhonda L. Millikin Mark J. Hipfner Scott Hatch Motohiro Ito Yutaka Watanuki Theresa M. Burg 《Marine Biology》2014,161(2):275-283
Data from eight microsatellite markers screened in 246 rhinoceros auklets (Cerorhinca monocerata) from across the North Pacific revealed multiple genetic groups. The east (North America) to west (Japan) split was clearly evident in all analyses. Within the eastern Pacific, a minimum of three genetic groups are present. Surprisingly, rhinoceros auklets from Triangle Island, British Columbia, were genetically isolated from other nearby populations, including the breeding colony on Pine Island (~100 km to the east). A fourth genetic cluster (Chowiet Is) was detected using principal coordinate’s analysis; however, sample sizes were limited. Patterns of differentiation correspond to nonbreeding distributions with the eastern and western Pacific birds spending time off the west coast of North America and Japan, respectively, and may represent historical isolation in separate refugia during the Pleistocene glaciations. The patterns of genetic structure result from a combination of historical and contemporary factors influencing dispersal of rhinoceros auklets. 相似文献