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131.
Restoring habitat corridors in fragmented landscapes using optimization and percolation models 总被引:2,自引:0,他引:2
Justin?C.?WilliamsEmail author Stephanie?A.?Snyder 《Environmental Modeling and Assessment》2005,10(3):239-250
Landscape fragmentation and habitat loss are significant threats to the conservation of biological diversity. Creating and
restoring corridors between isolated habitat patches can help mitigate or reverse the impacts of fragmentation. It is important
that restoration and protection efforts be undertaken in the most efficient and effective way possible because conservation
budgets are often severely limited. We address the question of where restoration should take place to efficiently reconnect
habitat with a landscape-spanning corridor. Building upon findings in percolation theory, we develop a shortest-path optimization
methodology for assessing the minimum amount of restoration needed to establish such corridors. This methodology is applied
to large numbers of simulated fragmented landscapes to generate mean and variance statistics for the amount of restoration
needed. The results provide new information about the expected level of resources needed to realize different corridor configurations
under different degrees of fragmentation and different characterizations of habitat connectivity (“neighbor rules”). These
results are expected to be of interest to conservation planners and managers in the allocation of conservation resources to
restoration projects. 相似文献
132.
We tested the sampling methods of a volunteer-based monitoring program designed to detect the non-indigenous spiny water flea, Bythotrephes longimanus, and found that the program could detect the majority of Bythotrephes invasions. Volunteers take two vertical hauls with a 30 cm diameter net at each of three pelagic stations. To determine if the volunteers were using a large enough net at their three stations, we performed a 17-lake comparison of the volunteer's net with a 75 cm diameter, research-grade net. We found no difference in the number of stations at which Bythotrephes was detected (paired t-test, p = 0.155) with the two nets, because Bythotrephes densities were above the detection limits for both nets. To determine if three stations were sufficient to detect the invader with the volunteer's net, we deployed it at 30 stations in two lakes with average (Harp Lake, 4.17 Bythotrephes m(-3)) vs. low Bythotrephes densities (Sugar Lake, 0.92 m(-3)). In Harp Lake, repeated randomized sampling of the 30 sets of data indicated that only three stations were needed for 100% capture success. In Sugar Lake, seven stations were needed for 100% capture success, but three stations, the current program design, failed to detect the invasion only 14% of the time. 相似文献
133.
Stephanie Meredith Christopher Kaposy Victoria J. Miller Megan Allyse Subhashini Chandrasekharan Marsha Michie 《黑龙江环境通报》2016,36(8):714-719
The ‘Stakeholder Perspectives on Noninvasive Prenatal Genetic Screening’ Symposium was held in conjunction with the 2015 annual meeting of the International Society for Prenatal Diagnosis. During the day-long meeting, a panel of patient advocacy group (PAG) representatives discussed concerns and challenges raised by prenatal cell-free DNA (cfDNA) screening, which has resulted in larger demands upon PAGs from concerned patients receiving prenatal cfDNA screening results. Prominent concerns included confusion about the accuracy of cfDNA screening and a lack of patient education resources about genetic conditions included in cfDNA screens. Some of the challenges faced by PAGs included funding limitations, lack of consistently implemented standards of care and oversight, diverse perspectives among PAGs and questions about neutrality, and lack of access to training and genetic counselors. PAG representatives also put forward suggestions for addressing these challenges, including improving educational and PAG funding and increasing collaboration between PAGs and the medical community. © 2016 John Wiley & Sons, Ltd. 相似文献
134.
The hypothesis that Vespula germanica foragers can recruit nestmates to food resources was tested using a protocol that controlled for the biasing effects of social factors at the resource, including local enhancement and food-site marking substances. Foragers from an observation colony in the field were trained to visit a dish of scented corn syrup solution 15?m east of the nest. A second feeding station, 22?m northeast of the nest, offered incoming foragers a choice between food with the training scent and food with a control scent. Significantly more naive foragers arriving at that station chose the food with the training scent. We conclude that the German yellowjacket is able to recruit nestmates to carbohydrate food sources, and that recruits use food odor to locate the source of food being brought into the nest. 相似文献
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136.
This study examines the capacity to support the cumulative effects assessment and management for watersheds. The research is set in the Lower Fraser River Basin, a densely populated sub-watershed in British Columbia’s lower mainland. Eight requirements or requisites for the watershed cumulative effects assessment and management are applied to evaluate current capacity for implementation in the Lower Fraser, and to identify the areas in need of capacity development. Results show that advancing watershed cumulative effects assessment and management requires not only good science but also leadership in the coordination of monitoring programs, and in ensuring the appropriate incentives and penalties for engagement and nonengagement. The lack of leadership in this regard is the result of existing governance structures arranged around the political boundaries, which have produced over time multiple agencies and jurisdictional fragmentation. Notwithstanding this, we argue that the watershed is the most appropriate scale for assessing and managing the cumulative effects to complex ecosystems. 相似文献
137.
Juice SM Fahey TJ Siccama TG Driscoll CT Denny EG Eagar C Cleavitt NL Minocha R Richardson AD 《Ecology》2006,87(5):1267-1280
Watershed budget studies at the Hubbard Brook Experimental Forest (HBEF), New Hampshire, USA, have demonstrated high calcium depletion of soil during the 20th century due, in part, to acid deposition. Over the past 25 years, tree growth (especially for sugar maple) has declined on the experimental watersheds at the HBEF. In October 1999, 0.85 Mg Ca/ha was added to Watershed 1 (W1) at the HBEF in the form of wollastonite (CaSiO3), a treatment that, by summer 2002, had raised the pH in the Oie horizon from 3.8 to 5.0 and, in the Oa horizon, from 3.9 to 4.2. We measured the response of sugar maple to the calcium fertilization treatment on W1. Foliar calcium concentration of canopy sugar maples in W1 increased markedly beginning the second year after treatment, and foliar manganese declined in years four and five. By 2005, the crown condition of sugar maple was much healthier in the treated watershed as compared with the untreated reference watershed (W6). Following high seed production in 2000 and 2002, the density of sugar maple seedlings increased significantly on W1 in comparison with W6 in 2001 and 2003. Survivorship of the 2003 cohort through July 2005 was much higher on W1 (36.6%) than W6 (10.2%). In 2003, sugar maple germinants on W1 were approximately 50% larger than those in reference plots, and foliar chlorophyll concentrations were significantly greater (0.27 g/m2 vs. 0.23 g/m2 leaf area). Foliage and fine-root calcium concentrations were roughly twice as high, and manganese concentrations twice as low in the treated than the reference seedlings in 2003 and 2004. Mycorrhizal colonization of seedlings was also much greater in the treated (22.4% of root length) than the reference sites (4.4%). A similar, though less dramatic, difference was observed for mycorrhizal colonization of mature sugar maples (56% vs. 35%). These results reinforce and extend other regional observations that sugar maple decline in the northeastern United States and southern Canada is caused in part by anthropogenic effects on soil calcium status, but the causal interactions among inorganic nutrition, physiological stress, mycorrhizal colonization, and seedling growth and health remain to be established. 相似文献
138.
Predictive abilities of numerical sediment quality guidelines in Sydney Harbour, Australia, and vicinity 总被引:1,自引:0,他引:1
Matching chemical and toxicological data of surficial sediments from Sydney Harbour, Australia, and vicinity, were collected to evaluate predictive abilities of Effects Range-Low (ERL), Effects Range-Median (ERM) and other sediment quality guidelines (SQGs). Samples (n=103) containing a wide range of chemicals and concentrations were subjected to a battery of 4-6 toxicity tests. ERLs and functionally equivalent low-range SQGs were highly predictive of non-toxicity when not exceeded, as incidences of toxicity were 0-8%. ERMs and other mid-range SQGs were predictive of toxicity in combined test data with > or = 80% of toxic samples with one or more SQG exceeded. Predictive abilities of mid-range SQGs were low for amphipod survival tests (generally < 20% toxic samples), but the incidence of toxicity increased with increasing numbers of SQGs exceeded and increasing mean SQG quotients. Predictive abilities of SQGs generally matched their narrative intent when outcomes of multiple toxicity tests were considered, and were consistent with North American data. Functionally equivalent SQGs gave comparable results (except where developed for single chemical classes), indicating that predictive abilities were primarily influenced by sensitivities of test species and/or the bioavailability of contaminants. 相似文献
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