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711.
Caveats to quantifying ecosystem services: fruit abortion blurs benefits from crop pollination. 总被引:2,自引:0,他引:2
Merijn M Bos Dorthe Veddeler Anne K Bogdanski Alexandra-Maria Klein Teja Tscharntke Ingolf Steffan-Dewenter Jason M Tylianakis 《Ecological applications》2007,17(6):1841-1849
The recent trend to place monetary values on ecosystem services has led to studies on the economic importance of pollinators for agricultural crops. Several recent studies indicate regional, long-term pollinator declines, and economic consequences have been derived from declining pollination efficiencies. However, use of pollinator services as economic incentives for conservation must consider environmental factors such as drought, pests, and diseases, which can also limit yields. Moreover, "flower excess" is a well-known reproductive strategy of plants as insurance against unpredictable, external factors that limit reproduction. With three case studies on the importance of pollination levels for amounts of harvested fruits of three tropical crops (passion fruit in Brazil, coffee in Ecuador, and cacao in Indonesia) we illustrate how reproductive strategies and environmental stress can obscure initial benefits from improved pollination. By interpreting these results with findings from evolutionary sciences, agronomy, and studies on wild-plant populations, we argue that studies on economic benefits from pollinators should include the total of ecosystem processes that (1) lead to successful pollination and (2) mobilize nutrients and improve plant quality to the extent that crop yields indeed benefit from enhanced pollinator services. Conservation incentives that use quantifications of nature's services to human welfare will benefit from approaches at the ecosystem level that take into account the broad spectrum of biological processes that limit or deliver the service. 相似文献
712.
Marsh surface sediment deposition and the role of tidal creeks: Implications for created and managed coastal marshes 总被引:3,自引:0,他引:3
Denise J. Reed Thomas Spencer Anne L. Murray Jonathan R. French Lynn Leonard 《Journal of Coastal Conservation》1999,5(1):81-90
The need to understand the processes contributing to marsh sedimentation has become more urgent with the recent recognition
of the role of tidal marshes as sea defences, as well as the many restoration efforts currently under way. This study was
designed to build upon previous sedimentation work at Scolt Head Island by Combining techniques for measuring short-term sedimentation,
with detailed assessment of hydroperiod, previously used only in comparison with longer-term accretion measurements or in
micro-tidal systems. Measurements of water level, sediment deposition (at various distances from the creek margin) and suspended
sediment concentration (SSC) (creek margin and an interior site) were made at Hut Marsh over three sequential over-marsh tides
during May 1994. Sediment trap data show a significant trend of declining sediment deposition away from the creek when data
from all three tides are combined. All tides show higher SSC on the flood tide than on the ebb tide at the creek margin location.
There is little difference in flood and ebb SSCs at the interior site. An order of magnitude decrease in sediment deposition
within 20 m on the creek shows the rapidity with which sediment is deposited on these marshes. Higher tides influence both
the magnitude and pattern of marsh surface sediment deposition. Increased creek velocities on higher tides provide more potential
for resuspension within the creek and increase the supply of sediment to the marsh surface. This study suggests that the design
of tidal creeks may be essential for the development of sustainable coastal marshes in restoration projects. 相似文献
713.
A class of catch-effort models, which allows for heterogeneous removal probabilities, is proposed for closed populations. The model includes three types of removal probabilities: multiplicative, Poisson and logistic. The usual removal and generalized removal models then become special cases. The equivalence of the proposed model and a special type of capture-recapture model is discussed. A unified estimating function approach is used to estimate the initial population size. For the homogeneous model, the resulting population size estimator based on optimal estimating functions is asymptotically equivalent to the maximum likelihood estimator. One advantage for our approach is that it can be extended to handle the heterogeneous populations in which the maximum likelihood estimators do not exist. The bootstrap method is applied to construct variance estimators and confidence intervals. We illustrate the method by two real data examples. Results of a simulation study investigating the performance of the proposed estimation procedure are presented. 相似文献
714.
Alison P. Murata Tariq Siddique Allen M. Jobson Alsu Kuznetsova Amalesh Dhar M. Anne Naeth 《补救:环境净化治理成本、技术与工艺杂志》2023,33(2):111-118
Chloroform, a probable human carcinogen, is mainly produced anthropogenically for industrial use and may be released to the environment from a large number of sources related to its manufacture and use, including pulp and paper mills, hazardous waste sites, and sanitary landfills. Remediation of chloroform through conventional technologies has been met with limited success due to the conditions required and the formation of hazardous substances such as dichloromethane. The objective of this study was to investigate chloroform reduction in multicontaminated fine-textured soil using zero-valent iron (Fe0) in anaerobic microcosms. Four amended matrices were tested: simple matrix control (glass beads), soil matrix control (glass beads + soil), Fe0 in a simple matrix (glass beads + Fe0), and Fe0 in a soil matrix (soil + Fe0). Headspace chloroform and its transformation products dichloromethane, chloromethane, and methane were measured over 230 days and during short intervals in the initial 3 days. Chloroform (~0.3 mM initial mass) persisted in both control microcosms but was completely transformed in microcosms containing soil + Fe0 by 12 h and glass beads + Fe0 by 48 h. Reductive dechlorination of chloroform occurred with simultaneous production of dichloromethane (~0.11 to 0.14 mM mass) and chloromethane (~0.02 to 0.13 mM mass). Little methane (~0.07 to 0.26 μM mass) production as an end product of chloroform reduction was observed in microcosms amended with Fe0. Produced dichloromethane and chloroform almost disappeared by 230 days. The results showed a complete chloroform transformation pathway that has good potential for the remediation of chlorinated compounds in fine-textured soil. The role of soil clay minerals in redox reactions can be further investigated to improve the reductive dechlorination of chlorinated compounds in contaminated environments. 相似文献
715.
Vagisha Pruthi Nimrah Abbasi Varsha Thakur Shiri Shinar Anne O’Connor Rachel Silver Tasha Simpson Tim Van Mieghem 《黑龙江环境通报》2023,43(7):881-888