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981.
Adaptive host choice and avoidance of superparasitism in the spawning decisions of bitterling (Rhodeus sericeus) 总被引:5,自引:0,他引:5
C. Smith John D. Reynolds William J. Sutherland Pavel Jurajda 《Behavioral ecology and sociobiology》2000,48(1):29-35
Choice of a site for oviposition can have fitness consequences. We investigated the consequences of female oviposition decisions
for offspring survival using the bitterling, Rhodeus sericeus, a freshwater fish that spawns inside living unionid mussels. A field survey of nine bitterling populations in the Czech
Republic revealed a significantly lower rate of release of juvenile bitterling from Anodonta cygnea compared to three other mussel species. A field experiment demonstrated that female bitterling show highly significant preferences
for spawning in A. anatina, Unio pictorum, and U. tumidus. Within a species, female bitterling avoided mussels containing high numbers of bitterling embryos. Mortality rates of bitterling
embryos in mussels were strongly density dependent and the strength of density dependence varied significantly among mussel
species. Female preferences for mussels matched survival rates of embryos within mussels and females distributed their eggs
among mussels such that embryo mortalities conformed to the predictions of an ideal free distribution model. Thus, female
oviposition choice is adaptive and minimizes individual embryo mortality.
Received: 6 October 1999 / Received in revised form: 7 January 2000 / Accepted: 13 March 2000 相似文献
982.
983.
984.
985.
A simple formula to calculate the ionization energies of two-, three-, and four-electron atomic ions
We have previously proposed a simple equation that is able to reproduce literature values (Moore 1970) for the ionization energies of one-electron (Lang and Smith 1981) and two-electron (Sabir Ali et al. 1984) atomic ions with very good agreement. However, our proposed equation has no firm theoretical basis, only that we consider
our potential energy approach a logical alternative to the usual kinetic relativistic/quantum mechanical methodology. The
results calculated from the equation give excellent agreement with literature values and differ by less than 1 eV and less
than 0.02% in all cases from hydrogen up to atomic number 20. This paper provides an updated version of the two-electron equation
adapted to calculate the ionization energies of three and four electron ions. Our equation also gives fairly good estimates
of first electron affinities. Comparisons are made with another published equation, sources of data are described, and the
calculated results are discussed. 相似文献
986.
The Texas National Coastal Assessment (NCA) program began with the immediate challenge of integrating the NCA effort with Texas Parks and Wildlife Department’s (TPWD) Coastal Fisheries Division and its existing probabilistic Fishery Independent Monitoring Program. Close coordination and detailed planning along with a novel two boat sampling operation helped to make this alliance work. Partnerships with National Estuary Programs and the Texas Commission on Environmental Quality (TCEQ) greatly improved coverage of the Texas coast over the initial fifty station design. Airboats, biobags, and polyvinyl chloride (PVC) corers were instrumental in overcoming numerous technical challenges. NCA data provide a more complete assessment of water and sediment quality than the traditional 305(b) report, with better spatial coverage and a measure of validity. There were differing patterns of PCBs, PAHs, DDTs and chlorinated pesticides, and metals such as mercury (Hg), arsenic (As), lead (Pb) and zinc (Zn) along the Texas coast. A confederation of Texas state agencies is considering ways to take advantage of probabilistic sampling designs to monitor the Texas coast. The TCEQ and TPWD are working on a joint project to redesign sediment and water quality monitoring that may serve as a springboard to a continuous monitoring program and opportunities for further improvement of ecosystem health assessment of the Texas coast. 相似文献
987.
988.
Accounting for risk and uncertainty in determining preferred strategies for adapting to future climate change 总被引:1,自引:1,他引:0
Tony Prato 《Mitigation and Adaptation Strategies for Global Change》2008,13(1):47-60
Individuals, businesses, and policymakers face the problem of selecting a preferred strategy for adapting a managed ecosystem
to future climate change when there is risk and/or uncertainty about future climate change and its ecosystem impacts, and
the conditional outcomes of adaptive strategies (i.e., performance of an adaptive strategy given a particular future climate
change scenario occurs). Evaluation methods for this purpose are described for two cases; one in which the decision-maker
can (climate risk case) and cannot (climate uncertainty case) assign probabilities to future climate change scenarios. Fuzzy
sets are used to characterize uncertainty regarding both future climate change, and the conditional outcomes of adaptive strategies.
The preferred conditional adaptive strategy for a future climate change scenario is determined by ordering the adaptive strategies
for that scenario using a fuzzy set operation. Two methods are described for determining the adaptive strategy that is preferred
across all climate change scenarios. The preferred overall adaptive strategy for the climate risk case is determined by maximizing
a performance index for strategies. The preferred overall adaptive strategy for the climate uncertainty case is determined
using the minimax regret criterion, which selects the strategy that minimizes the maximum loss in performance that can occur
across all strategies and climate change scenarios. Ways for making the evaluation methods dynamic are considered. 相似文献
989.
990.
V.Kerry Smith 《Journal of Environmental Economics and Management》1978,5(2):150-171
Concern over the implications of natural resource availability for economic well-being has been among the most long-lived policy issues involving economists. Scarcity and Growth by Barnett and Morse has remained the most influential evaluation of these issues. The purpose of this paper is to evaluate the Barnett-Morse methodology. Using the results from comparative static and dynamic models three scarcity indexes are evaluated for their consistency in signaling changes in the availability of natural resources. In addition, the paper reports a reconsideration of the movements in the relative prices of extractive outputs to 1973. This analysis indicates that the empirical evidence alone is not sufficient to arrive at a conclusion as to whether there is increasing scarcity of natural resources. 相似文献