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121.
Effects of copper on the latency of lysosomal hexosaminidase in the digestive cells of Mytilus edulis 总被引:1,自引:0,他引:1
Mytilus edulis collected from Tomales Bay, California, USA, during mid-winter 1979 were exposed to increased concentrations of dissolved copper under controlled laboratory conditions. A dose-dependent reduction in the latency of lysosomal hexosaminidase activity in digestive cells was induced after a 30 d exposure to copper. The half-time of the hexosaminidase staining reaction in sections of digestive gland from control mussels was 15.5 min; for mussels exposed to 25, 50, and 75 g Cu l-1 it was 11.8, 8.5 and 5.5 min, respectively. In addition, the dyecoupled reaction product was seen earlier in sections from individuals exposed to 50 and 75 g Cu l-1 (after 30 s) and 25 g Cu l-1 (1 min) than in sections from control individuals (2.5 min). Copper accumulations were demonstrated histochemically to have the same distribution as the hexosaminidase reaction product, indicating that copper is sequestered in lysosomes. Copper concentrations in digestive gland tissue, were related to the concentrations of copper in the water to which the mussels were exposed. 相似文献
122.
The radiocarbon content in creosote bush in the greater Los Angeles area has been found to reflect the distribution of smog. Indications are that smog in the even larger air basin of the San Joaquin Valley of California may be caused in part by recent biospheric emissions rather than by fossil fuel combustion alone. 相似文献
123.
Summary The prediction that mothers should invest more in sons than daughters was briefly examined in American bison (Bison bison) by Wolff (1988). He concluded that (a) male calves suckle more than females, (b) cows that had previously produced sons were more likely to be barren, and (c) cows that had male calves became estrous later in the year than other cows. In this paper we present data from two long term studies at different sites to show that Wolff's conclusions are equivocal at best and difficult to reconcile with predictions of the hypothesis because of questionable methods and assumptions.
Offprint requests to: W.C.H. Green 相似文献
124.
The importance of preserving both protected areas and their surrounding landscapes as one of the major conservation strategies
for tigers has received attention over recent decades. However, the mechanism of how land-use surrounding protected areas
affects the dynamics of tiger populations is poorly understood. We developed Panthera Population Persistence (PPP)—an individual-based
model—to investigate the potential mechanism of the Sumatran tiger population dynamics in a protected area and under different
land-use scenarios surrounding the reserve. We tested three main landscape compositions (single, combined and real land-uses
of Tesso-Nilo National Park and its surrounding area) on the probability of and time to extinction of the Sumatran tiger over
20 years in Central Sumatra. The model successfully explains the mechanisms behind the population response of tigers under
different habitat landscape compositions. Feeding and mating behaviours of tigers are key factors, which determined population
persistence in a heterogeneous landscape. All single land-use scenarios resulted in tiger extinction but had a different probability
of extinction within 20 years. If tropical forest was combined with other land-use types, the probability of extinction was
smaller. The presence of agroforesty and logging concessions adjacent to protected areas encouraged the survival of tiger
populations. However, with the real land-use scenario of Tesso-Nilo National Park, tigers could not survive for more than
10 years. Promoting the practice of agroforestry systems surrounding the park is probably the most reasonable way to steer
land-use surrounding the Tesso-Nilo National Park to support tiger conservation. 相似文献
125.
Recent studies on climate responses in ectothermic (cold-blooded) vertebrates have been few in number and focussed on phenology
rather than morphology. According to Bergmann’s rule, endothermic (warm-blooded) vertebrates from cooler climates tend to
be larger than congeners from warmer regions. Although amphibians are ectothermic vertebrates, weather and climatic conditions
may also impact on their morphology, and thereby affect their survival rates and population dynamics. In this paper, we show,
in a unique long-term study during the period 1963–2003 in an agricultural landscape in western Poland, that the body length
of two water frog parental species (males of both Rana ridibunda and R. lessonae) increased significantly. However, their hybridogenetic hybrid R. esculenta did not show similar changes. A significant relationship with a large-scale climatic factor, the winter North Atlantic Oscillation
index, was found positive for R. ridibunda males and R. lessonae females, and negative for R. esculenta females. Our findings, the first for amphibians, are consistent with other studies reporting that recent climate change has
affected the morphology of animals. However, we also show that changes in amphibian phenotype linked to climate may vary independently
between (even very similar) species. 相似文献