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141.
The data on the dynamics of population size and species composition of wasps from the families Pompilidae, Sphecidae, and Vespidae were obtained in the course of long-term studies carried out in successional pine forests of the Berezinskii Biosphere Reserve. The abundance and species diversity of wasps were significantly higher in a polewood forest (40 years) than in a young forest (20 years) and mature moss forest (70 years). In an overgrown ride in the moss pine forest, the composition of dominant wasp species remained relatively stable during the seven-year period of observations, although the number of species and their abundance varied significantly from year to year, depending on the weather. 相似文献
142.
Papastefanou C Manolopoulou M Stoulos S Ioannidou A Gerasopoulos E 《Journal of environmental radioactivity》2001,55(1):109-112
A coloured rain event originating from the Sahara Desert occurred on April 9, 2000 at Thessaloniki, Northern Greece (40 degrees 38'N, 22 degrees 58'E). The radioactive nuclides that were determined in a coloured rain dust sample were 137Cs of Chernobyl origin, 7Be of cosmogenic origin and 40K of terrestrial origin. Cesium-137 still remained 14 years after the Chernobyl accident, reaching 26.6 Bq kg-1 in the coloured rain dust. 相似文献
143.
Radioactive contamination of wood and its products 总被引:1,自引:0,他引:1
This paper presents research on radioactive contamination of the three most common kinds of wood in Croatia--beech, oak and fir as well as acorn. Gamma-spectrometric measurements carried out on the samples of bark and wood of beech, oak, fir and acorn have shown radioactivity contents ranging from 1.6 +/- 0.1 to 37.3 +/- 0.5 Bq/kg from deposited 137Cs, whose concentrations in the soil of Croatia have increased after the Chernobyl accident. Measurements have also shown the radioactivity originating from 40K and 214Bi, which are part of the natural composition of the soil. The distribution of the radionuclides in wood has been discussed, as well as the impact of radioactive contamination of wood by the artificial radionuclide 137Cs upon the forest ecosystem. According to the corresponding model, it has been calculated that a 10 h daily stay in a typical family house increases the annual radiation dose of the population, due to the deposited 137Cs in the structure or furniture, by 343 microSv. 相似文献
144.
Emerald, north-east Queensland, is at the northern margin of the wheat cropping region of Australia. The Emerald region was previously used predominantly for grazing beef cattle; however, cropping has developed in importance over the past 30 years. We use historical climate records (1890-1998) to simulate and compare wheat yields, grass production and live-weight gain (LWG) over time. The cropping expansion from the 1970s to the early 1990s has occurred in a unique period in the 108-year record with the highest average wheat yields, lowest wheat yield variability and the greatest relative productivity of wheat production against grass production. If this window of opportunity is a result of long-term climate variability, then cropping is likely to decline in the region as conditions return to those experienced earlier in the record. If this increase is related to climate change, then cropping is likely to persist in the region with productivity maintained at current levels particularly through the yield-enhancing effects of increased atmospheric CO2 concentrations. However, this persistence will be influenced by the frequencies of El Ni?o conditions that may increase with global warming. The high relative productivities experienced over the past few decades have probably biased producers' expectations, and applications for drought support need to take into account the longer-term perspective provided by this analysis. Nevertheless, the last 6 years have the lowest simulated mean LWG production on the record. The identification of poor production periods depended on the production element being addressed and the timescale involved. 相似文献
145.
The Lagoon Olho d'Água in Pernambuco State, Northeast Brazil has received increasing environmental concern due to significant stress from pollution in the catchment. The existing environmental problems are the result of great pressure from a broad range of human activities, especially in the last 10 years. Serious pollution exists mainly from some industrial and urban activities, which increased intensively after the eighties. There is a strong social and economical pressure for housing and construction near the lagoon, due to the available land nearby beaches and estuarine zone, and recently by growing tourism activities. Uncontrolled land use by low-income communities and the pressure for construction by developers have led to landfilling and to deterioration of water quality in the lagoon catchment. Improvement of the environmental conditions in the catchment needs integrated measures. Guidelines and some specific actions involving several institutions have been established and refer to sanitation and urban infrastructure as the main priorities. A main target is the construction of low-cost sewage system with smaller and decentralised treatment plants. 相似文献
146.
147.
The phenomenon of the formation of two damaged xylem layers in one frost ring is described in Siberian spruce grown in western Siberian forest-tundra. Temperature conditions providing for the formation of pathological cell and tissue structures are determined. The relationship between the formation of double frost injuries and cold periods is demonstrated. 相似文献
148.
The morphology and development are described for Siberian stone pine (Pinus sibiricaDu Tour) growing at the timberline in the Western Sayan Mountains. Throughout ontogeny, these plants have a short stem trailing in an approximately horizontal direction. Maximal longevity and viability are characteristic of basal branches, which are able to root and produce vegetative generations. This allows these plants to be classified with the procumbent tree life form, in which the clones of most adaptive genotypes not only survive under extreme environmental conditions, but can also reproduce vegetatively. 相似文献
149.
The effect of mountain relief and industrial air pollution on biometric parameters of pine stands was studied. The empirical–statistical models of the dependence of biometric characteristics on the parameters of forest sites were developed using raster modeling and multivariate analysis. The possibility of predicting changes in the biometric parameters at any site on the basis of these models is shown. 相似文献
150.
A recent cost-effectiveness analysis of a residential radon remediation programme considered and highlighted many areas of uncertainty in the parameters chosen for the analysis. One assumption not challenged in the study was the benefits stream profile adopted. There are several different ways of loading the benefits in terms of life years into the cost-effectiveness model and several of these are explored and the results are reported in this study. The benefits profile depends upon the lead-time to cancer manifestation post environmental carcinogen (radon) exposure. The literature reviewed suggests that there are many options for loading benefits to radon-induced lung cancer prevention programmes. In this study, the alternative benefits stream profiles are explored and their implications for the cost-effectiveness ratio are examined. Adopting different benefits stream profiles to the model results in a range of cost-effectiveness ratios from 14912.90 pounds per life year gained to 52416.27 pounds per life year gained. The preferred model is reported where the life years gained are assumed to be equally distributed over the last 15 years of the 40-year time horizon of the analysis (Y25-40) and the corresponding cost-effectiveness ratio is 37,943 pounds per life year gained. 相似文献