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41.
The Science of Nature - 相似文献
42.
Franz Wever 《Die Naturwissenschaften》1926,14(50-51):1217-1219
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Franz Beggel Isabella J. Nowik Michael Modigell Maxim G. Shalygin Vladimir V. Teplyakov Victor B. Zenkevitch 《Journal of Cleaner Production》2010
A novel gas purification system employing membrane contactors with dense membranes in the absorption as well as the desorption unit has been tested concerning the separation efficiency of CO2. The separation efficiency of potassium carbonate (K2CO3) promoted by piperazine (PZ) as absorption medium has been tested in the absorption unit. Since the absorbent will be regenerated in the desorption unit, the influence of temperature, sweep flow rate and absorbent type (0.5 M K2CO3 and 0.5 M K2CO3/0.5 M PZ) on the separation efficiency of CO2 in the desorption unit has been investigated. Desorption by vacuum has been considered as well.In addition experimental results of the coupling of a bioreactor producing hydrogen by anoxygenic photosynthesis (low and fluctuating product gas flow rates and fluctuating compositions) with a membrane contactor for gas purification are reported. This was done in order to show the applicability of this system to processes producing biogases. 相似文献
47.
The fate of microzooplankton production, whether it is channeled to mesozooplankton or recycled within the microbial food web, has major implications for the oceanic carbon cycle. The aim of this study was to estimate internal predation within naturally occurring microzooplankton communities. A dilution series based on the Landry and Hasset technique was created by mixing 200-μm-screened water (used as whole water) with 5-μm-screened seawater due to the dominance of pico- and small nanoplankton at our study site. This modification of the original technique allows for gradual reduction in microzooplankton abundance and thus internal predation while maintaining sufficient phytoplankton prey levels for microzooplankton growth in diluted treatments. Microzooplankton growth and mortality rates were calculated based on the changes in abundance during 24-h incubation. In the diluted treatments, microzooplankton growth rates were significantly higher (1.21 ± 0.20 day?1 for ciliates and 0.88 ± 0.05 day?1 for heterotrophic dinoflagellates) compared to those in whole seawater where microzooplankton abundance remained unchanged or even declined over time. Approximately 79 % of microzooplankton production was consumed within the microzooplankton, with aloricate ciliates being the most vulnerable to predation. These findings support the assumption that trophic interactions between microzooplankton can be an important factor controlling their production and, thus, energy transfer in picoplankton-dominated pelagic ecosystems. 相似文献
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This paper derives market equilibria (in demand functions and in bidding strategies) between oligopolists and oligopsonists in a market with intermediates and no competition in final markets. To the best of my knowledge, this theme has not been explored, despite two observations: Firstly, the commonly applied framework of non-competitive and competitive fringe firms has implausible properties for the limit of purely strategic players. Secondly, real world cases correspond at least potentially to such strategic interactions, e.g., non-competitive players selling and buying permits (CO2 and SO2). The major implications are that these non-competitive markets are characterized by a kind of double marginalization (on the demand and the supply side) resulting in too little trade and wrong price signals. 相似文献
49.
The topography and motion of contaminant plumes in groundwater may be determined by surveying the three-dimensional distribution of contaminant freights [1] as well as through a period-integral monitoring by contaminant dosimeters [1]. Conventional methods of taking water samples for chemical analysis cannot fulfill any of these requirements. Sorption active passive collectors suitable for corresponding surveys in gaseous phases are unsuitable for examination in aquifers. Passive collectors for the examination of undisturbed aquifers represent the central part of a probing device system developed by the authors for monitoring chemical and hydraulic parameters within all kinds of aquifers. These passive collectors permit both a determination of the relative contaminant freights at deliberate vertical spacing of vertically ordered measuring points, and period-integrating detection of vertical profiles of relative contaminant freights. The easy-to-handle passive collectors are suitable for the collection of organic and inorganic contaminants and may be evaluated by standardized chemical analysis methods. In this way, passive collectors fulfill the essential prerequisites for purpose-oriented monitoring of contaminant plumes. Moreover, passive collectors for ground water monitoring are well suited for the in situ-examination of any other aquifer, both still and fluent, regardless of its depth or extent. Examples of application may be sewage ducts, sewage plants, rivers, lakes, oceans, water samples and especially the identification of contaminants and trace substances. 相似文献
50.
D. R. Franz 《Marine Biology》1970,7(2):171-180
Currently available information on the distribution of species of the opisthobranch orders Cephalaspidea, Nudibranchia and Sacoglossa (Mollusca: Gastropoda) in the northwest Atlantic Ocean is presented. Except for Sacoglossa, the fauna is markedly amphiatlantic, but the temperate West Atlantic component increases southward and dominates south of New Jersey. Species' diversity of nudibranchs and cephalaspids on the continental shelf decreases between northern New England and Cape Hatteras in association with a southward decline in the proportion of amphiatlantic species. This is not evident for the cephalaspids of the continental slope, a higher percentage of which are amphiatlantic. The entire fauna is subdivided into 5 groups: arctic, boreo-subarctic, boreal, West Atlantic temperate, and West Atlantic tropical. The latter does not extend north of Cape Hatteras, but the remaining groups broadly overlap in the northwest Atlantic. The southward limits of amphiatlantic species are presented and related to sea surface temperatures. The thermal characteristics of a critical zone between Cape Cod and Connecticut are discussed, and a maximum temperature of 15 °C is suggested for successful reproduction of the boreo-subarctic component, and 25 °C for the boreal component. The distribution of boreal species on both sides of the North Atlantic is discussed, and a suggestion is made that the southward speread of these species in North America is limited by extreme summer warming south of New Jersey, despite favorable winter temperatures, which extend much farther south.Contribution No. 66 of the Marine Research Laboratory, University of Connecticut, USA. 相似文献