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221.
Aspects of feather star behavior and ecology were recorded by time-lapse cinematography approximately 1 frame min-1 on the Great Barrier Reef, Australia over a 1 mo period in 1983. The current regime influenced body postures of most species studied, whether nocturnal or not. Moreover, feather stars of several species crawled on the substratum with their arms; each crawling episode lasted roughly 10 min, and the maximum speed attained was about 1 arm length min-1. Nocturnal feather stars crawled to their nighttime feeding perches around dusk and crawled back to their daytime hiding places around dawn. Surprisingly, some species of feather stars living on the reef surface both day and night also crawled around at dawn and dusk for reasons that are not known. In the time-lapse films, and individual of Comanthus bennetti (sex undetermined) spawned for about 2 min just after dark on 5 July 1983. Another film showed possible predation on a feather star (Himerometra robustipinna) by a saddled coralfish (Chaetodon ephippium).  相似文献   
222.
223.
Watershed management program on Santiago Island,Cape Verde   总被引:1,自引:0,他引:1  
The Watershed Management Program (WMP) was put into operation in early 1985 on Santiago Island, Cape Verde, with the stated purpose, “to develop and protect the soil and water resources of the Program-designated watersheds … to stabilize the natural environment and increase agricultural production potential in the Program area.” The approach to soil and water conservation in the program has been to build erosion and flood control structures (engineering approach) and plant trees (biological approach) to decrease rill and gully erosion, trap sediment behind control structures, provide flood protection, increase infiltration, increase fuelwood and fodder production, and increase water supplies for irrigation. There have been many successes resulting from specific management activities, but flawed approach or implementation in a few key areas has acted to impede the program's complete success, including lack of a scientific basis for evaluating its impact on soil and water conservation; poor design, placement, and maintenance of some major hydraulic structures; inadequate intervention in stabilizing farmlands or education of farmers and landowners in the need for and benefits of agroforestry; and incomplete integration of engineering and biological approaches.  相似文献   
224.
ABSTRACT: The underwater light field of eight central New York lakes, which represent a wide range of trophic state, was characterized through paired measurements of Sechi disc transparency (SD, m) and diffuse light attenuation (Kd, m?1). A total of 90 paired measurements are included in the data base. Substantial variability in the Kd SD product with time within individual systems, and amongst systems, was observed, which indicates differences in the relative contributions of absorption and scattering to attenuation. More than 50 percent of the temporal variability in Kd was attributable to attendant variations in chlorophyll a (C, mg m?3) in only two of the lakes. Estimates of the adsorption (a, m?1) and scattering (b, m?1) coefficients based on paired Kd and SD measurements compared well with more precise determinations available for one of the lakes. Determinations of a and b for the eight lakes, from SD and Kd measurements, indicated great system-specificity and temporal variability in these characteristics. The temporal variability in relative contributions of a and b to Kd is consistent with covariation of different attenuating components and the lack of correlation between C and Kd in most of the study lakes.  相似文献   
225.
ABSTRACT: This paper describes the techniques of factor and discriminant analyses to isolate and quantify the statistical differences between firms located on flood plains and those located off flood plains. The research effort described consists of three segments: data collection, isolation of potential classification variables, and the determination of the appropriate discriminant functions to classify a given fm as either on or off the flood plain. Significant classification functions are developed for both manufacturing and commercial establishments, whose arguments include dollar sales volume, total shipping cost, total employee cost, dollar valuations on the building and inventories, all on an annual basis, and the square footage of the site.  相似文献   
226.
The subterrestrial groundwater treatment (in situ treatment) is a multifunctional technology which is effective for the removal of such water constituents as iron, manganese, arsenic and ammonia. The in situ treatment can be applied efficiently for decentralised water supply. Within the framework of a research project, biofilms which play an important role in the in situ treatment will be localised, isolated and examined. Microorganisms will be identified and characterised in order to make the in situ treatment controllable regarding both planning and design of facilities, and to increase the efficiency of the technology.  相似文献   
227.
Meyer S  Steinhart H 《Chemosphere》2000,40(4):359-367
The interaction phenomena during the biodegradation of typical coal tar polycyclic aromatic hydrocarbons and their heterocyclic analogues (N, S, O) were investigated in an artificially contaminated AhA1-horizon/compost mixture. All compounds were partly or completely biodegraded. Degradation of two- to five-ring PAHs was inhibited by the presence of hetero-PAHs, whereas degradation of just some hetero-PAHs was inhibited by the presence of PAHs. Among the hetero-PAHs the sulphur-containing compounds were less susceptible to degradation than the corresponding oxygen- or nitrogen-containing analogues. The basic azaarene acridine showed an extreme persistence and strong sorption to the soil matrix proved by an increase of recovery after saponification of the soil matrix.  相似文献   
228.
Shallow groundwater quality on dairy farms with irrigated forage crops   总被引:5,自引:0,他引:5  
California's dairies are the largest confined animal industry in the state. A major portion of these dairies, which have an average herd size of nearly 1000 animal units, are located in low-relief valleys and basins. Large amounts of liquid manure are generated and stored in these dairies. In the semi-arid climate, liquid manure is frequently applied via flood or furrow irrigation to forage crops that are grown almost year-round. Little is known about the impact of manure management practices on water quality of the extensive alluvial aquifers underlying these basins. The objective of this work is to assess nitrate and salt leaching to shallow groundwater in a relatively vulnerable hydrogeologic region and to quantify the impact from individual sources on dairies. The complex array of potential point and nonpoint sources was divided into three major source areas representing farm management units: (1) manure water lagoons (ponds); (2) feedlot or exercise yard, dry manure, and feed storage areas (corrals); and (3) manure irrigated forage fields (fields). An extensive shallow groundwater-monitoring network (44 wells) was installed in five representative dairy operations in the northeastern San Joaquin Valley, CA. Water quality (electrical conductivity, nitrate-nitrogen, total Kjehldahl nitrogen) was observed over a 4-year period. Nitrate-N, reduced nitrogen and electrical conductivity (EC, salinity) were subject to large spatial and temporal variability. The range of observed nitrate-N and salinity levels was similar on all five dairies. Average shallow groundwater nitrate-N concentrations within the dairies were 64 mg/l compared to 24 mg/l in shallow wells immediately upgradient of these dairies. Average EC levels were 1.9 mS/cm within the dairies and 0.8 mS/cm immediately upgradient. Within the dairies, nitrate-N levels did not significantly vary across dairy management units. However, EC levels were significantly higher in corral and pond areas (2.3 mS/cm) than in field areas (1.6 mS/cm) indicating leaching from those management units. Pond leaching was further inferred from the presence of reduced nitrogen in three of four wells located immediately downgradient of pond berms. The estimated minimum average annual groundwater nitrate-N and salt loading from manure-treated forage fields were 280 and 4300 kg/ha, respectively. Leaching rates for ponds are estimated to be on the order of 0.8 m/year, at least locally. Since manure-treated fields represent by far the largest land area of the dairy, proper nutrient management will be a key to protecting groundwater quality in dairy regions overlying alluvial aquifers.  相似文献   
229.
Froehner K  Meyer W  Grimme LH 《Chemosphere》2002,46(7):987-997
The significance of the duration of exposure for the detection of toxicity was evaluated in a 24 h long-term bioluminescence inhibition assay with Vibrio fischeri. Bioluminescence was measured over the time course of 24 h using microplates. The undisturbed luminescence of controls in this assay exhibited characteristic dynamics: a decrease within a period of 12 h with minimal luminescence followed by a continuous increase of luminescence beyond the starting value. To evaluate the toxic influence of compounds chosen to reflect immediate and delayed toxicity to V. fischeri, the bioluminescence was measured for 24 h at 30 min intervals. Luminescence inhibition patterns were recorded for subdinoseb, pentachlorophenol and 2,4,5-trichlorophenol) and for substances causing delayed toxicity (chloramphenicol, nalidixic acid and phosphomycin). The toxic influence of substances with immediate toxicity was observed directly after application, whereas the toxicity patterns of substances with delayed toxicity developed specifically over the time according to the different involved mechanisms of action. It is concluded that knowledge about time to toxicity in bioassays is necessary in order to identify suitable test endpoints as well as to recognize potential hazards related to time-dependent toxicity.  相似文献   
230.
In striped bass samples from the lower Hudson River and its estuary 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) was found at concentrations from 16 to 120 pg/g (ppt). Striped bass from two other locations (Rhode Island coastal waters and Chesapeake Bay, Maryland) had <5 ppt, 2,3,7,8-TCDD. The contaminant, 2,3,7,8-tetrachlorodibenzofuran (2,3,7,8-TCDF), was found in striped bass from all three locations with concentrations varying from 6 ppt in Chesapeake Bay to 78 ppt in the Hudson River. Results from a limited number of non-migratory fish (carp and goldfish) and sediments suggest that the upper Hudson River is not a source for 2,3,7,8-TCDD/2,3,7,8-TCDF contamination of striped bass.  相似文献   
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