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221.
Dieter Jendrossek Ingrid Knoke Rahim Bahodjb Habibian Alexander Steinbüchel Hans Günter Schlegel 《Journal of Polymers and the Environment》1993,1(1):53-63
Bacteria capable of growing on poly(3-hydroxybutyrate), PHB, as the sole source of carbon and energy were isolated from various soils, lake water, activated sludge, and air. Although all bacteria utilized a wide variety of monomeric substrates for growth, most of the strains were restricted to degrade PHB and copolymers of 3-hydroxybutyrate and 3-hydroxyvalerate, P(3HB-co-3HV). Five strains were also able to decompose a homopolymer of 3-hydroxyvalerate, PHV. Poly(3-hydroxyoctanoate), PHO, was not degraded by any of the isolates. One strain, which was identified asComamonas sp., was selected, and the extracellular depolymerase of this strain was purified from the medium by ammonium sulfate precipitation and by chromatography on DEAE-Sephacel and Butyl-Sepharose 4B. The purified PHB depolymerase was not a glycoprotein. The relative molecular masses of the native enzyme and of the subunits were 45,000 or 44,000, respectively. The purified enzyme hydrolyzed PHB, P(3HB-co-3HV), and—at a very low rate—also PHV. Polyhydroxyalkanoates, PHA, with six or more carbon atoms per monomer or characteristic substrates for lipases were not hydrolyzed. In contrast to the PHB depolymerases ofPseudomonas lemoignei andAlcaligenes faecalis T1, which are sensitive toward phenylmethylsulfonyl fluoride (PMSF) and which hydrolyze PHB mainly to the dimeric and trimeric esters of 3-hydroxybutyrate, the depolymerase ofComamonas sp. was insensitive toward PMSF and hydrolyzed PHB to monomeric 3-hydroxybutyrate indicating a different mechanism of PHB hydrolysis. Furthermore, the pH optimum of the reaction catalyzed by the depolymerase ofComamonas sp. was in the alkaline range at 9.4. 相似文献
222.
Exposure assessment of rarely measured substances or newly identified chemicals requires the usage of mathematical methods. The georeferenced exposure model GREAT-ER was designed to accurately predict the concentration of ‘down-the-drain’ chemicals under consideration of their spatial and temporal variability in surface waters. In the past, successful validations of the model have been performed predominantly for small and middle-sized catchments and were accompanied by extensive monitoring of the detergent-ingredients boron and linear alkylbenzene sulphonate (LAS). A proof of the adaptability of GREAT-ER to large catchments is given here by example of the Saale river basin. Furthermore, it could be shown that ammonium is a suitable parameter for validations of the model. This corroborated the hypothesis that the non-point-emissions of ammonium are of less importance in comparison to the ammonium loads in the effluents of wastewater treatment plants. 相似文献
223.
Alexander V. Fedorov Alexey V. Shulgin 《Journal of Loss Prevention in the Process Industries》2007,20(4-6):317-321
The distributed mathematical model of magnesium particle ignition is developed taking into account the heterogeneous chemical reaction and the domain of particle thermal influence on gas. The problem solvability in the stationary case has allowed one to expand classification of regular modes of heating as well as the modes of extinction and ignition of a particle. The limiting size of a gas layer near a particle is found that determines an ignition mode. It is shown that the ignition delay time grows if we take into account the gas layer near the particle. Stability of some heating modes within the framework of finite and infinitesimal perturbations is studied. An opportunity to control the ignition process by high-frequency thermal action on the unstable particle gas states is shown. 相似文献
224.
225.
The authors consider consumption of copper in the UK using data from 1920 to 1970. They draw up an overall balance sheet which, it is hoped, provides a firm foundation on which to base the total availability of copper and against which could be balanced the scrap which was recycled. 相似文献
226.
C. G. Alexander 《Marine Biology》1970,6(3):236-240
The osphradium of Conus flavidus, Lamarck has been examined by histological methods. Each lamella consists of 3 clearly defined regions: a dorsal spine and digitiform processes extending ventrally, composed of pseudostratified epithelium and occasional hair cells; a lateral and interdigitating region which contains numerous hair cells arranged in discrete ridges; a lamella nerve originating from the osphradial ganglion which sends a branch down the centre of each digitiform process. Each lamella has ciliary tracts which cause fluid, impinging on the osphradium, to be passed repeatedly between the lamellae and, therefore, to come into contact with the hair cells which are believed to be the primary sensory units of chemoreception in this organ. The whole structure responds immediately to substances dissolved in water by increased lamellar movement and by arching of the whole structure in towards the osphradial axis. 相似文献
227.
The dry deposition of ozone to aconiferous forest in northeastern Bavaria(southern Germany) was quantified during 1999with both the eddy correlation method and a bigleaf model. The model included parameterizationsof the atmospheric transfer resistances fromdirect measurements, stomatal resistance from aplant ecological model, and an estimation of thecuticle resistance as function of leaf wetness.Early in the season, the measured and themodelled deposition fluxes were in goodagreement, although the modelled fluxes tended tounderestimate the measured ones. Thisunderestimation was more pronounced in the latesummer, when high nocturnal fluxes werefrequently measured. The model parameterizationof the cuticle and the stomatal resistances didnot allow for such high fluxes. In these cases,the 24 hour average of the measured fluxes wereup to 4.5 times higher than the modelled ones.The reasons for these large discrepancies remainunknown. However, assigning the unaccounted partof the deposition to a nonstomatal surfacedeposition pathway, a new parameterization of therespective resistance yielded an average value of300 s m-1. It exhibited a decreasing trendthrough the vegetation period. 相似文献
228.
Elena A. Zakharova Paul V. Kosterin Vitaly V. Brudnik Alexander A. Shcherbakov Alexander A. Ponomaryov Lubov F. Shcherbakova Vladimir G. Mandich Eugenii E. Fedorov Vladimir V. Ignatov 《Environmental science and pollution research international》2000,7(4):191-194
A plant-based bioremediation (phytoremediation) strategy has been developed and shown to be effective for the clean-up of
soil contaminated by the breakdown products of the chemical warfare agent (CWA), yperite. The method involves exploiting the
plant growth hormone, indole-3-acetic acid (IAA), to intensify the phytoremediation. For determination of the yperite breakdown
products, gas chromatography is used.
Soil and plant samples were analysed with a gas chromatograph fitted with an atomic emission detector. The method of standard-free
determination was employed to identify sulphur-containing substances (SCSs). A series of soil tests was conducted, which showed
that the level of SCSs decreased 4, 8, and more than 20-fold compared with that found in contaminated soil. This decrease
was dependent upon the IAA concentrations used for plant treatment. The treated plants accumulated 2.7 to 2.9-fold larger
amounts of the SCSs than did the untreated plants. Owing to its simplicity, environmental safety and inexpensiveness, the
method can be recommended for the restoration of soil fertility in areas of storage and destruction of blister CWAs. 相似文献
229.
Relationship of properties of polycyclic aromatic hydrocarbons to sequestration in soil. 总被引:10,自引:0,他引:10
A study was conducted to determine whether the sequestration of 21 polycyclic aromatic hydrocarbons (PAHs) in soil was correlated with their properties. From 22 to 58% of the PAHs was not extracted with n-butanol after their addition to soil. After 28 days of aging, the percentage of the PAHs remaining in the soil increased to 47-77%; however, nearly all of each compound was recovered by Soxhlet extraction. Correlations were based on the amounts of aged compound extracted with butanol. Properties of compounds used in the correlations included Kow, molecular length and molecular-connectivity indices (MCIs). No one property, including log Kow, resulted in an R2 value greater than 0.26. A chain MCI (2 chi vCH) together with log Kow or a first-order MCI (1 chi) resulted in R2 values of 0.49 and 0.54, respectively. The data suggest that the properties tested are not important to predicting the sequestration of PAHs in soil. 相似文献
230.
Janzen-Connell effects are widespread and strong enough to maintain diversity in grasslands 总被引:1,自引:0,他引:1
Crop rotation schemes are believed to work by preventing specialist soil-borne pests from depressing the future yields of similar crops. In ecology, such negative plant-soil feedbacks may be viewed as a type of Janzen-Connell effect, which promotes species coexistence and diversity by preventing the same species from repeatedly occupying a particular site. In a controlled greenhouse experiment with 24 plant species and using soils from established field monocultures, we reveal community-wide soil-based Janzen-Connell effects between the three major functional groups of plants in temperate European grasslands. The effects are much stronger and more prevalent if plants are grown in interspecific competition. Using several soil treatments (gamma irradiation, activated carbon, fungicide, fertilizer) we show that the mechanism of the negative feedback is the buildup of soil pathogens which reduce the competitive ability of nearly all species when grown on soils they have formerly occupied. We further show that the magnitude of the change in competitive outcome is sufficient to stabilize observed fitness differences between functional groups in reasonably large communities. The generality and strength of this negative feedback suggests that Janzen-Connell effects have been underestimated as drivers of plant diversity in temperate ecosystems. 相似文献