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991.
Summary The Yellow River is renowned for its life-endangering floods, a problem augmented by the continuous heavy siltation of its lower flood plain. Major dam and reservoir projects have both positive and negative environmental impacts, and their construction requires careful environmental consideration. This paper outlines the key findings of environmental impact assessment reports related to the Xiaolangdi Yellow River dam/reservoir project. The authors conclude that the project, as planned, should provide an optimal mix of both economic and environmental benefits.This paper is modified from a presentation given to the 1993 Annual Meeting of the International Association for Impact Assessment (IAIA) in Shanghai, China. 相似文献
992.
993.
A weakness often found in conventional environmental management tools is that of treating the dynamics of environmental effects and the underlying dynamics of structural change as external factors, precluding their ability to capture the evolutionary behaviour which characterizes economic systems. This article suggests a spatial dynamic modelling framework which addresses explicitly complex sectorial linkages and their environmental effects. The economic dynamics of the model are given spatial reference by means of a set of sector-based suitabilities, which allows us to explore both local environmental degradation effects as they unfold, and how these impacts then affect the economic productivity of the system as a whole. The approach is illustrated by calibrating the model with 1971-1981 data for the island of Crete, and then running it to explore how the economic dynamics of the island might evolve to the year 2001. This article presents a means through which to endogenize the environment and its explicit linkages with sectorial economic dynamics which can be of considerable use to environmental management in all its dimensions. 相似文献
994.
Summary The Commission of the European Communities' directive on environmental impact assessment (EIA) finally came into force in July 1988. The main provisions of the Directive are described, together with the objectives it is intended to achieve and the key areas where member state legislation will need to be effective if the principal requirements of the Directive are to be properly implemented. These include adequate coverage of projects, sufficient information in EIA studies, and effective consultation and public participation. Most European countries have some experience with EIA but, as illustrated by the UK Channel Fixed Link reports, the quality of the studies undertaken is very variable. Recommendations are made for improvements in practice through more effective diffusion of best practice, better provision and use of EIA guidance, more focused EIA research, more effective consultation and closer collaboration between the different parties involved in the EIA process, and both quantitative and qualitative improvements in EIA training. The results of a recent survey of European EIA training activity indicate growing interest, but further progress in improving the provision of EIA training is needed before the Directive can be effectively implemented.Drs Christopher Wood and Norman Lee have both been involved on various Environmental Impact Assessment (EIA) studies for the European Commission and have written widely on EIA and related topics. Both are Senior Lecturers at the University of Manchester and they are co-Directors of its EIA Centre. Christopher Wood teaches mainly in the Department of Town and County Planning, Norman Lee in the Department of Economics. 相似文献
995.
The use of blood lead levels in assessing lead exposure in mute swans, Cygnus olor (Gmelin) is investigated. 823 blood samples were taken from 456 uniquely ringed mute swans at a coarse-fish angling site over a period of 24 months. Blood lead values in individual swans monitored over several weeks were shown to conform to a recently reported kinetic model for blood lead values in birds. The highest median lead levels for flock birds were recorded in the winter and spring and the lowest during the summer moulting period. The use of Free Red Blood Cell Protoporphyrin for detecting lead exposure was examined. Whole blood lead detected 44% (n = 357) with elevated lead, while free red blood cell protoporphyrin detected 34.50%. In a large number of cases levels of protoporphyrin were above the normal level, while the corresponding lead levels were low. The value of both methods and the need to correct each value for haemoglobin is discussed. 相似文献
996.
Attainable or obtained detection limits play an important role in the discussion of trace analysis of polychlorinated dibenzo-p-dioxins and -furans. Now-a-days state of the art is based as well on highly developed instrumental techniques as on sophisticated clean up methods. However, with this state of the art is not connected, necessarily, a defined level of detection limits. Comparison of detection limits obtained in various laboratories are difficult. Reasonable comparisons imply knowledge about definitions, ways of quantitation, strategies of improvement, their limitations, and the substances under investigations. Measures to improve detection limits and their limitations are interdependent in a complex manner. Examples are given in this presentation.
The group analysis of the degrees of chlorination of the dibenzo-p-dioxins and -furans deteriorates the detection limits with respect to the single isomer determitation because of the higher influence of the residual matrix. Particulary, these topics should be taken into consideration when planning and executing analytical work for regulatory enforcement and legal purposes. 相似文献
997.
998.
Ernesto Guzmán-Novoa Robert E. Page Jr. Norman E. Gary 《Behavioral ecology and sociobiology》1994,34(6):117-409
Variability exists among worker honey bees for components of division of labor. These components are of two types, those that affect foraging behavior and those that affect life-history characteristics of workers. Variable foraging behavior components are: the probability that foraging workers collect (1) pollen only; (2) nectar only; and (3) pollen and nectar on the same trip. Life history components are: (1) the age the workers initiate foraging behavior; (2) the length of the foraging life of a worker; and (3) worker length of life. We show how these components may interact to change the social organization of honey bee colonies and the lifetime foraging productivity of individual workers. Selection acting on foraging behavior components may result in changes in the proportion of workers collecting pollen and nectar. Selection acting on life-history components may affect the size of the foraging population and the distribution of workers between within nest and foraging activities. We suggest that these components define possible sociogenic pathways through which colony-level natural selection can change social organization. These pathways may be analogous to developmental pathways in the morphogenesis of individual organisms because small changes in behavioral or life history components of individual workers may lead to major changes in the organizational structure of colonies.
Correspondence to: R.E. Page, Jr. 相似文献
999.
Male red frog crabs, Ranina ranina, were collected year round in 1990 and 1991 off Hachijojima for histological study of the reproductive system and cycle. The testis containing the lobules and seminiferous ducts is surrounded by connective tissue. The seminiferous duct connects to the anterior end of the vas deferens, which can be histologically divided into three portions similar to one another in appearance. It was surrounded by fibrous connective tissue, muscle fibrils and columnar epithelium. Muscle fibrils were absent in the anterior portion. Multiple sperm masses were not formed in the vas deferens and ejaculatory duct, but the sperm mass was covered with a capsule composed of two layers. The outer layer of the capsule was periodic acid Schiff (PAS)-positive, but the inner layer was negative. Both layers were Alcian Blue negative, except the vacuoles in the outer layer that were stained blue. The small round androgenic gland was attached to the posterior end of the vas deferens of the coxa of the eighth thoracic appendage. The ejaculatory duct was distinguishable from the vas deferens by the absence of columnar epithelium and the presence of thick longitudinal muscle fibers. Spermatogenesis was histochemically examined. The acrosomal vesicle appeared to be derived from PAS-positive vesicles in the cytoplasm of the spermatid at the early stage of spermiogenesis. The arms were positive to the Feulgen reaction and the subacrosomal region was negative to PAS. Seasonal changes in reproductive cycle were inconspicuous histologically and microscopically. Sperm were always present in the testis and vas deferens throughout the year and occupied 5.1 to 19.6% of testis observed in cross sections. The minimum size of maturity is less than 39 mm carapace length, but the minimum size capable of successful mating was estimated to be ca. 55 mm. 相似文献
1000.