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991.
David R. Breininger Vickie L. Larson Brean W. Duncan Rebecca B. Smith Donna M. Oddy Michael F. Goodchild 《Conservation biology》1995,9(6):1442-1453
Remote sensing and geographical information systems are used to analyze landscapes important to species of conservation concern. The accuracy of the methods depends on how closely habitat mapping classes are linked to population demography. Habitat use by Florida Scrub Jays ( Aphelocoma c. coemlescens ) was quantified using circular plots. Habitat variation was mapped using high-resolution aerial photography on a site where all Florida Scrub Jays were color-banded. Nest site selection, nest success, yearling production, and breeder survival were measured within Florida Scrub Jay territories. Habitat use was lowest in areas without scrub oaks or areas within 136 m from forests. Open oak, dominated by scrub oaks and open sandy areas, had the highest use and nest success among habitats. Open oak occurred as narrow patches ( <20 m wide) in landscapes dominated by matrix habitat (palmetto-lyonia and swale marshes). Most wide patches (>50 m) of open oak were potential population sources, where reproduction exceeded mortality. Areas with patches of open oak of less than 1 ha were usually population sinks. Open oak occurred as less flammable patches in a landscape subject to frequent fires. Population sources varied temporally and spatially with fires and site potential to support scrub oaks (soils). Analyses of landscape patterns and dynamics indicated that habitat mapping should not only include patches of currently optimal habitat but should also include landscapes associated with open oak. The influences of landscape patterns on habitat use, reproductive success, survival, and territory size can be quantified at different scales starting with attributes associated with habitat patches, nest sites, and territories. Potential mapping errors occur, however, when habitats are used to quantify the areal extent of sources and sinks and similar population attributes important for species persistence. 相似文献
992.
993.
994.
Natural food items of five species of marine cladocerans, Evadne nordmanni, E. tergestina, Penilia avirostris, Podon leuckarti and P. polyphemoides, were investigated in the Inland Sea of Japan between April 1986 and May 1987. Gut content examination with SEM (scanning electron microscopy) revealed that feeding was largely limited to centric diatoms and a few exceptions of pennate diatoms and dinoflagellates. No animal remains were detected, and some unidentified materials were also found. Phytoplankton smaller than 35 m in size (cell diameter in centric diatoms and longest dimension in others) was found most frequently in the gut of cladocerans. The role of grazing of marine cladocerans in trophodynamic pathways of the pelagic realm is discussed. 相似文献
995.
Alkanes and alkenes in marine benthic algae 总被引:2,自引:0,他引:2
Saturated and olefinic hydrocarbons were determined in additional species of benthic marine algae from the Cape Cod (Massachusetts, USA) area (see: Youngblood et al., 1971). The distribution of homologous and isomeric olefins was studied in plants of different age and in morphologically different parts of the same specimen. With two minor exceptions, only normal alkanes and alkenes are present. The methylene-interrupted C19- and C21-polyolefins are particularly abundant; 1-heneicosahexaene and the corresponding pentaene are common to all brown algae, while the corresponding 3-isomers occur in green algae. The hydrocarbon concentration, the alkene-to-alkane ratio and the polyolefin content are highest in young plants or in rapidly growing tissues of older plants. This suggests a deeper involvement in cell biochemistry of straight-chain hydrocarbons than previously considered. The biosynthesis of the plant polyolefins remains to be explored; no immediately obvious precursors of the 1-polyolefins were found among the algal fatty acids. The hydrocarbon composition of these benthic algae differs greatly from that of fossil fuels in its simplicity and predominately unsaturated nature. The separation of the isomers by gas chromatography and their structural elucidation by mass spectrometry, alone and in combination with hydrogenation and ozonolysis, are discussed.Contribution No. 3155 of the Woods Hole Oceanographic Institution. 相似文献
996.
997.
Z.W. Birnbaum 《Environment international》1978,1(6):303-308
The history of problems dealing with competing risks is briefly outlined, beginning with Daniel Bernoulli's 1760 “Mémoir” on mortality due to smallpox and proceeding through the development of actuarial techniques and methods used in clinical research, reliability theory, population dynamics, and other areas of application. A probabilistic formulation of the theory of competing risks is then presented which appears applicable to all these areas. Within the framework of this theory, some fundamental problems are stated and discussed, such as questions of identifiability, choices of estimation procedures, or techniques for testing hypotheses. 相似文献
998.
W. A. Richkus 《Marine Biology》1978,49(3):277-284
Movements of the wooly sculpin Clinocottus analis between all pools in a designated area of a southern California (USA) intertidal zone were studied. Fish were captured during low tides, finclipped or bead-tagged, and released in the pool of capture. Percent recaptured in pool of first capture declined from 30 after 2 weeks to about 5 after 20 weeks. Percent recaptured in any pool in the study area declined from 50 after 2 weeks to 20 after 8 weeks, but remained at 20 through 16 weeks. A higher fidelity to an area of the intertidal zone than to a specific pool was suggested. Large fish exhibited higher probability of recapture than smaller individuals, indicating they become more sedentary with age. Changes in pool topography influenced percent recurrence in a pool, most likely as a consequence of changes in quality and quantity of cover available. Such responses to changes in specific pools and fidelity to intertidal areas containing several pools appear to be advantageous behavioral patterns in an environment where topographic change is frequent and often massive. 相似文献
999.
1000.