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501.
The use of transparency as camouflage in the epipelagic realm is complicated by the presence of ultraviolet radiation, because
the presence of UV-protective pigments decreases UV transparency and may reveal transparent zooplankton to predators and prey
with UV vision. During July 1999, September 1999, and June 2000, transparency measurements (from 280 to 500 nm) were made
on living specimens of 15 epipelagic (collection depth: 0–20 m, average: 11 ± 1 m) and 19 mesopelagic (collection depth: 150–790 m,
average: 370 ± 40 m) species of transparent zooplankton from Oceanographer Canyon and Wilkinson Basin in the Northwest Atlantic
Ocean. In addition, measurements of downwelling irradiance (from 330 to 500 nm) versus depth were made. The tissues from epipelagic
zooplankton had lower UV transparency than those from mesopelagic zooplankton, while the average visible transparency (at
480 nm) of the two groups was not significantly different. Percent transparency was positively correlated with wavelength
over most of the measured range, with a rapid decrease below a certain cutoff wavelength. In mesopelagic tissues, the cutoff
wavelength was generally 300 nm. In epipelagic tissues, the cutoff wavelength was between 300 and 400 nm. Twelve out of 19
epipelagic tissues had transparencies at 320 nm that were half or less than their 480 nm transparency values, versus only
4 out of 21 mesopelagic tissues. The effects of UV absorption on UV visibility and minimum attainable depth were modeled using
contrast theory and the physics of light attenuation. Because UV absorption was generally significantly greater in the UVB
than in the UVA spectrum (where UV vision occurs), and because the highest UV absorption was often found in less transparent
individuals, its modeled effects on visibility were slight compared to its effects on minimum attainable depth.
Received: 14 April 2000 / Accepted: 16 November 2000 相似文献
502.
503.
Relationship between Coefficient of Inbreeding and Parasite Burden in Endangered Gazelles 总被引:1,自引:0,他引:1
Jorge Cassinello Montserrat Gomendio Eduardo R. S. Roldan 《Conservation biology》2001,15(4):1171-1174
Abstract: We studied the effects of inbreeding depression on parasite infection in three species of endangered gazelles: Gazella cuvieri , G. dama, and G. dorcas . Coefficients of inbreeding were calculated for all individuals because complete genealogies were available. The levels of inbreeding differ both intra- and interspecifically. We collected samples of feces and determined nematode infection by counting nematode eggs in the samples. At the interspecific level, the species with the highest mean levels of inbreeding ( G. cuvieri ) had the highest levels of gastrointestinal parasites. Analyses done at the intraspecific level revealed a positive relationship between individual coefficient of inbreeding and parasite infection in G. cuvieri , but not in the species with the intermediate and lowest levels of inbreeding. Our findings suggest that high levels of inbreeding may make individuals more susceptible to parasitism, even under favorable environmental conditions, so this factor should be taken into account by those managing endangered species. 相似文献
504.
C.W.W. Pirk P. Neumann R.F.A. Moritz P. Pamilo 《Behavioral ecology and sociobiology》2001,49(5):366-374
The impact of intranest relatedness on nestmate recognition was tested in a population of polydomous and monodomous nests of the mound-building ant Formica pratensis. Nestmate recognition was evaluated by testing aggression levels between 37 pairs of nests (n=206 tests). Workers from donor colonies were placed on the mounds of recipient nests to score aggressive interactions among workers. A total of 555 workers from 27 nests were genotyped using four DNA microsatellites. The genetic and spatial distances of nests were positively correlated, indicating budding and/or fissioning as spread mechanisms. Monodomous and polydomous nests did not show different aggression levels. Aggression behavior between nests was positively correlated with both spatial distance and intranest relatedness of recipient colonies, but not with genetic distance or intranest relatedness of donor colonies. Multiple regression analysis revealed a stronger effect of spatial distance than of genetics on aggression behavior in this study, indicating that the relative importance of environment and genetics can be variable in F. pratensis. Nevertheless, the positive regression between intranest relatedness of recipient colonies and aggression in the multiple analysis supports earlier results that nestmate recognition is genetically influenced in F. pratensis and further indicates that foreign label rejection most likely explains our data. 相似文献
505.
Abstract: Because ambient temperature strongly influences reproduction in frogs, the seasonal timing of frog calling provides a sensitive index of biotic response to climate change. Over the last century, daily temperatures increased during 5 of the 8 months key to gametogenesis in frogs and toads near Ithaca, New York ( U.S.A.). Earliest dates of calling frogs recorded by Albert Hazen Wright between 1900 and 1912 near Ithaca were compared to those from the New York State Amphibian and Reptile Atlas Project for 1990–1999 for the three counties surrounding Ithaca. Four species are now calling 10–13 days earlier, two are unchanged, and none is calling later. The data suggest that climate has warmed in central New York State during this century and has resulted in earlier breeding in some amphibians—a possible first indication of biotic response to climate change in eastern North America. 相似文献
506.
507.
S.D.Limaye 《生态毒理学报》2001,(2):36-37,38
在西印度的硬岩地层,地下水是城市和城市周围贫民区供水的主要来源.这些贫民区不是连接到城市供水和排水网上.一个可以提供200人用水的带手泵的自流井,通常是提供安全饮用水的成本最小的方法.完全地补救被污染的地下水可能是不可行的. 相似文献
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