全文获取类型
收费全文 | 41809篇 |
免费 | 374篇 |
国内免费 | 424篇 |
专业分类
安全科学 | 1117篇 |
废物处理 | 1843篇 |
环保管理 | 4934篇 |
综合类 | 7239篇 |
基础理论 | 10882篇 |
环境理论 | 13篇 |
污染及防治 | 10774篇 |
评价与监测 | 3012篇 |
社会与环境 | 2530篇 |
灾害及防治 | 263篇 |
出版年
2022年 | 396篇 |
2021年 | 367篇 |
2020年 | 265篇 |
2019年 | 330篇 |
2018年 | 610篇 |
2017年 | 631篇 |
2016年 | 972篇 |
2015年 | 718篇 |
2014年 | 1139篇 |
2013年 | 3307篇 |
2012年 | 1346篇 |
2011年 | 1773篇 |
2010年 | 1539篇 |
2009年 | 1548篇 |
2008年 | 1729篇 |
2007年 | 1856篇 |
2006年 | 1639篇 |
2005年 | 1405篇 |
2004年 | 1338篇 |
2003年 | 1323篇 |
2002年 | 1295篇 |
2001年 | 1731篇 |
2000年 | 1200篇 |
1999年 | 740篇 |
1998年 | 497篇 |
1997年 | 510篇 |
1996年 | 556篇 |
1995年 | 600篇 |
1994年 | 562篇 |
1993年 | 467篇 |
1992年 | 505篇 |
1991年 | 471篇 |
1990年 | 493篇 |
1989年 | 469篇 |
1988年 | 423篇 |
1987年 | 368篇 |
1986年 | 338篇 |
1985年 | 360篇 |
1984年 | 377篇 |
1983年 | 363篇 |
1982年 | 376篇 |
1981年 | 329篇 |
1980年 | 275篇 |
1979年 | 325篇 |
1978年 | 281篇 |
1977年 | 265篇 |
1976年 | 226篇 |
1975年 | 230篇 |
1974年 | 237篇 |
1973年 | 224篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
211.
C. T. Achuthankutty Y. Shrivastava G. G. Mahambre S. C. Goswami M. Madhupratap 《Marine Biology》2000,137(1):19-22
Effect of salinity on the feeding rate and parthenogenetic reproduction of asexual females of the cladoceran Diaphanosoma celebensis Stingelin was studied. Short-term (10 h) grazing experiments were conducted using Isochrysis galbana as feed at 5, 17, 25 and 30 psu salinity. Gut pigment concentration showed a significantly higher rate of feeding at lower
salinities. Survival, growth, maturity attainment and neonate production of asexual females reared in the above four test
salinities indicated preference for lower salinities (5 and 17 psu). The mean size of adult females decreased from 909 to
593 μm, mean life span from 24 to 5 d, mean neonate production from 12 to 2 and mean size of neonates from 434 to 400 μm as
the salinity increased from 5 to 30 psu. Salinity variations also affected the size and age of primiparous females. Resting
egg formation and sexual reproduction did not occur at the tested salinities. The results indicate that D. celebensis is adapted to low saline, estuarine environments.
Received: 14 January 2000 / Accepted: 24 March 2000 相似文献
212.
213.
Population structure and reproductive ecology of the burrowing ghost shrimp Callianassa filholi Milne-Edwards, 1878 were studied in populations along a latitudinal gradient throughout New Zealand during the breeding season.
Size-frequency distributions revealed unimodal populations, with predominantly sexually mature shrimp. All populations showed
an unbiased sex-ratio, and there appeared to be no significant difference in size (carapace length, CL) between sexes. At
the same time, CL and size at maturity differed significantly between populations; however, a general increase in sizes from
north to south was not consistent throughout the latitudinal range studied. The timing of the breeding cycle differed significantly
between populations, and breeding started earlier in southern populations. Number of embryos (fecundity) increased linearly
with female CL at each location, but rates differed significantly between populations. Embryo size was not related to number
of embryos, and the former increased significantly with latitude. With the exception of embryo size, observed differences
in body size/size at maturity and reproductive timing between C. filholi populations are thought to be determined by food availability rather than temperature. Thus, further study is suggested on
these aspects of thalassinid reproductive biology.
Received: 17 June 1999 / Accepted: 8 January 2000 相似文献
214.
The pathway for the flow of salt-marsh grass production into marsh food-webs is still not well defined. We compared the abilities
of three marsh macroinvertebrates [salt marsh periwinkles, Littoraria irrorata (Say) (=Littorina irrorata), salt-marsh coffee-bean snails, Melampus bidentatus (Say); and a talitrid amphipod, Uhlorchestia spartinophila Bounsfield and Heard] to access standing-dead leaves of smooth cordgrass (Spartina alterniflora Loisel). The invertebrates were incubated with naturally-decaying leaves, and the rates of removal of organic matter and
living fungal biomass (ergosterol) were measured. The impact of invertebrate activity upon fungal growth rates was measured
as rates of fungal-membrane synthesis (incorporation of radioacetate into ergosterol). The removal rates of organic leaf biomass
per mg individual biomass were highest for amphipods (700 μg mg−1 d−1) and lowest for periwinkles (90 μg mg−1 d−1), but the relatively large biomass of the snails made their removal rates per individual greater than those of amphipods.
Net removal of ergosterol by all three invertebrates was >50% for yellow-brown (early-decay) leaf blades. For fully-brown
(advanced-decay) blades, >50% removal of ergosterol was found only for periwinkles; exposure to coffee-bean snails and amphipods
resulted in a net ergosterol reduction of ≤20%. The lower net reduction of living fungal biomass by coffee-bean snails and
amphipods may have been due to fungal-growth stimulation (2.3-fold stimulation in coffee-bean snails and 1.5-fold stimulation
in amphipods). Grazing by periwinkles did not stimulate fungal growth, possibly because of its high intensity. Grazing by
these three salt-marsh shredders may affect marsh-grass shoot-decay in different ways. Periwinkles may abbreviate the period
of fungal production, and incorporate the decaying material relatively quickly into snail biomass and fecal-pellet rain to
the sediments. Coffee-bean snails and amphipods may enhance and prolong fungal production, along with the formation of fecal-pellet
rain. All three invertebrates fed preferentially on leaf blades rather than leaf sheaths, and feeding rates of gastropods
were higher during the night than during the day.
Received: 25 November 1998 / Accepted: 4 November 1999 相似文献
215.
Cadmium accumulation in the female shore crab Carcinus maenas during the moult cycle and ovarian maturation 总被引:2,自引:0,他引:2
The influence of moulting and ovarian maturation on cadmium accumulation in the tissues of female shore crabs Carcinus maenas exposed to 1 mg Cd l−1 in the water was investigated. Cadmium accumulation in all tissues examined was markedly increased in crabs in the postmoult
stages (A and B) compared to crabs in all other moult stages. During the moult cycle, average cadmium accumulation in the
midgut gland ranged from 29 μg Cd g−1 dw at premoult stage (D2) to 589 μg Cd g−1 dw at postmoult stage (A). Average cadmium concentrations in the haemolymph ranged from 0.56 μg Cd ml−1 at intermoult stage (C4) to 4.6 μg Cd ml−1 at postmoult stage (A), while the gills accumulated from 103 μg Cd g−1 dw in intermoult stage (C3) to 352 μg Cd g−1 dw in postmoult stage (A). Cadmium concentration in gills and haemolymph was also significantly higher in crabs in late premoult
stage (D3) compared to C4-crabs, while midgut gland cadmium concentration remained elevated in C1- and C3- intermoult stages relative to C4. During ovarian maturation the cadmium accumulation in midgut gland, gills, ovaries and haemolymph decreased. Average cadmium
concentration in the midgut gland decreased from 63 μg g−1 dw in ovarian Stage I to 19 μg g−1 dw in ovarian Stage VI. The same pattern was observed for gills, haemolymph and ovaries. The present study demonstrates that
cadmium accumulation in the female shore crab strongly depends on the physiological status of the animal. A possible association
between physiological calcium requirements and cadmium accumulation during moulting is discussed.
Received: 20 January 2000 / Accepted: 20 July 2000 相似文献
216.
Genetic variation in 15 Holothuria (Microthele) nobilis (Selenka, 1867) populations on the Great Barrier Reef was studied at seven polymorphic allozyme loci. Although populations
were separated by distances up to 1300 km, there were no apparent restrictions to gene flow (F
ST
values were not significantly different from 0) and the maximum Nei's unbiased genetic distance was 0.003. Populations were
in Hardy–Weinberg equilibrium at all loci. The estimated maximum sexual input [this is the ratio of the number of sexually
produced individuals (N*) to the sample size (N
i
)] and the minimum sexual input [this is the ratio of the number of genotypes (N
go
) over the sample size (N
i
)] were used as estimators for the amount of asexual reproduction. Both parameters suggested that H. nobilis reproduces solely by sexual means (N*:N
i
: = 1; N
go
:N
i
= 0.74 to 1). The allozyme data indicated high gene flow between populations, but the possibility that allozyme frequencies
may not be at equilibrium means that it was not possible to distinguish whether the patterns reflect present-day dispersal
or dispersal that occurred in the past.
Received: 27 March 2000 / Accepted: 29 June 2000 相似文献
217.
The nature of heat coma was examined in the edible periwinkle Littorina littorea (L.). Duration of acclimation did not influence heat-coma temperature at 12 °C, although other acclimation temperatures were
important in influencing thermal tolerance, with positive shifts in coma temperature observed in response to elevated temperatures.
Previous thermal history also influenced heat-coma temperatures. Individuals subjected to repeat heat-coma events on a daily
basis showed significant declines (P < 0.05) in coma-temperature; in contrast individuals exposed to repeat heat-coma events on a weekly basis showed no decline
in thermal tolerance. Size-effects occurred at selected sites, where decreased heat-coma temperatures were recorded in large
individuals.
Received: 16 August 1999 / Accepted: 13 June 2000 相似文献
218.
Acoustic telemetry was used to examine patterns of activity and space utilisation of coelacanths, nocturnal predators which
spend the day in submarine caves. Nine coelacanths (Latimeria chalumnae) were tracked, each for a period of 1 to 16 nights at Grande Comore, West Indian Ocean. Activities lasted on average 9 h,
usually starting shortly after sunset and ending before sunrise. Vertically, coelacanths moved up and down at and below cave
level by following the bottom contour, mainly between 180 and 400 m depth. The deepest record was 698 m, the shallowest 133 m.
Most time was spent between 200 and 300 m depth. Large individuals performed deep excursions to depths below 400 m, usually
once per night. The fish spent most time in water temperatures of 15 to 19 °C; they rarely ventured into waters warmer than
22 °C measured at depths shallower than 160 m depth. Horizontally, coelacanths stayed in narrow areas ranging from <1 to 10 km
of coastline. Coelacanths are extremely slow drift-hunters with an estimated average swimming speed of 3.2 m min−1, often travelling not more than 3 km per night. They probably take advantage of local upwelling and downwelling and slow
currents occurring parallel to the steep slopes. This study shows that coelacanths are inhabitants of the subphotic zone,
where they are active mainly below the depth of their daytime refuges.
Received: 7 July 1999 / Accepted: 11 February 2000 相似文献
219.
An experimental study on recolonization and succession of marine macrobenthos in defaunated sediment 总被引:3,自引:0,他引:3
Hypoxia/anoxia in coastal waters is a world wide problem which often results in mass mortality and defaunation of benthos.
In this study, field experiments were carried out to examine recolonization and succession of macrobenthic infauna in defaunated
sediments, and the time required for recovery from complete defaunation to a stable community. Trays (33 cm length × 25.5 cm
width × 11 cm depth) of defaunated sediment were exposed at the subtidal of a pristine site in subtropical Hong Kong. Temporal
changes of macrobenthic communities in defaunated sediment were analyzed by univariate and multivariate statistics, and compared
with those in undisturbed natural sediment at the same site. Initial colonization of macrobenthos occurred rapidly. A total
of 42 species was found, with an average of 258 animals per tray and 24 species per tray recorded in the first month. Abundance
showed a small peak (496 animals per tray) after 3 months, reached a sharp peak (1154 animals per tray) after 6 months, and
declined thereafter. Species number increased gradually, reached a maximum (68 species per tray) after 9 months, and then
decreased. Recolonization was predominantly contributed by larval settlement rather than adult migration. Temporal changes
in abundance, species number and diversity of the macrobenthic community in defaunated sediment resemble the spatial changes
along a decreasing pollution gradient previously defined by other authors. Results of this experiment suggest that newly available
sediment may allow more species to colonize (or coexist) than sediment pre-occupied by an established community. This is probably
due to less interspecific competition in the former habitat. No significant difference in abundance or species richness was
observed between defaunated and natural sediments after 15 months, suggesting that a stable community had been achieved, although
minor variations in species composition were still discernible between defaunated and natural sediments.
Received: 24 May 1999 / Accepted: 20 October 1999 相似文献
220.
R. Wilson G. Peters J. Regel D. Grémillet K. Pütz M. Kierspel H. Weimerskirch J. Cooper 《Marine Biology》1998,130(4):559-566
Stomach temperature loggers have proved useful for the study of feeding activity in free-living seabirds, but their usage
has been restricted because they are frequently dislodged and lost during the seabirds' regular regurgitation of indigestible
prey remains. In the present study we examine the incidence of spontaneous regurgitation (pellet production) in free-living
seabirds, consider the effect this has on the likely retrieval of stomach temperature loggers and present a structural modification
of the logger housings which leads to a much lower incidence of regurgitation. Systems were tested on albatrosses, cormorants,
gannets and penguins.
Received: 15 July 1997 / Accepted: 31 October 1997 相似文献