全文获取类型
收费全文 | 11077篇 |
免费 | 17篇 |
国内免费 | 40篇 |
专业分类
安全科学 | 22篇 |
废物处理 | 854篇 |
环保管理 | 1355篇 |
综合类 | 1058篇 |
基础理论 | 3353篇 |
环境理论 | 2篇 |
污染及防治 | 2238篇 |
评价与监测 | 1273篇 |
社会与环境 | 975篇 |
灾害及防治 | 4篇 |
出版年
2023年 | 59篇 |
2022年 | 172篇 |
2021年 | 114篇 |
2020年 | 25篇 |
2019年 | 47篇 |
2018年 | 1508篇 |
2017年 | 1421篇 |
2016年 | 1274篇 |
2015年 | 166篇 |
2014年 | 91篇 |
2013年 | 179篇 |
2012年 | 519篇 |
2011年 | 1417篇 |
2010年 | 743篇 |
2009年 | 652篇 |
2008年 | 945篇 |
2007年 | 1278篇 |
2006年 | 63篇 |
2005年 | 52篇 |
2004年 | 55篇 |
2003年 | 81篇 |
2002年 | 125篇 |
2001年 | 22篇 |
2000年 | 17篇 |
1999年 | 7篇 |
1998年 | 12篇 |
1997年 | 2篇 |
1996年 | 6篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1985年 | 2篇 |
1984年 | 13篇 |
1983年 | 12篇 |
1982年 | 5篇 |
1979年 | 2篇 |
1966年 | 1篇 |
1965年 | 2篇 |
1964年 | 2篇 |
1962年 | 2篇 |
1961年 | 4篇 |
1958年 | 3篇 |
1957年 | 3篇 |
1956年 | 2篇 |
1955年 | 4篇 |
1953年 | 1篇 |
1935年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 404 毫秒
991.
We tested joint effects of predator loss and increased resource availability on the grazers’ trophic level and the propagation
of trophic interactions in a benthic food web by excluding larger predatory fish from cages and manipulating nutrients in
the coastal zone of the Baltic Sea. The combination of nutrient enrichment and excluding larger predators induced an increase
in medium-sized predatory fish (three-spined stickleback). The meso-predator fish in turn did not change the total abundance
of the invertebrate herbivores, but did cause a substantial shift in their community composition towards the dominance of
gastropods by reducing amphipods by 40–60%, while gastropods were left unchanged. The shift in grazer composition generated
a 23 times higher producer biomass, but only under nutrient enrichment. Our results show that top-predator declines can substantially
shift the species composition at the grazers’ level, but that cascading effects on producers by a trophic cascade strongly
depend on resource availability. 相似文献
992.
Effects of oceanic and terrestrial sediment suspensions on the behavioral traits activity, colony expansion, and mucus formation
of the gorgonian octocoral Subergorgia suberosa (Pallas, 1766) were studied in the laboratory. Increased sediment concentration significantly changed the logits of activity
indices (as colony expansion) and was correlated with decreased activity. For both sources of sediments, the activity index
decreased as the concentration of sediment increased. The level of decrease was more significance for terrestrial sediments.
The activity index showed no clear time pattern for the control group, but a decrease over time occurred in both sediment
treatment groups. Activity change was linearly correlated with exposure time and concentration of terrestrial and ocean sediments.
The activity indices of polyps were negatively correlated with the formation of mucus sheets (correlation = −0.536, p = 0.048). For both sources of sediments, the frequency of mucus sheet formation (MSF) increased with sediment concentration.
Increases in terrestrial sediment loads resulted in more striking effects. The probability for MSF under different sediment
groups at different concentrations over time was modeled by regressions. Frequency of polyp activity is suggested as a suitable
biomarker to monitor the effects of sedimentation stress. 相似文献
993.
Rosemary E. Golding Donald J. Colgan Guy Nelmes Tina Reutelshöfer 《Marine Biology》2011,158(6):1259-1269
DNA sequences of the mitochondrial cytochrome c oxidase subunit I (COI) gene were collected from estuarine snails in the genus
Phallomedusa to examine the effects of estuarine isolation on population structure and gene flow. Three clades were recovered, one corresponding
to Phallomedusa austrina and two others with the morphology of Phallomedusa solida. The haplotype diversity in all three clades indicated recent population expansion. Phallomedusa austrina was restricted to the west of a previous land bridge in the Bass Strait between mainland Australia and Tasmania, and P. solida to its east and to northern Tasmania. Phylogeographic analysis of P. austrina and P. solida shows strong geographic separation of species, but no local genetic structure indicative of regional or estuarine isolation.
The clades of P. solida exhibit substantial genetic divergence and were sympatric across their entire distribution in eastern Tasmania and mainland
Australia. Such a situation, which has not previously been observed in phylogeographic studies of southeast Australia, suggests
that P. solida has had a complex refugial history during periods of environmental challenge. 相似文献
994.
Andrea Gori Sergio Rossi Cristina Linares Elisa Berganzo Covadonga Orejas Mark RT Dale Josep-Maria Gili 《Marine Biology》2011,158(8):1721-1732
In the Western Mediterranean Sea, the gorgonian Eunicella singularis (Esper, 1794) is found at high densities on sublittoral bottoms at depths from 10 to 70 m. Shallow colonies have symbiotic
zooxanthellae that deeper colonies lack. While knowledge of the ecology of the shallow populations has increased during the
last decades, there is almost no information on the ecology of the deep sublittoral populations. In October and November 2004
at Cap de Creus (42°19′12″ N; 03°19′34″ E), an analysis of video transects made by a remotely operated vehicle showed that
shallow populations (10–25 m depth) were dominated by small, non-reproductive colonies, while deep sublittoral populations
(50–67 m depth) were dominated by medium-sized colonies. Average and maximum colony heights were greater in the deeper populations,
with these deeper populations also forming larger patch sizes and more extensive regions of continuous substrate coverage.
These results suggest that shallow habitats are suitable for E. singularis, as shown by the high recruitment rate, but perturbations may limit or delay the development of these populations into a
mature stage. This contrasts with the deep sublittoral habitats where higher environmental stability may allow the development
of mature populations dominated by larger, sexually mature colonies. 相似文献
995.
The present study addresses the effect of maternal diet on hatching success and condition of embryos and larvae of Antarctic
krill Euphausia superba. Lipid and fatty acid content and composition were determined in field and laboratory samples. Developmental stages analyzed
in embryos included: multiple-cell, gastrula, and limb-bud stages. Larval stages analyzed included: nauplius I, nauplius II,
and metanauplius. Laboratory-reared embryos were spawned by gravid females incubated under three feeding groups: (1) phytoplankton
mixture, (2) phytoplankton mixture and minced clam, and (3) phytoplankton mixture, minced clam, and commercial larval food.
Hatching success was highest in group 3 (100%), lowest in group 1 (0%), and highly variable in field samples (0–48%). Lipid
decreased slightly in embryos during embryonic development, while large decreases in lipid were found during nauplius development.
High levels of 18:2(n-6), 20:4(n-6), and 22:6(n-3) observed with group 3 samples coincided with high hatching success in krill
embryos. The ratio of 22:6(n-3)/20:5(n-3) also correlated to hatching success of embryos. The fatty acid profile of embryos
in group 3 was similar to that of the field-collected embryos, reflecting the contribution of the commercial larval food in
the maternal diet. In our study, the maternal diet was found to influence the fatty acid composition of embryos and in turn
affects the hatching success of krill. Specific polyunsaturated fatty acids appeared to play important roles in embryogenesis
in krill. 相似文献
996.
M. Koopmans P. van Rijswijk D. Martens T. A. Egorova-Zachernyuk J. J. Middelburg R. H. Wijffels 《Marine Biology》2011,158(1):9-20
The carbon metabolism of two marine sponges, Haliclona oculata and Dysidea avara, has been studied using a 13C isotope pulse-chase approach. The sponges were fed 13C-labeled diatoms (Skeletonema costatum) for 8 h and they took up between 75 and 85%. At different times, sponges were sampled for total 13C enrichment, and fatty acid (FA) composition and 13C enrichment. Algal biomarkers present in the sponges were highly labeled after feeding but their labeling levels decreased
until none was left 10 days after enrichment. The sponge-specific FAs incorporated 13C label already during the first day and the amount of 13C label inside these FAs kept increasing until 3 weeks after labeling. The algal-derived carbon captured by the sponges during
the 8-h feeding period was thus partly respired and partly metabolized during the weeks following. Apparently, sponges are
able to capture enough food during short periods to sustain longer-term metabolism. The change of carbon metabolic rate of
fatty acid synthesis due to mechanical damage of sponge tissue was studied by feeding sponges with 13C isotope–labeled diatom (Pheaodactylum tricornutum) either after or before damaging and tracing back the 13C content in the damaged and healthy tissue. The filtration and respiration in both sponges responded quickly to damage. The
rate of respiration in H. oculata reduced immediately after damage, but returned to its initial level after 6 h. The 13C data revealed that H. oculata has a higher metabolic rate in the tips where growth occurs compared to the rest of the tissue and that the metabolic rate
is increased after damage of the tissue. For D. avara, no differences were found between damaged and non-damaged tissue. However, the filtration rate decreased directly after
damage. 相似文献
997.
Prevailing oceanographic processes, pelagic larvae, adult mobility, and large populations of many marine species often leads
to the assumption of wide-ranging populations. Applying this assumption to more localized populations can lead to inappropriate
conservation measures. The Pacific ocean perch (Sebastes alutus, POP) is economically and ecologically valuable, but little is known about its population structure and life history in Alaskan
waters. Fourteen microsatellite loci were used to characterize geographic structure and connectivity of POP collections (1999–2005)
sampled along the continental shelf break from Dixon Entrance to the Bering Sea. Despite opportunities for dispersal, there
was significant, geographically related genetic structure (F
ST = 0.0123, P < 10−5). Adults appear to belong to neighborhoods at geographic scales less than 400 km, and possibly as small as 70 km, which indicates
limited dispersal throughout their lives. The population structure observed has a finer geographic scale than current management,
which suggests that measures for POP fisheries conservation should be revisited. 相似文献
998.
Neill A. Herbert Jon E. Skjæraasen Trygve Nilsen Anne G. V. Salvanes John F. Steffensen 《Marine Biology》2011,158(4):737-746
The frequency of low O2 (hypoxia) has increased in coastal marine areas but how fish avoid deleterious water masses is not yet clear. To assess whether
the presence and oxygen pressure (PO2) level of an O2 refuge affects the hypoxia avoidance behaviour of fish, individual Atlantic cod (Gadus morhua L.) were exposed to a range of O2 choices in a 2-way choice chamber at 11.4°C over two different experiments. Cod in the first experiment were allowed access
to a fixed O2 refuge (fully air-saturated seawater) whilst oxygen pressure (PO2) on the other side was reduced in steps to a critically low level, i.e. 4.3 kPa—a point where cod can no longer regulate
O2 consumption. Under these conditions, cod did not avoid any level of hypoxia and fish swimming speed also remained unchanged.
In contrast, strong avoidance reactions were exhibited in a second experiment when fish were again exposed to 4.3 kPa but
the safety, i.e. PO2, of the refuge was reduced. Fish not only spent less time at 4.3 kPa as a result of fewer sampling visits but they also swam
at considerably slower speeds. The presence of an avoidance response was thus strongly related to refuge PO2 and it is unlikely that cod, and possibly other fish species, would enter low O2 to feed in the wild if a sufficiently safe O2 refuge was not available. It is therefore hypothesized that the feeding range of fish may be heavily compressed if hypoxia
expands and intensifies in future years. 相似文献
999.
Northern and Spotted Wolffishes (Anarhichas denticulatus and A. minor) are demersal marine fishes listed as “threatened” in Canadian waters. Both species have unusually large benthic eggs and
large size at hatch, which should reduce passive dispersal. We examined population differentiation with microsatellite and
AFLP loci across the ranges of both species in the North Atlantic Ocean. Although significant population structure was documented,
differentiation was less than expected based on knowledge of life history characteristics. Significant differentiation was
found in Northern Wolffish between the Barents Sea and other samples based on both microsatellite and AFLP data. In contrast,
population structure in the Spotted Wolffish was notably weaker, particularly with microsatellites. Both species were characterized
by low genetic diversity for marine fishes and had significantly lower genetic diversity than the congeneric Atlantic Wolffish.
This finding was consistent with the conservation status of these three species and suggests potential vulnerability to over-exploitation
in Northern and Spotted Wolffishes. 相似文献
1000.
The feeding ecology of Merluccius hubbsi was investigated in 2 regions of SE Brazil. The major food sources for the hakes were fish, crustaceans, and squid. In the
upwelling system of Cabo Frio, the diet was very similar in the summers of 2001/2002 and spring 2002; fish were the most important
prey followed by crustaceans. In Ubatuba, euphausiids were an important prey during the winter 2001 (100 m), while in the
summer 2002, fish and amphipods predominated in the diet in the shallower site (40 m) and squid in the deeper site (100 m).
The hakes showed temporal differences in stable isotope signatures in both regions, while C:N ratios varied only in Cabo Frio.
δ15N and δ13C (bulk and corrected for lipid content) increased with fish length, which seems to be related to the increasing importance
of fish and decreasing importance of euphausiids and amphipods in the diet of larger hakes. The mean trophic level of 3.7
for M. hubbsi was estimated using δ15N of bivalves as baseline and the fractionation of 3.4‰ between trophic levels. 相似文献