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61.
62.
This study assessed the effect of nutrient enrichment on rates of decomposition, ergosterol concentrations (as a measure of
fungal biomass), and rates of fungal sporulation of sweet chestnut (Castanea sativa Miller) leaves in a 3rd order stream (Central Portugal), with medium to high background values of nutrients. Coarse and fine
mesh leaf bags were attached to nutrient diffusing substrata containing NaNO3, KH2PO4, both nutrients, or no additions. Leaf breakdown rates were similar in the four treatments and in the two mesh sizes (k=−0.0155 to −0.0219 day−1). Phosphorus content of P or N + P enriched leaves was higher than in the other treatments after 28 days, but there were
no differences in N concentrations. Ergosterol concentrations associated with decomposing leaves were similar among treatments.
The peak sporulation rates of aquatic hyphomycetes were stimulated by the addition of N + P and N but not by P alone. Results
from the experiment provide evidence that leaf breakdown in the study stream, as a model for streams with naturally medium
to high level of nutrients, was not nutrient-limited, and that fungal reproductive activity was limited by dissolved N but
not by dissolved P in stream water. 相似文献
63.
Australian science has made rapid advances in the last decade in understanding eutrophication processes in inland waters and
estuaries. The freshwater research on which these advances are based was triggered by well-publicised blooms of cyanobacteria
during the 1980s and early 1990s, particularly a 1000 km long bloom on the Darling River. In estuaries the study which greatly
enhanced our understanding but simultaneously served to stimulate further research into estuarine eutrophication, the Port
Phillip Bay Study, was initially designed to address perceived problems of toxicants in the Bay but provided profound insights
into drivers for, and ecosystem responses to, eutrophication. Subsequent estuarine research has largely been stimulated by
management questions arising from Australia’s increasing coastal development for residential purposes. The research has shown
that some of the beliefs extant at the time of the blooms were incorrect. For example, it is now clear that stratification
and light penetration, not nutrient availability, are the triggers for blooms in the impounded rivers of southeastern Australia,
although nutrient exhaustion limits the biomass of blooms. Again, nitrogen seems to play as important a role as phosphorus
does in controlling the biomass of these freshwater blooms. The research has also shown that aspects of eutrophication, such
as nutrient transport, are dominated by different processes in different parts of Australia. Many of the biophysical processes
involved in eutrophication have now been quantified sufficiently for models to be developed of such processes as sediment-nutrient
release, stratification, turbidity and algal growth in both freshwater and estuarine systems. In some cases the models are
reliable enough for the knowledge gained in particular waterbodies to be applied elsewhere. Thus, there is now a firm scientific
foundation for managers to rely upon when managing algal blooms. Whilst these findings have already been presented to managers
and communities throughout Australia, there is still a considerable way to go before they are absorbed into their modus operandi. 相似文献
64.
Recent histories of six productive lakes in the Irish Ecoregion based on multiproxy palaeolimnological evidence 总被引:2,自引:2,他引:0
D. Taylor C. Dalton M. Leira P. Jordan G. Chen L. León-Vintró K. Irvine H. Bennion T. Nolan 《Hydrobiologia》2006,571(1):237-259
Palaeolimnological data from six mesotrophic, eutrophic and hypertrophic lakes in the Irish Ecoregion, in the form of microfossil
(cladocera, diatoms and pollen) and sediment chemistry data from radiometrically dated sediment cores, were used to reconstruct
past variations in lake water quality and catchment conditions. Basal sediments from sediment cores from the six sites ranged
in age from the late 18th century to the early 20th century. A weighted averaging partial least squares regression model was
developed to reconstruct past epilimnetic total phosphorus concentrations. The results indicate that all but one of the study
sites currently are in a far more productive state compared with the beginning of the sediment core record and that those
same five lakes have experienced accelerated enrichment post c. 1980. Two of the sites demonstrated long-term enrichment,
in one case beginning in the late 19th century, while both eutrophication and oligotrophication have occurred at three sites.
The results highlight the difficulties in applying a general temporal end-point for reference conditions and demonstrate that
productive lakes in the Irish Ecoregion have complex, locally specific and often long histories of enrichment. These may not
be responsive to reduced external loadings of phosphorus and, as a result, restoration could prove particularly challenging.
The results also provide evidence of the ways in which palaeolimnological techniques can assist implementation of the EU Water
Framework Directive.
Electronic supplementary material Electronic supplementary material is available for this article at
and accessible for authorised users. 相似文献
65.
To determine relationships between soil nutrient status and known gradients in primary production, we collected and analyzed
soils from 17 LTER sampling sites along two transects through south Florida wetland ecosystems. Through upstream freshwater
marsh, a middle reach including the oligohaline marsh/mangrove ecotone, and downstream estuarine habitats, we observed systematic
variation in soil bulk density, organic content, and pools of phosphorus (P), inorganic sulfur, and extractable iron. Consistent
with observed differences in wetland productivity known to be limited by P availability, total P averaged ~200 μg g dw−1 in soils from the eastern Taylor Slough/Panhandle and was on average three times higher in soils from the western Shark River
Slough. Along both transects, the largest pool of phosphorus was the inorganic, carbonate-bound fraction, comprising 35–44%
of total P. Greater than 90% of the total inorganic sulfur pool in these south Florida wetland soils was extracted as pyrite.
Freshwater marsh sites typically were lower in pyrite sulfur (0.2–0.8 mg g dw−1) relative to marsh/mangrove ecotone and downstream estuary sites (0.5–2.9 mg g dw−1). Extractable iron in freshwater marsh soils was significantly higher from the Taylor Slough/Panhandle transect (3.2 mg g dw−1) relative to the western Shark River Slough transect (1.1 mg g dw−1), suggesting spatial variation in sources and/or depositional environments for iron. Further, these soil characteristics
represent the collective, integrated signal of ecosystem structure, so any long-term changes in factors like water flow or
water quality may be reflected in changes in bulk soil properties. Since the objective of current Everglades restoration initiatives
is the enhancement and re-distribution of freshwater flows through the south Florida landscape, the antecedent soil conditions
reported here provide a baseline against which future, post-restoration measurements can be compared. 相似文献
66.
采用田间微区试验,研究了施用有机物料对土壤氮磷的变化动态及活性的影响.结果表明,水稻生长过程中土壤溶液中水溶性氮(铵态氮、硝态氮)及磷的含量都随着时间的延长而下降,且氮、磷含量的变化与施入的化学肥料量以及溶液中DOC含量有关;有机物料施用增加了水稻的生物量和对氮、磷的吸收利用;15N示踪显示,与对照的化肥处理相比,施用有机物料处理的微区氮肥利用率及土壤残留率明显增加,同时减少了土壤氮磷的损失. 相似文献
67.
水培经济植物对污水中磷的吸收利用及去除效果 总被引:13,自引:0,他引:13
对13种经济植物在污水水培条件下净化污水中磷的能力进行了研究。结果表明,黑麦草(Lolium multiflorum)、水芹(Oenanthe stolonifera)、莴苣(Lactuca sativavar.angustana)、酸模(Poly-gonum iapathifolium)、生菜(Lactuca sativa)、小葱(Allium ascalonicum)、五月慢青菜(Brassica chinen-sis)等品种具有较高的净化能力。在4个半月的水培中,TP的去除量分别达到10.27、10.35、6.5~6.896、.91、5.72、5.46和6.19 g.m-2;TP的去除率分别达到94.5%、95.2%、93.6%~99.3%、99.6%、99.5%、95%和89.2%。植物吸收作用是最主要的污水磷去除机制,沉淀在污水磷净化中的作用较小。污水中磷的去除与植物的生长期密切相关。黑麦草、水芹等7种植物适宜作为苏南地区冬季化粪池污水水培植物。 相似文献
68.
长江口崇明东滩湿地沉积物对磷的吸附特征 总被引:8,自引:0,他引:8
研究了崇明东滩湿地低(S1)、中(S2)、高(S3)潮滩沉积物对磷的吸附特征。结果表明,沉积物吸磷过程主要发生在前24 h内,随后近于达到平衡状态。沉积物对PO43--P的平均吸附速率在0~0.5 h内最大,均超过了140 mg.kg-1.h-1;快速吸附过程主要发生在前11 h,前11 h的平均快速吸附速率表现为S1>S3>S2,且沉积物中细颗粒成分越多,沉积物对PO43--P的平均快速吸附速率越大。沉积物对磷的吸附等温线符合Langmuir吸附等温方程,根据Langmuir方程计算,沉积物对磷的吸附容量均>200 mg.kg-1,同时沉积物对PO43--P的吸附容量也表现为S1>S3>S2。原因可能同S1中细颗粒成分、有机碳和常量金属元素(Al、Ca、Fe、Mg)的百分含量较多而S2中细颗粒成分、有机碳和常量金属元素的百分含量较少有关。温度和pH值也影响沉积物对PO43--P的吸附作用。 相似文献
69.
湖泊底泥磷释放影响因素显著性试验分析 总被引:8,自引:0,他引:8
通过底泥正交模拟实验分析认为,温度、溶解氧、pH值和水动力均是影响双龙湖底泥磷释放的显著因素,各因素水平间有显著差异;影响因素显著性排序从大到小依次为溶解氧、温度、pH值、水动力;提高双龙湖水体的溶解氧水平是降低底泥磷释放的有效手段. 相似文献
70.