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101.
K. Ohki 《Plant and Soil》1987,98(2):195-202
Summary Sorghum plants were grown in the greenhouse in modified Steinberg nutrient solution containing ten Al rates (0 to 297 μM) and harvested 28 days after transplanting. Top and root dry weight were not affected by added Al up to 74 μM; but decreased sharply at concentration of 148 μM and greater. Aluminum concentrations in blade 1 (recently matured blade) and plants remained constant from 0 to 297 μM added Al. Root Al concentration increased as added Al increased. No correlation existed between top dry weight and Al concentration
in blade 1 or in plant. Root Al concentration was related to top dry weight and root dry weight to estimate the Al critical
toxicity level. The Al critical toxicity levle in the root was 54 mmol kg−1 root dry weight basis for either top or root dry weight. In blade 1 Cu concentration negatively correlated with Al while
Fe and P were positively correlated. In roots Ca, Mg, Mn and Fe concentrations were negatively correlated with Al while Zn,
Cu, P, and K were positively correlated with Al concentration. 相似文献
102.
Effect of seed manganese content on the growth of wheat (triticum aestivum) under manganese deficiency 总被引:1,自引:0,他引:1
Summary The importance of seed manganese (Mn) content for seedling growth of two wheat cultivars under soil Mn deficiency was demonstrated
in growth cabinet experiments. Seed was obtained from different field sites (giving a Mn content range of 0.1 to 6.4 μg Mn
seed−1), as well as from soaking seed in MnSO4 prior to sowing. Seed soaking greatly increased the seed Mn content, however, only about 15–20% of this additional Mn was
recovered in the seedlings after 26 days growth. In these experiments, the seed rather than the soil provided the major source
of plant Mn. Manganese critical deficiency levels (CDLs) were also obtained for leaves, shoots and roots. Increased grain
yields from seed soaking were also evident in the field. 相似文献
103.
Michel Beden 《Geobios》1980,13(6):891-901
A revision of the presently available materialrefered to the species Elephas reckiDietrich.. 1915, collected in East african plio-pleistocene levels, leads up to distinguish a succession of five subspecies within the species: E. r. brumpti n. subsp.; E. r. shungurensis n. subsp.; E. r. atavusArambourg 1947; E. r. ileretensis n. subsp. and E. r. reckiDietrich,, 1915.The five subspecies diagnosis are proposed here. They together represent a monophyletic lineage, the study of which allows to propose new interpretations regarding the history and evolutionary trends of the genus in Africa. 相似文献
104.
本文依据国内外土壤环境质量标准的研究现状,在提出土壤环境标准制定依据和原则的基础上,对Hg、Cd、Pb和As的土壤环境质量标准进行了研究。研究表明,我国土壤环境质量功能分区可包括:(1)自然保护区或“清洁”无污染区;(2)农牧区;(3)森林区;(4)城市区、废物处置区和工矿区。其相应的土壤环境质量标准,汞为0.10、0.20、0.50和1.00mg/kg;镉为0.15、0.30、0.50和1.00mg/kg;铅为30、60、100和300mg/kg;砷为15、20、27和30(砂土区除外)mg/kg,并论证这些标准值在全国应用的可能性。为全国土壤质量的宏观管理与控制污染提供了科学依据。 相似文献
105.
Numerous model studies demonstrate that ecosystems might not shift smoothly with a gradual change in resource concentration. At specific points, vegetation can suddenly shift from one stable state to another. To predict such undesirable shifts, statistical indicators are proposed for early warning prediction. These so-called classical indicators can address whether vegetation state is moving towards the tipping point of an abrupt transition, however when the transition will occur is hard to predict. Recent studies suggest that complex network based indicators can improve early warning signals of abrupt transitions in complex dynamic systems. In this study, both classical and network based indicators are tested in a coupled land–atmosphere ecological model in which a scale-dependent hydrology-infiltration feedback and a large scale vegetation–precipitation feedback are represented. Multiple biomass equilibria are found in the model and abrupt transitions can occur when rainfall efficiency is decreased. Interaction network based indicators of these transitions are compared with classical indicators, such as the lag-1 autocorrelation and Moran's coefficient, with particular focus on the transition associated with desertification. Two criteria are used to evaluate the quality of these early warning indicators and several high quality network based indicators are identified. 相似文献
106.
Fernando Diaz Alfredo SalasAna Denisse Re Marco GonzalezIzbelt Reyes 《Journal of thermal biology》2011,36(1):34-37
The thermoregulatory behavior of the wavy turban snail Megastrea (Lithopoma) undosa was determined in a horizontal thermal gradient and was 16.31 in day cycle and 14.4 °C in night cycle. Displacement velocity of adults was 29.3±4.2 cm h−1 during the light phase and 26.1±3.2 cm h−1 during the dark phase. The critical thermal maxima of the wavy turban snail were determined. As a measure of thermal tolerance, snails were subjected to increasing water temperatures at a rate of 1 °C every 30 min until they were detached from the substrate. The critical thermal maximum at 50% was 29.7 °C. 相似文献
107.
Critical nutrient loads to prevent duckweed dominance loads in polder ditches were assessed using the eutrophication model
PCDitch. In this article the ecological target was set at 50% duckweed coverage. This may be very high for ditches with a
nature function, but is not unreasonable for ditches in agricultural areas, with upwelling nutrient rich groundwater, run-off
and drainage. Since the change from a ditch with submersed vegetation to duckweed coverage is often a sudden shift, the choice
of the amount of duckweed coverage does not influence the calculated loading very much. The main topic of this paper is to
present a method to calculate critical loads of nutrients when ecological targets have been set. Sediment type, residence
time and water depth influenced the critical loading rates. The calculated critical phosphorus load ranged from 1.8 to 10.2 g P m−2 year−1, while the calculated critical nitrogen load stretched from 12.1 to 43.8 g N m−2 year−1. The concentration ranges that were derived from the loading rate were 0.19–0.42 mg P l−1 and 1.3–3.3 mg N l−1. Since PCDitch does not distinguish between Lemna spp. and Azolla spp., no definite conclusions were drawn concerning the effects of nitrogen reduction. In a model situation a pristine ditch
was loaded with phosphorus, which resulted into complete duckweed coverage during summer within a few years. When reducing
the phosphorus load, it took 10 years before the original situation was reached again. Dredging would accelerate the process
of recovery significantly, because the water depth would increase and the phosphorus release from the sediments in summer
would decrease.
Received September 2003; accepted in revised form February 2005 相似文献
108.
Ben J. Kefford Dayanthi Nugegoda Liliana Zalizniak Elizabeth J. Fields Kathryn L. Hassell 《Aquatic Ecology》2007,41(2):335-348
The tolerance to high salinity of older life stage macroinvertebrates could underestimate the effects of increasing salinity
on freshwater macroinvertebrates. The salinity tolerance of the eggs and/or hatchlings of Glyptophysa gibbosa (Planorbidae), Glyptophysa aliciae, Glacidorbis sp. (Glacidorbidae), a Glossiponiidae, Piona cumberlandis (Pionidae), and Chironomus sp. (Chironomidae) were determined. The salinity tolerances of younger life-stages of species studied here and elsewhere
were then compared to salinity tolerances of their mature aquatic or dominant life-stage. A diversity of responses have been
observed with some species having similar salinity tolerances in all life-stages examined, whilst the eggs or hatchlings of
other species had salinity tolerances ranging from 4% to 88% of their older life stages. On present knowledge, this diversity
of responses presents some difficulties for simple rules of thumb to approximate sensitivity of young life-stages of freshwater
macroinvertebrates inferred from their dominant stage’s tolerance. 相似文献
109.
U.R. Zargar M.Z. Chishti Fayaz Ahmad M.I. Rather 《Saudi Journal of Biological Sciences》2015,22(1):14-18
How changes in biodiversity alter the transmission of infectious diseases is presently under debate. Epidemiologists and ecologists have put a lot of effort to understand the mechanism behind biodiversity–disease relationship. Two important mechanisms, i.e. dilution and amplification theories have in some manner made it clear that biodiversity and disease outcome have an intimate relationship. The dilution effect theory seems to answer some overarching questions, but paucity of information about many disease systems is a real obstacle for its acceptance. Also, there is hardly any agreement on host population threshold and critical community size vis-à-vis wild life diseases. We suggest a multidimensional approach whereby the same disease system needs to be studied in different ecological zones and then the effect of biodiversity on disease outcome needs to be ascertained. Nonetheless, caution is to be taken while jumping to any conclusion as biodiversity–disease relationship is a multifactorial process.Abbreviations: CEM, Classical Epidemiological Model; DEH, dilution effect; MNV, Murine Norovirus 相似文献
110.
G Davidowitz HF Nijhout DA Roff 《Evolution; international journal of organic evolution》2012,66(9):2916-2928
A great deal is known about the evolutionary significance of body size and development time. They are determined by the nonlinear interaction of three physiological traits: two hormonal events and growth rate (GR). In this study we investigate how the genetic architecture of the underlying three physiological traits affects the simultaneous response to selection on the two life-history traits in the hawkmoth Manduca sexta. The genetic architecture suggests that when the two life-history traits are both selected in the same direction (to increase or decrease) the response to selection is primarily determined by the hormonal mechanism. When the life-history traits are selected in opposite directions (one to increase and one to decrease) the response to selection is primarily determined by factors that affect the GR. To determine how the physiological traits affect the response to selection of the life-history traits, we simulated the predicted response to 10 generations of selection. A total of 83% of our predictions were supported by the simulation. The main components of this physiological framework also exist in unicellular organisms, vertebrates, and plants and can thus provide a robust framework for understanding how underlying physiology can determine the simultaneous evolution of life-history traits. 相似文献