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311.
ANNETTE BAATTRUP‐PEDERSEN KAREN M. B. JENSEN HANS THODSEN HANS E. ANDERSEN PETER M. ANDERSEN SØREN E. LARSEN TENNA RIIS DAGMAR K. ANDERSEN JOACHIM AUDET BRIAN KRONVANG 《Freshwater Biology》2013,58(4):817-827
1. Effects of the frequency and duration of flooding on the structural and functional characteristics of riparian vegetation were studied at four sites (n = 80, 50 × 50 cm, plots) along medium‐sized naturally meandering lowland streams. Special focus was on rich fens, which – due to their high species richness – are of high priority in nature conservation. 2. Reed beds, rich fens and meadows were all regularly flooded during the 20‐year study period, with a higher frequency in reed bed areas than in rich fen and meadow areas. In rich fens, species richness was higher in low frequency flooded areas (≤3 year?1) than in areas with a high frequency of flooding (>3 year?1) or no flooding, whereas species richness in reed beds and meadows was unaffected by flood frequency. 3. The percentage of stress‐tolerant species was higher in low intensity flooded rich fen areas than in high intensity and non‐flooded areas, indicating that the higher species richness in low frequency flooded rich fens was caused by competitive release. We found no indication that increased productivity was associated with high flooding frequencies. 4. We conclude that the restoration of morphological features in stream channels to increase the flooding regime can be beneficial for protected vegetation within riparian areas, but also that groundwater discharge thresholds and critical levels for protected vegetation should be identified and considered when introducing stream ecosystem restoration plans. 相似文献
312.
IGOR FLOREZ‐SARASA HANS LAMBERS XING WANG PATRICK M. FINNEGAN MIQUEL RIBAS‐CARBO 《Plant, cell & environment》2014,37(4):922-928
Plant adaptations associated with a high efficiency of phosphorus (P) acquisition can be used to increase productivity and sustainability in a world with a growing population and decreasing rock phosphate reserves. White lupin (Lupinus albus) produces cluster roots that release carboxylates to efficiently mobilize P from P‐sorbing soils. It has been hypothesized that an increase in the activity of the alternative oxidase (AOX) would allow for the mitochondrial oxidation of NAD(P)H produced during citrate synthesis in cluster roots at a developmental stage when there is a low demand for ATP. We used the oxygen‐isotope fractionation technique to study the in vivo respiratory activities of the cytochrome oxidase pathway (COP) and the alternative oxidase pathway (AOP) in different root sections of white lupins grown hydroponically with and without P. In parallel, AOX protein levels and internal carboxylate concentrations were determined in cluster and non‐cluster roots. Higher in vivo AOP activity was measured in cluster roots when malate and citrate concentrations were also high, thus confirming our hypothesis. AOX protein levels were not always correlated with in vivo AOP activity, suggesting post‐translational regulation of AOX. 相似文献
313.
Does elevated atmospheric CO2 concentration inhibit mitochondrial respiration in green plants? 总被引:1,自引:0,他引:1
B. G. DRAKE J. AZCON-BIETO J. BERRY J. BUNCE P. DIJKSTRA J. FARRAR R. M. GIFFORD M. A. GONZALEZ-MELER G. KOCH H. LAMBERS J. SIEDOW & S. WULLSCHLEGER 《Plant, cell & environment》1999,22(6):649-657
ATP, adenosine triphosphateKm, Michaelis-Menton coefficientCa, concentration of CO2 in the air (μmol mol–1)NAD, oxidized nicotin adenine dinucleotideNADH, reduced nicotin adenine dinucleotideNADP, oxidized nicotin adenine phosphate dinucleotideNADPH, reduced nicotine adenine phosphate dinucleotideR, rate of respiration per unit DW [μmol g DW–1], Rubisco, ribulose-1,5-bisphosphate carboxylase/oxygenaseVc,max, maximum in vivo rate of carboxylation at Rubisco (μmol m–2 s–1)There is abundant evidence that a reduction in mitochondrial respiration of plants occurs when atmospheric CO2 (Ca) is increased. Recent reviews suggest that doubling the present Ca will reduce the respiration rate [per unit dry weight (DW)] by 15 to 18%. The effect has two components: an immediate, reversible effect observed in leaves, stems, and roots of plants as well as soil microbes, and an irreversible effect which occurs as a consequence of growth in elevated Ca and appears to be specific to C3 species. The direct effect has been correlated with inhibition of certain respiratory enzymes, namely cytochrome-c-oxidase and succinate dehydrogenase, and the indirect or acclimation effect may be related to changes in tissue composition. Although no satisfactory mechanisms to explain these effects have been demonstrated, plausible mechanisms have been proposed and await experimental testing. These are carbamylation of proteins and direct inhibition of enzymes of respiration. A reduction of foliar respiration of 15% by doubling present ambient Ca would represent 3 Gt of carbon per annum in the global carbon budget. 相似文献
314.
CYNTHIA P. E. VAN RIJN INGRID HEERSCHE YVONNE E. M. VAN BERKEL EVIATAR NEVO HANS LAMBERS & HENDRIK POORTER 《The New phytologist》2000,146(3):471-481
Hordeum spontaneum shows a large genetic variation and occupies a wide range of different habitats. The aim of this study was to quantify variation in growth characteristics of H. spontaneum from different sites in Israel and to relate this variation to different environmental conditions. To this end, 84 accessions of 21 populations were grown in a growth chamber in near-optimal conditions and a range of physiological, morphological, allocation- related and chemical characteristics were measured. These parameters included rates of photosynthesis, shoot and root respiration, specific leaf area, biomass allocation and seed mass. Averaged over all traits variation explained by differences between populations was 26%, between accessions 21%, whereas that within accessions was 53%. By contrast with most genetic studies, we found variation between populations larger than between accessions. The largest between-population variation (46%) was for morphological traits. In particular, seed mass, leaf thickness and leaf width differed strongly between populations. Variation in growth characteristics between populations was poorly related to mean annual rainfall, mean humidity or January temperature at the sites of origin. We expect that differences between populations to be larger and correlation with environmental parameters stronger in plants grown in stressful conditions. According to our study, seed mass is more important than relative growth rate in determining variation in early plant biomass in H. spontaneum . 相似文献
315.
Summary The influence of juvenile hormone (JH)-active chemicals on the settlement and metamorphosis of metatrochophore larvae of the polychaete annelid Capitella sp. I of the Capitella complex has been investigated. These studies demonstrate that JH-active chemicals are able to induce settlement and metamorphosis of Capitella larvae, and that these effects may possibly be mediated by protein kinase C induction. Evidence for the presence of JH-active compounds in marine sediments is also presented, suggesting that these chemicals may serve a natural role as chemical cues for settlement and metamorphosis for Capitella larvae in the marine environment. 相似文献
316.
THE CONTROL OF PLANT GROWTH AND DEVELOPMENT BY LIGHT 总被引:1,自引:0,他引:1
HANS MOHR 《Biological reviews of the Cambridge Philosophical Society》1964,39(1):87-112
317.
LENE ROSTGAARD NIELSEN ROBYN S. COWAN HANS R. SIEGISMUND HENNING ADSERSEN MARIANNE PHILIPP MICHAEL F. FAY 《Botanical journal of the Linnean Society. Linnean Society of London》2003,143(3):243-254
Analysis of the stem vasculature of the American climbing palm Desmoncus reveals structural features differing significantly from the Old World rattan genus Calamus . Desmoncus has a more directly continuous vascular system but nevertheless shows a vessel distribution that makes for high hydraulic resistance in the axial xylem. Desmoncus is like Calamus in having a single very wide metaxylem vessel in each central axial bundle and is also without direct vascular contact between protoxylem and metaxylem tracheary elements. However, in Desmoncus the stem vascular bundle system resembles that in tree palms (as has been described in the model palm Rhapis excelsa ) in having a continuing axial bundle that branches from each outgoing leaf trace together with a large number of bridge connections between leaf traces and peripheral axial bundles. Resistance to axial water transport is, however, evident in the narrowness of the continuing metaxylem elements in the peripheral stem vascular region. Desmoncus has scalariform perforation plates with few thickening bars in the metaxylem vessels, unlike the simple perforation plates found in Calamus . Thus, Desmoncus shows only limited convergence in stem vascular architecture toward the extreme modifications found in Calamus . This is not unexpected since it is clear that the climbing habit evolved independently in the two genera. © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society, 2003, 142 , 243−254. 相似文献
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Attempts were made to inject different substances into epidermaland stomatal cells in order to observe their movement from cellto cell and their effects on guard cell metabolism. Althoughinjections of neutral red were successful and provided usefulinformation, injections of ABA and KCl did not yield any worthwhileresults. Measurements of pressure potentials in stomatal cells of fourspecies were carried out. These throw light on the role of epidermalturgor in influencing stomatal movements and thus on hypothesesof a mechanical advantage of subsidiary cells. 相似文献