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701.
Denuded landscapes adjacent to big polluters represent an extremely harsh environment for plants due to a unique combination of soil toxicity and physical stress. In a 5‐year experiment we tested whether survival and performance of seedlings of Mountain birch (Betula pubescens ssp. czerepanovii) planted in two barren sites around the nickel–copper smelter at Monchegorsk, northwestern Russia, can be enhanced by physical sheltering and how large the supposed benefits to survival and performance are in relation to liming. Seedling performance was assessed by measuring growth parameters and chlorophyll fluorescence. Physical sheltering was found to be beneficial in some conditions: when soil characteristics were not so harsh as to cause 100% mortality, sheltering increased both survival and performance of birch seedlings. Although the benefits of liming on seedling performance and survival were stronger than the benefits of sheltering, sheltering may still have its uses in restoration when large‐scale liming is not applicable, for example, when the ecological side effects of liming are to be avoided. 相似文献
702.
Attraction of willow warblers to sawfly‐damaged mountain birches: novel function of inducible plant defences? 总被引:1,自引:0,他引:1
Plants wounded by invertebrate herbivores emit volatile compounds which invertebrate predators and parasitoids can utilize in locating herbivore prey or hosts. We studied the possibility that an analogical phenomenon might operate between plants and avian insectivores. We show that foliar damage by sawfly larvae on the mountain birch led a passerine bird (willow warbler) to prefer intact branches from trees with introduced larvae over intact branches from control trees. Besides olfaction, the UV vision of birds offers a possible mechanism, as some herbivore‐inducible leaf compounds, e.g. surface flavonoids, have UV spectral maxima well within the range of birds’ UV vision. 相似文献
703.
Tord Johansson 《Trees - Structure and Function》1996,10(4):223-230
Three different experiments in birch (Betula pubescens Ehrh. andBetula pendula Roth) stands were conducted during summer 1991: an evaluation of the accuracy of the vertical tube method measuring crown free projection (CFP) in four birch stands; a study of relative irradiance (RI; photosynthetically active radiation, PAR), in birch stands differing in stem density and basal area; and an estimation of the CFP in different types of birch stands and the correlation between RI and CFP. The results indicate that the number of observation points well distributed over an area of 0.1 ha can vary between 50 and 200 to achieve sufficient accuracy. There were no significant differences in the CFP estimates made on the same plot by different observers including an untrained observer. CFP was related to basal area, stem number and diameter sum in a non-linear regression, CFP = A*e-BX. The correlations between RI and basal area, density and diameter sum, respectively, were 0.54, 0.57 and 0.67 for PAR. The coefficients of determination for RI (PAR) and CFP were high (0.86). 相似文献
704.
Photosynthetic and transpiration (E) rates, stomatal conductance, and leaf nitrogen content were surveyed for Myrica gale
var. tomentosa, a N2-fixing wetland shrub, Betula platyphylla var. japonica, and Rhododendron japonicum in Ozegahara moor, an oligotrophic moor
in Central Japan. Net photosynthetic rate saturated with irradiance (Pmax) of M. gale was 15.2-16.5 μmol(CO2) m-2 s-1, higher than those of the other species throughout the growing season. Pmax was positively correlated with leaf N content among the three species. The large leaf N content in M. gale was due to N2-fixation in root nodules. In a comparison of M. gale in two habitats, Pmax, leaf N content, and root nodule development were larger in the wetter habitat. M. gale showed high E and no midday depression
of Pmax even under high irradiance and large vapour pressure deficit between leaves and ambient air on a midsummer day. These traits
of photosynthesis and water relations were associated with the dominance of this shrub in wetter sites such as stream sides
and hollows.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
705.
706.
707.
708.
Consequences of defoliation on phenological interaction between Epirrita autumnata and its host plant, Mountain Birch 总被引:1,自引:0,他引:1
1. Defoliation-induced changes in the budbreak phenology of Mountain Birches ( Betula pubescens ssp. tortuosa (Ledeb.) Nyman), and their effects on herbivore performance, were investigated during an outbreak of the spring-feeding geometrid, Epirrita autumnata (Bkh.).
2. Total defoliation (followed by refoliation) by E. autumnata larvae was required to achieve significant delaying of budbreak of Mountain Birch one year after damage.
3. Delayed budbreak has potentially deleterious effects on herbivore performance. However, E. autumnata larvae show phenotypic responses that increase the synchrony between larvae and leaves: high larval density, a prerequisite for severe defoliation, delays egg hatch in the following year.
4. Late hatching larvae performed as well on birches with delayed budbreak due to the previous year's total defoliation as did early hatching larvae on birches with earlier budbreak. 相似文献
2. Total defoliation (followed by refoliation) by E. autumnata larvae was required to achieve significant delaying of budbreak of Mountain Birch one year after damage.
3. Delayed budbreak has potentially deleterious effects on herbivore performance. However, E. autumnata larvae show phenotypic responses that increase the synchrony between larvae and leaves: high larval density, a prerequisite for severe defoliation, delays egg hatch in the following year.
4. Late hatching larvae performed as well on birches with delayed budbreak due to the previous year's total defoliation as did early hatching larvae on birches with earlier budbreak. 相似文献
709.
Abstract. 1. The birch ( Betula )-feeding aphid, Monaphis antennata, is always found at low densities on individual hosts and has low local abundance, but another birch-feeding aphid, Euceraphis betulae , is often found at high densities on individual hosts and has high local abundance.
2. This work attempts to establish whether the interaction between M. antennata and its host or the behaviour of individuals limits its densities.
3. Both species were reared on saplings, and population sizes were monitored for 6 weeks. Two levels of host quality were used and feeding space was kept constant throughout the experiment. Adults were prevented from leaving the saplings by clipping their wings, and predators were excluded.
4. On plants of similar host quality, both species achieved similar population sizes.
5. It is concluded that resource availability or the interactions between individuals are unlikely to be important causes of rarity. 相似文献
2. This work attempts to establish whether the interaction between M. antennata and its host or the behaviour of individuals limits its densities.
3. Both species were reared on saplings, and population sizes were monitored for 6 weeks. Two levels of host quality were used and feeding space was kept constant throughout the experiment. Adults were prevented from leaving the saplings by clipping their wings, and predators were excluded.
4. On plants of similar host quality, both species achieved similar population sizes.
5. It is concluded that resource availability or the interactions between individuals are unlikely to be important causes of rarity. 相似文献