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931.
932.
G. J. Niemann 《Planta》1985,166(1):51-56
Ilex leaves can utilize sucrose and mevalonate for the synthesis of triterpene esters. Mevalonate is also used for the synthesis of free triterpenoid alcohols, but sucrose is not. The selectivity of precursor utilization indicates separate sites for triterpenol and triterpenol-ester synthesis. The sites of synthesis are not found at the main locations of accumulation of triterpenols (the epicuticular wax) or triterpene esters (the cytoplasmatic lipid globules). Transport from the site of synthesis to the lipid globules, and especially towards the epicuticular wax, is slow.Abbreviations MVA
mevalonic acid lactone
- TLC
thin layer chromatography 相似文献
933.
Magnitude and variability of process rates in fungal diversity-litter decomposition relationships 总被引:4,自引:0,他引:4
There is compelling evidence that losses in plant diversity can alter ecosystem functioning, particularly by reducing primary production. However, impacts of biodiversity loss on decomposition, the complementary process in the carbon cycle, are highly uncertain. By manipulating fungal decomposer diversity in stream microcosm experiments we found that rates of litter decomposition and associated fungal spore production are unaffected by changes in decomposer diversity under benign and harsher environmental conditions. This result calls for caution when generalizing outcomes of biodiversity experiments across systems. In contrast to their magnitude, the variability of process rates among communities increased when species numbers were reduced. This was most likely caused by a portfolio effect (i.e. statistical averaging), with the uneven species distribution typical of natural communities tending to weaken that effect. Curbing species extinctions to maintain ecosystem functioning thus can be important even in situations where process rates are unaffected. 相似文献
934.
Abstract The fruit spotting bug, Amblypelta lutescens lutescens, is one of the principal insect pests of cashews in Australia. Its population dynamics were studied using field observations and long-term monitoring to find suitable management methods. Observations of bugs reared in netting bags showed a sequence of change in bug-damage symptoms after 12 h and up to 3 d. Field observations revealed that adults preferred to feed and rest on the shady side of the tree. The number of bugs observed accounted for only 17–35% of the total variability in the number of damaged shoots, suggesting that the number of flushing shoots (leaf, flower or young nuts) with fresh damage symptoms was a more reliable parameter for determining the presence and level of activity of bugs than was a direct estimate of the number of bugs. The green tree ant, Oecophylla smaragdina (F), was the most important factor regulating bug populations. When predation was excluded as a factor, the number of flushing shoots and maximum temperature accounted for 80% of the total variability in the bug damage. Green tree ants should be considered as an important biological control agent for fruit spotting bug, and monitoring should be commenced when cashew trees start to flush (using damaged shoots as indicator). 相似文献
935.
Summary A numerical model of an eusocial colony foraging for food showed that, for each set of values of resource density, resource size and recruitment system employed, a given optimal proportion of scouts in the colony maximize the amount of resources retrieved by a colony during a fixed period. The model predicts that ants using mass recruitment systems should have larger colonies with small foragers, and should forage on large food sources. Retrieval of small food sources by small colonies is best achieved with large workers using individual foraging strategies. For mass foragers, several food sources are best retrieved using democratic decision-making systems in recruitment, whereas for very large food sources at very low mean food patch density, autocratic decision-making systems are optimal. Some of the experimental evidence available is discussed in the light of these findings, as they confirm the prediction that large colonies with small workers have mass recruitment systems, whereas workers of small colonies with large workers are generally lone foragers. 相似文献
936.
The mean annual litterfall at two dry woodland sites in central Queensland was 1129 kg ha–1 for an open E. populnea F. Muell. woodland (n = 2 years), and 2318 kg ha–1 for a woodland dominated by E. cambageana Maiden (n = 1 year). Leaves formed the largest component of total litterfall, which varied seasonally with a spring–summer maximum. Annual litterfall at these sites conformed with a pattern of decreasing litter production with declining annual rainfall, consistent with a range of eucalypt-dominated communities. 相似文献
937.
Sex allocation in a facultatively polygynous ant: between-population and between-colony variation 总被引:5,自引:0,他引:5
We investigated sex allocation in three U.K. populations ofthe
facultatively polygynous ant Leptothorax acervorum over1-3 years.
The first main finding was that, across sites, thepopulation sex-investment
ratio changed from significantly femalebiased to significantly male biased
with increasing polygyny.This was consistent with workers controlling sex
allocationand reacting to changes in their population-level relatedness
asymmetry.It was also consistent with local resource competition due to
reproductionby colony budding under polygyny. Worker control was supportedby
the finding that queen number had no effect on sex allocationamong polygynous
colonies. The second main result was that monogynouscolonies consistently
produced more female-biased sex-investmentratios than polygynous colonies in
one site only (Santon). Theresults from Santon supported both the relative
relatednessasymmetry hypothesis and the idea of sex ratio compensationdue to
colony budding. The workers' response to their population-levelrelatedness
asymmetry reinforced the case for relatedness asymmetrybeing influential at
the colony level. The other populationscould have lacked split sex ratios
because polygynous colonieswere either comparatively rare or common, making
them behaveas almost entirely monogynous (Aberfoyle) or polygynous (Roydon)
populations.In Roydon, this was consistent with the inference from allozyme
datathat monogynous and polygynous colonies did not differ in theirworker
relatedness asymmetries. The final principal findingwas that, of hypotheses
linking the colony sex-investment ratiowith sexual productivity, there was
support for the constantfemale hypothesis but not for the constant male, cost
variation,or multifaceted parental investment hypotheses. 相似文献
938.
939.
Rescue behavior is observed when 1 individual provides help to another individual in danger. Most reports of rescue behavior concern ants (Formicidae), in which workers rescue each other from various types of entrapment. Many of these entrapment situations can be simulated in the laboratory using an entrapment bioassay, in which ants confront a single endangered nest mate entrapped on a sandy arena by means of an artificial snare. Here, we compared numerous characteristics of rescue actions (contact between individuals, digging around the entrapped individual, pulling at its body parts, transport of the sand covering it, and biting the snare entrapping it) in Formica cinerea ants. We performed entrapment tests in the field and in the laboratory, with the latter under varying conditions in terms of the number of ants potentially engaged in rescue actions and the arena substrate (marked or unmarked by ants’ pheromones). Rescue actions were more probable and pronounced in the field than in the laboratory, regardless of the type of test. Moreover, different test types in the laboratory yielded inconsistent results and showed noteworthy variability depending on the tested characteristic of rescue. Our results illustrate the specifics of ant rescue actions elicited in the natural setting, which is especially important considering the scarcity of field data. Furthermore, our results underline the challenges related to the comparison of results from different types of entrapment tests reported in the available literature. Additionally, our study shows how animal behavior differs in differing experimental setups used to answer the same questions. 相似文献
940.