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41.
42.
To determine the effect of shade on morphology, growth and biomass allocation in Picea sitchensis, Larix × eurolepis and Thuja plicata, seedlings were grown in the open or under shadehouses providing 25%, 50% and 75% reductions of full-light for two growing
seasons. For most of the characteristics assessed there was no significant interaction between species and shade indicating
that the morphological responses to changing shade treatments were not species-dependent. After two growing seasons the mean
height increment for the three species was significantly greater in 25% (76.1 cm) and 50% shade (74.9 cm) than in the open
(69.5 cm). Root collar diameter increment, shoot, root and total biomass declined significantly with increasing shade while
the opposite was true for the height:diameter ratio. In both western red cedar and hybrid larch the shoot:root ratio was significantly
greater in the shade while in Sitka spruce this characteristic was not influenced by shade. While all species had significantly
greater specific shoot areas in 75% shade than in 0% shade, this trend was particularly pronounced in hybrid larch. In hybrid
larch and western red cedar, the normalised specific projected shoot area increased significantly with increasing shade. The
opposite trend was observed for Sitka spruce. We conclude that in the main the species studied demonstrated similar shade
acclimation responses despite their reported differences in shade tolerance. 相似文献
43.
西藏野生动物资源及其监测体系的探讨 总被引:1,自引:0,他引:1
结合西藏2000年野生动物资源监测调查,对监测调查结果进行了分析与评价,在此基础上,对建立西藏野生动物资源监测体系进行了探讨。 相似文献
44.
This study examined the hypothesis that incorporation of Gliricidia sepium (Jacq.) Walp.) (gliricidia), a fast-growing, nitrogen-fixing tree, into agroforestry systems in southern Malawi may be used
to increase the input of organic fertilizer and reduce the need for expensive inorganic fertilizers. The productivity of maize
(Zea mays L.), pigeonpea (Cajanus cajan L.) and gliricidia grown as sole stands or in mixed cropping systems was examined at Makoka Research Station (latitude 15°
30′ S, longitude 35° 15′ E) and a nearby farm site at Nazombe between 1996 and 2000. Treatments included gliricidia intercropped
with maize, with or without pigeonpea, and sole stands of gliricidia, maize and pigeonpea. Trees in the agroforestry systems
were pruned before and during the cropping season to provide green leaf manure. Maize yields and biomass production by each
component were determined and fractional light interception was measured during the reproductive stage of maize. Substantial
quantities of green leaf manure (2.4 to 9.0 Mg ha−1 year−1) were produced from the second or third year after tree establishment. Green leaf manure and fuelwood production were greatest
when gliricidia was grown as unpruned sole woodlots (c. 8.0 and 22 Mg ha−1 year−1 respectively). Improvements in maize yield in the tree-based systems also became significant in the third year, when c. 3.0 Mg ha−1 of grain was obtained. Tree-based cropping systems were most productive and exhibited greater fractional light interception
(c. 0.6 to 0.7) than cropping systems without trees (0.1 to 0.4). No beneficial influence of pigeonpea on maize performance
was apparent either in the presence or absence of gliricidia at either site in most seasons. However, as unpruned gliricidia
provided the greatest interception of incident solar radiation (>0.9), coppicing may be required to reduce shading when gliricidia
is grown together with maize. As pigeonpea production was unaffected by the presence of gliricidia, agroforestry systems containing
gliricidia might be used to replace traditional maize + pigeonpea systems in southern Malawi.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
45.
Assessment of allometric algorithms for estimating leaf biomass, leaf area index and litter fall in different-aged Sitka spruce forests 总被引:1,自引:0,他引:1
Tobin Brian; Black Kevin; Osborne Bruce; Reidy Brian; Bolger Tom; Nieuwenhuis Maarten 《Forestry》2006,79(4):453-465
The relationship between leaf area and diameter at breast height(d.b.h.) or sapwood area (AS) has been used to estimate standleaf area or biomass of forest canopies. It has been suggestedthat intra-specific variations in the relationship between standleaf area and d.b.h. or AS can introduce a systematic errorin these estimates for younger and older stands unless additionalparameters relating to canopy structure are included in allometricfunctions. We collected data from a Sitka spruce chronosequenceto parametrize and test different algorithms for the estimationof foliar biomass (FB) and litter inputs over a range of forestages. FB estimates were significantly improved when additionalbiometric information relating to crown structure (canopy opennessand height of live crown) was included in the models. Althoughthe use of the relationship between leaf area and AS for theestimation of leaf area is justified by theoretical considerations(pipe model theory), we show that d.b.h. and other canopy parametersprovided the most robust estimation of leaf area across different-agedstands. Our results also suggest that the accuracy of litterinput estimates depends on needle retention time and annualturnover rate, particularly immediately before and after canopyclosure. 相似文献
46.
About 95% of swamp tupelo (Nyssa sylvatica var. biflora (Walt.) Sarg.) and sweetgum (Liquidambar styraciflua L.) seedlings survived continuous root flooding for more than two years, whereas none of the swamp chestnut oak (Quercus michauxii Nutt.) and cherrybark oak (Q. falcata var. pagodifolia Ell.) seedlings survived one year of flooding. Death of oak seedlings occurred in phases associated with periods of major vegetative growth, e.g., after bud burst in spring, after summer stem elongation, and during the winter deciduous stage, suggesting that stored reserves and sources were inadequate to maintain the seedlings when vegetative sinks were forming. Additional evidence that flooding induced a source deficiency in oak was that leaves of flooded oak were 65 to 75% smaller than leaves of nonflooded oak. Flooded swamp tupelo seedlings had a normal leaf size and patchy stomatal opening compared with nonflooded seedlings. Flooding caused increases in alcohol dehydrogenase (ADH) specific activity in taproot cambial tissues and increases in starch concentrations of swamp tupelo seedlings that were reversed when seedlings were removed from flooding. Flooding had little effect on soluble sugar concentrations in swamp tupelo or sweetgum. In the long-term flood-dry-flood treatment, in which all species had survivors, upper canopy leaf photosynthetic rates were higher in all species during the dry period than in nonflooded controls, whereas their starch and soluble sugars concentrations were similar to those of nonflooded controls. Based on seedling survival and the sink-source relationships, the order of flood tolerance was: swamp tupelo > sweetgum > swamp chestnut oak > cherrybark oak. 相似文献
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