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Methyl anthranilate (MA), a food grade flavor and fragrance additive, has been reported to be an effective non-lethal bird repellent in a variety of situations. Despite the experimental success of MA, field studies have yielded widely differing levels of efficacy. Diminished efficacy in some field trials probably results from the failure of specific formulations to retain or protect the active ingredient under natural conditions. Therefore, a clearer understanding of the physical and chemical factors affecting the stability of MA is needed. We undertook a series of laboratory studies on hydrolysis, photolysis and microbial degradation of MA, the results of which could be useful in the development of appropriate formulation strategies and residue analyses. We found the n-octanol:water partition coefficient, (P) to be 84. MA is not subject to hydrolysis at 25°C in phosphate buffer media at pH 5·0, 7·0 and 9·0. MA slowly photodegrades under simulated UV ‘sunlight’. Forty-four percent of MA is lost after 432 h illuminance at 1·25 mW cm−2, which is equivalent to approximately 1200 h natural sunlight (40°N, noontime, June). Kinetic data indicate that the initial step of photolysis, subsequent to excitation, is a second-order reaction with respect to MA. A major photodegradation product appeared in an amount of about 10% of the mass balance and was determined to be an oxidized trimer of MA. MA is primarily affected by aerobic microbial degradation. For a 12:12 h light:dark, under laboratory illumination, 12% of water-solubilized material can be lost in the first seven days. Losses were 30% and 42% at 16 and 27 days, respectively. Under conditions of optimal bacterial growth (warmth and darkness) loss of MA was 22% at nine days and 100% by 20 days. The susceptibility of MA to microbial degradation is promising for the prospects of developing formulated, environmentally safe, bird repellents. 相似文献
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本文在对城市边缘森林公园分区理论研究的基础上,全面考量森林公园的功能性、适宜性、生态性、多样性、开发利用的立体性等诸多特点,从理论支持到各分区方法以及方法间优劣势对比,利用数学方法和现代空间信息技术方法深化森林功能分区研究,使森林功能分区工作进一步科学化、规范化和标准化,以提升城市边缘土地利用价值,实现社会、经济、生态... 相似文献
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Anne C. Lang Werner Härdtle Helge Bruelheide Christian Geißler Karin Nadrowski Andreas Schuldt Mingjian Yu Goddert von Oheimb 《Forest Ecology and Management》2010
Trees are able to respond to their local biotic and abiotic environment with morphological adjustments which improve resource acquisition and, thus, growth. In forests, light is broadly recognised as one of the major factors determining growth, and morphological responses comprise changes in crown architecture and stem stature. On sloping terrain, the interplay of phototropism and gravitropism may further affect morphological growth characteristics. However, different tree species are expected to show species-specific responses. In this study, we analysed three growth characteristics of tree individuals belonging to four species of two functional groups (evergreen: Schima superba, Castanopsis eyrei, deciduous: Quercus serrata var. brevipetiolata, Castanea henryi) in a species-rich Chinese subtropical forest. Crown projection area, relative crown displacement and stem inclination were related to biotic (local species richness, functional richness, competition, stand age) and abiotic (slope aspect and inclination, soil depth) variables in the local neighbourhood of the tree individuals. We hypothesised that (i) there are species-specific differences in the morphological response of crown architecture and stem stature and (ii) that crown size and asymmetry as well as stem inclination are influenced by both, biotic and abiotic factors. In contrast to our expectations we were unable to reveal any species-specific differences in any of the three growth characteristics. The results of mixed effects models showed that crown area was mainly affected by the target tree's dbh and biotic variables related to neighbours (competition, functional diversity), whereas stem inclination was mainly influenced by slope. Relative crown displacement was influenced by both, biotic and abiotic variables. We conclude that growth responses resulting in crown displacement and stem inclination seem to be an important mechanism to ameliorate foraging for light in our study area, but that these responses appear to be species-independent. The interplay of stem inclination and crown displacement allows for a plastic response of tree individuals in biotically and abiotically heterogeneous environments. Our results indicate that forest management in this region should focus on functionally diverse stands which are promoting crown area positively resulting in increased growth rates of individual trees. 相似文献
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林业向可持续发展过渡的阶段划分理论研究 总被引:1,自引:0,他引:1
根据马克思主义经济学和西方经济学关于经济社会发展阶段划分理论,对林业向可持续发展过渡进行了阶段划分,确定了划分标准和各阶段的区别. 相似文献
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The Swertia japonica is used clinically as a remedy for gastrointestinal symptoms in Japan. We examined the effects of a S. japonica and swertiamarin on gastric emptying and gastrointestinal motility in atropine-, dopamine-, and 5-hydroxytryptamine (5-HT)-treated mice. All three preparations inhibited reductions in gastric emptying and gastrointestinal motility induced by dopamine (1 mg/kg, intraperitoneal injection, ip). Neither the powder, swertiamarin, nor itopride had any effect on the reductions in gastric emptying and gastrointestinal motility caused by 5-HT (4 mg/kg, ip). These findings suggest that the powder and swertiamarin stimulate gastric emptying and gastrointestinal motility by inhibiting the dopamine D2 receptor. 相似文献
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Many ecologists regard nitrogen as a key element in the life-histories of herbivore populations. Consequently, those studying interactions between plants and animals often attempt to link feeding to the concentration of nitrogen (N) in plants. This approach disregards the possibility that in many plants, especially those rich in tannins, animals cannot digest much of the N. The ubiquity of tannins in plants led us to hypothesise that the concentrations of available nitrogen may be more informative for ecologists than are measures of total N. Eucalypts provide a good model for examining this hypothesis because subgeneric differences in foliar chemistry cause dietary niche separation in marsupials. 相似文献
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Marlin Bowles Steven ApfelbaumAlan Haney Susan LehnhardtTom Post 《Forest Ecology and Management》2011,262(11):1972-1982
Savanna vegetation is characterized by high and variable ground layer species richness regulated by functional group interactions with fire regimes and canopy cover. Frequent fire selects for C4 grasses and prairie forbs in canopy openings and C3 graminoid species and shade-adapted forbs and shrubs in canopy shade. Frequent fire also maximizes heterogeneity in partial canopy cover and species richness across the full canopy gradient. However, few studies have linked fire induced change in tree canopy cover with groundlayer vegetation dynamics in relation to this model. In 1986 and in 2007, we measured canopy cover and sampled groundlayer vegetation in 1 m2 plots along 53 transects at the Tefft Savanna, a fire managed 197 ha eastern sand savanna with strong canopy cover and elevation gradients. We analyzed temporal change in canopy cover and groundlayer vegetation, correlating percent change in canopy cover with change in ground layer functional groups. After 20 years of burning at 3 fires/decade, elevation accounted for 62% of the variation in an NMS ordination of groundlayer vegetation. However, canopy cover, which averaged 24-86% in 2007, had a significant secondary effect on the ordination. Five vegetation types classified by TWINSPAN varied significantly in elevation and canopy cover. Woody vegetation comprised 8 of the 12 species with greatest niche breadths, and tended to predominant in woodland or forest, where tree cover averaged 50% or more. Forbs had greater richness in savanna, which averaged less than 30% canopy cover. The C3 sedge Carex pensylvanica was the dominant graminoid species under woodland canopy cover, and was co-dominant with the C4 grasses Andropogon scoparius and Sorghastrum nutans under savanna canopy cover. As in other savannas, N-fixing species sorted across shade and canopy openings, and heterogeneity among transects was maximized at mid-canopy cover. Over time, canopy cover decreased up to 50%, creating more open savanna conditions at mid to high elevations. This decrease was associated with a 20-100 % increase in species richness and was significantly correlated with increasing richness and cover of C4 grasses and summer flowering prairie and woodland forbs. These results support a canopy cover model of fire-maintained savanna vegetation, with greater abundance of C4 grasses and prairie forb species associated with lower canopy cover, greater heterogeneity at mid-canopy cover, and species richness maximized across the light gradient. They also indicate that decreasing canopy cover caused by repeated burning increases species richness and abundance of C4 and prairie forb species. 相似文献
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