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1.
2.
Pinus radiata seedlings were inoculated with basidiospores of Rhizopogon roseolas and Suillus granulatus, and with chlamylospores of two unidentified but highly effective mycorrhizal fungi in undisturbed cores of natural soil fumigated with methyl bromide. Fumigation stimulated mycorrhizal infection rate and enhanced the response of seedlings to increasing concentrations of both inoculum types, but the effect of chlamydospore inoculum was more favoured by fumigation than that of basidio-spores. Chlamydospore inocula appear more sensitive to competitive and antagonistic soil microorganisms than basidiospores. Soil fumigation appears a necessary adjunct to the use of chlamydospores as inoculants in nurseries and is discussed in relation to nursery culture of pines. 相似文献
3.
Abstract. The histological features of the disease caused by infection of turbot by Herpesvirus scophthalmi are described. Infection of epidermal cells of skin and gill resulted in the formation of giant cells showing a variety of nuclear and cytoplasmic changes associated with the replication of the virus. The effects of the condition together with possible control measures are discussed. 相似文献
4.
Perilipins have been reported to limit the interaction of lipases with neutral lipids within the droplets, thereby regulating neutral lipid accumulation and utilization. This study aimed to identify the location and expression of PLIN1 and PLIN2 in porcine oocytes during maturation. Quantitative real‐time polymerase chain reaction (qRT‐PCR), immunostaining and Western blot methods were used to characterize the expression and distribution patterns of PLIN1 and PLIN2 in porcine oocytes. The results showed that PLIN1 was not detectable in porcine oocytes. PLIN2 and BODIPY 493/503‐detected neutral lipid droplets appeared identical distribution patterns and extensive colocalization in both GV and MII porcine oocytes. PLIN2 protein expression was higher in GV oocytes than that in MII oocytes (p < 0.05), although PLIN2 mRNA expression was similar in both groups. These findings suggested that PLIN2 was a major lipid droplet‐associated protein in porcine oocytes. 相似文献
5.
Although there has been increasing research on the adoption of agroforestry technologies over the last decade, few such studies have assessed uptake over a long period and many are based on a single snapshot in time. Furthermore, most of these studies have mainly looked at non-adopters and adopters: only recently have social scientists considered testers. A further category of users neglected in adoption studies has been re-adopters of technologies. Studying this group provides an interesting and more nuanced understanding of adoption and re-adoption. Methodologically, most adoption studies use quantitative methods and fail to link their findings to wider socio-economic, political and institutional settings. This paper presents a study of the dynamics of improved tree fallow use by farmers in Siaya and Vihiga districts of western Kenya over a period of eight years. It uses both qualitative and quantitative data to critically discuss the motivations of adopters, testers/rejecters and re-adopters. The results show that the process of adoption is highly dynamic and variable with farmers planting improved fallows and discontinuing or re-adopting them due to a whole range of factors, of which soil fertility improvement is just one. These factors included incentives from projects, the tying of adoption to credit programmes, prestige, participation in seminars/tours and the availability of a seed market from projects promoting improved fallows. Farmers planting improved fallows for such reasons may be termed ‘pseudo-adopters’. There were significant differences in adoption between the two districts, with more farmers in Siaya planting improved fallows than in Vihiga. A majority of farmers in Vihiga (53%) who were given seed never planted improved fallows, even though they had been exposed to the technology. Some 40% of farmers in Siaya and 38% in Vihiga planted improved fallows but later rejected them. This has some important implications for research and development. For improved fallow technologies to be attractive to farmers, they must provide other tangible economic benefits besides soil fertility improvement. This presents a challenge to researchers who must better attune themselves to the needs and demands of farmers if they wish to see their research findings widely adopted. 相似文献
6.
7.
Olga Singurindy Marina Molodovskaya Brian K. Richards Tammo S. Steenhuis 《Water, air, and soil pollution》2008,195(1-4):285-299
Urine-treated soils make a significant contribution to gaseous N losses to the atmosphere. Our goal was to investigate the influence of clay type and content on ammonia (NH3) and nitrous oxide (N2O) emissions from urine under different wetting–drying soil conditions and to relate these results to urine-N transformation processes in soil. Three types of silt loam soils and synthetic sand–clay aggregates with three different clay-dominated materials (kaolinite, montmorillonite and vermiculite) were used in this laboratory study. Bulk soil, 4–4.75 mm and 9.5–11.2 mm aggregates were incubated with synthetic urine at 50% and 75% saturation under aerobic conditions. Repeated urine application affected the properties of the aggregates depending on the type of clay present. Greater clay content increased aggregate stability and reduced NH3 volatilization. The variation in clay ammonium (NH4 +) fixation capacities was reflected in NH3 volatilization as well as in the onset of N2O emissions, occurring first from kaolinite-dominated and last from vermiculite-dominated soils. Nitrous oxide production was greater in aggregates than in bulk soil, a difference that consistently increased with repeated urine applications for kaolinitic and vermiculitic treatments. A dual-peak N2O emission pattern was found, with the second maximum increasing with the number of urine applications. Emission of 15N-labeled N2 was found at 75% saturation in kaolinite and vermiculite-dominated samples. Anaerobic conditions were less pronounced with montmorillonite-dominated samples because shrink–swell action caused aggregate breakage. 相似文献
8.
Mark P. Richards Roman Aranda IV Cai He George N. Phillips Jr. 《Journal Of Aquatic Food Product Technology》2013,22(4):416-423
pH can be manipulated to alter the oxidative stability of fish-based foods during storage. X-ray diffraction was used to investigate the ability of reduced pH to cause structural changes in fish hemoglobins that lead to enhanced oxidative degradation. Decreasing pH from 8.0 to 6.3 and 5.7 created a large channel for solvent entry into the heme crevice of perch hemoglobin beta chains. The proton-induced opening of this channel occurred between site CD3 and the heme-6-propionate. Solvent entry into the heme crevice can enhance metHb formation and hemin loss, processes that accelerate lipid oxidation. Reduced pH also decreased the distance between Ile at E11 in one of the alpha chains and the ligand above the heme iron atom. This sterically displaces O2 and protonated O2 which increases metHb formation. These studies demonstrate that pH reduction causes structural changes in perch hemoglobin which increase oxidative degradation of the heme pigment. 相似文献
9.
Michael Misiko Pablo Tittonell Ken E. Giller Paul Richards 《Agriculture and Human Values》2011,28(1):27-38
It is widely recognized that mineral fertilizers must play an important part in improving agricultural productivity in western
Kenyan farming systems. This paper suggests that for this goal to be realized, farmers’ knowledge must be strengthened to
improve their understanding of fertilizers and their use. We analyzed smallholder knowledge of fertilizers and nutrient management,
and draw practical lessons from empirical collective fertilizer-response experiments. Data were gathered from the collective
fertilizer-response trials, through focus group discussions, by participant observation, and via in-depth interviews representing
40 households. The collective trials showed that the application of nitrogen (N) or phosphorous (P) alone was insufficient
to enhance yields in the study area. The response to P on the trial plots was mainly influenced by incidences of the parasitic
Striga weed, by spatial variability or gradients in soil fertility of the experimental plots, and by interactions with N levels.
These results inspired farmer to design and conduct experiments to compare crop performance with and without fertilizer, and
between types of fertilizers, or responses on different soils. Participating farmers were able to differentiate types of fertilizer,
and understood rates of application and the roles of respective fertilizers in nutrient supply. However, notions were broadly
generated by unsteady yield responses when fertilizers were used across different fertility gradients, association with high
cost (especially if recommended rates were to be applied), association of fertilizer use with hybrids and certain crops, historical
factors, among other main aspects. We identified that strengthening fertilizer knowledge must be tailored within existing,
albeit imperfect, systems of crop and animal husbandry. Farmers’ perceptions cannot be changed by promoting more fertilizer
use alone, but may require a more basic approach that, for example, encourages farmer experimentation and practices to enhance
soil properties such as carbon build-up in impoverished local soils. 相似文献
10.
The effects of incubation time, vegetation type (represented by a pine plantation, a protected and a periodically burnt eucalypt forest), lime and finely ground pine needles on the transformation of (15NH4)2SO4 and K15NO3 were studied in incubation experiments with a sandy lateritic podzolic soil from south-east Queensland. Microorganisms were counted so as to relate N transformations to particular groups of microorganisms.The heterotrophic miroflora utilized NH+4 as a source of N in preference to NO?3, and autotrophic nitrifiers seemed to be weak competitors for NH+4. Lime caused a slight loss of NO?3 and this was accompanied by an increase in the population of denitrifying bacteria.Lime promoted immobilization of NH+4 by heterotrophic bacteria and subsequent mineralization by nitrifying bacteria, but when pine needles were also added the nitrifiers were suppressed and immobilization by heterotrophic bacteria dominated. Pine needles alone stimulated fungi to immobilize NH+4.While reforestation with exotic pines caused a loss of total-N there was evidence of increased turnover, i.e. more rapid immobilization and nitrification, in pine plantation soils. Prescribed burning also promoted nitrification while reducing total-N. 相似文献