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Some strains of Rhizobium japonicum can use hydrogen as an energy source for growth under microaerophilic conditions. Mutant strains have been selected that use hydrogen in the presence of high partial pressures of oxygen. The mutants contain more hydrogenase than the parent strain, both as free-living cells and as bacteroids in nitrogen-fixing soybean root nodules. 相似文献
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Juan Kruze Miguel Salgado Enrique Paredes Armin Mella Michael T Collins 《Journal of veterinary diagnostic investigation》2006,18(5):476-479
In October 2004, 41 goats > 2 years old from a Saanen dairy goat herd located in Purranque County, 10th Region, Chile, were sampled and tested for paratuberculosis. While collecting samples it was observed that several goats were thin and emaciated. One goat was sufficiently debilitated to warrant humane euthanasia. This animal was brought to the Veterinary School at the Universidad Austral de Chile for necropsy. The goat selected for necropsy was a 12-year-old doe. The animal showed classical clinical signs of caprine paratuberculosis: emaciation despite willingness to eat, dry and rough hair coat, and no evidence of diarrhea. Gross pathology and histopathology of the necropsied goat were consistent with paucibacillary paratuberculosis. Bacteriology, serology, and PCR confirmed the diagnosis. This is the first published report of goat paratuberculosis in Chile confirming a case of caprine paucibacillary paratuberculosis. 相似文献
4.
We measured dormant season (November through February) maintenance respiration rates (R(m)) in stems and branches of 9-year-old loblolly pine (Pinus taeda L.) growing in plots under conditions of controlled nutrient and water supply in an effort to determine the relationships between R(m) and tissue size (surface area, sapwood volume, sapwood dry weight), tissue nitrogen content and temperature. Dormant season R(m) per unit size (i.e., surface area, &mgr;mol m(-2) s(-1); sapwood volume, &mgr;mol m(-3) s(-1); or sapwood dry weight, nmol g(-1) s(-1)) varied with tissue size, but was constant with respect to tissue nitrogen content (&mgr;mol mol(-1) N s(-1)). Cambium temperature accounted for 61 and 77% of the variation in stem and branch respiration, respectively. The basal respiration rate (respiration at 0 degrees C) increased with tissue nitrogen content, however, the Q(10) did not. Improved nutrition more than doubled stem basal respiration rate and increased branch basal respiration by 38%. Exponential equations were developed to model stem and branch respiration as a function of cambium temperature and tissue nitrogen content. We conclude that failure to account for tissue nitrogen effects on respiration rates will result in serious errors when estimating annual maintenance costs. 相似文献
5.
Maier NR 《Science (New York, N.Y.)》1938,87(2263):439-441
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Armin L.?OppeltEmail author Winfried?Kurth Georg?Jentschke Douglas?L.?Godbold 《Agroforestry Systems》2005,65(1):1-11
To assess the possible degree of root competition from fruit trees which could potentially be used in agroforestry systems,
fine root density of fruit trees Strychnos cocculoides Bak., Strychnos spinosa Lam. (Loganiaceae) and Vangueria infausta Burch. (Rubiaceae), as well as from the shrubby species, Grewia flava DC. (Tiliaceae) was investigated. Vangueria infausta had the highest fine root densities in both vertical and horizontal extensions. In Vangueria infausta fine root density decreased with increasing soil depth. For the other species in the 80 cm soil profile investigated, no
significant changes in fine root density with soil depth were found. For Strychnos cocculoides almost no fine roots were detected in the upper soil horizon (0–20 cm). Using fine root surface area densities, exploration
and exploitation indices were calculated. Vangueria infausta had the highest value of the exploration index compared to the other species. For use in agroforestry systems Vangueria infausta was estimated to be the most competitive of the investigated species, whereas Strychnos cocculoides seems to be the less competitive. Strychnos cocculoides has additionally spatial arrangements of fine roots favourable for agroforestry, slowly increasing with depth and additionally
low concentrations in upper soil layers. 相似文献
8.
Concentrations of total soluble phenolics, catechin, proanthocyanidins (PA), lignin and nitrogen (N) were measured in loblolly pine (Pinus taeda L.) needles exposed to either ambient CO(2) concentration ([CO(2)]), ambient plus 175 or ambient plus 350 micromol CO(2) mol(-1) in branch chambers for 2 years. The CO(2) treatments were superimposed on a 2 x 2 factorial combination of irrigation and fertilization treatments. In addition, we compared the effects of branch chambers and open-top chambers on needle chemistry. Proanthocyanidin and N concentrations were measured in needles from branch chambers and from trees in open-top chambers exposed concurrently for two years to either ambient [CO(2)] or ambient plus 200 micromol CO(2) mol(-1) in combination with a fertilization treatment. In the branch chambers, concentrations of total soluble phenolics in needles generally increased with needle age. Concentrations of total soluble phenolics, catechin and PA in needle extracts increased about 11% in response to the elevated [CO(2)] treatments. There were no significant treatment effects on foliar lignin concentrations. Nitrogen concentrations were about 10% lower in needles from the elevated [CO(2)] treatments than in needles from the ambient [CO(2)] treatments. Soluble phenolic and PA concentrations were higher in the control and irrigated soil treatments in about half of the comparisons; otherwise, differences were not statistically significant. Needle N concentrations increased 23% in response to fertilization. Treatment effects on PA and N concentrations were similar between branch and open-top chambers, although in this part of the study N concentrations were not significantly affected by the CO(2) treatments in either the branch or open-top chambers. We conclude that elevated [CO(2)] and low N availability affected foliar chemical composition, which could in turn affect plant-pathogen interactions, decomposition rates and mineral nutrient cycling. 相似文献
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10.
Ana Afonso Jose Cortinas Abrahantes Franz Conraths Anouk Veldhuis Armin Elbers Helen Roberts Yves Van der Stede Estelle Méroc Kristel Gache Jane Richardson 《Preventive veterinary medicine》2014
During the Schmallenberg virus (SBV) epidemic, the European Food Safety Authority (EFSA) collected data on SBV occurrence across Europe in order to provide an assessment of spread and impact. By May 2013, twenty-nine countries were reporting to EFSA and twenty-two countries had reported cases of SBV. The total number of SBV herds reported was 13,846 and the number of SBV laboratory confirmed herds was 8730. The surveillance activities were based on the detection of SBV clinical cases (either adults or newborns). Malformation in newborns was the most commonly reported clinical sign of SBV-infection. All countries were able to provide the date when the first suspicion of SBV in the herd was reported and nineteen could report the location of the herd at a regional level. This allowed the spread of SBV in Europe to be measured both temporally and spatially. The number of SBV confirmed herds started to increase in December 2011 and two peaks were observed in 2012 (February and May). Confirmed herds continued to be reported in 2012 and into 2013. An increase during winter 2012 and spring 2013 was again observed, but the number of confirmed herds was lower than in the previous year. SBV spread rapidly throughout Europe from the initial area of detection. SBV was detected above the latitude of 60° North, which exceeds the northern expansion observed during the bluetongue virus serotype 8 epidemic in 2006–2009. The impact of SBV was calculated as ratio of the number of herds with at least one malformed SBV positive foetus and the total number of herds in this region. The 75th percentile of the malformations ratio in the various affected countries for the whole reporting period was below 1% and 3% for cattle and sheep herds, respectively. International data collection on emerging diseases represents a challenge as the nature of available data, data quality and the proportion of reported cases may vary widely between affected countries. Surveillance activities on emerging animal diseases are often structured only for case detection making the estimation of infection/diseases prevalence and the investigation of risk factors difficult. The impact of the disease must be determined to allow risk managers to take appropriate decisions. Simple within-herd impact indicators suitable for emerging disease outbreaks should be defined that could be measured as part of routine animal health surveillance programmes and allow for rapid and reliable impact assessment of emerging animal health diseases. 相似文献