全文获取类型
收费全文 | 188篇 |
免费 | 27篇 |
专业分类
林业 | 12篇 |
农学 | 10篇 |
基础科学 | 2篇 |
38篇 | |
综合类 | 7篇 |
农作物 | 16篇 |
水产渔业 | 38篇 |
畜牧兽医 | 80篇 |
园艺 | 3篇 |
植物保护 | 9篇 |
出版年
2023年 | 2篇 |
2022年 | 1篇 |
2021年 | 8篇 |
2020年 | 16篇 |
2019年 | 7篇 |
2018年 | 20篇 |
2017年 | 7篇 |
2016年 | 7篇 |
2015年 | 9篇 |
2014年 | 9篇 |
2013年 | 7篇 |
2012年 | 11篇 |
2011年 | 12篇 |
2010年 | 9篇 |
2009年 | 8篇 |
2008年 | 9篇 |
2007年 | 11篇 |
2006年 | 9篇 |
2005年 | 11篇 |
2004年 | 6篇 |
2003年 | 2篇 |
2002年 | 4篇 |
2001年 | 4篇 |
2000年 | 5篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1995年 | 3篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1982年 | 2篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1945年 | 1篇 |
排序方式: 共有215条查询结果,搜索用时 222 毫秒
11.
self-(in)compatibility almond genotypes: A review 总被引:1,自引:0,他引:1
To compile self-(in)compatibility almond genotypes, a review of 133 commercial cultivars of wide geographical origin was made. The information gathered from own and mainly published work will be useful for both grower's cultivar choice when planting and for breeder's cross design when planning. The almond S genotypes compiled were identified using five different methods: biological (pollination tests in the field and in the laboratory) and molecular (RNases, PCR and sequencing). In most cases, genotypes were assigned after combining more than one technique. Cultivars were classified into three categories: self-incompatible (99), self-compatible (16) and doubtful self-incompatible (18). The database is divided in 9 fields (name, origin, parentage, obtention year (crossing, selection or release), S genotype, technique used, reference, consensus genotype, and cross incompatibility group). A study of the 27 S alleles already identified and their geographical distribution within the cultivated almond is also presented. The study was divided into cultivars of known and unknown parentage and the distribution of S alleles frequencies was uneven among the 133 cultivars. S allele frequencies are related to geographical origin. Some alleles (S
1, S
5, S
7 and S
8) are more frequently observed than the others among cultivars of both known and unknown parentage. In the cultivated almond, the S
f allele is only found in the Puglia region, Italy. The S
f
frequency is three times higher in cultivars released from breeding programmes than in cultivars selected by growers. From the 351 resulting possible genotypes by combination of the 27 S alleles identified only 20 CIG (0-XIX) have been established, which represents a small fraction of the whole genetic diversity of this polymorphic gene in almond. 相似文献
12.
Long-term monitoring of physical and biological parameters is essential for understanding the effects of El Niño on bird populations, particularly for small or declining populations. We examined the biological effects of El Niño activity from 1965 to 2004 using instrumental sea-surface temperatures from the Galápagos Islands and 20 years of census counts of the Galápagos penguin. Between 1965 and 2004, nine El Niño events were recorded of which two were strong and seven were weak. The two strong El Niño events of 1982-1983 and 1997-1998 were followed by crashes of 77% and 65% of the penguin population, respectively. The evidence suggests that the increased frequency of weak El Niño events limits population recovery. The 2004 penguin population is estimated to be at less than 50% of that prior to the strong 1982-1983 El Niño event. We discuss the biological effects of increased El Niño intensity and frequency within the context of a 6000-year record of El Niño influence and in the light of increasing anthropogenic threats operating after 1535, when the Archipelago was discovered by Europeans. 相似文献
13.
Cyanobacteria are important for global nitrogen cycle and often form complex associations referred to as cyanobacterial mats
or periphyton that are common in tropical, limestone-based wetlands. The objective of this study was to monitor the nitrogen
fixation rate using the acetylene reduction assay of these cyanobacterial mats in a tropical, unfertilized, and protected
wetland. To account for temporal and spatial variation of nitrogenase activity, we were interested in seasons in a hydrological
cycle (dry, rains, and end of rains), sites with different vascular vegetation, and rates of nitrogenase activity in a 24-h
cycle. The annual average of nitrogenase activity was 22 nmol C2H4 cm−2 h−1, with a range of <6 to 35 nmol C2H4 cm−2 h−1, and the annual nitrogen fixation rate of our study site (9.0 g N m−2 year−1) is higher than similar estimates from other freshwater wetlands. There was a clear temporal pattern in nitrogenase activity
with a maximum rate occurring during the rainy season (August) and a maximum nitrogenase activity occurring between 0600 and
1200 hours. We found spatial differences in nitrogenase activity among the four sites that could be attributed to variations
in species composition within the periphyton. 相似文献
14.
15.
16.
Gabriela Vargas Jos Verdejo Adrian Rivera Domingo Surez Cristian Youlton Juan L. Celis-Diez Yves Le Bissonnais Elvira A. Dovletyarova Alexander Neaman 《植物养料与土壤学杂志》2019,182(2):159-166
The structural stability of soil is a physical characteristic that affects soil degradation processes. Calcium‐based amendments, such as calcium carbonate, calcium sulfate, and calcium oxide/hydroxide, have been shown to improve the stability of soil aggregates. This study seeks to determine which calcium‐based soil amendments, and at what concentration, are the most efficient in improving aggregate stability of sandy topsoils derived from granitic and metamorphic parent materials, and to analyze the mechanisms involved. In the pot experiment, soils amended with CaCO3, CaCl2, and CaSO4 did not present significant differences in aggregate stability compared to the control or among each other. In contrast, Ca(OH)2 soil amendment brought the greatest stability to the soil aggregates. A dose of 1% Ca(OH)2 significantly increased the stability of soil aggregates. This effect is due to the reaction of Ca(OH)2 with atmospheric CO2 which leads to the formation of CaCO3, a delayed reaction not showed by the other soil amendments tested. Likewise, the greater solubility of Ca(OH)2 compared to CaCO3 exerts a greater aggregation effect on soil. Thus, the mechanism of action of Ca(OH)2 is related to cementation, rather than flocculation. Future studies should be carried out to demonstrate the effectiveness of Ca(OH)2 under field conditions. 相似文献
17.
Dinorah Vargas Lilia Gutierrez Ivan Juárez Francisco Gonzalez Héctor Sumano 《American journal of veterinary research》2008,69(8):1085-1090
OBJECTIVE: To determine the pharmacokinetics after SC administration of an experimental, long-acting parenteral formulation of doxycycline hyclate in a poloxamer-based matrix and after IV and IM administration of an aqueous formulation of doxycycline hyclate in goats. ANIMALS: 30 clinically normal adult goats. PROCEDURES: Goats were allocated to 3 groups (10 goats/group). One group of goats received doxycycline hyclate (10 mg/kg) IM, a second group received the same dosage of doxycycline hyclate IV, and the third group received the long-acting parenteral formulation of doxycycline hyclate SC. Serum concentrations of doxycycline were determined before and at various intervals after administration. RESULTS: The long-acting parenteral formulation of doxycycline hyclate had the greatest bioavailability (545%); mean +/- SD maximum serum concentration was 2.4 +/- 0.95 microg/mL, peak time to maximum concentration was 19.23 +/- 2.03 hours, and elimination half-life was 40.92 +/- 4.25 hours. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that the long-acting parenteral formulation of doxycycline hyclate distributed quickly and widely throughout the body after a single dose administered SC, and there was a prolonged half-life. Bioavailability of the longacting parenteral formulation of doxycycline hyclate after SC administration was excellent, compared with bioavailability after IV and IM administration of an aqueous formulation of doxycycline hyclate. Although no local tissue irritation and adverse effects were detected, clinical assessment of drug-residues and toxicologic evaluations are warranted before this long-acting parenteral formulation of doxycycline hyclate can be considered for use in goats with bacterial infections. 相似文献
18.
Danilo V. G. Vieira Jos H. V. Silva Fernando G. P. Costa Thiago S. Melo Matheus R. Lima Danilo T. Cavalcante Jos G. de Vargas Júnior Talita P. Bonaparte Lorena C. Oliveira 《Journal of animal physiology and animal nutrition》2019,103(1):116-124
Experiment I: T1‐1 = basal diet with 25% crude protein (CP) + limiting amino acids (LA); T1‐2 = 20% CP + LA; T1‐3 = 20% CP + LA + L‐glycine; T1‐4 = 20% CP + LA + L‐glutamate; T1‐5 = 20% CP + LA + L‐glycine + L‐glutamate. Experiment II: T2‐1 = basal diet with 22% CP + LA; T2‐2 = 20% CP + LA; T2‐3 = 17.6% CP + LA + L‐glycine; T2‐4 = 17.6% CP + LA + L‐glutamate; T2‐5 = 17.6% CP + LA + L‐glycine + L‐glutamate. The reduction of dietary protein based on the concept of ideal protein decreases nitrogen excretion in quails when L‐glycine is added to the diets. Quails fed diets supplemented with L‐glutamate as the non‐specific nitrogen source equivalent to the nitrogen level of the control diet had increased nitrogen excretion. However, quails had reduced nitrogen excretion in both experiments when L‐glycine was added to diets with L‐glutamate. Carcass fat was increased by reducing dietary protein, but fat deposition was reduced by adding L‐glutamate and L‐glycine, or both. The dietary addition of L‐glutamate and L‐glycine in quails based on the ideal protein concept is not necessary (Exp. I). Although the total nitrogen, electrolytic balance and glycine level were adjusted in diets, quails had decreased performance. Therefore, other hypotheses besides protein reduction need to be studied (Exp. II). Protein reduction with supplementation of only limiting essential amino acids does not affect quail performance. Dietary addition of L‐glycine reduces nitrogen excretion. 相似文献
19.
Changes in the prevalence,genotypes and antimicrobial resistance phenotypes of non‐typhoidal Salmonella recovered from mail‐order hatchling poultry sold at US feed stores, 2013–2015
下载免费PDF全文
![点击此处可从《Zoonoses and public health》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A. Sharma M. M. Erdman L. Muñoz‐Vargas D. F. Mollenkopf G. G. Habing 《Zoonoses and public health》2018,65(1):e102-e112
Every year, multiple outbreaks of salmonellosis in humans are linked to contact with mail‐order chicks and ducks. The objective of this study was to describe the temporal changes in the prevalence of serovars, genotypes and antimicrobial resistance (AMR) phenotypes of non‐typhoidal Salmonella (NTS) recovered from shipped boxes of mail‐order hatchling poultry in the United States during 2013 to 2015. In each year, a sample of feed stores belonging to a single national chain participated in the study. The store employees submitted swabs or hatchling pads from hatchling boxes and shipment tracking information of the arriving boxes to the investigators. NTS was cultured from the samples and isolates were sent to the National Veterinary Services Laboratories (Ames, IA) for serotyping, pulsed‐field gel electrophoresis (PFGE) and AMR phenotyping. The PFGE patterns of Salmonella serovars isolated from hatchling boxes were compared with those from human outbreaks of salmonellosis linked to live poultry contact. The box‐level prevalence of NTS was significantly higher in 2015 compared to 2014. Also, the population of Salmonella serovars recovered in 2015 was more diverse and substantially different from those recovered in the previous two years. Of PFGE patterns recovered from hatchling boxes, seven distinct patterns in 2015, three in 2014 and four in 2013 were indistinguishable from the PFGE patterns of human outbreaks‐associated strains in the respective years. Importantly, a significant positive correlation was found between the box‐level prevalence of PFGE patterns and the number of human illnesses associated with the same patterns. Also, the proportion of multidrug‐resistant isolates was higher in 2014 and 2015 compared to that in 2013. The results demonstrate that shipments of mail‐order hatchling poultry are frequently contaminated with Salmonella genotypes indistinguishable from human outbreaks‐associated strains each year, and control efforts at hatchery level are likely to have an important public health impact. 相似文献
20.
Spontaneous and experimental poisoning with the swainsonine-containing and calystegine-containing plant Ipomoea carnea subsp fistulosa is described. Three of 8 goats presenting with emaciation, weakness, symmetrical ataxia, posterior paresis, proprioceptive deficits, abnormal posture, abnormal postural reaction, and muscle hypertonia were necropsied. I fistulosa was suspected to be the cause of the neurologic disease in all cases. An experiment was conducted to confirm the diagnosis using 12 goats and diets containing 3 different concentrations of the plant. All goats fed I fistulosa developed neurological signs that were similar to those observed in the spontaneous intoxication. Muscle atrophy and pallor were the only macroscopic changes observed in spontaneous and in experimental intoxication. Histological lesions of spontaneous and experimental animals were similar. The most prominent lesion was cytoplasmic vacuolation in neurons of the central and the autonomous nervous system, pancreatic acinar cells, hepatocytes, Kupffer cells, follicular epithelial cells of the thyroid gland, and macrophages of the lymphatic tissues. Neuronal necrosis, axonal spheroids formation, and astrogliosis were additionally observed in the brain. Ultrastructurally, the cytoplasmic vacuoles consisted of distended lysosomes surrounded by a single-layered membrane. Nonreduced end-rests or sequence of alpha-Man, alpha-Glc, beta(1-4)-GlcNAc, and NeuNAc on lysosomal membrane were revealed by lectin histochemistry. Samples of plants used in the experimental trial contained swainsonine and calystegine and their intermediary derivate. We conclude that I fistulosa induces a glycoprotein storage disease primarily based on the inhibition of the lysosomal alpha-mannosidase by the alkaloid swainsonine. 相似文献