全文获取类型
收费全文 | 1794篇 |
免费 | 14篇 |
专业分类
林业 | 53篇 |
农学 | 1篇 |
334篇 | |
综合类 | 379篇 |
农作物 | 27篇 |
水产渔业 | 21篇 |
畜牧兽医 | 946篇 |
园艺 | 1篇 |
植物保护 | 46篇 |
出版年
2012年 | 132篇 |
2011年 | 186篇 |
2010年 | 33篇 |
2009年 | 18篇 |
2008年 | 146篇 |
2007年 | 176篇 |
2006年 | 155篇 |
2005年 | 158篇 |
2004年 | 116篇 |
2003年 | 118篇 |
2002年 | 108篇 |
2001年 | 83篇 |
2000年 | 85篇 |
1999年 | 46篇 |
1997年 | 3篇 |
1996年 | 6篇 |
1995年 | 9篇 |
1994年 | 12篇 |
1993年 | 10篇 |
1992年 | 8篇 |
1991年 | 10篇 |
1990年 | 7篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 5篇 |
1986年 | 9篇 |
1985年 | 9篇 |
1984年 | 8篇 |
1983年 | 8篇 |
1982年 | 4篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1977年 | 3篇 |
1973年 | 5篇 |
1971年 | 4篇 |
1966年 | 4篇 |
1963年 | 3篇 |
1958年 | 3篇 |
1957年 | 3篇 |
1956年 | 6篇 |
1953年 | 3篇 |
1948年 | 4篇 |
1947年 | 3篇 |
1946年 | 3篇 |
1945年 | 4篇 |
1943年 | 3篇 |
1931年 | 4篇 |
1925年 | 3篇 |
1889年 | 2篇 |
1886年 | 2篇 |
排序方式: 共有1808条查询结果,搜索用时 93 毫秒
991.
992.
Mangen MJ Jalvingh AW Nielen M Mourits MC Klinkenberg D Dijkhuizen AA 《Preventive veterinary medicine》2001,48(3):177-200
Two alternative emergency-vaccination strategies with a marker vaccine that could have been applied in the 1997/1998 Dutch Classical Swine Fever (CSF) epidemic were evaluated in a modified spatial, temporal and stochastic simulation model: InterCSF. In strategy 1, vaccination would be applied only to overcome a shortage in destruction capacities. Destruction of all pigs on vaccinated farms distinguishes this strategy from strategy 2, which assumes intra-Community trade of vaccinated pig meat. InterCSF simulates the spread of CSF between farms through local spread and three contact types. Disease spread is affected by control measures implemented through different mechanisms. Economic results were generated by a separate model that calculated the direct costs (including the vaccination costs) and consequential losses for farmers and related industries subjected to control measures. The comparison (using epidemiological and economic results) between the different emergency-vaccination strategies with an earlier simulated preventive-slaughter scenario led to some general conclusions on the Dutch CSF epidemic. Both emergency-vaccination strategies were hardly more efficient than the non-vaccination scenario. The intra-Community trade strategy (vaccination-strategy 2) was the least costly of all three scenarios. 相似文献
993.
1. This paper is a report of biological agents that contaminate Greater Rhea (Rhea americana) eggs during artificial incubation. 2. The cleanliness of eggs when collected, and the period of storage prior to incubation, were investigated to assess their effects on microbial contamination and hatchability. 3. A total of 14 bacteria and 4 fungi species were isolated within the egg in the laboratory. 4. Microbial contamination was higher (24%) in very dirty eggs than in eggs which were clean or dirty (16%). Hatching success was lower (30%) for very dirty eggs, compared with 42% for clean or dirty eggs. 5. The percentage of microbial contamination of stored eggs (10%) did not differ significantly from that of non-stored ones (5%). 6. The extreme lower and upper limits of infection rate estimated for artificially incubated Greater Rhea eggs were 4% and 40%, respectively, being higher than in poultry species. 7. It is concluded that collecting eggs soon after laying will reduce the risk of microbial contamination. 相似文献
994.
The objective of this study was to examine the effect of abrupt weaning (inclusive of social group disruption and maternal separation) on the physiological mediators of stress and measures of immune function. Thirty-six male and 36 female calves (Limousin and Charolais crosses), habituated to handling, were blocked by sex, weight, and breed of dam and randomly assigned, within block, to either a control or abruptly weaned group. Animals were separated into the respective treatment groups at 0 h. Calves were bled at -168, 6 (males only), 24, 48, and 168 h after weaning, and the behavioral reaction of calves to handling was scored. Cortisol, catecholamine (not sampled at -168 h), acute-phase protein concentrations, and in vitro interferon-gamma production and neutrophil:lymphocyte ratio were measured. The effects of weaning, calf sex, time, and their respective interactions were described. Disruption of the established social group at 0 h increased (P < 0.001) the plasma cortisol concentration and neutrophil:lymphocyte ratio and decreased the leukocyte concentration (P < 0.001) and the in vitro interferon-gamma response to the mitogen concanavalin-A (P < 0.001) and keyhole limpet hemocyanin (P < 0.001) for weaned and control animals compared with -168 h. There was no effect of weaning or sex on the behavioral reaction of calves to handling. Plasma cortisol and adrenaline concentrations were not affected by weaning or sex. Plasma noradrenaline concentration was influenced by weaning x sex (P < 0.05) and time x sex (P < 0.05). The response increased for male calves with weaning and increased with each sampling time after weaning. For heifers, the response was not affected by weaning and plasma concentrations decreased at 168 h after weaning. There was no effect of weaning or sex on leukocyte concentration. The neutrophil:lymphocyte ratio increased after weaning (P < 0.01) and was affected by sex (P < 0.05). Weaning decreased (P < 0.05) the in vitro interferon-gamma response to the antigen keyhole limpet hemocyanin. There was a time x weaning x sex (P < 0.05) interaction for fibrinogen concentration but no effect of treatment on haptoglobin concentration. Abrupt weaning increased plasma cortisol and noradrenaline concentrations that were accompanied by attenuation of in vitro interferon-gamma production to novel mitogen and antigen complexes up to 7 d after weaning. 相似文献
995.
Thurmond MC Gibbs EP Brown CC Wagner GG Wilson TM Lautner BA 《Journal of the American Veterinary Medical Association》2003,222(10):1352-1357
Veterinary medical education in FADs has been and will continue to be critically important if veterinarians are expected to fulfill the profession's primary obligations to society--those of protecting our animals' health, conserving our animal resources, and promoting public health. It is imperative that curricula and instruction in veterinary schools and colleges provide the depth and breadth of knowledge and understanding necessary to prepare all veterinarians, including those in private practice, for their key role in defending against FADs. Development and implementation of governmental and military programs to diagnose, prevent, control, and eradicate FADs will require a dedicated cadre of public sector veterinarians who have a solid educational foundation in FADs and understand the contemporary issues and global challenges we face. Animal-related industries, associations, and organizations will increasingly rely on well-educated veterinarians to help guide them in ways that will protect animals, clientele, consumers, and trading partners from effects of FADs. Agencies and organizations concerned with conservation of animal resources will require veterinary expertise necessary to prevent FADs in a multitude of animal species, including marine animals, wildlife, endangered species, zoologic specimens, and important genetic lines as well as our domestic companion and livestock species. Species affected by FADs also include human beings for those disease agents with zoonotic potential; thus, veterinary education also plays a key role in public health. 相似文献
996.
997.
In cattle and sheep, a progestogenated uterus is susceptible to infections, but this is not well documented for pigs. Therefore, the effects of day of the estrous cycle and progesterone on the susceptibility to uterine infections were evaluated. Gilts (n = 5 per group) were assigned to treatments in 2 x 2 factorial arrays. In Exp. 1, day of cycle and bacterial challenge were main effects. On d 0 or 8, uteri were inoculated with either 70 x 10(7) cfu of Escherichia coli and 150 x 10(7) cfu of Arcanobacterium pyogenes in PBS or with PBS. In Exp. 2, ovariectomy (OVEX) and progesterone treatment were main effects. On d 0, gilts were ovariectomized or a sham procedure was performed. After surgery, gilts received i.m. injections of progesterone (10 mg/5 mL) or 5 mL of safflower oil diluent twice daily. On d 8, gilts were inoculated with the same doses of bacteria as in Exp. 1. In Exp. 1 and 2, vena caval blood was collected for 4 d, after which uteri were collected. Sediment and ability to culture E. coli and A. pyogenes from uterine flushings were used to diagnose infections. Differential white blood cell counts and lymphocyte response to concanavalin A (Con A) and lipopolysaccharides (LPS) were used to measure lymphocyte proliferation. Progesterone, estradiol-17beta, prostaglandin F2alpha, (PGF2alpha), and prostaglandin E2 (PGE2) were measured in vena caval blood. In Exp. 1, d-8 gilts receiving bacteria developed infections, but d-0 gilts receiving bacteria did not. Daily percentages of neutrophils and lymphocytes changed (P < 0.05) with cycle day and bacterial challenge. Basal- and Con A-stimulated lymphocyte proliferation were greater (P < 0.05) for d-0 than for d-8 gilts. Concentrations of PGF2, (P < 0.01) and PGE2 (P < 0.05) increased after bacterial challenge, regardless of stage of the estrous cycle at the time of inoculation. In Exp. 2, OVEX decreased (P < 0.001) and progesterone treatment increased (P < 0.001) progesterone concentrations, and OVEX decreased (P < 0.01) estradiol-17beta. Gilts with ovarian and/or exogenous progesterone developed infections. Daily percentages of neutrophils and lymphocytes changed in response to OVEX, and neutrophils changed (P < 0.05) in response to endogenous and exogenous progesterone. Lymphocyte proliferation in response to Con A and LPS increased (P < 0.05) with OVEX and decreased (P < 0.05) with progesterone treatment. We conclude that endogenous and exogenous progesterone reduce the ability of the uterus in gilts to resist infections. 相似文献
998.
999.
1000.