全文获取类型
收费全文 | 731篇 |
免费 | 63篇 |
专业分类
林业 | 16篇 |
农学 | 13篇 |
基础科学 | 2篇 |
85篇 | |
综合类 | 154篇 |
农作物 | 13篇 |
水产渔业 | 58篇 |
畜牧兽医 | 392篇 |
园艺 | 12篇 |
植物保护 | 49篇 |
出版年
2023年 | 9篇 |
2021年 | 10篇 |
2020年 | 9篇 |
2019年 | 4篇 |
2018年 | 14篇 |
2017年 | 9篇 |
2016年 | 19篇 |
2015年 | 15篇 |
2014年 | 17篇 |
2013年 | 28篇 |
2012年 | 29篇 |
2011年 | 33篇 |
2010年 | 30篇 |
2009年 | 12篇 |
2008年 | 21篇 |
2007年 | 35篇 |
2006年 | 35篇 |
2005年 | 23篇 |
2004年 | 39篇 |
2003年 | 23篇 |
2002年 | 18篇 |
2001年 | 19篇 |
2000年 | 25篇 |
1999年 | 21篇 |
1998年 | 7篇 |
1997年 | 5篇 |
1996年 | 5篇 |
1995年 | 10篇 |
1994年 | 8篇 |
1992年 | 20篇 |
1991年 | 10篇 |
1990年 | 20篇 |
1989年 | 7篇 |
1988年 | 16篇 |
1987年 | 9篇 |
1986年 | 18篇 |
1985年 | 14篇 |
1984年 | 8篇 |
1983年 | 5篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1975年 | 4篇 |
1974年 | 5篇 |
1973年 | 9篇 |
1972年 | 12篇 |
1971年 | 14篇 |
1970年 | 10篇 |
1969年 | 5篇 |
1966年 | 6篇 |
1885年 | 3篇 |
排序方式: 共有794条查询结果,搜索用时 15 毫秒
51.
H. Bair‐Brake T. Bell A. Higgins N. Bailey M. Duda S. Shapiro H. E. Eves N. Marano G. Galland 《Zoonoses and public health》2014,61(2):97-104
Bushmeat, defined as meat derived from wild animals, is a potential source of zoonotic pathogens. Bushmeat from restricted animals is illegal to import into the United States under US federal regulations. We reviewed US Centers for Disease Control and Prevention (CDC) port of entry surveillance records from September 2005 through December 2010 and conducted focus group studies to describe trends in and reasons for bushmeat importation into the United States. In total, 543 confiscated bushmeat items were recorded. Half of the confiscated bushmeat items identified were rodents. Africa was the most frequent continent of origin. Seasonality was evident, with bushmeat confiscations peaking in late spring to early summer. Four times more bushmeat was confiscated during an enhanced surveillance period in June 2010 compared with the same period in previous years, suggesting that routine surveillance underestimated the amount of bushmeat detected at US Ports of Entry. Focus groups held in three major US cities revealed that bushmeat importation is a multifaceted issue. Longstanding cultural practices of hunting and eating bushmeat make it difficult for consumers to acknowledge potential health and ecologic risks. Also, US merchants selling African goods, including bushmeat, in their stores have caused confusion among importers as to whether importation is truly illegal. Enhancing routine surveillance for bushmeat and consistent enforcement of penalties at all ports of entry, along with health education aimed at bushmeat importers, might be useful to deter illegal importation. 相似文献
52.
John Gordon Bell Fiona Strachan Joanne E Good & Douglas R Tocher 《Aquaculture Research》2006,37(6):606-617
Echium oil (EO) is a vegetable oil in which percentages of stearidonic acid (STA, 18:4n‐3) often exceed those of its n‐6 series equivalent γ‐linolenic acid (GLA, 18:3n‐6). Stearidonic acid is elongated to 20:4n‐3 in fish cell cultures, suggesting that EO could be included in diets for marine fish to increase tissue 20:4n‐3 and 20:3n‐6 and, thereby, modulate eicosanoid metabolism. Thus, the present study aimed to test the hypotheses that dietary EO would increase tissue 20:4n‐3 and 20:3n‐6 and modulate immune function and eicosanoid production in juvenile Atlantic cod (Gadus morhua L.) fed a diet where fish oil (FO) was replaced by EO. Duplicate groups of juvenile cod (initial weight ca. 4 g) were fed for 18 weeks on fish meal‐based diets (55% protein and 16% lipid) that differed in oil source (FO or EO). There were no significant differences in growth and feed efficiency, hepato‐somatic index, percentages of liver and flesh lipids and lipid class compositions for cod fed FO and EO. Percentages of 18:4n‐3, 18:3n‐6 and 20:3n‐6 in the total lipids of flesh and liver were higher, and percentages of 20:5n‐3 and 20:4n‐6 were both lower in fish fed EO than in those given FO. In flesh, the increased 18:3n‐6 and 18:4n‐3 were primarily located in phosphatidylcholine and, to a lesser extent, phosphatidylethanolamine, whereas 20:3n‐6 concentration was highest in phosphatidylinositol. Desaturation of 18:3n‐3 (to tetraene products) and 20:5n‐3 to 22:6n‐3 in hepatocytes was very low but was increased by dietary EO. Echium oil significantly decreased the production of prostaglandin F from gill cells stimulated with calcium ionophore A23187, and reduced head kidney macrophage activity, but had no effect on serum lysozyme activity or basic haematology. In conclusion, dietary EO may have beneficial effects on some immune parameters including eicosanoid metabolism in marine fish although this may be primarily because of decreased 20:4n‐6 rather than increasing tissue levels of 20:3n‐6 or 20:4n‐3. 相似文献
53.
Freshly isolated rainbow trout hepatocytes were exposed to tert-butyl hydroperoxide (BuOOH), a substrate for glutathione peroxidase.
BuOOH at a concentration approximately equimolar (1 mM) with intracellular reduced glutathione (GSH) caused a reversible increase
in intracellular glutathione disulphide (GSSG) but did not compromise cell viability or damage membrane lipids. BuOOH at 10
mM caused a large irreversible increase in intracellular GSSG followed by efflux into the medium. Considerable leakage of
lactate dehydrogenase and loss of highly unsaturated fatty acids, particularly docosahexaenoic acid also occurred. Dependence
of hydroperoxide removal on flux through the hexose monophosphate pathway was suggested by the increased release of 14CO2 from [1-14C] glucose from hepatocytes incubated with BuOOH. 相似文献
54.
Urban derelict space can form a valuable complementary element to the formal green spaces of a city: wastelands are often biologically diverse and their unregulated status can provoke innovative spatial activities by a wide range of users. Using the case of an urban brownfield in Tallinn, Estonia, this paper examines how such a space is used and evaluates the magnitude of the impact of minor design interventions – so-called urban acupuncture – on the activities carried out by the users. The study used field observations and behaviour mapping to compare the spatial pattern of the users before and after small design interventions. Although there was widespread use beforehand there was both an increase in use and a different pattern afterwards, which was clearly detectable from the composite behaviour maps of both arrangements, where users follow the properties of the particular environment. The small improvements tested showed the largest effect on the female and the older user groups, raising the number of overall visits and increasing the occurrence of active behaviour almost five times. The research demonstrates that small, inexpensive and possibly temporary interventions can have a major positive effect. 相似文献
55.
T A Bell 《Aquaculture Research》1995,26(9):679-685
Aquaculture, for better or worse, depends in part on drugs for the prevention, control and eradication of a variety of diseases. The US Food and Drug Administration's Centre for Veterinary Medicine, through the Federal Food, Drug and Cosmetic Act, strictly controls the approval and use of drugs in animals, including aquatic animals. Laws and regulations exist that regulate the investigational use and approval of new animal drugs for all animals. However, in reality, these mandates must be uniquely interpreted for aquatic species. Very few drugs are approved for use in aquatic species. There is a growing effort by non-traditional sponsors (aquaculturists as opposed to pharmaceutical firms) to gain approvals for several new animal drugs. Simultaneously, the federal government, including the Centre for Veterinary Medicine, is working aggressively with the private and public aquaculture sectors to facilitate submission and subsequent approval of new animal drug applications. The drug approval procedures and requirements for aquatic animals are discussed. Special attention is given to their similarities and differences, relative to traditional terrestrial animals. 相似文献
56.
Three contagious poultry diseases in Mauritania were studied. Serum samples and tracheal swabs were taken from 80 chickens in village poultry flocks in each of three different regions. Antibodies against Newcastle disease virus (NDV) were detected in 4.8% of chickens, antibodies against Gumboro disease virus in 15.8% of chickens and antibodies against Salmonella pullorum in 6.2% of chickens. Six isolates of NDV were made, of which four formed plaques on chicken embryo fibroblast monolayers. Seropositivity was highest in the Trarza region, bordering the River Senegal, and four out of six of the NDV isolates were made from chickens in this region. 相似文献
57.
C. May S. D. Cartert† A. Barnes † S. Bell D. Bennett 《The Journal of small animal practice》1991,32(4):170-174
Lyme disease is a chronic, multisystemic, inflammatory disorder of man and animals associated with infection by the tick-borne spirochaete, Borrelia burgdorferi. Lyme disease was recently reported for the first time in a dog in the UK (May and others 1990). Using an enzyme-linked immunosorbent assay (ELISA), we have performed a serological survey to investigate the prevalence of antibodies to B burgdorferi in UK dogs. The survey has shown that dogs from many areas in the UK have serum antibodies to B burgdorferi, that the presence of serum antibodies is associated with known exposure to ticks and that some dogs seropositive for B burgdorferi have clinical signs consistent with Lyme disease. High levels of serum anti-Borrelia antibodies are not diagnostic for canine Lyme disease, but, in association with appropriate clinical signs, they help to confirm the diagnosis in suspected cases. 相似文献
58.
59.
Eckert RE Neuder LE Bell JL Trujillo JC Jones SL 《Veterinary immunology and immunopathology》2007,118(3-4):294-303
The goal of this study was to define the role for p38 mitogen-activated kinase (MAPK) in the signaling mechanism regulating pro-inflammatory cyclooxygenase (COX) gene expression in lipopolysaccharide (LPS)-activated equine leukocytes for the purposes of identifying novel targets for anti-inflammatory therapy in endotoxemic horses. The p38 MAPK has been shown to positively regulate inflammatory gene expression in human leukocytes and can be activated by a variety of stimuli including LPS, TNF-alpha, and IL-1. Activation-associated phosphorylated p38 MAPK has been implicated in the up-regulation of several inflammatory genes, including COX-2 which ultimately results in the production of prostanoids that are responsible for the pathophysiology associated with endotoxemia. Our hypothesis is that activation of p38 MAPK is essential for LPS-induced COX-2 expression in equine peripheral blood leukocytes. We tested our hypothesis by investigating the effects of the specific p38 MAPK inhibitors SB203580 and SB202190 on LPS-induced COX-2 protein expression and PGE(2) production in equine leukocytes. LPS stimulation activated p38 MAPK and increased COX-2 expression in a dose-dependent manner with maximal activation observed after 30min and 4h, respectively, at a concentration of 10 ng/ml LPS. In contrast, LPS stimulation did not affect COX-1 protein expression. Pretreatment with SB203580 or SB202190 significantly inhibited LPS-induced activation-associated p38 MAPK phosphorylation, COX-2 mRNA and protein levels, and PGE(2) production in equine leukocytes. Maximal inhibition of LPS-induced COX-2 protein expression was achieved at a concentration of 10 microM SB203580. We concluded that p38 MAPK is essential for LPS-induced COX-2 expression suggesting that p38 MAPK is a potential target for anti-inflammatory therapy during equine endotoxemia. 相似文献
60.
Norin‐PL8 (‘PL8’) is an extremely cool‐tolerant line of rice in Japan that contains genes for cool tolerance originating from a javanica landrace. It was investigated to see whether the dwarfing gene d18‐k (kotaketamanishiki dwarf) exerts its pleiotropic effect on enhancing the cool tolerance at the booting stage in the genetic background of PL8. The d18‐k isogenic line of the recurrent parent PL8 (D8), PL8, and two commercial cultivars ‘Hayayuki’ and ‘Kirara 397’ were used. For each line/cultivar, the 12°C‐5‐day treatment was conducted at various times during the booting stage. In addition to spikelet fertility, the ratio (%) of the fertilized‐spikelet number of each treated panicle to the varietal mean of fertilized‐spikelet number per panicle in the control (FS‐T/C) was adopted to estimate cool temperature damage. For FS‐T/C, the lines‐cultivars ranked in the order of D8 > PL8 > ‘Hayayuki’ > ‘Kirara 397’, reflecting their cool tolerances. D8 exceeded PL8 in both pollen grain number per anther in the control and as an indicator of pollen fertility after the treatment, as a result of the effects of d18‐k. Consequently, d18‐k can be used to develop super‐highly cool‐tolerant cultivars for cool‐weather areas. 相似文献