全文获取类型
收费全文 | 498篇 |
免费 | 42篇 |
国内免费 | 1篇 |
专业分类
林业 | 8篇 |
农学 | 2篇 |
基础科学 | 5篇 |
16篇 | |
综合类 | 127篇 |
农作物 | 27篇 |
水产渔业 | 14篇 |
畜牧兽医 | 309篇 |
园艺 | 7篇 |
植物保护 | 26篇 |
出版年
2019年 | 5篇 |
2017年 | 7篇 |
2016年 | 16篇 |
2015年 | 7篇 |
2014年 | 13篇 |
2013年 | 17篇 |
2012年 | 12篇 |
2011年 | 16篇 |
2010年 | 6篇 |
2009年 | 8篇 |
2008年 | 20篇 |
2007年 | 15篇 |
2006年 | 18篇 |
2005年 | 12篇 |
2004年 | 10篇 |
2003年 | 12篇 |
2002年 | 6篇 |
2001年 | 8篇 |
2000年 | 11篇 |
1999年 | 7篇 |
1998年 | 10篇 |
1997年 | 8篇 |
1995年 | 8篇 |
1993年 | 7篇 |
1992年 | 13篇 |
1991年 | 10篇 |
1990年 | 12篇 |
1989年 | 6篇 |
1988年 | 8篇 |
1987年 | 6篇 |
1986年 | 12篇 |
1985年 | 12篇 |
1984年 | 8篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1979年 | 10篇 |
1978年 | 6篇 |
1976年 | 4篇 |
1974年 | 9篇 |
1973年 | 11篇 |
1972年 | 10篇 |
1971年 | 6篇 |
1970年 | 8篇 |
1969年 | 5篇 |
1967年 | 9篇 |
1966年 | 5篇 |
1963年 | 6篇 |
1960年 | 4篇 |
1939年 | 4篇 |
排序方式: 共有541条查询结果,搜索用时 15 毫秒
81.
Cows in a 250-cow Holstein-Friesian herd were allocated at random to be treated with either a homoeopathic nosode or a negative control, both treatments being applied by means of an aerosol spray to the vulval mucous membranes. A total of six treatments were given over a period of three days and milk samples were taken for the determination of somatic cell counts (SCC) on days -3, 3, 7, 9, 14, 21 and 28. Individuals applying the treatments or carrying out the SCC determination were unaware of which animals were receiving which treatment. Owing to the wide natural variations in SCC, the trial had only a 71 per cent possibility of detecting a 30 per cent difference in SCC between the two groups. There were no significant differences between the SCC of the two groups on any sample day, but there were significant variations between the SCC on different days (P=0.003) in both groups. 相似文献
82.
83.
84.
85.
Kuiken T Holmes EC McCauley J Rimmelzwaan GF Williams CS Grenfell BT 《Science (New York, N.Y.)》2006,312(5772):394-397
Most emerging infectious diseases in humans originate from animal reservoirs; to contain and eradicate these diseases we need to understand how and why some pathogens become capable of crossing host species barriers. Influenza virus illustrates the interaction of factors that limit the transmission and subsequent establishment of an infection in a novel host species. Influenza species barriers can be categorized into virus-host interactions occurring within individuals and host-host interactions, either within or between species, that affect transmission between individuals. Viral evolution can help surmount species barriers, principally by affecting virus-host interactions; however, evolving the capability for sustained transmission in a new host species represents a major adaptive challenge because the number of mutations required is often large. 相似文献
86.
Mumby PJ Dahlgren CP Harborne AR Kappel CV Micheli F Brumbaugh DR Holmes KE Mendes JM Broad K Sanchirico JN Buch K Box S Stoffle RW Gill AB 《Science (New York, N.Y.)》2006,311(5757):98-101
Since the mass mortality of the urchin Diadema antillarum in 1983, parrotfishes have become the dominant grazer on Caribbean reefs. The grazing capacity of these fishes could be impaired if marine reserves achieve their long-term goal of restoring large consumers, several of which prey on parrotfishes. Here we compare the negative impacts of enhanced predation with the positive impacts of reduced fishing mortality on parrotfishes inside reserves. Because large-bodied parrotfishes escape the risk of predation from a large piscivore (the Nassau grouper), the predation effect reduced grazing by only 4 to 8%. This impact was overwhelmed by the increase in density of large parrotfishes, resulting in a net doubling of grazing. Increased grazing caused a fourfold reduction in the cover of macroalgae, which, because they are the principal competitors of corals, highlights the potential importance of reserves for coral reef resilience. 相似文献
87.
Holmes MA Townsend HG Kohler AK Hussey S Breathnach C Barnett C Holland R Lunn DP 《Veterinary immunology and immunopathology》2006,111(1-2):67-80
Horses are commonly vaccinated to protect against pathogens which are responsible for diseases which are endemic within the general horse population, such as equine influenza virus (EIV) and equine herpesvirus-1 (EHV-1), and against a variety of diseases which are less common but which lead to greater morbidity and mortality, such as eastern equine encephalomyelitis virus (EEE) and tetanus. This study consisted of two trials which investigated the antigenicity of commercially available vaccines licensed in the USA to protect against EIV, EHV-1 respiratory disease, EHV-1 abortion, EEE and tetanus in horses. Trial I was conducted to compare serological responses to vaccines produced by three manufacturers against EIV, EHV-1 (respiratory disease), EEE, and tetanus given as multivalent preparations or as multiple vaccine courses. Trial II compared vaccines from two manufacturers licensed to protect against EHV-1 abortion, and measured EHV-1-specific interferon-gamma (IFN-gamma) mRNA production in addition to serological evidence of antigenicity. In Trial I significant differences were found between the antigenicity of different commercial vaccines that should be considered in product selection. It was difficult to identify vaccines that generate significant immune responses to respiratory viruses. The most dramatic differences in vaccine performance occurred in the case of the tetanus antigen. In Trial II both vaccines generated significant antibody responses and showed evidence of EHV-1-specific IFN-gamma mRNA responses. Overall there were wide variations in vaccine response, and the vaccines with the best responses were not produced by a single manufacturer. Differences in vaccine performance may have resulted from differences in antigen load and adjuvant formulation. 相似文献
88.
Trajectory shifts in the Arctic and subarctic freshwater cycle 总被引:1,自引:0,他引:1
Peterson BJ McClelland J Curry R Holmes RM Walsh JE Aagaard K 《Science (New York, N.Y.)》2006,313(5790):1061-1066
Manifold changes in the freshwater cycle of high-latitude lands and oceans have been reported in the past few years. A synthesis of these changes in freshwater sources and in ocean freshwater storage illustrates the complementary and synoptic temporal pattern and magnitude of these changes over the past 50 years. Increasing river discharge anomalies and excess net precipitation on the ocean contributed approximately 20,000 cubic kilometers of fresh water to the Arctic and high-latitude North Atlantic oceans from lows in the 1960s to highs in the 1990s. Sea ice attrition provided another approximately 15,000 cubic kilometers, and glacial melt added approximately 2000 cubic kilometers. The sum of anomalous inputs from these freshwater sources matched the amount and rate at which fresh water accumulated in the North Atlantic during much of the period from 1965 through 1995. The changes in freshwater inputs and ocean storage occurred in conjunction with the amplifying North Atlantic Oscillation and rising air temperatures. Fresh water may now be accumulating in the Arctic Ocean and will likely be exported southward if and when the North Atlantic Oscillation enters into a new high phase. 相似文献
89.
Florfenicol pharmacokinetics in healthy adult alpacas after subcutaneous and intramuscular injection
Holmes K Bedenice D Papich MG 《Journal of veterinary pharmacology and therapeutics》2012,35(4):382-388
Holmes, K., Bedenice, D., Papich, M. G. Florfenicol pharmacokinetics in healthy adult alpacas after subcutaneous and intramuscular injection. J. vet. Pharmacol. Therap. 35 , 382–388. A single dose of florfenicol (Nuflor®) was administered to eight healthy adult alpacas at 20 mg/kg intramuscular (i.m.) and 40 mg/kg subcutaneous (s.c.) using a randomized, cross‐over design, and 28‐day washout period. Subsequently, 40 mg/kg florfenicol was injected s.c. every other day for 10 doses to evaluate long‐term effects. Maximum plasma florfenicol concentrations (Cmax, measured via high‐performance liquid chromatography) were achieved rapidly, leading to a higher Cmax of 4.31 ± 3.03 μg/mL following administration of 20 mg/kg i.m. than 40 mg/kg s.c. (Cmax: 1.95 ± 0.94 μg/mL). Multiple s.c. dosing at 48 h intervals achieved a Cmax of 4.48 ± 1.28 μg/mL at steady state. The area under the curve and terminal elimination half‐lives were 51.83 ± 11.72 μg/mL·h and 17.59 ± 11.69 h after single 20 mg/kg i.m. dose, as well as 99.78 ± 23.58 μg/mL·h and 99.67 ± 59.89 h following 40 mg/kg injection of florfenicol s.c., respectively. Florfenicol decreased the following hematological parameters after repeated administration between weeks 0 and 3: total protein (6.38 vs. 5.61 g/dL, P < 0.0001), globulin (2.76 vs. 2.16 g/dL, P < 0.0003), albumin (3.61 vs. 3.48 g/dL, P = 0.0038), white blood cell count (11.89 vs. 9.66 × 103/μL, P < 0.044), and hematocrit (27.25 vs. 24.88%, P < 0.0349). Significant clinical illness was observed in one alpaca. The lowest effective dose of florfenicol should thus be used in alpacas and limited to treatment of highly susceptible pathogens. 相似文献
90.