全文获取类型
收费全文 | 2218篇 |
免费 | 123篇 |
国内免费 | 2篇 |
专业分类
林业 | 86篇 |
农学 | 31篇 |
基础科学 | 22篇 |
289篇 | |
综合类 | 705篇 |
农作物 | 51篇 |
水产渔业 | 122篇 |
畜牧兽医 | 827篇 |
园艺 | 42篇 |
植物保护 | 168篇 |
出版年
2021年 | 17篇 |
2020年 | 36篇 |
2019年 | 28篇 |
2018年 | 29篇 |
2017年 | 30篇 |
2016年 | 32篇 |
2015年 | 32篇 |
2014年 | 35篇 |
2013年 | 92篇 |
2012年 | 99篇 |
2011年 | 137篇 |
2010年 | 87篇 |
2009年 | 50篇 |
2008年 | 152篇 |
2007年 | 147篇 |
2006年 | 144篇 |
2005年 | 124篇 |
2004年 | 116篇 |
2003年 | 114篇 |
2002年 | 150篇 |
2001年 | 44篇 |
2000年 | 42篇 |
1999年 | 27篇 |
1998年 | 26篇 |
1997年 | 18篇 |
1996年 | 22篇 |
1995年 | 22篇 |
1994年 | 29篇 |
1993年 | 29篇 |
1992年 | 29篇 |
1991年 | 22篇 |
1990年 | 14篇 |
1989年 | 23篇 |
1988年 | 13篇 |
1987年 | 16篇 |
1986年 | 12篇 |
1985年 | 11篇 |
1984年 | 13篇 |
1983年 | 16篇 |
1982年 | 12篇 |
1981年 | 8篇 |
1979年 | 17篇 |
1978年 | 12篇 |
1977年 | 10篇 |
1974年 | 14篇 |
1972年 | 11篇 |
1970年 | 9篇 |
1969年 | 11篇 |
1968年 | 11篇 |
1966年 | 8篇 |
排序方式: 共有2343条查询结果,搜索用时 15 毫秒
71.
Mellor DJ Stafford KJ Todd SE Lowe TE Gregory NG Bruce RA Ward RN 《Australian veterinary journal》2002,80(4):228-233
AIM: To compare the changes in plasma concentrations of noradrenaline, adrenaline and cortisol in lambs after ring castration plus tailing and in calves after dehorning with or without prior local anaesthesia. METHODS: Male lambs were castrated and tailed with rings and calves were dehorned by amputation using a scoop with or without prior local anaesthesia. Blood samples were taken before and after treatment and plasma concentrations of noradrenaline, adrenaline and cortisol were determined. RESULTS: Castration plus tailing of lambs resulted in a rapid increase in noradrenaline concentrations, a lack of an adrenaline response and a marked increase in cortisol concentration. There were similar changes in catecholamine concentrations in calves that were dehorned both with and without local anaesthetic, with adrenaline being elevated within 5 min of treatment and noradrenaline exhibiting a more protracted response. Dehorning caused a marked cortisol increase which was reduced to control concentrations by local anaesthesia for as long as the associated nerve blockade lasted. CONCLUSIONS: The very short-lived adrenaline responses in calves were attributed to dehorning-induced nociceptor input leading to sympathetic stimulation of the adrenal medulla. The longer lasting noradrenaline responses in lambs and calves were thought be due to 'wash-out' of noradrenaline from damaged tissue associated with rings and amputation wounds, respectively. 相似文献
72.
73.
ABSTRACT Phaeocryptopus gaeumannii is a widespread foliar parasite of Douglas-fir. Although normally innocuous, the fungus also causes the defoliating disease Swiss needle cast in heavily infected needles. The extent of P. gaeumannii colonization in Douglas-fir foliage was estimated with real-time quantitative polymerase chain reaction (PCR) using TaqMan chemistry. In order to derive a normalized expression of colonization, both pathogen and host DNA were simultaneously amplified but individually detected by species-specific primers and TaqMan probes labeled with different fluorescent dyes. Detection of host DNA additionally provided an endogenous reference that served as both an internal positive control and adjusted for variation introduced by sample-to-sample differences in DNA extraction and PCR efficiencies. The genes employed for designing the TaqMan probes and primers were beta-tubulin for the pathogen and a LEAFY/FLORICAULA-like gene involved in floral development for the tree host. Both probe/primer sets exhibited high precision and reproducibility over a linear range of 4 orders of magnitude. This eliminated the need to analyze samples in multiple dilutions when comparing lightly with heavily infected needles. Quantification of the fungus within needles was successful as early as 1 month after initial infection. Real-time PCR is the only method currently available to quantify P. gaeumannii colonization early in the first year of the colonization process. 相似文献
74.
Mendoza-Reyes A Judkins MB Ackerman CJ Balok CC Holcombe DW Bruce LB 《Journal of animal science》2000,78(3):735-741
Twelve ruminally cannulated steers (Angus x Holstein; average initial BW = 533 +/- 3.28 kg) were randomly allotted to one of three treatments (four steers/treatment) to evaluate the use of pretanned leather shavings as a component of a protein supplement for steers grazing dormant intermediate wheatgrass (Thinopyrum intermedium Host). Steers were allotted to one of three treatments: 1) no supplement (control); 2) supplementation intraruminally at 0700 with soybean meal at .2% of BW (as-fed basis); 3) supplementation intraruminally with soybean meal and pretanned leather shavings (17:8 ratio, respectively) at .16% of BW (as-fed basis). Supplements were formulated so that intakes were isonitrogenous and were placed intraruminally once daily (0700). Sampling periods were conducted February 3 to 16 and February 17 to March 5, 1995. In situ organic matter disappearance of the soybean meal supplement was greater (P > .05) than that of the leather shavings supplement at all incubation times (1, 3, 6, 9, 12, 24, and 48 h). Data suggested that pretanned leather shavings within the leather shavings supplement were only 25% degradable within the rumen. Forage OM intake (control = 12.7, soybean meal = 12.7, and leather shavings = 13.4 g/kg of BW), grazing time, and grazing efficiency were not altered (P > .10) by supplementation or type of supplement provided but did increase between the February and March samplings. Total intake was increased (P = .09) with supplementation and reflected the addition of the protein supplements. Particulate and fluid passage estimates were unaffected (P > .10) by the supplements; however, gastrointestinal fill increased (P = .01) between the February and March samplings. Ruminal pH was lower (P = .04) and ruminal NH3 N concentration was greater (P = .02) for supplemented steers than for control steers, and supplementation treatments did not differ (P > .10). Total VFA concentrations were increased (P = .01) by supplementation but were not affected by type of supplement provided (P > .10). Ruminal molar proportions of acetate and propionate and the ratio of these two VFA did not differ (P > .10) between supplementation types. Nonetheless, supplementation increased molar proportions of butyrate (P = .04), valerate (P = .02), and isovalerate (P = .05), and leather shavings supplementation increased (P = .10) isobutyrate proportions over those in steers supplemented with soybean meal. Combining pretanned leather shavings with soybean meal seemed to have no deleterious effects on forage intake, digesta passage, grazing behavior, or ruminal fermentation and seemed to provide effects similar to those of soybean meal alone. 相似文献
75.
Todd SE Mellor DJ Stafford KJ Gregory NG Bruce RA Ward RN 《Research in veterinary science》2000,68(2):125-134
The effects of food withdrawal for 30 hours and transport for up to 12 hours on 5- to 10-day-old calves were determined by monitoring plasma concentrations of glucose, beta-hydroxybutyrate, urea, lactate and creatine phosphokinase. In addition gamma-glutamyl transferase activity, packed cell volume, total plasma protein concentration, bodyweight and rectal temperature were recorded. Food withdrawal for 30 hours caused hypoglycemia but calves maintained normothermia and although their beta-hydroxybutyrate level increased indicating lipid mobilisation, the changes in blood urea level were minimal indicating low amino acid catabolism. When calves were transported for 12 hours in addition to having food withdrawn for 30 hours, they remained normoglycemic for six hours longer than non-transported calves, probably due to an effect of muscular activity during bracing against truck movements. Stocking calves at a lower density during transport apparently had a beneficial effect, as calves were able to lie down throughout the journey and therefore produced a similar metabolic profile to resting, non-transported animals. Transport and food withdrawal had no obvious effects on calf hydration. The results of this study suggest that food withdrawal for up to 30 hours and transport for up to 12 hours had no detrimental effects on the metabolism of healthy and clinically normal calves. With correct feeding regimes and transport protocols, welfare compromise in young, healthy calves being transported for up to 12 hours can be minimised when they are slaughtered within 30 hours of the start of transport. 相似文献
76.
Mark Sklansky Gregg Levine Dielle Havlis Nicole West Michael Renner Curtis Rimmerman Rae Stone 《Journal of zoo and wildlife medicine》2006,37(4):454-463
Safe and effective echocardiography would represent a valuable tool for marine mammal veterinarians and physiologists evaluating the dolphin heart. Unfortunately, conventional ultrasound technology (transthoracic echocardiography) has been limited by logistic, anatomic, and behavioral challenges. Five mature male Atlantic bottlenose dolphins (Tursiops truncatus) were trained for echocardiographic imaging (four for both transthoracic and transesophageal imaging, and one for only transthoracic imaging). It was noted that transesophageal image quality transiently improved when the dolphins spontaneously exhaled. Subsequently, dolphins were conditioned to hold their breath following forced exhalation, and imaging proceeded during such behavioral breath holds. Over 25 transthoracic and 100 transesophageal echocardiographic studies were performed, including both two-dimensional imaging and color flow mapping. Transthoracic imaging yielded poor-quality images of only small portions of the heart. In contrast, transesophageal imaging, which improved dramatically with behavioral breath holding following exhalation, yielded consistently high-quality images of the entire heart (mitral, tricuspid, aortic, and pulmonary valves, atrial and ventricular septa, left and right atria, left and right ventricles, and ascending aorta and main pulmonary artery). Color flow mapping demonstrated mild tricuspid regurgitation in all dolphins, and mild aortic regurgitation in one dolphin found to have a pedunculated mass arising from the sinutubular junction just above the aortic valve. There were no complications in nonsedated dolphins. The heart of the bottlenose dolphin can be safely, effectively, and reproducibly evaluated with the use of transesophageal echocardiography in conjunction with behavioral breath holding following forced exhalation. This approach, and the normative echocardiographic data generated from this work, lays the foundation for future echocardiographic studies of cetaceans. 相似文献
77.
78.
Bruce K Wobeser Beverly A Kidney Barbara E Powers Stephen J Withrow Monique N Mayer Maria T Spinato Andrew L Allen 《Journal of veterinary diagnostic investigation》2007,19(4):439-443
Agreement among pathologists interpreting histologic specimens is an area of interest within human pathology, but little work in this area has been reported in the veterinary literature. Agreement among pathologists evaluating routine histologic sections of amputated digits from cats and dogs submitted to multiple diagnostic centers was examined. Histologic sections from surgical specimens were reviewed in a blinded fashion by two pathologists, and a comparison to the original diagnosis, as stated in the diagnostic report, was recorded. A total of 513 cases were reviewed, and complete agreement was reached in 409 (79.7%). Of the 104 instances of disagreement, 77 (74.0%) were considered to be of clinical significance. The diagnosis of keratoacanthoma was disagreed with in 19 of 21 diagnoses (90.4%). No other individual diagnosis was similarly disputed. The overall level of disagreement is large and is similar to that reported in human pathology and suggests that further study of this issue would be useful in veterinary pathology. 相似文献
79.
John M Sykes Michael M Garner Leah L Greer Nancy P Lung Rob L Coke Frank Ridgley Mitch Bush Richard J Montali Ben Okimoto Robert Schmidt Jack L Allen Bruce A Rideout Patricia A Pesavento Edward C Ramsay 《Journal of zoo and wildlife medicine》2007,38(2):300-308
Oral eosinophilic granulomas were diagnosed in 16 tigers (Panthera tigris). All lesions were located on the hard or soft palate and typically consisted of flat or slightly raised circular ulcers. Histologic features of these lesions were essentially identical to those seen in oral eosinophilic granulomas of domestic cats and dogs. No clinical signs were noted in eight cases, though various degrees of inappetence, excessive salivation, and dysphagia were noted in the other eight tigers. Six cases were not treated. Treatment for the remaining 10 cases centered on corticosteroids and additional treatments included surgical removal, cryotherapy, antibiotics, and chlorpheniramine. Treatment with corticosteroids did appear to be effective in some cases, though lesions would worsen after cessation of therapy and no cases were cured. In addition, three cases developed complications possibly related to this corticosteroid therapy. The etiology of these lesions remains unknown, though an underlying allergic condition is likely. 相似文献
80.
A.Bruce Webster 《中国家禽》2007,29(19):48-49
当发生禽流感时,对规定范围内家禽必须进行扑杀清群.目前使用比较普遍的清群方法有:颈椎脱臼、水基泡沫、投毒、气体致死等.…… 相似文献