全文获取类型
收费全文 | 14789篇 |
免费 | 680篇 |
国内免费 | 17篇 |
专业分类
林业 | 815篇 |
农学 | 613篇 |
基础科学 | 144篇 |
2197篇 | |
综合类 | 1577篇 |
农作物 | 784篇 |
水产渔业 | 841篇 |
畜牧兽医 | 6687篇 |
园艺 | 317篇 |
植物保护 | 1511篇 |
出版年
2023年 | 77篇 |
2022年 | 112篇 |
2021年 | 192篇 |
2020年 | 227篇 |
2019年 | 254篇 |
2018年 | 253篇 |
2017年 | 248篇 |
2016年 | 283篇 |
2015年 | 222篇 |
2014年 | 312篇 |
2013年 | 830篇 |
2012年 | 698篇 |
2011年 | 904篇 |
2010年 | 488篇 |
2009年 | 468篇 |
2008年 | 875篇 |
2007年 | 817篇 |
2006年 | 779篇 |
2005年 | 803篇 |
2004年 | 724篇 |
2003年 | 725篇 |
2002年 | 667篇 |
2001年 | 325篇 |
2000年 | 302篇 |
1999年 | 294篇 |
1998年 | 137篇 |
1997年 | 128篇 |
1996年 | 122篇 |
1995年 | 151篇 |
1994年 | 124篇 |
1993年 | 118篇 |
1992年 | 161篇 |
1991年 | 170篇 |
1990年 | 195篇 |
1989年 | 153篇 |
1988年 | 141篇 |
1987年 | 119篇 |
1986年 | 115篇 |
1985年 | 121篇 |
1984年 | 115篇 |
1983年 | 90篇 |
1982年 | 62篇 |
1981年 | 66篇 |
1980年 | 78篇 |
1979年 | 74篇 |
1978年 | 61篇 |
1977年 | 60篇 |
1976年 | 57篇 |
1975年 | 62篇 |
1974年 | 56篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
van Overbeke I Chiers K Donne E Ducatelle R Haesebrouck F 《Journal of veterinary medicine. B, Infectious diseases and veterinary public health》2003,50(6):289-293
The efficacy of two bacterins containing an Actinobacillus pleuropneumoniae serotype 10 strain was evaluated. The bacterial cells constituting bacterin 1 and 2 were grown under nicotinamide adenine dinucleotide (NAD)-rich (low-adherence capacity to alveolar epithelial cell cultures) and NAD-restricted (high-adherence capacity to alveolar epithelial cell cultures) conditions, respectively. Ten pigs were vaccinated twice with the bacterin 1 and nine pigs with the bacterin 2. Ten control animals were injected twice with a saline solution. Three weeks after the second vaccination, all pigs were endobronchially inoculated with 106.5 colony-forming units (CFU) of an A. pleuropneumoniae serotype 10 strain. In the bacterin 1 and 2 group, three and two pigs died after inoculation, respectively. Only two pigs of the control group survived challenge. Surviving pigs were killed at 7 days after challenge. The percentage of pigs with severe lung lesions (> 10% of the lung affected) was 100% in the control group, 70% in the bacterin 1 group and 22% in the bacterin 2 group. Actinobacillus pleuropneumoniae was isolated from the lungs of all animals. The mean bacterial titres of the caudal lung lobes were 7.0 x 10(6) CFU/g in the control group, 6.3 x 10(5) CFU/g in the bacterin 1 group and 1.3 x 10(6) CFU/g in the bacterin 2 group. It was concluded that both bacterins induced partial protection against severe challenge. Furthermore, there are indications that the bacterin 2, containing A. pleuropneumoniae bacteria grown under conditions resulting in high in vitro adhesin, induced better protection than the bacterin 1. 相似文献
52.
Nielsen R van den Bosch JF Plambeck T Sørensen V Nielsen JP 《Veterinary microbiology》2000,71(1-2):81-87
The reference strains of the 12 serotypes of Actinobacillus pleuropneumoniae express one or two of three different RTX exotoxins designated Apx I, Apx II and Apx III. The toxins are important virulence factors. In the present study, ELISAs with purified Apx I, Apx II and Apx III, respectively, as antigen were evaluated as candidates for serological diagnosis of Actinobacillus pleuropneumoniae infection in pigs. The pigs were inoculated with biotype 1, serotypes 1-12, and biotype 2, serotype 14, respectively. A strong humoral antibody response was seen to all the three antigens in most pigs irrespective of the serotype used for inoculation. However, titers to the exotoxins secreted by the serotype used for inoculation were generally highest. The results show that toxin proteins of Actinobacillus pleuropneumoniae are antigenically related and that a correlation between serotype and secretion of exotoxin is not revealed serologically in the ELISA test. 相似文献
53.
Helen L. Orbell John S. Munday Geoffrey M. B. Orbell Craig E. Griffin 《Veterinary dermatology》2020,31(5):401-403
A 12‐year‐old spayed English pointer dog developed multiple skin lesions including pigmented viral plaques, basal cell carcinomas, squamous cell carcinomas and trichoblastomas. Canine papillomavirus type 3 was detected in multiple lesions suggesting common aetiology.
54.
John Ellis Sheryl Gow Nicholas Pilfold Stacey Lacoste Nicholas J. Lunn Evan S. Richardson David McGeachy Megan Owen Bruce Rideout 《The Canadian veterinary journal. La revue veterinaire canadienne》2021,62(7):725
Bordetella bronchiseptica is a promiscuous bacterium that infects a variety of species but has not been reported in free-ranging polar bears (Ursus maritimus). Sera from 385 polar bears from the western Hudson Bay region, 1986 to 2017, were tested for reactivity to B. bronchiseptica with enzyme-linked immunosorbent assays using anti-canine IgG and Streptococcus protein G as secondary reagents. Sera from bears had variable reactivity to B. bronchiseptica antigens, and there was no difference among bears that had a history of coming near the town of Churchill, Manitoba, and bears that did not. Although the sources of exposure were not determined, equivalent results in both groups suggest that potential exposure to humans (aside from handling during sampling) and their animals (dogs) was not an important co-factor in sero-positivity to B. bronchiseptica. 相似文献
55.
Charles Rodde Hugues de Verdal Marc Vandeputte Franois Allal Julie Nati Mathieu Besson Felipe R Blasco John A H Benzie David J McKenzie 《Journal of animal science》2021,99(6)
Feed efficiency (FE) is the amount of body weight gain for a given feed intake. Improving FE through selective breeding is key for sustainable finfish aquaculture but its evaluation at individual level is technically challenging. We therefore investigated whether individual routine metabolic rate (RMR) was a predictor of individual FE in the European sea bass Dicentrarchus labrax, a major species in European mariculture. The European sea bass has three genetically distinct populations across its geographical range, namely Atlantic (AT), West Mediterranean (WM), and East Mediterranean (EM). We compared FE and RMR of fish from these three populations at 18 or 24 °C. We held 200 fish (62 AT, 66 WM, and 72 EM) in individual aquaria and fed them from ad libitum down to fasting. FI was assessed for an ad libitum feeding rate and for a fixed restricted ration (1% of metabolic body weight·day−1, with metabolic body weight = body weight0.8). After being refed 12 wk in a common tank, individual RMR was measured over 36 h by intermittent flow respirometry. There was a significant effect of temperature whereby fish at 18 °C had greater mean FE (P < 0.05) and lower RMR (P < 0.001). There was also a significant effect of population, where AT fish had lower FE (P < 0.05) and greater RMR (P < 0.001) than WM and EM, at both temperatures. Despite these differences in temperature and population means, individual FE and RMR were not significantly correlated (P > 0.05). Therefore, although the results provide evidence of an association between metabolic rate and FE, RMR was not a predictor of individual FE, for reasons that require further investigation. 相似文献
56.
57.
Yoshimitsu Ouchi Vishwajit S. Chowdhury John F. Cockrem Takashi Bungo 《Animal Science Journal》2021,92(1):e13632
Avian uncoupling protein (av-UCP) is a key protein for thermoregulation in poultry. A single nucleotide polymorphism (SNP) in the av-UCP gene has been reported in chickens. The purpose of the current study was to clarify the association between this av-UCP gene mutation and thermoregulation in chickens. Wild and mutant type chicks for the av-UCP gene SNP (g. 1270 of the av-UCP gene exon 3 with C to T substitution and amino acid substitution) were exposed to high ambient temperature. Rectal temperature, radiation temperature on the body surface, and the expression of heat dissipation behavior (wing drooping and panting) during heat exposure were measured. In addition, oxygen consumption rate in the thermoneutral zone in wild and mutant type chicks was measured. Changes in wing temperature during heat exposure in wild-type chicks were lower than those in mutants. The latency of continuous wing drooping during heat exposure in wild-type chicks was shorter than in mutant chicks. It was also found that the SNP in the av-UCP gene caused reduced oxygen consumption. These results suggest that the av-UCP gene mutation affects thermoregulation, especially heat production, in chickens. 相似文献
58.
59.
60.
Whitfield J 《Science (New York, N.Y.)》2007,318(5852):910-911