全文获取类型
收费全文 | 865篇 |
免费 | 41篇 |
专业分类
林业 | 146篇 |
农学 | 64篇 |
基础科学 | 5篇 |
95篇 | |
综合类 | 116篇 |
农作物 | 16篇 |
水产渔业 | 34篇 |
畜牧兽医 | 388篇 |
园艺 | 15篇 |
植物保护 | 27篇 |
出版年
2021年 | 11篇 |
2020年 | 8篇 |
2019年 | 11篇 |
2018年 | 15篇 |
2017年 | 21篇 |
2016年 | 13篇 |
2015年 | 18篇 |
2014年 | 18篇 |
2013年 | 31篇 |
2012年 | 39篇 |
2011年 | 36篇 |
2010年 | 15篇 |
2009年 | 25篇 |
2008年 | 35篇 |
2007年 | 33篇 |
2006年 | 30篇 |
2005年 | 25篇 |
2004年 | 19篇 |
2003年 | 35篇 |
2002年 | 23篇 |
2001年 | 27篇 |
2000年 | 28篇 |
1999年 | 12篇 |
1998年 | 8篇 |
1997年 | 8篇 |
1996年 | 8篇 |
1994年 | 9篇 |
1992年 | 12篇 |
1991年 | 15篇 |
1990年 | 10篇 |
1989年 | 20篇 |
1988年 | 18篇 |
1987年 | 11篇 |
1985年 | 10篇 |
1984年 | 9篇 |
1983年 | 11篇 |
1980年 | 5篇 |
1979年 | 8篇 |
1978年 | 10篇 |
1977年 | 14篇 |
1975年 | 8篇 |
1974年 | 10篇 |
1973年 | 6篇 |
1972年 | 11篇 |
1971年 | 9篇 |
1969年 | 8篇 |
1967年 | 8篇 |
1966年 | 14篇 |
1924年 | 5篇 |
1921年 | 9篇 |
排序方式: 共有906条查询结果,搜索用时 15 毫秒
771.
1000 random serum samples of pet dogs were examined in the serum tube agglutination test for antibodies to Brucella canis. Agglutinating antibodies to Br. canis antigen were detected in 18 cases in a serum dilution of 1 : 50, in 29 cases in a serum dilution of 1 : 100, in 13 cases in a serum dilution of 1 : 200 and in a serum dilution 1 : 400. But the positive results of the agglutination tests were confirmed by complement fixation, agargel-precipitation and indirect immunofluorescence only in 2 cases (0,2%) with titers of 1 :200 and 1 :400. These serological findings indicate that in the Federal Republic of Germany Br. canis infections are rarely in pet dogs as compared with dogs (Beagles) held in research kennels. 相似文献
772.
773.
774.
Hatchery propagation techniques, such as pellet-rearing, can result in altered feeding behaviour. Walleye Sander vitreus (Mitchill) is a commonly propagated sportfish, yet little is known regarding its ability to switch to live prey post-stocking. The objectives were to evaluate temporal changes in diet composition and condition as well as evaluate the relationship between total length and presence of different prey consumed by stocked walleye fry and fingerlings. Fingerling walleye had higher average proportions of empty stomachs and benthic invertebrates but less fish that stocked walleye fry. The presence of zooplankton, benthic invertebrates or fish was not related to walleye length. Walleye condition was similar between cohorts and did not change over days post-stocking. Percent similarity index values between cohorts were variable (0.0 to 67.9%). It was concluded that stocked walleye fingerlings consume lower quality prey items than stocked fry counterparts at least up to 49-day post-stocking, which may have implications for post-stocking survival. 相似文献
775.
Despite recent insight regarding the history and current state of the Moon from satellite sensing and analyses of limited Apollo-era seismic data, deficiencies remain in our understanding of the deep lunar interior. We reanalyzed Apollo lunar seismograms using array-processing methods to search for the presence of reflected and converted seismic energy from the core. Our results suggest the presence of a solid inner and fluid outer core, overlain by a partially molten boundary layer. The relative sizes of the inner and outer core suggest that the core is ~60% liquid by volume. Based on phase diagrams of iron alloys and the presence of partial melt, the core probably contains less than 6 weight % of lighter alloying components, which is consistent with a volatile-depleted interior. 相似文献
776.
Integrated control of bovine virus diarrhoea virus, bovine herpesvirus-1, Leptospira interrogans serovar hardjo subtype hardjobovis, Mycobacterium avium subsp. paratuberculosis, and Salmonella dublin in dairy herds may provide economic benefits superior to those obtained by sequential disease control, because, among other things, it allows optimization of voluntary culling. However, in practice there are no adequate instruments to establish priorities in voluntary culling. Therefore, in this study the priorities in decision-making for voluntary culling of infected cattle, as indicated by more than 300 cattle veterinarians, were analysed. Based on our results and supplementary considerations, the priorities for voluntary culling in the Netherlands can be ranked as: 1st. cull S. dublin carriers, 2nd. cull persistently infected BVDV carriers, 3rd. cull paratuberculosis faecal culture positive cattle and their last offspring, 4th. cull, in paratuberculosis infected herds, paratuberculosis ELISA positive cattle and their last offspring and cull, in low prevalence herds, BHV1 gE-positive cattle, and 5th. cull leptospirosis seropositive cattle. Since this ranking was based on one case study only, other priorities may prevail in other herds. 相似文献
777.
778.
Scott P Terrell Deidre K Fontenot Michele A Miller Martha A Weber 《Journal of zoo and wildlife medicine》2003,34(4):380-384
An 11-yr-old female cheetah (Acinonyx jubatus) was diagnosed clinically with hepatic and renal disease and euthanatized after an extended illness. Postmortem examination revealed 8-10 L of milky white fluid in the abdominal cavity and markedly dilated lymphatic vessels within the intestinal mesentery. The abdominal fluid was a chylous effusion based on the cytologic predominance of lymphocytes and macrophages and comparison of cholesterol and triglyceride levels in the fluid and in serum. Gross and histopathologic lesions in the liver were consistent with a diagnosis of venoocclusive liver disease. Chylous ascites is uncommon with human chronic liver disease and is rarely identified in animals. 相似文献
779.
780.
Ohne Zusammenfassung 相似文献