全文获取类型
收费全文 | 197858篇 |
免费 | 11172篇 |
国内免费 | 818篇 |
专业分类
林业 | 7942篇 |
农学 | 6655篇 |
基础科学 | 1447篇 |
24725篇 | |
综合类 | 34150篇 |
农作物 | 7957篇 |
水产渔业 | 10140篇 |
畜牧兽医 | 100980篇 |
园艺 | 2949篇 |
植物保护 | 12903篇 |
出版年
2020年 | 1774篇 |
2019年 | 2110篇 |
2018年 | 3016篇 |
2017年 | 3501篇 |
2016年 | 3142篇 |
2015年 | 2876篇 |
2014年 | 3462篇 |
2013年 | 8119篇 |
2012年 | 6200篇 |
2011年 | 7424篇 |
2010年 | 5097篇 |
2009年 | 5049篇 |
2008年 | 7196篇 |
2007年 | 6947篇 |
2006年 | 6473篇 |
2005年 | 5934篇 |
2004年 | 5619篇 |
2003年 | 5648篇 |
2002年 | 5253篇 |
2001年 | 6501篇 |
2000年 | 6273篇 |
1999年 | 5037篇 |
1998年 | 2110篇 |
1997年 | 2036篇 |
1996年 | 1840篇 |
1995年 | 2213篇 |
1994年 | 1901篇 |
1993年 | 1959篇 |
1992年 | 3933篇 |
1991年 | 4070篇 |
1990年 | 4000篇 |
1989年 | 4104篇 |
1988年 | 3649篇 |
1987年 | 3757篇 |
1986年 | 3756篇 |
1985年 | 3563篇 |
1984年 | 2868篇 |
1983年 | 2592篇 |
1982年 | 1790篇 |
1979年 | 2444篇 |
1978年 | 1962篇 |
1977年 | 1707篇 |
1976年 | 1653篇 |
1975年 | 1775篇 |
1974年 | 2113篇 |
1973年 | 2239篇 |
1972年 | 2096篇 |
1971年 | 1903篇 |
1970年 | 1930篇 |
1969年 | 1767篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
251.
252.
The detection of Mycobacterium paratuberculosis organisms in bovine faeces by isolation was compared with that by the microscopical examination of Ziehl-Neelsen stained faecal smears for the presence of clumps of acid-fast M. paratuberculosis organisms. Faeces were obtained from cattle naturally or experimentally infected with M. paratuberculosis as well as from uninfected cattle. Microscopical examination was an unreliable method for the detection of M. paratuberculosis organisms, since the organisms were only detected in 99 (=55.9%) of 177 culturally positive faecal samples. 1111 addition, clumps of acid-fast organisms indistinguishable from M. paratuberculosis were also observed iin three of 18 samples from cattle free from Johne's disease and in 18 of 37 culturally negative samples from paratuberculous cattle. When M. paratuberculosis organisms were added to faeces from an uninfected cow, results showed that isolation attempts should be positive when 15 or more M. paratuberculosis organisms per gram of faeces are present. 相似文献
253.
254.
Six shipments totaling 3452 mummies of the blackmargined aphid,Monellia caryella (Fitch), parasitized withAphelinus perpallidus Gahan, were obtained by air freight during the years 1982-1985 from Texas A&M Research Center, El Paso, Texas. About two-thirds of the mummies did not yield parasites. A colony ofA. perpallidus was established in the laboratory. Under laboratory conditions the percentage of emerged parasites was higher than that in the imported mummies, and the parasite had very limited impact on the aphid population. Field releases of the parasite were made but no establishment ofA. perpallidus was observed through the years. 相似文献
255.
256.
Norman C 《Science (New York, N.Y.)》1988,242(4884):1372-1374
257.
258.
In a balance trial with 10 pigs (mean body mass 50 kg) the influence of a bacterial protein supplement (Alcaligenes eutrophus) on N-metabolism was investigated. The bacteria were included into the diet at levels of 7 and 14% at the expense of extracted soyabean meal. Thus bacterial "pure protein" (bacterial non-nucleic acid N X X 6.25) amounted to 30 and 60% of the protein of the ration. Consuming 2 kg of feed dry matter per day the animals of the control group (I) and the experimental groups (II and III) ingested 48 g, 52 g and 55 g of total N respectively. The difference in N-intake is explained by the additional nucleic acid-N, amounting to 19,8% of total bacterial N. Daily weight gain (on average 1054 g) and feed conversion efficiency (feed ingested/weight gain; on average 1,9) were relatively improved at the highest dietary level of bacterial cell mass. Faecal N-excretion was increased significantly, whereas renal N-excretion remained unchanged. Mean apparent N-digestibility was 87,4% showing no significant difference between the experimental groups. N-balance values were noticibly increased following the intake of the bacterial protein supplement. The excretion of urinary urea-N was slightly reduced whereas 4-6 times as much allantoin-N was excreted when bacteria were fed. It is calculated that about 80% of the bacterial purines are renally excreted as allantoin and uric acid. 相似文献
259.
Guttural pouch hemorrhage associated with lesions of the maxillary artery in two horses 总被引:2,自引:2,他引:0 下载免费PDF全文
Smith KM Barber SM 《The Canadian veterinary journal. La revue veterinaire canadienne》1984,25(6):239-242
A two year old Thoroughbred gelding, presented with guttural pouch hemorrhage, had the internal and external carotid arteries ligated. Guttural pouch mycosis was detected on endoscopic examination. After one month of topical antifungal therapy, the horse was returned and euthanized because of recurrent epistaxis. A bacterial infection of the guttural pouch with associated ulceration and hemorrhage from the maxillary artery was found at necropsy.
A two year old grade gelding had ulceration and hemorrhage from the external carotid artery. Utilizing balloon-tipped catheters and arterial ligation, hemestasis was achieved in the internal carotid artery and the external carotid artery and its branches. Mycotic ulceration of the internal carotid artery was detected endoscopically and treated with local antifungal therapy for one month. Thirty-three days postoperatively the horse returned, bleeding from a lesion in the maxillary artery. The rationale for surgical intervention to prevent epistaxis associated with guttural pouch mycosis and possible etiologies for postsurgical epistaxis are discussed.
相似文献260.