首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   241篇
  免费   7篇
林业   15篇
农学   2篇
  45篇
综合类   17篇
农作物   5篇
水产渔业   17篇
畜牧兽医   138篇
园艺   3篇
植物保护   6篇
  2022年   2篇
  2021年   1篇
  2020年   2篇
  2019年   5篇
  2018年   5篇
  2017年   2篇
  2016年   3篇
  2015年   2篇
  2014年   6篇
  2013年   11篇
  2012年   9篇
  2011年   8篇
  2010年   8篇
  2009年   9篇
  2008年   11篇
  2007年   12篇
  2006年   3篇
  2005年   9篇
  2004年   11篇
  2003年   9篇
  2002年   7篇
  2001年   3篇
  2000年   10篇
  1999年   5篇
  1998年   3篇
  1997年   1篇
  1996年   2篇
  1995年   7篇
  1994年   3篇
  1993年   4篇
  1992年   3篇
  1991年   4篇
  1990年   3篇
  1989年   3篇
  1988年   5篇
  1987年   5篇
  1986年   5篇
  1985年   8篇
  1984年   7篇
  1983年   5篇
  1982年   1篇
  1981年   2篇
  1980年   6篇
  1979年   4篇
  1978年   4篇
  1977年   3篇
  1976年   4篇
  1975年   1篇
  1969年   1篇
  1966年   1篇
排序方式: 共有248条查询结果,搜索用时 15 毫秒
101.
In Denmark, organic feeding is typically based on homegrown feed with a high proportion of roughage. Which crop to grow and use as supplementary feed is investigated in this paper. In three experiments, barley (B) was compared with another type of supplementary feed: a concentrate mixture (C), grass pellets (G), or fodder beets (F). The concentrate mixture resulted in a higher (P=0.002) milk yield (25.9 vs. 23.7 kg), a tendency of a lower (P=0.07) fat content (4.08 vs. 4.25%), and a higher (P=0.006) ECM yield (25.7 vs. 24.1 kg) compared to feeding barley as supplement at the same energy level. Grass pellets resulted in a lower (P=0.01) milk fat content (3.74 vs. 4.07%), a tendency of a lower (P=0.12) protein content (3.14 vs. 3.23%), but no different milk or ECM yield compared to feeding barley as supplement at the same dry matter level. Fodder beet tended to decrease (P=0.12) the milk yield (20.7 vs. 22.0 kg), and the ECM yield (P=0.05) was lower (21.5 vs. 22.9 kg) whereas the composition of the milk was unaffected compared to the total mixed ration with barley.  相似文献   
102.
Recent plant diversity changes on Europe's mountain summits   总被引:2,自引:0,他引:2  
In mountainous regions, climate warming is expected to shift species' ranges to higher altitudes. Evidence for such shifts is still mostly from revisitations of historical sites. We present recent (2001 to 2008) changes in vascular plant species richness observed in a standardized monitoring network across Europe's major mountain ranges. Species have moved upslope on average. However, these shifts had opposite effects on the summit floras' species richness in boreal-temperate mountain regions (+3.9 species on average) and Mediterranean mountain regions (-1.4 species), probably because recent climatic trends have decreased the availability of water in the European south. Because Mediterranean mountains are particularly rich in endemic species, a continuation of these trends might shrink the European mountain flora, despite an average increase in summit species richness across the region.  相似文献   
103.
Diagnosis of Microsporum canis infection is a challenge in cats with suspected asymptomatic carriage. The aim of this study was to compare the carpet method and the toothbrush method of sample collection for dermatophyte culture. The study was conducted on apparently healthy cats in a chronically infected cattery. Sampling was performed with both a sterilized piece of carpet and a toothbrush applied to the entire body surface. Samples were inoculated on Sabouraud's media (with chloramphenicol and cycloheximide). Multiple (6) applications with the toothbrush were necessary to obtain a similar surface area of inoculation. Cultures were incubated at 27°C, then examined from day 5 to 21 for the presence and number of colonies of M. canis and other fungi. Some samples were inoculated twice (initially negative or with a low number of M.canis ). A total of 112 cultures were performed (14 duplicates) from 44 cats. On day 21, infection was detected in 23 cats (54.7%): 20 (87%) with the carpet method and 21 (91%) with the toothbrush method. None of the replicated cultures allowed the detection of new cases but three were subsequently negative. In eight cases, only one to six colonies of M. canis were obtained. Both methods used are easy to perform on cats and have a similar sensitivity of approximately 90%. The carpet method is, however, much less expensive, easier to prepare, mail, store and inoculate. The lack of growth in some duplicate cultures (initial development of one or two colonies) may explain the limits of diagnosis of infection and justify the need for multiple inoculations of agar with the toothbrush method.
Funding: Self-funded.  相似文献   
104.
Ultrastructure of the Uterotubal Junction in Preovulatory Pigs   总被引:2,自引:0,他引:2  
The ultrastructure of the surface epithelia from the uterotubal junction (UTJ), and the adjacent tubal isthmic and endometrial regions, was studied in preovulatory oestrus gilts, either unmated or inseminated 12 h before with fresh boar semen. The simple columnar epithelium of the UTJ consisted of non-ciliated (secretory) and ciliated cells. Secretory vesicles occurred in the secretory cells, especially in inseminated gilts. Lymphocytes, monocytes and macrophages were found dispersed basally among the epithelial cells. Phagocytosis of epithelial cells undergoing apoptosis was seen throughout the UTJ at oestrus, increasing after insemination. Neutrophilic granulocytes were found in the lamina propria of the uterine component of the UTJ, but only occasionally in the epithelium. After insemination, neutrophils invaded the uterine epithelium, to actively participate in intraepithelial phagocytosis or move into the lumen, engulfing spermatozoa. Neutrophils were absent from the UTJ proper and the isthmic epithelium, irrespective of the presence of spermatozoa in the lumen. Those spermatozoa in the uterine lumen that escaped phagocytosis had severely damaged plasma membranes, whereas those in the UTJ proper--concentrated towards the deep furrows of the diverticulae--mostly showed normal sperm ultrastructure.  相似文献   
105.
Chicken IgY: Utilizing the evolutionary difference   总被引:9,自引:0,他引:9  
Chicken antibodies offer advantages over traditional ones (e.g. rabbit antibodies) due to the evolutionary difference between these immunoglobulins. Chicken give better antibody response against conserved mammalian antigens, they do not react with rheumatoid factors, bacterial or mammalian Fc receptors and can reduce background reactions due to cross-reactivity of anti-IgG antibodies.  相似文献   
106.
The capacity of different vitrification media and methods was tested onto in vivo and in vitro produced bovine morula/blastocysts and their ultrastructure and survival studied post-thawing. Two vitrification solutions were finally selected, named 40 ES (40% ethylene glycol in PBS containing 0.5 M sucrose) and 35 EFS (composed of 35% (v/v) ethylene glycol in PBS containing 0.5 M/l sucrose and 30% (w/v) Ficoll 70). The straws were either precooled or not precooled in nitrogen vapour, plunged and stored in LN2 for 10–25 days, and then thawed in a 20° C waterbath. The content of the straws was rediluted in 1M sucrose solution in PBS and later cocultured with BOEC for 48 h. The overall survival rates for in vitro and in vivo embryos were 36% (12 of 33) and 20% (3 of 15) after 24 h and 21% (7 of 33) and 33% (5 of 15 ) after 48 h. The survival rates for precooled embryos were significantly higher than for not precooled (48% vs 13% after 24 h and 44% vs 4% after 48 h) when tested across vitrification media. The in vitro-produced embryos presented an ultrastructure similar to the pre-freeze state, irrespective of the vitrification media used. The in vivo developed embryos showed a rather modified post-thaw ultrastructure, with clear signs of osmotic changes at both the trophoblastic and embryonic cells. The results indicated that in vitro and in vivo developed bovine embryos can survive vitrification using ethylene glycol as a cryoprotectant.  相似文献   
107.
108.
109.
Zollinger-Ellison syndrome in three dogs   总被引:4,自引:0,他引:4  
The main clinical signs of three dogs with Zollinger-Ellison syndrome were vomiting, diarrhoea, poor appetite and weight loss. The diagnosis was confirmed by histological examination and by gastrin immunocytochemistry. Gastrin was extracted from pancreatic tumours of two dogs. Gastrin-component III predominated in one dog while gastrin-component II and gastrin-component III were demonstrated in almost equal amounts in the other dog. In one dog serum gastrin concentration was high. Postmortem examination revealed pancreatic tumours in all three dogs and metastases in the regional lymph nodes and liver in two. The pancreatic tumours contained three patterns of growth: solid, trabecular and acinar. Electron microscopy of liver metastases showed cells with secretory granules. In all three dogs there was an erosive oesophagitis and thick gastric mucosa caused mainly by glandular proliferation. Two dogs had erosions and ulcers in the duodenum, one also in the first part of the jejunum. Villous atrophy and cellular infiltration of the duodenal mucosa were found in all dogs.  相似文献   
110.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号