全文获取类型
收费全文 | 88篇 |
免费 | 9篇 |
专业分类
林业 | 2篇 |
13篇 | |
综合类 | 7篇 |
农作物 | 3篇 |
水产渔业 | 1篇 |
畜牧兽医 | 71篇 |
出版年
2023年 | 1篇 |
2019年 | 1篇 |
2018年 | 4篇 |
2017年 | 4篇 |
2016年 | 1篇 |
2015年 | 1篇 |
2014年 | 4篇 |
2013年 | 9篇 |
2012年 | 3篇 |
2011年 | 2篇 |
2010年 | 4篇 |
2009年 | 3篇 |
2008年 | 3篇 |
2007年 | 2篇 |
2006年 | 1篇 |
2005年 | 6篇 |
2004年 | 1篇 |
2003年 | 4篇 |
2002年 | 3篇 |
2001年 | 3篇 |
2000年 | 3篇 |
1999年 | 4篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 7篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 2篇 |
排序方式: 共有97条查询结果,搜索用时 78 毫秒
81.
Archaeological surveys in woodland have always been problematicand many woodlands contain an unrecorded archaeological resource.For other types of rural landscape, aerial photographs are oftenused to map archaeological features but woodland cover has alwaysimpeded such disclosure. Remote sensing methods are rapidlyevolving and are used both within forestry and archaeologicaldisciplines for a range of applications. This paper considersthe exciting application of the remote sensing technique ofairborne Light Detection and Ranging (LiDAR) to reveal archaeologicalevidence previously hidden below a woodland canopy. Our researchshows how different types of woodland canopy and understoreyvegetation greatly influence the effectiveness of the LiDARto perform these surveys. A simple, visual vegetation mappingassessment is tested and its ability to predict the potentialof the LiDAR considered. This work highlights the importanceof vegetation awareness when considering both a new LiDAR surveyfor a woodland, and when interpreting the data. Simple estimatesof LiDAR penetration of the woodland canopy and understoreyvegetation can be used to predict the effectiveness of a LiDARsurvey in disclosing archaeological evidence and aid the interpretationof results. 相似文献
82.
During the last 30 years, 434 epiphytic lichen taxa have beenrecorded from the native pinewoods of Scotland. Of these lichens,about 219 have been recorded from the bark, lignum or stumpsof pine (Pinus sylvestris) itself. Eighteen species are, inthe British Isles, confined to these native pinewoods, whichare themselves confined to the Scottish Highlands. A resumeis presented of the habitats and niches available to lichensin the native pinewoods, using examples of the most characteristicspecies for each. The pinewood habitat for epiphyticlichens is by no means restricted to pine, but also includesassociated trees, shrubs and subshrubs, especially birch, rowan,holly, aspen, juniper and heather. The strong eastwestvariation in the composition of the lichen flora is outlined.By comparison of species lists from pinewood stands of knownancientness with those from mature plantations distant fromthe core pinewoods, an additional c. 60 speciescan be considered as indicative of an ecological continuityof the pinewood habitat. From this pool of c. 77 species, aNative Pinewood Index of Ecological Continuity is presentedas a useful tool for biodiversity assessments of pinewoods. 相似文献
83.
GH Miller JW Magee BJ Johnson ML Fogel NA Spooner MT McCulloch LK Ayliffe 《Science (New York, N.Y.)》1999,283(5399):205-208
More than 85 percent of Australian terrestrial genera with a body mass exceeding 44 kilograms became extinct in the Late Pleistocene. Although most were marsupials, the list includes the large, flightless mihirung Genyornis newtoni. More than 700 dates onGenyornis eggshells from three different climate regions document the continuous presence of Genyornis from more than 100,000 years ago until their sudden disappearance 50,000 years ago, about the same time that humans arrived in Australia. Simultaneous extinction of Genyornis at all sites during an interval of modest climate change implies that human impact, not climate, was responsible. 相似文献
84.
Two‐dimensional isoelectric focusing (IEF) × PAGE gels were used to compare the endoproteolytic (gelatinase) activities of germinated barley with those of bread and durum wheat, rye, triticale, oat, rice, buckwheat, and sorghum. Barley was used as the standard of comparison because its endoproteinase complement has been studied previously in the greatest detail. The characteristics of the grain proteases were appraised from their migration patterns and by how they were affected by pH levels. All of the germinated grains contained multiple enzyme activities and their separation patterns and pH levels were at least similar to those of barley. The proteinases of the bread and durum wheats, rye, oat, and sorghum were most similar to those of barley, whereas the other grains provided more varied patterns. The rice and buckwheat proteinases developed much more slowly than those of the other grains. The activity patterns of the triticale resembled those of the parents, wheat and rye, but the triticale contained many more activities and higher overall proteolytic activities than any of the other species. These results should be applied to scientific or commercial procedures with caution because grains contain potent endogenous proteinase inhibitors that could inactivate some of these enzymes in various tissues or germination stages. 相似文献
85.
86.
H D Blackburn J L Rocha E P Figueiredo M E Berne L S Vieira A R Cavalcante J S Rosa 《Veterinary parasitology》1992,44(3-4):183-197
Weaned wether goats (n = 144) approximately 6 months of age were placed in a 2 x 3 factorial experiment to test the effects and interaction of two levels of nutrition (growth+maintenance, NUT1; and twice growth+maintenance, NUT2) and three levels of Haemonchus contortus burden (0, 500, and 2000 larvae administered every 2 weeks; W0, W500, and W2000, respectively) on packed cell volume, red blood cell count, total serum protein and leukocytes. The statistical analysis revealed clear and proportionate differences among levels of infection for all variables. A significant (P < 0.05) nutritional effect was also found associated with all the variables except leukocytes. Nutrition by worm load interactions were found for packed cell volume and leukocytes. The neutrophil/lymphocyte ratio was higher in the NUT1-infected animals, leading to the nutrition by worm load interaction for leukocytes. An analysis for the different leukocyte types revealed significant (P < 0.05) differences among infection levels for lymphocytes, while nutrition level was found to be a significant effect for basophil count and immature white cells. Several significant correlations were observed between pairs of variables. Faecal egg output could be predicted from actual worm count in three of the four necropsy periods. The clear differences observed for blood parameters were not present in production traits, suggesting that physiological thresholds may play an important role in framing the metabolic activity of biological organisms. Total serum protein was the best indicator of these effects on production parameters. 相似文献
87.
An American Cocker Spaniel with low plasma taurine concentration (< 2 nmol/mL) was presented with dyspnoea associated with pulmonary oedema and a left ventricular shortening fraction of 9%. Emergency therapy with furosemide, dobutamine, nitroglycerine and oxygen supplementation led to a good response. Chronic therapy was started with enalapril, furosemide, digoxin and taurine. Improvement in all echocardiographic indices were noted over a 22 week follow-up, most notably an increase in left ventricular shorteningfraction to 20%, a decrease of E-point septal separation from 14 mm to 7 mm and marked left ventricular remodelling. This degree of improvement in myocardial function may represent a direct link between dilated cardiomyopathy in the American Cocker Spaniel andplasma taurine deficiency. Alternatively, this response may reflect a breed-related cardiomyopathy with a natural history and therapeutic response not commonly seen in the morecommon large breed cardiomyopathy presentations. 相似文献
88.
89.
90.