全文获取类型
收费全文 | 1039篇 |
免费 | 40篇 |
专业分类
林业 | 240篇 |
农学 | 19篇 |
391篇 | |
综合类 | 79篇 |
农作物 | 34篇 |
水产渔业 | 32篇 |
畜牧兽医 | 250篇 |
园艺 | 7篇 |
植物保护 | 27篇 |
出版年
2021年 | 10篇 |
2020年 | 18篇 |
2019年 | 16篇 |
2018年 | 29篇 |
2017年 | 12篇 |
2016年 | 13篇 |
2015年 | 20篇 |
2014年 | 27篇 |
2013年 | 33篇 |
2012年 | 42篇 |
2011年 | 41篇 |
2010年 | 25篇 |
2009年 | 24篇 |
2008年 | 44篇 |
2007年 | 61篇 |
2006年 | 54篇 |
2005年 | 41篇 |
2004年 | 32篇 |
2003年 | 39篇 |
2002年 | 30篇 |
2001年 | 13篇 |
2000年 | 14篇 |
1998年 | 7篇 |
1996年 | 8篇 |
1995年 | 6篇 |
1994年 | 9篇 |
1992年 | 17篇 |
1991年 | 11篇 |
1990年 | 11篇 |
1989年 | 14篇 |
1988年 | 13篇 |
1987年 | 10篇 |
1986年 | 7篇 |
1985年 | 21篇 |
1984年 | 18篇 |
1982年 | 6篇 |
1978年 | 9篇 |
1977年 | 7篇 |
1976年 | 6篇 |
1943年 | 8篇 |
1942年 | 9篇 |
1936年 | 6篇 |
1935年 | 8篇 |
1933年 | 9篇 |
1928年 | 14篇 |
1926年 | 13篇 |
1919年 | 10篇 |
1911年 | 6篇 |
1896年 | 6篇 |
1895年 | 6篇 |
排序方式: 共有1079条查询结果,搜索用时 828 毫秒
131.
The objective of this study was to establish a technique for radiographic examination of the coxofemoral joint and adjacent bony structures in standing cattle. Left (or right) 30° dorsal-right (or left) ventral radiographic views of the coxofemoral joint region of standing cattle (n = 10) with hind limb lameness were evaluated retrospectively. In addition, an experimental study of oblique laterolateral views of the coxofemoral joint region of a bovine skeleton at angles of 15-45° was carried out to determine the optimal position for visualization of the hip region. In the 10 clinical patients, the bodies of the ilium and ischium, the acetabulum and proximal third of the femur could be assessed. Six of these cattle had fractures of the body of the ilium and body of the ischium, five with and one without involvement of the acetabulum, two had craniodorsal and one caudoventral luxation of the femur and one had a femoral neck fracture. The described laterodorsal-lateroventral radiographs of the hip region in standing cattle were suitable for assessing the coxofemoral joint, the proximal aspect of the femur and parts of the ischium, ilium and pubis. After testing the optimal angle on the skeleton, it was seen that distortion and superimposition were minimized by positioning the X-ray beam at an angle of 25° to the horizontal plane. It can be concluded that the described technique improves the evaluation of injuries of the coxofemoral region in cattle. With the appropriate angle, the technique can also be applied in recumbent cattle. 相似文献
132.
The involvement of the greater omentum in reconstructive, abdominal and thoracic surgery is based on its manifold qualities, which include immunological support, lymphatic drainage, angiogenesis, adhesion, haemostasis and fat storage. The purpose of this study was to determine whether the greater omentum could be extended to the head. In addition, we evaluated the surgical procedures necessary for this extension. Our study reveals that specific surgical lengthening techniques of the greater omentum, such as dorsal extension and inverted L-shape elongation, are necessary to successfully transpose the omentum to the head in cats. As the survival of the omentum after transposition procedures is still unknown, its application in chronic non-healing wounds of the head in cats warrants further investigation. 相似文献
133.
Anna A. Filatenko Karl Hammer Sulaiman Al Khanjari Andreas Buerkert 《Genetic Resources and Crop Evolution》2010,57(8):1135-1139
Due to its geographic position on the northeastern tip of the Arabian Peninsula and its sea trade relationships with Asia,
East Africa and the Middle East, Oman has for millennia been at the cross-roads of inter-regional exchange of cultivated plants.
This is reflected in recent findings of new cultivars of banana (Musa spp.) and wheat (Triticum spp.) in remote oases of the Hajar Mountains in northern Oman. Material collected in 2003 and 2004 contained six new botanical
varieties of wheat which are described here. One of them belongs to the tetraploid T. aethiopicum, the others are hexaploid. 相似文献
134.
Solomon Benor Frank R. Blattner Sebsebe Demissew Karl Hammer 《Genetic Resources and Crop Evolution》2010,57(2):293-306
Little information is available regarding the biodiversity and potential use of jute (Corchorus species) in Ethiopian agriculture. The present study summarizes species’ occurrence, use, geographical distribution, ecology,
and ethnobotany of Corchorus species in Ethiopia. An ecogeographical study, conducted in the Amhara, Oromia and Gambella Regional States in 2005 and 2008
resulted in the collection of seven different species with more than 100 accessions. The study revealed low similarity in
species composition between the Regional States, indicating that each region has its own unique set of species. Species numbers
are higher in the north-eastern and south-western than the central part of the country. C. aestuans L. and C. tridens L. are restricted to humid lowlands of south-western part of Ethiopia, growing at elevations up to 490 m, whereas, C. urticifolius Wight et Arn., C. trilocularis L. and C. schimperi Cufod. were collected only in the north-eastern part of the country with elevation ranges of 1,380–2,130 m. The only species
collected at a higher elevation (>2,100 m) was C. schimperi Cufod. Farmers’ perception, indigenous knowledge and folk taxonomy of jute species are better in Gambella than the other
studied regions. Although several Corchorus species are reported from Ethiopia, these species are neither cultivated nor popularly used as leafy vegetables. This is
mainly due to lack of awareness or knowledge about the species use, and abundant distribution of the species that allows gathering
of edible leaves with little expenditure of time, labour and other resources. Our results revealed that some species are threatened,
which necessitates highest priority for jute germplasm conservation in the country. In addition, creating public awareness
about the use of jute species as a cheap source of leafy vegetable will play an important role to diversify food sources,
reduce malnutrition, and contribute to household income generation of the farming community. 相似文献
135.
Since recent studies reveal citric acid to be favorable for estimating plant‐available P in soils, we investigated if it can also be used for assessing other nutrients. According to our results, it provides stronger correlations with the tree nutrition for Mg (beech, spruce), Ca+K (beech) and Fe (spruce) than the standard methods for determining exchangeable cations. Thus, when estimating plant‐available P by citric acid‐extraction, these cations should be additionally measured in ICP analysis. 相似文献
136.
Human-wildlife conflict in the Kingdom of Bhutan: Patterns of livestock predation by large mammalian carnivores 总被引:1,自引:0,他引:1
We examined predation activity throughout Bhutan by tiger (Panthera tigris), common leopard (Panthera pardus), snow leopard (Uncia uncia) and Himalayan black bear (Ursus thibetanus) on a variety of livestock types using data gathered over the first two years (2003-2005) of a compensation scheme for livestock losses. One thousand three hundred and seventy five kills were documented, with leopards killing significantly more livestock (70% of all kills), than tigers (19%), bears (8%) and snow leopards (2%). About 50% of livestock killing were of cattle, and about 33% were of horses, with tigers, leopards and snow leopards killing a significantly greater proportion of horses than predicted from availability. Examination of cattle kills showed that leopards killed a significantly greater proportion of smaller prey (e.g., calves), whereas tigers killed a significantly greater proportion of larger prey (e.g., bulls). Overall, livestock predation was greatest in summer and autumn which corresponded with a peak in cropping agriculture; livestock are turned out to pasture and forest during the cropping season, and subsequently, are less well guarded than at other times. Across Bhutan, high horse density and low cattle and yak density were associated with high rates of livestock attack, but no relationship was found with forest cover or human population density. Several northern districts were identified as ‘predation hotspots’, where proportions of livestock lost to predation were considerable, and the ratio of reported kills to relative abundance of livestock was high. Implications of our findings for mitigating livestock losses and for conserving large carnivores in Bhutan are discussed. 相似文献
137.
138.
Pugnose minnow (Opsopoeodus emiliae) is a small, reclusive species that is widespread in North America, but is one of the rarest fishes in Canada, found in less than 12 known localities in southwestern Ontario. In contrast to most pugnose minnow populations across the global range, Canadian populations are primarily found in turbid systems, potentially indicating persistence in suboptimal conditions. We used data from a multi-gear species and habitat survey in the Canard River, Ontario, a system dominated by agricultural inputs and the best-known capture site of the species in Canada, to parameterise multi-gear occupancy models for understanding the relationship between pugnose minnow occupancy and microhabitat features, including the role of turbidity. Almost 300 pugnose minnow were captured, representing the largest single collection of the species in Canadian history. The best occupancy model indicated that the probability of pugnose minnow occupancy was highest in the deepest sites with the lowest water clarity (i.e. high turbidity); however, competing models suggested that occupancy was highest at sites with wild celery (Vallisneria americana) and higher water clarity, signifying that habitats with low turbidity may be utilised if sufficient physical cover exists. Together, our results suggest that Canadian pugnose minnow populations occupy and potentially favour turbid conditions, possibly to avoid visual predators in clearer habitats. It remains uncertain whether this abiotic association represents a long-term, viable, local adaptation or whether persistence of pugnose minnow in the Canard River is at risk unless significant water quality improvements can be made. 相似文献
139.
Experiments were carried out to establish an infection and disease model for Clostridium perfringens in broiler chickens. Previous experiments had failed to induce disease and only a transient colonization with challenge strains had been obtained. In the present study, two series of experiments were conducted, each involving four groups of chickens with each group kept in separate isolators. A coccidial vaccine given at 10 times the prescribed dosage was used to promote the development of necrotic enteritis. In the first experiment, cultures of C. perfringens were mixed with the feed at day 9, 10, 11, and 12, and the coccidial vaccine was given at day 10, whereas in the second experiment, C. perfringens cultures were mixed with the feed at day 17, 18, 19, and 20, and the coccidial vaccine was given at day 18. Chickens were examined at day 9, 11, 12, and 15 (Experiment 1), and at day 17, 18, 20, and 24 (Experiment 2). There was no mortality in any of the groups; however, chickens in the groups receiving both coccidial vaccine and C. peifringens developed the subclinical form of necrotic enteritis, demonstrated by focal necroses in the small intestine, whereas chickens in control groups or groups receiving only coccidial vaccine or only C. perfringens cultures developed no necroses. The results underline the importance of predisposing factors in the development of necrotic enteritis. 相似文献
140.
A long-term study of apicoectomy and endodontic treatment of apically infected cheek teeth in 12 horses 总被引:2,自引:2,他引:0
The aim of this study was to evaluate the long-term results of apicoectomy and retrograde endodontic treatment in 12 horses with apical cheek teeth infections. The affected apices were removed using a diamond bur mounted on a dental drill, and after pulp removal the root canals were filed with Hedstrøm files and then alternately flushed with sodium hypochlorite, hydrogen peroxide and alcohol. The pulp canals were dried and filled with endodontic cement and gutta-percha points. An undercut was made in the apical aspect of the root canals that were then sealed with self-curing glass ionomer cement.Follow up information was obtained 38–67 months following treatment and indicated that the treatment had been successful in 7/12 horses (58%), partially successful in 2 horses (17%) and unsuccessful in 3 (25%). With good case selection, apicoectomy can preserve a proportion of apically infected cheek teeth. The use of advanced imaging techniques and improved surgical techniques could increase the success rate. 相似文献