全文获取类型
收费全文 | 536篇 |
免费 | 28篇 |
专业分类
林业 | 42篇 |
农学 | 9篇 |
基础科学 | 1篇 |
83篇 | |
综合类 | 108篇 |
农作物 | 15篇 |
水产渔业 | 43篇 |
畜牧兽医 | 192篇 |
园艺 | 13篇 |
植物保护 | 58篇 |
出版年
2023年 | 4篇 |
2021年 | 12篇 |
2020年 | 12篇 |
2019年 | 11篇 |
2018年 | 14篇 |
2017年 | 8篇 |
2016年 | 11篇 |
2015年 | 9篇 |
2014年 | 14篇 |
2013年 | 25篇 |
2012年 | 26篇 |
2011年 | 31篇 |
2010年 | 15篇 |
2009年 | 12篇 |
2008年 | 42篇 |
2007年 | 31篇 |
2006年 | 25篇 |
2005年 | 34篇 |
2004年 | 29篇 |
2003年 | 31篇 |
2002年 | 39篇 |
2001年 | 13篇 |
2000年 | 12篇 |
1999年 | 3篇 |
1998年 | 10篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 6篇 |
1992年 | 6篇 |
1990年 | 7篇 |
1989年 | 2篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1979年 | 3篇 |
1977年 | 1篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1973年 | 2篇 |
1971年 | 3篇 |
1969年 | 2篇 |
1967年 | 4篇 |
1966年 | 2篇 |
1964年 | 1篇 |
1947年 | 1篇 |
1945年 | 1篇 |
排序方式: 共有564条查询结果,搜索用时 15 毫秒
491.
COMPUTED TOMOGRAPHIC ANATOMY AND CHARACTERISTICS OF RESPIRATORY ASPERGILLOSIS IN JUVENILE WHOOPING CRANES 下载免费PDF全文
Tobias Schwarz Cristin Kelley Marie E. Pinkerton Barry K. Hartup 《Veterinary radiology & ultrasound》2016,57(1):16-23
Respiratory diseases are a leading cause of morbidity and mortality in captivity reared, endangered whooping cranes (Grus americana). Objectives of this retrospective, case series, cross‐sectional study were to describe computed tomography (CT) respiratory anatomy in a juvenile whooping crane without respiratory disease, compare CT characteristics with gross pathologic characteristics in a group of juvenile whooping cranes with respiratory aspergillosis, and test associations between the number of CT tracheal bends and bird sex and age. A total of 10 juvenile whooping cranes (one control, nine affected) were included. Seven affected cranes had CT characteristics of unilateral extrapulmonary bronchial occlusion or wall thickening, and seven cranes had luminal occlusion of the intrapulmonary primary or secondary bronchi. Air sac membrane thickening was observed in three cranes in the cranial and caudal thoracic air sacs, and air sac diverticulum opacification was observed in four cranes. Necropsy lesions consisted of severe, subacute to chronic, focally extensive granulomatous pathology of the trachea, primary bronchi, lungs, or air sacs. No false positive CT scan results were documented. Seven instances of false negative CT scan results occurred; six of these consisted of subtle, mild air sacculitis including membrane opacification or thickening, or the presence of small plaques found at necropsy. The number of CT tracheal bends was associated with bird age but not sex. Findings supported the use of CT as a diagnostic test for avian species with respiratory disease and tracheal coiling or elongated tracheae where endoscopic evaluation is impractical. 相似文献
492.
Idiopathic Canine Laryngeal Paralysis as One Sign of a Diffuse Polyneuropathy: An Observational Study of 90 Cases (2007–2013) 下载免费PDF全文
Lauren C. Bookbinder James Flanders Paul F. Bookbinder H. Jay Harvey Jay S. Barry Jon Cheetham 《Veterinary surgery : VS》2016,45(2):254-260
Objective
To determine survival and incidence of complications in dogs with idiopathic laryngeal paralysis (ILP) and concurrent neurologic signs.Study Design
Observational study.Animals
Dogs (n = 90) with ILP.Methods
Medical records (January 2007–June 2013) of dogs with ILP were reviewed. Neurologic comorbidities, including pelvic limb neurologic abnormalities and esophageal abnormalities were identified. Using medical record information and client interviews, the relationship between these comorbidities and postoperative survival (primary outcome measure) and postoperative complications (secondary outcome measure) was identified.Results
Dogs that had surgical correction of ILP had a 2.6‐fold reduction in the hazard of death throughout the study period (HR = 2.6; 95% CI: 1.34–4.84, P = .006). Owner assessed patient quality of life (10‐point scale) increased by an average of 4.1 ± 1.4 units immediately postoperatively, and 4.9 ± 0.9 units until death or followup compared with preoperative values. Thirty‐five of 72 dogs available for followup had evidence of diffuse neurologic comorbidities. Overall complication rate for dogs with neurologic comorbidities was 74%, compared with 32% for dogs without neurologic comorbidities. Presence of any neurologic comorbidity was associated with a significantly greater odds of any complication (OR = 4.04; 95% CI: 1.25–13.90, P = .019) as well as recurring complications (OR = 8.00; 95% CI: 1.49–54.38; P = .015).Conclusion
Surgical correction of ILP was positively associated with survival, and dogs with neurologic comorbidities were at greater risk for developing postoperative complications.493.
494.
Hedged stock plants of four full-sib families [27-2 × 27-5, 27-3× 27-1, 27-2 × 27-1, and 27-6 × 27-1 (designated B, G, R, andW)] of loblolly pine (Pinus taeda L.) were fertilizeddailywith a complete nutrient solution containing N at either 10, 25, 40, 55, or 70mg·L–1. May (spring softwood), July(summersoftwood), and January (winter hardwood) terminal stem cuttings were taken fortissue analysis and rooting studies. Spring cuttings rooted in the highestpercentages (59.5%), followed by winter (40.5%), and summer (34.7%). Maximumrooting for spring (70.0%), summer (48.6%), and winter (55.6%) occurred withcuttings taken from hedges that received N at 55mg·L–1. Genetic differences among familieswere evident as families G and W rooted in greater percentages at lower appliedN rates and family B was the best rooting family at the highest applied N rate.When internal N levels were considered families G and W also rooted best at lowinternal N levels, while family B was the best rooting family at high internalNlevels. Neither total nonstructural carbohydrates (TNC) nor any of severalspecific carbohydrates were correlated with rooting and an optimal TNC : Nratiofor rooting was not found. Root counts generally increased with increases inapplied N. Root number was weakly correlated with TNC (R = 0.29, P 0.01) and several specific sugars, but was not correlated with internal N.Totalroot dry weight, total root length, and total root area responded similarly. 相似文献
495.
The Center for Agroforestry at the University of Missouri has tested numerous native legumes for potential use in agroforestry
and selected Illinois bundleflower (Desmanthus illinoensis (Michaux) MacMillan ex Robinson and Fern.) and panicled tick clover (Desmodium paniculatum (L.) DC.) for further testing. Our objective was to document the effect of arbuscular mycorrhizae (AM) (Glomus spp.) and Rhizobium on growth and nutrient concentration of these legumes. Seeds were planted in a greenhouse and inoculated with one of two
species of AM and/or one of two strains of Rhizobium. Plants were harvested after 80 d and data taken on leaf and stem dry weight, root fresh weight, stem height, nodulation,
AM colonization, and N, P, K, Ca, and Mg concentration. Inoculation with Rhizobium did not affect plant growth in Illinois bundleflower, but colonization by Glomus intraradices increased all plant growth variables except stem height. Nutrient concentration was unaffected by the presence of either
endophyte. In contrast, inoculation of panicled tick clover with Rhizobium str. 41Z10 increased leaf dry weight (32%) compared to the control and root fresh weight (41%) compared to str. 32Z3, and
colonization by G. intraradices increased leaf dry weight (35%) and stem height (26%). Both species of AM increased P and K concentration (41% and 55%, respectively)
in panicled tick clover. Our results suggest that the growth of these legumes can be improved by the use of proper AM species
and/or Rhizobium strains. However, additional research to identify the best Rhizobium and AM inoculates for these plant species is important in developing strategies for their use in agroforestry.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
496.
Alongi Daniel M. Ayukai Tenshi Brunskill Gregg J. Clough Barry F. Wolanski Eric 《Mangroves and Salt Marshes》1998,2(4):237-242
A mass balance for organic carbon in Hinchinbrook Channel was constructed to identify major sources, sinks, and the magnitude of organic matter available for export to the adjacent coastal zone. Total organic carbon input from the Herbert River and from net production of mangroves, phytoplankton, seagrasses, and benthic microalgae is 8.94 ×109M Corgyr–1 (moles organic carbon per year). Mangroves and river inputs are the largest carbon sources, accounting for 56% and 27% of the total annual input, respectively. Benthic respiration and burial in sediments are the major sinks, accounting for 46% and 41% respectively of total losses (3.09 ×109 M Corgyr–1). This mangrovedominated coastal ecosystem is net autotrophic, with 5.85×109M Corgyr–1 (65% of total Corg input) available for export to the adjacent nearshore zone. Total export of organic carbon from the region (adding carbon export from Missionary Bay mangroves on the northern end of Hinchinbrook Island) amounts to 82,800 metric tons of organic carbon per year. These results confirm earlier evidence indicating that much of the particulate sediment carbon in the adjacent coastal zone is of mangrove origin. This mass balance, although preliminary, demonstrates the importance of Hinchinbrook Channel as a source of organic matter for the Great Barrier Reef lagoon. 相似文献
497.
The flesh-footed shearwater (Puffinus carneipes) is a medium-sized seabird (ca. 700 g) that is incidentally killed during longline fishing operations. We examined the levels of bycatch in Australia’s Eastern Tuna and Billfish Fishery and developed a model to examine the impact of this fishery on the eastern Australian population of flesh-footed shearwaters, which breeds at only one site, Lord Howe Island. Observed bycatch rates for flesh-footed shearwaters were 0.378 birds/1000 hooks for night sets, and 0.945 birds/1000 hooks for day sets. The mean number of birds killed from 1998 to 2002 was estimated to be 1794-4486 birds per year, with the estimated total killed over this period ranging from 8972 to 18,490 birds. Models incorporating both density-independent and density-dependent scenarios were applied to levels of bycatch representative of that observed in the fishery. Density-independent scenarios showed that fishing mortality levels caused declines in the majority of simulated populations. In contrast, density-dependent scenarios produced populations that were more resilient to fishing mortalities. Although some modelling scenarios led to population growth, under most stochastic simulations median population halving and quasi-extinction times were less than 55 and 120 years, respectively. We conclude that the level of bycatch observed in the fishery is most likely unsustainable and threatens the survival of the Lord Howe Island population. This situation can be improved only with the development and implementation of mitigation measures that will halt or greatly reduce the level of bycatch currently observed. Improved knowledge on a range of demographic parameters for the species, combined with a clearer idea of the at-sea distribution of breeding and non-breeding shearwaters, will greatly assist in improving understanding and the management of this population. 相似文献
498.
William D. Riley Alan M. Walker Barry Bendall Mark J. Ives 《Ecology of Freshwater Fish》2011,20(4):628-635
Abstract – The movements of wild European eels (Anguilla anguilla L.) were monitored continuously over a 2‐year period in a tributary of the River Itchen, Hampshire, UK, using a passive integrated transponder (PIT) antenna system. The time of these movements was then related to a number of monitored and calculated environmental parameters. No eel movements were recorded in the winter months when mean stream temperature was below 10 °C. The numbers of movements peaked in May, when mean water temperatures and day length were increasing. The movement of eels was significantly (P < 0.001, R2 = 0.45, N = 72) correlated with the time of sunset, with the majority (72%) recorded during the hours of darkness. The results of this investigation have implications for the design/timing of surveys of yellow eel populations and their habitat associations and suggest that successfully determining the microhabitat preferences of active resident eels will require remote monitoring throughout the 24‐h period. 相似文献
499.
Nitish Kunte Erin McGraw Sydney Bell David Held Luz‐Adriana Avila 《Pest management science》2020,76(1):26-41
RNA interference is a phenomenon in which the introduction of double‐stranded RNA (dsRNA) into cells triggers the degradation of the complementary messenger RNA in a sequence‐specific manner. Suppressing expression of vital genes could lead to insect death, therefore this technology has been considered as a potential strategy for insect pest control. There are three main routes of dsRNA administration into insects: (i) injections to the hemolymph, (ii) topical, and (iii) feeding. In this review, we focus on dsRNA administration through feeding. We summarize novel strategies that have been developed to improve the efficacy of this method, such as the use of nano‐based formulations, engineered microorganisms, and transgenic plants. We also expose the hurdles that have to be overcome in order to use this technique as a reliable pest management method. © 2019 Society of Chemical Industry 相似文献
500.