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81.
VALERIE J. MOORMAN JOHN F. MARSHALL DUSTIN V. DEVINE MARK PAYTON HENRY W. JANN ROBERT BAHR 《Veterinary radiology & ultrasound》2009,50(6):577-583
Radiographic diagnosis of equine bone disease using digital radiography is prevalent in veterinary practice. However, the diagnostic quality of digital vs. conventional radiography has not been compared systematically. We hypothesized that digital radiography would be superior to film-screen radiography for detection of subtle lesions of the equine third metacarpal bone. Twenty-four third metacarpal bones were collected from horses euthanized for reasons other than orthopedic disease. Bones were dissected free of soft tissue and computed tomography was performed to ensure that no osseous abnormalities were present. Subtle osseous lesions were produced in the dorsal cortex of the third metacarpal bones, and the bones were radiographed in a soft tissue phantom using indirect digital and conventional radiography at standard exposures. Digital radiographs were printed onto film. Three Diplomates of the American College of Veterinary Radiology evaluated the radiographs for the presence or absence of a lesion. Receiver operator characteristic curves were constructed, and the area under these curves were compared to assess the ability of the digital and film-screen radiographic systems to detect lesions. The area under the ROC curves for film-screen and digital radiography were 0.87 and 0.90, respectively ( P =0.59). We concluded that the digital radiographic system was comparable to the film-screen system for detection of subtle lesions of the equine third metacarpal bone. 相似文献
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Efficiency of Tree Crowns and Stemwood Production at Different Canopy Leaf Densities 总被引:2,自引:0,他引:2
Variation in the unit leaf rate in trees, i.e. the weight ofwood increment per unit of leaf area, arises from disproportionatechanges in their rates of net photosynthesis and in the allocationof carbohydrates. Changes in unit leaf rate in response to variationsin canopy density were investigated in a thinning experimentestablished in a 36 year-old Douglas fir forest. Tree growthwas estimated from increment cores and leaf area by linear correlationwith sapwood basal area. Net assimilation and mean growth ofindividual trees expressed as basal area and volume decreasedin direct proportion to increase in canopy density from 3.6to 12.0 m2m2 of projected leaf area. These relationshipswere linear with multiple correlation coefficients (r2)0.97. Net stand increment, in contrast to unit leaf rate, culminatedas projected leaf area approached 6 m2m2 and decreasedat the higher canopy densities due to mortality. The approachdeveloped in this paper could be applicable in predicting growthin response to various silvicultural treatments. 相似文献
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85.
Bone scintigraphy is often used in horses because of its sensitivity and noninvasive nature. A 99mTc labeled radiopharmaceutical is injected at a dose of between 5.7 and 7.3GBq. Images are acquired immediately postinjection and 2-4h post. People are often in the room with the horse during the acquisition process. Objectives of this study were to (a) document the radiation exposure rates at different distances from various sites of the horse at varying times post injection and (b) study the usefulness of wearing lead aprons to reduce exposure rates to personnel. Radiation exposure rates were measured in at three distances (at skin surface and at 30 and 100 cm from the skin) from three sites (shoulder, thorax, and pelvis) in 19 horses. Exposure rates were measured with and without shielding by a 0.5-mm lead equivalent apron during both the pool and delayed phases. A 0.5mm equivalent lead apron significantly decreases radiation exposure (P<0.05) at these three distances from the three sites during both image acquisition phases. Mean dose reduction factors from the lead apron range from 3.6 to 5.7. 相似文献
86.
Reduced herbicide doses in field crops: A review 总被引:2,自引:1,他引:2
ROBERT E. BLACKSHAW JOHN T. O'DONOVAN K. NEIL HARKER GEORGE W. CLAYTON ROBERT N. STOUGAARD 《Weed Biology and Management》2006,6(1):10-17
Farmers are becoming increasingly interested in more comprehensive weed management programs that reduce weed populations over time and in the use of reduced herbicide doses that lower their production costs. Research indicates that there is good potential to reduce the number of herbicide applications and utilize lower herbicide doses within competitive cropping systems. Diverse crop rotations, competitive cultivars, higher crop seed rates, reduced row spacing, specific fertilizer placement, and cover crops have been identified as integral components of competitive cropping systems. This review paper explores the potential for successful use of reduced herbicide doses within competitive cropping systems that have a multiyear approach to weed management. The utilization of decision support systems or new methods of assessing active weed growth are discussed in light of further enhancing the successful use of reduced herbicide doses and advising farmers on when (and when not) they might be a viable option. 相似文献
87.
Invasive species often require mutualistic relationships to successfully invade new environments. Insect pollination is an example of a mutualism that is required for seed-set in the invasive species, Rosa multiflora Thunb. (Rosaceae), an obligate outcrosser. To determine the insect pollinators visiting R. multiflora flowers in Iowa, USA, we collected insects on yellow sticky traps placed on plants during the period of blooming and visually observed insects visiting the flowers. The common insect orders that were collected on the sticky traps included Coleoptera, Diptera, Hemiptera, Hymenoptera, Mecoptera, and Thysanoptera. Many of the insects found on the sticky cards were known to feed on pollen. However, we did not collect Apidae (bumble bees and honey bees) on the sticky cards. We observed Bombus spp. and Apis mellifera foraging on the flowers. Syrphid flies were the most commonly observed taxa visiting the flowers. Our results indicate that R. multiflora is utilizing common generalist insect pollinators in Iowa and that pollination is not a limiting factor for this invasive species. 相似文献
88.
Rosa multiflora Thunb. (Rosaceae) is an invasive species in the USA, where it grows in pastures and wooded areas. A disease of unknown etiology, rose rosette disease (RRD), infects R. multiflora and other Rosa spp. The goal of this research was to determine the effects of habitat and disease symptoms on the abundance of Phyllocoptes fructiphilus Keifer (Acari: Eriophyidae) , the presumed vector of RRD, and other arthropods on R. multiflora . We collected branch tips from healthy R. multiflora plants growing in the sun and shade, as well as RRD-infected R. multiflora growing in the sun. The samples were collected from June 2002 to April 2004 from three sites in Iowa, USA. The samples were collected approximately every 2 weeks during the summer, monthly during the fall, and once during early spring. The fall samples were only taken from RRD-infected plants because they retain leaves throughout the winter. We found that P. fructiphilus was present on diseased and healthy R. multiflora growing in the sun and on healthy R. multiflora growing as understory plants under a tree canopy (shaded), but the greatest numbers were observed on the diseased plants growing in the sun. Several other mite species, both predatory and phytophagous, Chaetosiphon sp. aphids, and the thrips species, Frankliniella exigua Hood and Neohydatothrips variabilis Beach, occur in the same plant microhabitat as P. fructiphilus . This is the first study to document the presence of additional arthropods in the same microhabitat (branch tips) as P. fructiphilus . Future research needs to isolate and identify the causal agent of RRD so it can be confirmed that, of the many arthropods feeding on R. multiflora , only P. fructiphilus vectors RRD. 相似文献
89.
R. REID HANSON DVM Diplomate ACVS JAMES C. WRIGHT DVM PhD Diplomate ACVPM JOHN SCHUMACHER DVM MS Diplomate ACVIM Diplomate ABVP A.N. BAIRD DVM MS Diplomate ACVS JAY HUMBURG DVM MS Diplomate ABVP D.G. PUGH DVM MS Diplomate ACT Diplomate ACVN 《Veterinary surgery : VS》1998,27(6):555-560
Objective —To evaluate the seasonal influence, signalment, type of hay consumed, clinical examination findings, and outcome after surgery for horses with ileal impaction. Study Design —A retrospective study. Results —Between 1988 and 1993, 28 horses had surgical correction of ileal impaction. There was a significantly higher rate of ileal impaction during the Fall (September-November, P= .0041). Mean duration of clinical signs of abdominal pain before referral was 15 hours. Transrectal palpation was used to localize the impaction in 11 horses. The ileal impaction was reduced by extraluminal massage aided by admixing of intestinal fluid oral to the impaction or injection of fluids intraluminally and then movement of the ingesta into the cecum alone in 24 horses. A total of 26 horses recovered from surgery; 24 horses were discharged from the hospital and eventually returned to previous use. Two horses had fatal postoperative complications: jejunocec-ostomy dehiscence and development of extensive small intestine adhesions after manual reduction of the impaction. One horse initially treated by manual reduction required jejunocecostomy twice for management of recurrent ileal impaction. Follow-up information was obtained for 21 horses, of which 20 were alive 1 year or longer after surgery. A total of 27 of 28 horses were fed Coastal Bermudagrass hay as the primary type of hay consumed. A total of 9 horses continued to be fed Coastal Bermudagrass hay as the only roughage source, whereas 6 horses were fed Coastal Bermudagrass with at least 50% other hay, and in 6 horses, Coastal Bermudagrass hay was entirely eliminated from the diet. Conclusion and Clinical Relevance—Ileal impactions can be successfully reduced by celiotomy and extraluminal massage and injection techniques to soften the ingesta for passage into the cecum without enterotomy or bypass techniques in most horses. Changes in weather and feeding practices in the Fall may account for an increased risk of ileal impaction in horses in the southeastern United States at that time of year. 相似文献
90.