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   402篇
  免费   0篇
  国内免费   2篇
林业   5篇
农学   51篇
  12篇
综合类   3篇
农作物   1篇
水产渔业   35篇
畜牧兽医   282篇
植物保护   15篇
  2013年   2篇
  2012年   5篇
  2011年   8篇
  2010年   17篇
  2009年   19篇
  2008年   12篇
  2007年   10篇
  2006年   12篇
  2005年   4篇
  2004年   2篇
  2002年   3篇
  1999年   2篇
  1998年   12篇
  1997年   16篇
  1996年   18篇
  1995年   22篇
  1994年   20篇
  1993年   23篇
  1992年   23篇
  1991年   16篇
  1990年   24篇
  1989年   6篇
  1988年   5篇
  1987年   19篇
  1986年   9篇
  1985年   9篇
  1984年   8篇
  1983年   7篇
  1982年   9篇
  1981年   2篇
  1980年   4篇
  1979年   4篇
  1978年   9篇
  1977年   6篇
  1976年   11篇
  1975年   3篇
  1974年   2篇
  1973年   2篇
  1972年   2篇
  1971年   5篇
  1970年   1篇
  1969年   1篇
  1968年   2篇
  1966年   1篇
  1965年   1篇
  1961年   1篇
  1960年   1篇
  1959年   1篇
  1954年   1篇
  1948年   1篇
排序方式: 共有404条查询结果,搜索用时 15 毫秒
31.
Comminuted first phalanx fractures were diagnosed in 30 horses. One leg was involved in each horse. Five horses were presented with open fractures. Nine horses had a portion of intact cortex (strut) extending from the proximal to distal joint. Ten horses were euthanized, including one with an open fracture, without treatment. The remaining 20 horses were treated by open reduction with a neutralization plate (8 horses, including one with an open fracture), open reduction with lag screw fixation (3 horses), lag screw fixation through stab incisions (2 horses), external coaptation with a cast (3 horses), and external skeletal fixation using a weight supporting shoe (4 horses, including 3 with open fractures).
Thirteen horses were euthanized following treatment because of persistent infection (9), chronic lameness (2), and third metacarpal bone fractures (2). Seven horses survived longer than 1 year after treatment. Six were lame and used as breeding animals, and one horse went on to race successfully. All four horses with open fractures that were treated were subsequently euthanized.
Significantly more horses with an intact strut of bone survived after treatment (4 of 7 [57%]) when compared to horses without an intact strut of bone that were treated (3 of 13 [23%]) (p < 0.05).
Invasive surgical approaches used for the repair of comminuted first phalanx fractures in this study were associated with an unacceptable infection rate (55%). Techniques involving less trauma to the compromised soft tissue around the fracture should afford a better chance for a successful outcome.  相似文献   
32.
Congenital lobar emphysema is described in two dogs. The condition was characterized by progressive dyspnoea and cyanosis from a very young age. There was marked expiratory effort, and wheezing and crackling were evident on auscultation. Radiographic examination revealed overdistension and emphysema of the right middle lobe with displacement of the heart and mediastinum to the opposite side. The pathology and possible treatments are discussed.  相似文献   
33.
Traditional univariate shift-share studies of employment provide an unreliable indicator of the relative performance of a region or an industry for they fail to separate the effects of output and productivity change on the demand for labor. An extended shift-share model is proposed that overcomes this weakness and permits identification of different processes of regional development. This model is used to investigate annual employment change in twenty (two-digit SIC) manufacturing industries in nine census regions of the U.S. between 1950 and 1986. The timing and depth of the exodus of manufacturing jobs from the snowbelt to the sunbelt is illustrated along with the business cycle performance of industries and regions. Productivity growth in the sunbelt is positively associated with rapid output expansion, whereas in the snowbelt it is associated with the loss of market share and economic rationalization.  相似文献   
34.
This paper discusses recent shifts in the overseas investment strategies of Japan's major multinational manufacturing companies (MNCs). Based on a survey of twenty corporations it is postulated that the move towards the globalization of these companies has taken place in three distinct but overlapping phases: (1) a linear link-up to Japan, (2) a transition stage, based upon international specialization and‘mesh’strategies, and (3) a tetra-polar strategic division of the world. The paper commences with a discussion of recent trends in MNC behavior, and then shows how overseas corporate organization has changed in the Japanese firms surveyed, especially after 1985. The implications of these changes among the major global regions is examined. The paper concludes with an assessment of whether the strategies of Japanese MNCs have converged with those. of United States or European MNCs, and to what degree they have retained their own distinctive attributes.  相似文献   
35.
36.
Experiments with 15N labelled fertilizers often show that plants given fertilizer N take up more N from the soil than plants not given N—the priming effect or ‘added nitrogen interaction’(ANI). This paper is a theoretical study of ANIs and how they can affect the interpretation of experiments with 15N labelled fertilizers. ANIs can be ‘Real’, if for example, fertilizer N increases the volume of soil explored by roots, or ‘apparent’, caused by pool substitution or by isotope displacement reactions. Pool substitution is the process by which added labelled N stands proxy for native unlabelled N that would otherwise have been removed from that pool. Microbial immobilization of N, whether driven by the decomposition of soil organic matter or by the decomposition of plant roots, can lead to pool substitution and is the dominant cause of apparent ANIs. Denitrification and plant uptake of N can also, under special circumstances, lead to pool substitution and thus give rise to apparent ANIs. Isotope displacement reactions, in which the added labelled N displaces native unlabelled N from a ‘bound’ pool, can lead to apparent ANIs but are only likely to be of significance in exceptional circumstances. The relationship between ANIs, ‘A’ values and N fertilizer uptake efficiencies are examined by means of a simple model for uptake of 15N-labelled fertilizer by a crop. A positive ‘apparent’ ANI is accompanied by an ‘A’ value that changes as fertilizer applications increase. Likewise, a positive ‘apparent’ ANI also causes fertilizer uptake efficiency to appear lower when measured by the uptake of 15N than when measured by the non-isotopic ‘difference’ method.  相似文献   
37.
The starry sky hepatic pattern is an unusual ultrasonographic appearance of equine liver characterized by numerous small, hyperechoic foci, some of which cast an acoustic shadow, distributed randomly throughout the hepatic parenchyma. Our objectives were to describe the signalment, clinical signs, clinicopathological findings, primary disease process, and ultrasonographic findings of horses with this ultrasonographic pattern, as well as determine the associated gross and histologic changes. The starry sky pattern was identified in 18 adult horses of mixed gender and breed. The horses had various clinical signs, with weight loss and anorexia reported most commonly. Liver size and parenchymal echogenicity were normal in most horses. The hyperechoic foci frequently caused acoustic shadowing. Biliary dilation was noted rarely. The ultrasonographic pattern was the result of numerous fibrosing hepatic granulomas in all horses evaluated histologically. γ‐Glutamyltransferase was the most commonly elevated hepatic enzyme, though it was increased in fewer than half the horses. Fifteen horses had an additional disease that was identified as the apparent cause of clinical signs. Three horses had primary hepatic disease while 12 had diseases of other body systems. Therefore, the starry sky ultrasonographic pattern is likely incidental in most horses and not clinically significant. Improved recognition of this pattern and further investigation of affected horses may help refine the etiology and clinical significance of the granulomas.  相似文献   
38.
Nine normal juvenile dogs were evaluated with direct jejunal contrast‐enhanced ultrasonography via midline celiotomy. Three different doses of ultrasound contrast medium (Definity®) were injected through a peripheral venous catheter. Time‐intensity curves were used to calculate baseline, time to initial rise, inflow slope, time‐to‐peak, peak intensity (PI), and outflow slope for each administered dose. PI was directly proportional to dose. Outflow slope was similar for all patients, independent of dose. The most favorable images were acquired with a dose of 0.030 ml/kg given as a rapid intravenous manual bolus. The technique and normal jejunal perfusion pattern described herein may provide useful data for evaluation of intestinal vascular, inflammatory, and neoplastic disease in the dog.  相似文献   
39.
The competitive outcomes between weedy rice from Malaysia (MWR), the Philippines (PWR), and Vietnam (VWR) and cultivated rice (IR64) grown in pots were evaluated in a replacement series experiment with added N (0, 50, 100, and 150 kg N ha?1) and competition with IR64 plants (no competition, eight weedy rice plants : 0 IR64 plants; low competition, six weedy rice plants : two IR64 plants; and high competition, two weedy rice plants : six IR64 plants). The growth observations were taken at 10 weeks after sowing. When grown in a monoculture (no competition with IR64 plants), the PWR plants had a lower shoot biomass across N rates than did the MWR and VWR plants. The leaf area and shoot biomass of weedy rice across populations significantly increased with an increase in the N application rate. Each weedy rice population and the IR64 population showed linear responses of the leaf area and shoot biomass to the N rate at all levels of competition. The weedy rice and IR64 plants, when grown without competition, had a similar rate of response in the shoot biomass to the N rate. However, when grown in competition, the response to the added N varied among the weedy rice populations. The MWR plants under competition produced a similar amount of shoot biomass to the IR64 plants per unit addition of N. In contrast, the PWR and VWR populations under competition produced a greater amount of shoot biomass with each additional unit of N, compared to the IR64 population. The results illustrate that N fertilizer management might affect the outcome of weedy rice competition. This information could be incorporated into weedy rice management strategies.  相似文献   
40.
Résumé— La distribution des bactéries, autres que les staphlocoques sur la tige des poils, à la surface cutanée et dans les follicules pileux de 8 chiens est analysée. Sur la tige des poils Micrococcus spp. et les bactéries aérobies gram mégatifs sont plus nombreuses avec des numérations variant de 1,12 à 0,84 log10 (colonies formant unites par cm2). Des nombres hautement significatifs (p < 0,05) sont également trouvés. A la surface cutanée Micrococcus spp. des bactéries aérobies gram négatifs et Clostridium sp. sont les plus nombreuses avec des numérations respectives variant de 0,62, 1,12 et 0,84 log10 (colonies formant unités par cm2). Des nombres hautement significatifs (p < 0,05) de Micrococcus spp. sont trouvés de façon plus importante à l'intérieur des follicules pileux qu' à la surface cutanée, les Streptocoques et Bacillus sp. ont été trouvés respectivement sur cinq et quatre chiens. Proteus sp., Pseudomonas sp. Nocardia sp. sont occasion-nellement trouvés. [HARVEY, R.G., LLOYD, D.H. The distribution of bacteria (other than Staphylococci and Propionibacterium acnes) on the hair, at the skin surface and within the hair follicles of dogs (Distribution des bactéries autres que Staphylococci et Propionibacterium acnes) sur le poil, à la surface de al peau et dans les follicules pileux). Resumen— Presentamos la localizatión de bacterias noestafilocócicas en el pelo, en la superficie cutánea y dentro del foliculo piloso de ocho perros. En los pelos, Micrococcus spp. abundantes, con contajes medios entre 1.12 a 0.84 Log10 (unidades formadoras de colonias +1) cm-1, respectivamente. Se encontró a nivel proximal un número significativamente mayor (p < 0.05) de bacterias aeróbicas gram-negativas y Bacillus spp. En la superficie cutánea, Micrococcus spp., las bacterias aeróbicas contajes medios de 0.62, 1.12 y 0.84 Log10 (unidades formadoras de colonias +1) cm“2, respectivamente. Se aisló un número significativamente mayor (p < 0.05) de Micrococcus spp. dentro de los foliculos pilosos que en la superficie cutánea (p < 0.05). Se aisló Streptococi y Bacillus spp. en cinco y cuatro perros, respectivamente. Proteus spp., Pseudomonas spp. y Nocardia spp. fueron hallados ocasionalmente. [HARVEY, R.G., LLOYD, D.H. The distribution of bacteria (other than Staphylococci and Propionibacterium acnes) on the hair, at the skin surface and within the hair follicles of dogs (Localizatión de bacterias (exceptuando Staphilococci y Propionibacterium acnes) en el pelo, en la superficie cutánea y dentro de los foliculos pilosos). Abstract— The distribution of bacteria, other than staphylococci, on the hair shaft, at the skin surface and within the hair follicles of eight dogs is reported. On the hair shafts Micrococcus spp. and aerobic Gram-negative bacteria were most numerous, with mean counts ranging from 1.12 to 0.84 Log10(colony forming units + 1) cm“1 respectively. Significantly higher numbers (p < 0.05) of Gram-negative bacteria and Bacillus sp. were found proximally. At the skin surface Micrococcus spp., aerobic Gram-negative bacteria and Clostridium spp. were the most numerous with mean counts of 0.62, 1.12 and 0.84 Log10(colony forming units + 1) cm”2, respectively. Significantly higher numbers (p < 0.05) of Micrococcus spp. were found within the hair follicles than on the skin surface (p < 0.05). Streptococci and Bacillus spp. were found on five and four dogs, respectively. Proteus spp., Pseudomonas spp. and Nocardia spp. were occasionally found.  相似文献   
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