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   359篇
  免费   27篇
  国内免费   1篇
林业   18篇
农学   3篇
基础科学   4篇
  53篇
综合类   64篇
农作物   8篇
水产渔业   20篇
畜牧兽医   204篇
园艺   1篇
植物保护   12篇
  2023年   3篇
  2021年   4篇
  2020年   8篇
  2019年   4篇
  2018年   5篇
  2017年   7篇
  2016年   8篇
  2015年   4篇
  2014年   6篇
  2013年   9篇
  2012年   23篇
  2011年   22篇
  2010年   10篇
  2009年   10篇
  2008年   10篇
  2007年   10篇
  2006年   12篇
  2005年   14篇
  2004年   8篇
  2003年   15篇
  2002年   9篇
  2001年   12篇
  2000年   10篇
  1999年   15篇
  1998年   6篇
  1997年   6篇
  1995年   3篇
  1993年   4篇
  1992年   9篇
  1991年   6篇
  1990年   12篇
  1989年   5篇
  1987年   3篇
  1986年   5篇
  1985年   6篇
  1984年   9篇
  1983年   3篇
  1982年   4篇
  1979年   3篇
  1977年   8篇
  1974年   5篇
  1972年   6篇
  1970年   3篇
  1969年   2篇
  1968年   2篇
  1967年   2篇
  1966年   3篇
  1957年   2篇
  1941年   2篇
  1938年   2篇
排序方式: 共有387条查询结果,搜索用时 15 毫秒
281.
282.
283.
The aim of the present study was to investigate the prevalence of Trichinella infection in wolves (Canis lupus) in a 17,468 km2 area in Croatia. Muscle samples were collected from 67 wolves between 1996 and 2007 and analyzed by artificial digestion. Muscle larvae were detected in 21 wolves (31%) and genotyped by multiplex PCR. Trichinella britovi was the predominant species confirmed in 90% (19 wolves) while Trichinella spiralis was detected in 9% (2 wolves). The presence of the so called “domestic” Trichinella species was a surprise since, to date, only T. britovi had been reported in wild animals in this region. The larval burdens in infected animals ranged from 0.3 to 45.9 larvae per gram. The prevalence of infected animals varied by geographic region; infected animals were found in the region of Gorski Kotar (20%) which has very similar environment to the region of Lika, where almost all wolves were found infected. Interestingly, this is the first report of infected wolves in Dalmatia.  相似文献   
284.
285.
Enteric microbial pathogens originating from agricultural practices pose a serious threat to surface water quality and human health. A two-phase study was conducted in southern Illinois that examined the ability of various riparian buffer species to attenuate fecal coliform bacteria and Escherichia coli (E. coli) in overland flow, while also assessing E. coli persistence in associated buffer soils. Plots established with giant cane (Arundinaria gigantea (Walt.) Muhl.), Kentucky Bluegrass (Poa pratensis), Orchardgrass (Dactylis glomerata L.), and non-vegetated control buffers were subjected to artificial flooding with cattle (Bos taurus) manure-laden water. Mean bacteria concentrations in overland flow exiting all plots were significantly higher than concentrations found in the source slurry. To assess E. coli persistence in plots, overland flow was collected from a simulated rainfall event 4 days following slurry application, and from natural rainfall events 22, 46, 94, 97, and 111 days after the application. Overland flow exiting all plots (including non-vegetated controls) exhibited mean E. coli concentrations significantly higher than those found in the initial slurry applied. The observed concentrations may have been the result of overland flow characteristics and high levels of ambient fecal indicator bacteria (FIB) present with plots. The moist, shaded conditions created by plot vegetation may have produced prime habitat to harbor FIB. Vegetated buffer strips (VBS) may have been effective at attenuating FIB, however, performance may have been masked by the exceptionally high ambient FIB populations that were present in adjacent soils. The young age of the VBS (<1 year) may have also influenced their seemingly poor FIB attenuation. As the VBS age, increases in above and below ground vegetative material may act to increase VBS attenuation capabilities.  相似文献   
286.
Lymphocytes from healthy lambs produced vigorous but variable responses to phytolectins when tested in whole blood culture. Differences between groups with low glutathione peroxidase (GSHPx) activities and groups supplemented with selenium were not significant. However, animals with low GSHPx activities and white muscle disease reacted feebly to mitogen. No correlation was found between levels of GSHPx activity and the numbers of leucocytes in the circulation.  相似文献   
287.
Objective: To describe an unusual site of hemorrhage in a case of anticoagulant rodenticide toxicity. Case summary: A dog treated for Brodifacoum anticoagulant rodenticide intoxication was referred for treatment of thrombocytopenia and dysuria. Sonographic examination revealed a large blood clot within the urinary bladder, extending proximally along both ureters, and a bilateral hydronephrosis. In this dog, management of the vitamin K1‐dependent coagulopathy was unusually complicated by uremia and thrombocytopenia. New information provided: This is the first reported case of hydronephrosis secondary to anticoagulant rodenticide intoxication in a dog.  相似文献   
288.
Photodynamic threshold doses in dogs with spontaneous tumors can be achieved through a mathematical model. For this to be clinically relevant, it is important to know the treatment parameters for tissue necrosis. The threshold dose for three photosensitizers (porfimer sodium, aluminum cholorophthalocyanine [AlClPc], and tin ethyl etiopurpurin [SnET2]) commonly used in veterinary chemotherapy protocols was evaluated in 12 dogs with spontaneous tumors. To derive the photodynamic threshold dose, the tissue optical properties of each compound were determined by diffuse reflectance and thus the light fluence rate. Uptake was measured by fluorimetry using tissue solubilization techniques. The threshold values calculated were highest for AlClPc (irradiated 48 hours after administration). The radius of necrosis (4.00 to 5.48 mm) and photosensitizer uptake (3.4 to 6.91 microg/g) were elevated after injection of porfimer sodium. The threshold dose model described here is photosensitizer dependent but independent of photosensitizer uptake and light dose. This study indicates that more photon absorption is needed for tumor necrosis with AlClPc than for either SnET2 or porfimer sodium.  相似文献   
289.
On December 2, 1999, 120 pregnant cows were weighed, their body condition scored, and then sorted into six groups of 20 stratified by BCS, BW, breed, and age. Groups were assigned randomly to six, 5.1-ha dormant common bermudagrass (Cynodon dactylon [L.] Pers.) pastures for 2 yr to determine the effects of supplemental Se and its source on performance and blood measurements. During the winter, each group of cows had ad libitum access to bermudagrass/dallisgrass (Paspalum dilatatum Poir.) hay plus they were allowed limited access (1 to 4 d/wk) to a 2.4-ha winter-annual paddock planted in half the pasture. Treatments were assigned randomly to pastures (two pastures per treatment), and cows had ad libitum access to one of three free-choice minerals: 1) no supplemental Se, 2) 26 mg of supplemental Se from sodium selenite/kg, and 3) 26 mg of supplemental Se from seleno-yeast/kg (designed intake = 113 g/cow daily). Data were analyzed using a mixed model; year was the random effect and treatment was the fixed effect. Selenium supplementation or its source had no effect (P > or = 0.19) on cow BW, BCS, conception rate, postpartum interval, or hay DMI. Birth date, birth weight, BW, total BW gain, mortality, and ADG of calves were not affected (P > 0.20) by Se or its source. Whole blood Se concentrations and glutathione peroxidase (GSH-Px) activity at the beginning of the trial did not differ (P > or = 0.17) between cows receiving no Se and cows supplemented with Se or between Se sources. At the beginning of the calving and breeding seasons, cows supplemented with Se had greater (P < 0.01) whole blood Se concentrations and GSH-Px activities than cows receiving no supplemental Se; cows fed selenoyeast had greater (P < or = 0.05) whole blood Se concentrations than cows fed sodium selenite, but GSH-Px did not differ (P > or = 0.60) between the two sources. At birth and on May 24 (near peak lactation), calves from cows supplemented with Se had greater (P < or = 0.06) whole blood Se concentrations than calves from cows fed no Se. At birth, calves from cows fed seleno-yeast had greater (P < or = 0.05) whole blood Se concentrations and GSH-Px activities than calves from cows fed sodium selenite. Although no differences were noted in cow and calf performance, significant increases were noted in whole blood Se concentrations and GSH-Px activities in calves at birth as a result of feeding of seleno-yeast compared to no Se or sodium selenite.  相似文献   
290.
OBJECTIVE: To determine the prevalence of feline polycstic kidney disease in Persian cats presented to the University of Melbourne Veterinary Clinic and Hospital between February and August 1999. DESIGN: A prospective clinical study using client owned animals was performed. PROCEDURE: Two hundred and fifty Persian cats, ranging in age from 13 weeks to 10 years, were presented to the University of Melbourne Veterinary Clinic and Hospital for ultrasound examination of both kidneys. The cats were placed in dorsal and lateral recumbency and alcohol and ultrasonic coupling gel were applied to the skin. The kidneys were examined ultrasonographically in longitudinal, sagittal and transverse planes. Results were recorded for each cat at the time of examination as either negative or positive for PKD. In addition 14 Exotics (short-haired Persians), 4 Ragdolls and 3 British Short-Hair cats were examined. RESULTS: Forty five percent of Persian cats examined were found to be positive for feline polycystic kidney disease on the basis of presence of anechoic cysts within the renal parenchyma. These cats ranged in age from 13 weeks to 10 years. Fifty per cent of the Exotic cats were positive for polycystic kidney disease whereas all Ragdolls and British Short Hairs were negative for the disease. Only one positive cat was reported to be showing clinical signs of renal disease. CONCLUSION: The prevalence of feline polycstic disease in Persian cats presented to the University of Melbourne between February and August 1999 was 45%. Exotic cats were found to have the slightly higher incidence of 50%.  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