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   150篇
  免费   0篇
林业   12篇
农学   1篇
  24篇
综合类   19篇
农作物   2篇
水产渔业   3篇
畜牧兽医   84篇
植物保护   5篇
  2021年   2篇
  2020年   1篇
  2019年   1篇
  2018年   1篇
  2014年   1篇
  2013年   5篇
  2012年   3篇
  2011年   4篇
  2010年   3篇
  2009年   1篇
  2008年   4篇
  2007年   11篇
  2006年   5篇
  2005年   7篇
  2004年   9篇
  2003年   8篇
  2002年   7篇
  2001年   11篇
  2000年   8篇
  1999年   1篇
  1998年   3篇
  1996年   3篇
  1995年   2篇
  1994年   2篇
  1993年   2篇
  1992年   1篇
  1991年   3篇
  1990年   3篇
  1989年   3篇
  1988年   2篇
  1987年   1篇
  1986年   3篇
  1985年   2篇
  1984年   5篇
  1983年   4篇
  1982年   1篇
  1981年   1篇
  1979年   1篇
  1978年   2篇
  1977年   1篇
  1974年   3篇
  1973年   3篇
  1969年   1篇
  1967年   1篇
  1966年   2篇
  1965年   1篇
  1937年   1篇
排序方式: 共有150条查询结果,搜索用时 0 毫秒
101.
Techniques were devised for real-time ultrasound examination of the coffin joint, navicular bursa, navicular bone and deep digital flexor tendon of the forelimb of the horse, including their anatomical relationships and associated fluid spaces. Correlation was made between the echogram, positive contrast arthrograms, and freeze dried gross specimens. Anatomical structures were imaged in a midsagittal plane, of a standing, clinically normal horse.  相似文献   
102.
Two experiments were conducted to determine if exposure of prepubertal heifers to supplemental lighting hastens the onset of puberty. In Exp. 1, 16 heifers were paired according to birth date (April 21 to July 4) and assigned randomly to exposure to either 18 h light/d (L) or natural photoperiods (N) from 22 wk of age until puberty. Twenty-two heifers in Exp. 2, born between February 27 and March 31 and between May 3 and May 17, 1981, were exposed to L or N from 24 wk of age until March 23, 1982. In Exp. 2, animals were bred at all estrous periods until conception. Age at first ovulation and first estrus were less (P less than .01 for Exp. 1 and P less than .10 for Exp. 2) for L than N heifers. Average ages at first estrus were 318 (L) and 367 d (N) for Exp. 1 and 367 (L) and 394 d (N) for Exp. 2. Age at conception in Exp. 2 was similar for L (380 d) and N (396 d) groups. There were no significant differences between L and N heifers in changes in body weight for either experiment. There was a photoperiod X age interaction (P less than .06) for ovarian volume in Exp. 1 because the rate of ovarian growth was greater for L than N heifers. Concentrations of LH were not affected by photoperiod in Exp. 1 and not measured in Exp. 2. There were no significant changes in LH concentrations between 22 and 34 wk of age. When expressed relative to first ovulation, LH levels were highest at 7 and 2 wk before first ovulation. Concentrations of prolactin in Exp. 1 were not significantly affected by photoperiod. It was concluded that supplemental lighting after 22 or 24 wk of age reduced ages at first ovulation and first estrus in heifers born from February to July. These effects of photoperiod were accompanied by changes in ovarian development.  相似文献   
103.
A mammary gland tumour (MGT) was clinically diagnosed in 136 dogs. Histologically 71% were malignant and 29% benign. Intrathoracic metastatic disease was noted or suspected radiographically in 13.5% of the dogs with malignant and in 2.5% of the dogs with benign MGT. Six dogs with malignant MGT were necropsied, 5 had pulmonary metastases but only 1 had radiographic signs of intrathoracic metastatic disease. We conclude that radiographs are not very sensitive for detection of early intrathoracic metastatic disease of MGT.  相似文献   
104.
The risk management at the Federal Veterinary Office (FVO) is responsible for the arrangement and initiation of actions to minimize or prevent risks in the fields of animal health and food safety of animal products. In absence of a scientific basis, the risk management may initiate a formal risk assessment according to a standardised protocol. The risk assessment is conducted by an assigned team of risk analysts, according to scientific criteria, international standards and methods. The "Basic principles for risk analysis at the Swiss Federal Veterinary Office" describe the principles and the procedure of a risk analysis (risk management, risk communication and risk assessment), furthermore the interactions of concerned divisions at the FVO are laid down. Experience at the FVO confirms, that risk analyses may be performed efficiently, if the following decisive conditions are met. The responsibilities of all parties involved are defined, the risk profile and the precise question are amicably phrased, necessary resources are provided, well-trained risk analysts with experience in project management coordinate the risk assessment and interdisciplinary expertise is available.  相似文献   
105.
A special form of keratitis in the cat is described on the basis of 8 clinical cases. The disease has been known in the United States and the United Kingdom for some time, however, it has, to our knowledge, never been described in Switzerland. This keratitis is characterized by chronicity and infiltration of the cornea by mast cells and eosinophils. It is usually an unilateral and painless condition. We describe the clinical features and diagnostic examinations of the disease. Cytology of a corneal scraping is usually diagnostic. As in the cases described in the literature the cats were successfully treated with oral megestrol acetate. The aetiology of the disease is unknown.  相似文献   
106.
A 13-year-old Siamese cat was presented for investigation of lethargy and progressive abdominal enlargement. Serum chemistry revealed severe reduction of total and ionised serum calcium. The omentum appeared hyperechoic with scattered hypoechoic foci on abdominal ultrasound examination. Elevated serum parathormone and low fractional excretion of calcium excluded a parathyroid disorder and renal loss of the electrolyte. During laparotomy the omentum appeared opaque, white and firm. Post-mortem examination revealed that the thoracic and subcutaneous fat was also affected. Histopathology confirmed the diagnosis of pansteatitis with diffuse calcium soaps formation. While, severe hypocalcaemia is occasionally seen in cats, the association with pansteatitis has not been reported previously. In man, a cause-and-effect relationship between calcium soaps and hypocalcaemia is recognised, though the association is rare.  相似文献   
107.
108.
The amounts of earthworm surface casts were monitored for 200 days after commencement of casting in three alley cropping experiments of different ages and hedgerow species. Casts were collected twice per week in transects from under the hedgerow to the middle of the interrow space. Average annual cumulative amounts of casts were higher in alley cropping systems with one to five years of cropping than in the no-tree control. After five years of cropping, amounts of casts were similar in all treatments. Within the alley cropping systems, casting activity was highest immediately under the hedgerows and decreased towards the middle of the interrow space. In systems using Leucaena leucocephala as hedgerow species, the hedgerow to interrow space gradient of casting activity became more pronounced with increasing length of cropping. Casting activity in the interrow space was reduced by 12%, 55%, 80% and 86% in the first, fourth, sixth and seventh year of cropping, respectively, compared to the casting activity under the hedgerows. Senna siamea, which produced a more recalcitrant mulch, did not show such a strong decline in casting in the interrow space. In a Dactyladenia barteri system, the difference in casting between interrow space and hedgerows was insignificant. With perpendicular distance from the hedge, largest gradients in casting activity occurred close to the hedgerows with up to −4.00 Mg ha−1 cm−1 in L. leucocephala but only −1.23 and −0.76 Mg ha−1 cm−1 in S. siamea and D. barteri, respectively. The shading effect of trees and a relatively low level of soil disturbance is apparently more beneficial for earthworms in a cropped system than a high supply of readily available food from fast decomposing L. leucocephala prunings. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   
109.
Plantain grown after forest slash-and-burn raises concerns due to the release of CO2 and the destruction of biodiversity. Plantain yields are presented after forest biomass was burned or retained in combination with sucker sanitation versus traditional planting. Biomass burning did not affect plant crop and total yield. Soil chemical properties were weakly positively affected by burning. Sucker sanitation increased total yield at one site from 6.2 to 9.7 Mg ha?1 (p = 0.015), without effects on root health. In the second site, sucker sanitation had no effect on fresh bunch yield (mean 8.59 Mg ha?1), yet significantly improved root health parameters. Thus, at the first site, sucker sanitation elicited a positive response via a mechanism different from nematode control. At the second site, by contrast, nematode control was not the most important factor in yield formation. These data do not support the notion that retaining biomass increases plantain production. Other factors related to labor requirements and later weed infestation are probably more important in farmers' decision making on biomass management.  相似文献   
110.
The impact on arthropod populations of toxaphene (camphechlor) used as a herbicide was compared with cultivation and pre-emergence herbicide usage for control of sicklepod, Cassia obtusifolia L., in soybean. Soybean yields and weed control were also evaluated. Pest resurgence due to toxaphene was found to be limited, but significantly more soybean plants had main stems girdled due to the threecornered alfalfa hopper, Spissistilus festinus (Say), than those plants where toxaphene had not been applied. Both toxaphene usage and cultivation reduced early season predator abundance significantly compared with soybean where weeds were not controlled. However, the greater abundance of predators in soybeans with weeds appeared to be attributable to the increase in habitat diversity provided by the weeds and soybeans and not to a reduction in predator numbers caused by toxaphene in the treated plots. Neither soybean yields, nor the degree of sicklepod control, differed significantly between toxaphene usage and cultivation. Permethrin usage significantly reduced both pest and predator abundance in soybean.  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