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   533篇
  免费   26篇
林业   34篇
农学   9篇
基础科学   1篇
  79篇
综合类   103篇
农作物   19篇
水产渔业   42篇
畜牧兽医   203篇
园艺   13篇
植物保护   56篇
  2023年   4篇
  2021年   12篇
  2020年   10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   27篇
  2012年   33篇
  2011年   32篇
  2010年   14篇
  2009年   14篇
  2008年   40篇
  2007年   31篇
  2006年   19篇
  2005年   32篇
  2004年   27篇
  2003年   30篇
  2002年   38篇
  2001年   12篇
  2000年   9篇
  1999年   3篇
  1998年   7篇
  1995年   6篇
  1994年   3篇
  1993年   6篇
  1992年   4篇
  1990年   8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   6篇
  1982年   4篇
  1979年   3篇
  1977年   2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
  1956年   2篇
  1947年   1篇
  1945年   1篇
排序方式: 共有559条查询结果,搜索用时 15 毫秒
201.
202.
A toy Australian shepherd dog was referred for bile peritonitis following excision of a biliary mucocele. Subsequent delayed gastric emptying was refractory to prokinetic therapy but responded to injection of botulinum toxin A into the muscularis layer of the pylorus; a novel therapy for delayed gastric emptying in dogs.  相似文献   
203.
A dog that was referred to the University of Florida Veterinary Medical Center was discovered to have a bamboo skewer within the right atrium and right ventricle, traversing the tricuspid valve. The skewer was ingested approximately four months prior to referral and was partially removed via gastrotomy. The presenting complaint at the time of referral included coagulopathy, anemia and leukocytosis. A linear, hyperechoic structure was identified in the right heart during an echocardiogram. The foreign body was suspected to be a portion of the skewer that the patient had previously ingested. Cardiopulmonary bypass was performed and the foreign body was removed successfully. Complications following surgery included the development of tricuspid valve and ventricular wall thrombi, atrial flutter and amiodarone toxicity. Many indications have been described in the veterinary literature for cardiopulmonary bypass. However, to the best of the authors' knowledge, successful removal of an intracardiac foreign body with cardiopulmonary bypass has not been reported in a veterinary patient. This represents a new indication for cardiopulmonary bypass in veterinary medicine.  相似文献   
204.
The reported effects of feeding on growth hormone (GH) secretion in ruminants have been inconsistent, and are likely influenced by energy status of animals. High-producing dairy cows in early lactation and late lactation were used to assess the effects of energy balance on temporal variation of plasma metabolites and hormones. Cows were fed a single diet once daily, and feed was withdrawn for 90 min prior to feeding. Beginning at the time of feed withdrawal, plasma samples were collected via jugular catheters hourly for 24h. Concentrations of non-esterified fatty acids and GH were measured for all samples, while insulin, glucose, and acylated (active) ghrelin were quantified for four sample times around feeding. As expected, calculated energy balance was significantly lower in early lactation than late lactation cows (-43.5 MJ retained/day versus 7.2 MJ retained/day). Following the primary meal of the day, a GH surge was observed in early lactation but not in late lactation cows. This difference was not explained by temporal patterns in non-esterified fatty acid, insulin, or glucose concentrations. However, a preprandial ghrelin surge was observed in early lactation only, suggesting that ghrelin was responsible for the prandial GH surge in this group. Results of a stepwise regression statistical analysis showed that both preprandial ghrelin concentration and energy balance were significant predictors of prandial GH increase over baseline. Adaptations to negative energy balance in lactating dairy cattle likely include enhanced ghrelin secretion and greater GH response to ghrelin.  相似文献   
205.
206.
207.
208.
Cowpea (Vigna unguiculata Walp.) is the most economically important legume crop in arid regions of sub-Saharan Africa. Cowpea is grown primarily by subsistence farmers who consume the leaves, pods and grain on farm or sell grain in local markets. Processed cowpea foods such as akara (a deep-fat fried fritter) are popular in the rapidly expanding urban areas. Demand far exceeds production due, in part, to a variety of insect pests including, in particular, the lepidopteran legume pod borer (LPB) Maruca vitrata. Genetically engineered Bt-cowpea, based on cry1Ab (Event 709) and cry2Ab transgenes, is being developed for use in sub-Saharan Africa to address losses from the LBP. Before environmental release of transgenic cowpeas, the Bt Cry proteins they express need to be assessed for potential effects on non-target organisms, particularly arthropods. Presented here is an assessment of the potential effects of those Cry proteins expressed in cowpea for control of LPB. Based on the history of safe use of Bt proteins, as well as the fauna associated with cultivated and wild cowpea in sub-Saharan Africa results indicate negligible effects on non-target organisms.  相似文献   
209.
Twenty-four red deer hinds with their calves were released on to a newly established pure red clover sward and, 2 days later, red staining of the tail, perineum and hocks was observed. This was presumed to be of urinary origin. Observation of micturition showed that when urine was passed, it was a normal straw colour but it turned scarlet-red about 1 hour after exposure to air. Midstream urine remained the normal colour when held under a pure nitrogen atmosphere immediately after micturition, but it turned red when held in air in the dark, suggesting that the colour change was due to an oxidative rather than a photosensitive reaction. All deer grazing red clover were affected but this did not occur in deer grazing ryegrass/white clover swards. No adverse effects were observed in the deer grazing the red clover, and calf growth was significantly higher than on ryegrass/white clover, suggesting that the red urine had no effect on health or productivity. Blood and urine analyses showed no signs of haemolysis, haematuria or haemoglobinuria. Preliminary chemical analyses suggest that the compounds involved are not those found in the urine of sheep grazing oestrogenic clover. The nature of the compounds have yet to be determined.  相似文献   
210.
Symptoms of spotted wilt of peanut were evaluated in a field experiment over three years (2010–2012) near Marianna, Florida. Assessment included three visual measures of disease and ImmunoStrip (a form of ELISA) testing of root crowns for the presence of Tomato spotted wilt virus (TSWV), the causal agent of spotted wilt in peanut. Foliar symptoms of spotted wilt on a 1 to 10 scale and on a disease incidence rating (DIR) were highly correlated (r = 0.88; < 0.001). Foliar symptoms were moderately correlated (0.45 < r < 0.54; < 0.001) with TSWV infection. However, symptoms on the testa were highly correlated with TSWV infection (r = 0.78; < 0.001). These results indicate that foliar symptomology is less reliable in assessing TSWV infection than testa symptomology. Regression analysis showed that foliar symptoms underestimated the proportion of plants infected by TSWV. Seed inspection may be a good predictor of plant infection and therefore useful in breeding programmes because it is much less expensive than ELISA. Resistance to TSWV infection is characteristic of some resistant peanut genotypes and a lack of testa symptomology could help to identify those genotypes.  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