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   981篇
  免费   76篇
  国内免费   1篇
林业   82篇
农学   39篇
基础科学   15篇
  197篇
综合类   76篇
农作物   58篇
水产渔业   134篇
畜牧兽医   362篇
园艺   18篇
植物保护   77篇
  2024年   2篇
  2023年   19篇
  2022年   17篇
  2021年   44篇
  2020年   61篇
  2019年   51篇
  2018年   51篇
  2017年   45篇
  2016年   36篇
  2015年   38篇
  2014年   46篇
  2013年   53篇
  2012年   84篇
  2011年   78篇
  2010年   44篇
  2009年   40篇
  2008年   38篇
  2007年   50篇
  2006年   28篇
  2005年   24篇
  2004年   26篇
  2003年   27篇
  2002年   24篇
  2001年   11篇
  2000年   10篇
  1999年   16篇
  1998年   4篇
  1997年   4篇
  1996年   6篇
  1995年   3篇
  1994年   2篇
  1993年   5篇
  1992年   9篇
  1991年   7篇
  1990年   3篇
  1989年   4篇
  1988年   7篇
  1987年   3篇
  1986年   4篇
  1985年   2篇
  1984年   3篇
  1983年   2篇
  1979年   3篇
  1978年   2篇
  1973年   2篇
  1972年   2篇
  1970年   4篇
  1965年   3篇
  1963年   2篇
  1954年   1篇
排序方式: 共有1058条查询结果,搜索用时 15 毫秒
991.
Milkofix (M), a health friendly preservative substance, to be used for milk sample preservation (Trzicky, 1990), was compared with other preservatives. Untreated milk samples (N) were tested against samples treated with sodium azide (A; 0.0085 g NaN3 and 0.0630 g NaCl), bronopol (B; 0.0100 g bronopol and 0.090 g NaCl), potassium dichromate (C; 0.0330 g K2Cr2O7 and 0.0670 g KCl) and Milkofix (M; 0.1250 g). The doses of the preservatives A, B, C and M are per 25 ml milk. The somatic cell counts (SB) were determined on a FOSSOMATIC 90 apparatus (FOSS ELECTRIC, DENMARK). In the treated milk samples taken from individual cows the values of SB counts were significantly higher than in N samples if determined within eight hours after sampling (Tab. I): in A higher by 18.6%, B by 26.3%, C by 26.4% and M by 24.3% (P less than 0.05). The significantly higher values of SB counts were recorded in bulk milk samples treated with preservatives in comparison with N samples immediately after sampling: in A by 6.0%, in B, C and M by 12.9% (P less than 0.01; Tab. II). After one-day storage of N samples at a temperature of 4 degrees C these differences are insignificant (P greater than 0.05), thus the results of N, A, B, C and M samples obtained after one-day storage at 4 degrees C can be taken as actual and mutually comparable.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
992.
Outbreaks of mastitis in a sheep flock and a goat herd caused by Pseudomonas aeruginosa, and their control are described.The morbidity rates of mastitis in a sheep flock and in a goat herd were 18.7 and 18.2 per cent, respectively. The lethality and involuntary culling rates of the animals with sub-clinical mastitis correspond to the morbidity rate.The highest morbidity rates were noted in yearlings--22.5 and 30 per cent, as well as in animals pre- and post partum (7 and 20 per cent, in sheep and goats, respectively). The morbidity periods in the flock and in the herd were 20 and 27 months, respectively. A strict-hygiene milking programme and maintenance of the milking devices was introduced. In addition, prevention of crowding, provision of dry bedding and thorough cleaning of water troughs have also been instituted. Ruthless culling of all infected and carrier animals was an essential part of the control program against Pseudomonas aeruginosa mastitis.  相似文献   
993.
This study describes an outbreak of ulcerative posthitis that eventually affected 76 of 80 of rams in a flock of Rasa Aragonesa sheep on a legume-rich diet. Lesions were confined to the prepuce and varied from mild hyperaemia to ulcerations. Corynebacterium renale was isolated from the lesions. Treatment of an initial group of 17 was based on a change of diet and topical treatment with Veterin Banedif with prednisolone once a day for 15 days and was successful. Lesions in this group were completely resolved after 15 days. The relationship between a legume-rich diet, ruminal alkalosis, elevated urine pH and posthitis is discussed.  相似文献   
994.
Forty vineyards from four wine making regions of Spain were sampled at three different growth stages in 2002 and 2003. The aim was to study the fungi associated with grapes and their ability to produce ochratoxin A (OTA) on synthetic media. Among the total mycoflora, 464 (7.7%) and 648 (10.8%) Aspergillus section Nigri (black aspergilli) strains were isolated in 2002 and 2003, respectively, and were classified into three groups: isolates with uniseriate heads, A. niger aggregate and A. carbonarius. The latter presented the highest percentage of OTA-positive strains (82% in 2002 and 76% in 2003) and produced the highest levels of toxin (2.5–25 μg g−1). The sampling year, sampling date, the region and their interactions presented significant differences in the number of black aspergilli isolated. Most black aspergilli were found in 2003 and at harvest. A positive correlation between the number of black aspergilli found in grapes and the temperature in the field was found. Grapes from 2003, the warmest year, and from Costers del Segre, the warmest region, were significantly the most contaminated. No significant correlation between black aspergilli presence and other meteorological factors such as relative humidity or rainfall could be established. Musts from all the vineyards were also analysed in both years, although no OTA was found in either year.  相似文献   
995.
1. The effects of whole grains of wheat on the digestive tract of broiler chickens was studied. A complete pelleted feed was compared with free choice feeding of whole wheat and a pelleted protein concentrate, given from 7 to 29 d of age. 2. Pepsin activity in proventriculus tissue was lower in whole wheat-fed birds than in complete diet-fed birds. The weight (g/kg body weight) of the gizzard was higher in whole wheat-fed birds and its contents had a lower pH. 3. In the intestine, there were no differences in deoxyribonucleic acid (DNA) concentration, protein/DNA, ribonucleic acid (RNA)/DNA, RNA/protein ratios or alkaline phosphatase activity expressed per tissue weight. The weight (g/kg body weight) of the duodenum was lower in whole wheat-fed birds and its contents had a higher pH. Also the activities of alkaline phosphatase and leucine aminopeptidase in the duodenum, and maltase in the ileum, expressed per unit of bird weight, were lower in whole wheat-fed birds. 4. These results suggest that whole grain feeding increases the chemical (pepsin in proventriculus) and physical (gizzard muscle) functionality of the upper part of the digestive tract but decreases the digestive capacity of the intestine. Higher gizzard functionality may play a positive role in the control of bacterial populations. The lower digestive enzyme activities in the intestine may be detrimental in situations of mucosal deterioration caused by intestinal disease.  相似文献   
996.
997.
The objective of this study was to determine the prevalence and importance of porcine cysticercosis in rural areas of Zambia. The study involved an abattoir survey of 1316 pigs at a slaughter slab in Lusaka and two field surveys in villages in Southern and Eastern provinces. Lingual examination of live pigs and visual inspection of their carcass as well as blood sampling for measuring circulating parasite antigen by enzyme-linked immunosorbent assay (Ag-ELISA) were used as parameters to measure infection. In the field surveys, a questionnaire was administered to every household whose pigs were examined to obtain information on pig husbandry practices and to study risk factors for the infection. Out of the 1316 pigs examined at the slaughter slab, 143 (10.9%) and 271 (20.6%) were positive by lingual examination and meat inspection, respectively. Most of the pigs were very heavily infected with predominantly live cysts. The field surveys revealed that eight (8.2%) out of 98 pigs from Southern province and eight (5.2%) out of 151 pigs from Eastern province were positive for cysticercosis by tongue palpation. Using the Ag-ELISA 20 (20.8%) and 14 (9.3%) pigs were positive in Southern and Eastern provinces, respectively. The questionnaire survey revealed poor pig husbandry practices, absence of meat inspection and control, poor knowledge of the disease and poor sanitation in the surveyed villages. The prevalence of pig cysticercosis found in this study ranks among the highest in the southern African region, in Africa and in the world. The current study suggests the presence of human tapeworm carriers and a high risk of human cysticercosis in the surveyed areas as well as in urban centres where pigs from rural areas are increasingly sold, slaughtered and consumed.  相似文献   
998.
Ovine meat production in France, which is continually regressing due to economic difficulties, is based on two main production systems. The first system is located in plains in which one part of the lambs born in the spring are fed grass, and the other part of the lambs are from out of the season parturitions following hormonal treatments and are fattened in sheep houses. The second system is represented by farms in the mountains using hardy breeds which have a natural faculty for out of the season breeding and whose lambs are fattened indoors, whatever the season of birth. Amongst the sanitary problems encountered, parasitism in particular of young animals, is crucial, especially for farms on plains practising grass fattening. These farmers systematically use conventional anthelmintic treatments, in particular against Moniezia and Strongyles. With organic farming, the limited number of conventional anthelmintic treatments is a strong constraint, especially for the management of young grass-fed animals. A study of 10 organic farming farms or farms converting to organic farming (six in the mountains and four in the plains) showed that the size of these farms is inferior to that of conventional ones and have technical performances which are comparable to the average with 20 to 30% extra over-prices on lamb sales. Despite this, the gross margins per ewe in organic farming are equal to the average of those for conventional farms. This is due to the high consumption of concentrate at a high cost (50 to 100% greater than that for conventional farms). Finally, to prevent sanitary risks, certain organic farmers use important amounts of feed supplements containing phytotherapy products whose costs burden a part of the financial results of the farm. On the contrary, other organic farmers are able, by adapting breeding and grazing managements, to significantly decrease animal health costs without increasing feed supplements nor decreasing zootechnical performances.  相似文献   
999.
1000.
A big epidemic of classical swine fever (CSF) occurred in the European Community in 1997. The first case was reported at the beginning of January 1997 from Germany. The disease presumably spread to the Netherlands, and from there to Italy, Spain and eventually to Belgium. About 30 isolates from these outbreaks were analysed by comparison of the nucleotide sequence data generated from fragments of both the E2 glycoprotein gene (190 nucleotides) and from the 5'-nontranslated region (5'-NTR; 150 nucleotides). By combining epidemiological data with genetic typing, it was found that the outbreaks were related and caused by a virus belonging to the genetic subgroup 2.1. As this type of virus had been reported infrequently in Europe and not at all since 1993, we postulate that it was newly introduced into the European Union (EU).  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