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   152824篇
  免费   8598篇
  国内免费   85篇
林业   6085篇
农学   4664篇
基础科学   1054篇
  18526篇
综合类   25640篇
农作物   5709篇
水产渔业   8002篇
畜牧兽医   78859篇
园艺   1889篇
植物保护   11079篇
  2018年   2138篇
  2017年   2340篇
  2016年   2219篇
  2015年   1891篇
  2014年   2291篇
  2013年   5844篇
  2012年   4361篇
  2011年   5262篇
  2010年   3208篇
  2009年   3232篇
  2008年   5091篇
  2007年   4822篇
  2006年   4620篇
  2005年   4336篇
  2004年   4195篇
  2003年   4182篇
  2002年   4060篇
  2001年   4809篇
  2000年   4652篇
  1999年   3798篇
  1998年   1489篇
  1997年   1509篇
  1996年   1427篇
  1995年   1754篇
  1994年   1589篇
  1993年   1518篇
  1992年   3219篇
  1991年   3335篇
  1990年   3373篇
  1989年   3384篇
  1988年   3099篇
  1987年   3193篇
  1986年   3281篇
  1985年   3132篇
  1984年   2646篇
  1983年   2342篇
  1982年   1594篇
  1981年   1499篇
  1980年   1449篇
  1979年   2357篇
  1978年   1955篇
  1977年   1661篇
  1976年   1471篇
  1975年   1564篇
  1974年   2116篇
  1973年   2115篇
  1972年   2108篇
  1971年   1867篇
  1970年   1733篇
  1969年   1593篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
Tropical Animal Health and Production - A study was conducted with the objective to characterize the morphology of Socorro Island Merino sheep. A total of 67 sheep, 62 females, 26 purebred and 36...  相似文献   
972.
Abstract

Extract

Sir.—I refer to the paper by Day(1 Day, A. M. 1979. Induced termination of the calving season. N.Z. vet. J., 27: 2229. [Taylor &; Francis Online], [Web of Science ®] [Google Scholar]) on induction of parturition in a dairy herd. This report was read with a considerable degree of interest as it included results which are significantly different from those which we would have expected from extensive field experience in New Zealand and overseas.  相似文献   
973.
974.
In a field experiment, moderate to heavy natural concomitant infections with immature and mature Fasciola hepatica were treated with triclabendazole at a dose rate of 10 mg/kg and an efficiency of 99.8% was achieved. Subsequent treatments of all susceptible farm animals at the same dose rate at intervals of eight to eleven weeks were carried out for 14 months; no patent infections could be detected in sheep and cattle during the whole period. Evidence is presented that pasture contamination with liver fluke was reduced to a negligible level for a further 12 months after the final treatment. It is suggested that, if regular treatments with triclabendazole are given within the pre-patent period of Fasciola hepatica infection for the whole season, the infection can be eradicated or reduced to such a low level that control of the disease could be maintained with less frequent strategic drenching for a considerable period.  相似文献   
975.
Abstract

Extract

Madam:—I read with interest the letter Fu et al.(3 Fu, Z.F., Robinson, A.J., Dickinson, L.G. and Grimmett, J.B. 1986. Equine herpesvirus type 1 (EHV-1) infection and vaccination with an inactivated EHV-1 vaccine. N.Z. vet. J., 34: 1415. [Taylor &; Francis Online], [Web of Science ®] [Google Scholar]in which they state that “Preliminary investigations on this stud have indicated that equine herpesvirus type 1 (EHV1) and type 2 (EHV2) were frequently isolated and might be the initiators of the respiratory disease observed”. Additional evidence that links EHV2 (equine cytomegalovirus or slowly growing equine herpesvirus) to equine respiratory disease will be important. There is some evidence and a very high level of suspicion that recurrent respiratory disease, malaise and poor performance are associated with EHV2 but providing definite evidence has been elusive and tends to be confounded by the fact that EHV2 can be isolated from more than 70% of horses, in some populations at least, but unassociated with recognisable disease.  相似文献   
976.
A study was undertaken to indicate the importance of different causes of death in goats and to investigate the management factors which influence these problems. Over a 15 month period, 324 dead goats were received from 67 farms in the Horowhenua, Wairarapa, Wanganui and Wellington regions. Although a wide range of diseases was encountered in the study, the major causes of mortality could be divided into 4 groups: problems directly related to management, microbial diseases, nematode parasitism, and trace element related deficiencies and toxicities. The highest proportion of deaths related directly to management problems and included deaths from hypothermia, mismothering, premature birth, ruminal acidosis, pregnancy toxaemia, trauma, and plant and chemical toxicities. In larger flocks, microbial diseases including Pasteurella pneumonia and yersiniosis were major problems. Deaths from nematode parasitism were predominantly observed in goats 12 months of age and older. White muscle disease (selenium/vitamin E deficiency) was the major trace element deficiency causing death in goats.

The influence of factors including age of goat, flock size and management practices on the major causes of death are discussed.  相似文献   
977.
Amended insulin to glucose ratios were calculated from the concentrations of serum insulin and blood glucose measured concurrently during either a glucagon tolerance test or after feeding in healthy dogs. Values greater than 30 𝛍U/mg which are supportive of a diagnosis of insulinoma were obtained at certain times during the test period. Amended insulin to glucose ratios calculated from serum insulin and blood glucose concentrations obtained during a glucagon tolerance test and an oral glucose tolerance test on a dog with an insulinoma were less than 30 𝛍U/mg, or equivocal, at different times during the test period. This indicates that under some circumstances healthy dogs may have elevated amended insulin to glucose ratios, and dogs with insulinoma may have a normal amended insulin to glucose ratio. Care is essential for interpretation of amended insulin to glucose ratios, and a diagnosis of insulinoma using the ratio must be made in conjunction with appropriate clinical signs of hvnoglvcaemia.  相似文献   
978.
Summary

The feet of three two‐humped camels (Camelus bactrianus), one lama (Lama glama) and four alpacas (Lama pacos) from zoos and a circus in the Netherlands were examined for the mange‐mite Choroptes bovis. Mites were found on two of the camels, the lama, and three of the alpacas. On one camel and one alpaca small mange lesions on the feet were present. This is the first report of Chorioptes bovis and chorioptic mange in the two‐humped camel.  相似文献   
979.
Summary

The macroscopic and histological appearance of jejunal antimesenteric incisions approximated with two different absorbable suture materials (monofilament versus multifilament) and three closure techniques (appositional single layer, crushing single layer, and double layer) were compared in healthy dogs at 14 or 28 days, postoperatively. No significant differences between the two suture materials were observed for most of the macroscopic or histological variables. However, the monofilament suture material caused significantly more fibrous tissue reaction in the muscular layer of the jejunum than did the multifilament suture material. Of the three enterotomy closure techniques used in this study, the appositional single‐layer method proved to be the best. The double‐layer closure method caused a significant decrease in the incisional circumference, the relative circumference, and volume of the jejunum, and a significant increase in jejunal wall thickness. Our findings suggest that canine jejunal enterotomy incisions can be closed using an appositional suture pattern with relatively rapidly absorbable monofilament suture material. The use of double‐layer suture patterns for closure of jejunal enterotomy incisions should be avoided because the size of the intestinal lumen may be reduced.  相似文献   
980.

Four cow routing treatments related to fully automatic milking were compared consecutively in one group of 24 Holstein Friesian cows. The objective of the experiment was to investigate how cow traffic towards the automatic milking system (AMS) should be routed and whether a preselection or a waiting area in front of the AMS should be used. The treatments were (1) free routing with selection of cows in the AMS (FREE); (2) free routing with a preselection system in front of the AMS (FREE_SS); (3) free routing with a preselection system and a waiting area in front of the AMS (FREE_WA); and (4) one-way gates resulting in forced routing with preselection and a waiting area in front of the AMS (FORCED_WA). Evaluation of the treatments revealed that FREE may be questionable with regard to the cows' visiting frequency to the AMS and that the use of a waiting area in combination with free routing (FREE_WA) may slow down the passing through the AMS. FORCED_WA may be the best option in relation to the cows' use of the AMS, but this traffic system seems to postpone or even thwart the feeding. The treatment that appears to give the best results is FREE_SS. The type of AMS visit appeared to have a marked influence on the cows' subsequent behaviour. Cows returned to the AMS sooner after non-milking visits and failed attachments (P<0.01). This increases the occupation rate of the AMS and may induce some extra unrest in the herd.  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