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   60305篇
  免费   3487篇
  国内免费   35篇
林业   2425篇
农学   1851篇
基础科学   301篇
  6616篇
综合类   10236篇
农作物   2078篇
水产渔业   2802篇
畜牧兽医   33064篇
园艺   705篇
植物保护   3749篇
  2018年   896篇
  2017年   913篇
  2016年   808篇
  2015年   773篇
  2014年   840篇
  2013年   2576篇
  2012年   1670篇
  2011年   2023篇
  2010年   1272篇
  2009年   1252篇
  2008年   1881篇
  2007年   1850篇
  2006年   1730篇
  2005年   1586篇
  2004年   1501篇
  2003年   1549篇
  2002年   1471篇
  2001年   1812篇
  2000年   1785篇
  1999年   1469篇
  1998年   622篇
  1997年   608篇
  1996年   547篇
  1995年   642篇
  1994年   601篇
  1993年   572篇
  1992年   1224篇
  1991年   1372篇
  1990年   1260篇
  1989年   1269篇
  1988年   1167篇
  1987年   1138篇
  1986年   1197篇
  1985年   1197篇
  1984年   965篇
  1983年   901篇
  1982年   583篇
  1979年   893篇
  1978年   702篇
  1977年   696篇
  1976年   711篇
  1975年   716篇
  1974年   866篇
  1973年   844篇
  1972年   812篇
  1971年   728篇
  1970年   769篇
  1969年   733篇
  1968年   650篇
  1967年   656篇
排序方式: 共有10000条查询结果,搜索用时 359 毫秒
991.
992.
Painful foot horn lesions of breeding sows fed rations of low biotin content responded to a biotin supplement, and a herd lameness problem was overcome.  相似文献   
993.
Dissection of the heads of 12 male Red deer revealed that the innervation and blood supply of the antler resembles those in the goat, in that the infratrochlear and zygomaticotemporal nerves supply the antler pedicle accompanied by two main branches of the superficial temporal artery and vein. Analgesia of the antler should be produced by injecting local anaesthetic solution both dorsal to the orbital rim and immediately caudal to the zygomatic process of the frontal bone.  相似文献   
994.
Extract

Evidence that feeding massive doses, of calciferol prior to calving may be a useful method of preventing milk fever was obtained by Hibbs and co-workers (1950, 1951) at Ohio State University. The treatment causes a rise in serum calcium and if dosing is suitably timed the post-partum fall in serum calcium may be countered, thus making up for the presumed parathyroid failure which occurs at this lime and which is believed by many to be the underlying cause of milk fever.  相似文献   
995.
Extract

Mr. President, Ladies and Gentlemen, I can assure you that I speak with complete sincerity when I say I regard it as a very great honour indeed to be asked to open this conference. I value the invitation to do so for my own sake (today's will be a memory to cherish when I have returned to Britain) and, not less, for the implied compliment to the High Commissioner for the United Kingdom (whose adviser I am) and to the British Ministry of Agriculture who employ me. It is also particularly valuable to me, in my work, to get among a body of people who are so very much part and parcel of the farming industry of the Dominion. And, not least, my wife and I are delighted to be able to spend a weekend in such pleasant surroundings and in such congenial company. This is indeed the art of “conferring” brought to the ultimate degree of luxury!  相似文献   
996.
Extract

Sir,—During the survey on the cestode problems of food animals and dogs in New Zealand, Multiceps multi-cops (Leske, 1780) and its metacestode Coenurus cerebralis have been observed in the dog and sheep respectively in mid-Canterbury. An unconfirmed case has also been reported recently in a lamb's brain exported to Australia.  相似文献   
997.
The lateral nasal (salt-secreting) glands of S. demersus were found to be morphologically and histologically similar to the salt glands of marine birds in general. No significant differences were recorded in the ionic and osmotic composition of nasal and cloacal fluid that was collected at 18ÅC and 28ÅC respectively. The daily intake of 220 g of fish per bird, however, had a significant influence on the diurnal variation of the potassium values of the cloacal fluid. A very low flow-rate and high osmotic concentration of the nasal gland exudate was recorded, indicating the efficiency of the nasal glands as auxiliary osmoregulatory organs.  相似文献   
998.
Gilroy DJ, Jensen OP, Allen BC, Chandra S, Ganzorig B, Hogan Z, Maxted JT, Vander Zanden MJ. Home range and seasonal movement of taimen, Hucho taimen, in Mongolia.
Ecology of Freshwater Fish 2010: 19: 545–554. © 2010 John Wiley & Sons A/S Abstract –  Taimen, Hucho taimen, is the world’s largest salmonid and a prized sport fish. We used radio and acoustic telemetry to characterise movements of adult taimen in an extensive river system, the Eg–Uur, in north‐central Mongolia. Forty‐six taimen were tagged with transmitters (27 radio, 17 acoustic and 2 radio‐acoustic combined) and tracked from 2004 to 2008 using mobile surveys and fixed receivers. The mean home range of individual taimen tracked for an average of 2.4 years was 23 km (N = 41, range = 0.5–93.2 km). Of the fish with over 10 relocations (N = 16), 90% remained within a range of 38 km. Four distinct movement patterns were observed: (i) restricted core home range, (ii) core range with seasonal departures, (iii) core range with separate seasonal range and (iv) home range transfer. Movement was greatest in May and June (spawning and postspawning period) with another peak period of movement in September and October (water temperature cooling).  相似文献   
999.
1000.
A captive reticulated giraffe was observed constantly for three weeks prior to, and periodically for 90 days subsequent to, the birth of her calf. Extensive observations were made of the birth sequence, feeding, drinking, sleeping and one instance of an infant distress call, as well as observations of the initiation of maternal behaviour (including licking, nursing, placentophagia, and what appeared to be helping the calf to stand, guiding the calf's movements, and attempts to respond to the calf's distress call).  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