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   70537篇
  免费   2854篇
  国内免费   33篇
林业   5837篇
农学   3198篇
基础科学   436篇
  10327篇
综合类   9839篇
农作物   3837篇
水产渔业   4690篇
畜牧兽医   28416篇
园艺   1686篇
植物保护   5158篇
  2019年   456篇
  2018年   3828篇
  2017年   3921篇
  2016年   2072篇
  2015年   736篇
  2014年   823篇
  2013年   1845篇
  2012年   2375篇
  2011年   4309篇
  2010年   3754篇
  2009年   2935篇
  2008年   3472篇
  2007年   3876篇
  2006年   1619篇
  2005年   1603篇
  2004年   1588篇
  2003年   1652篇
  2002年   1353篇
  2001年   1968篇
  2000年   2061篇
  1999年   1531篇
  1998年   590篇
  1997年   514篇
  1996年   465篇
  1995年   632篇
  1994年   531篇
  1993年   496篇
  1992年   1205篇
  1991年   1224篇
  1990年   1193篇
  1989年   1128篇
  1988年   1085篇
  1987年   1097篇
  1986年   1041篇
  1985年   983篇
  1984年   810篇
  1983年   694篇
  1982年   425篇
  1979年   648篇
  1978年   506篇
  1977年   462篇
  1976年   416篇
  1975年   457篇
  1974年   531篇
  1973年   518篇
  1972年   537篇
  1971年   453篇
  1970年   433篇
  1969年   471篇
  1967年   390篇
排序方式: 共有10000条查询结果,搜索用时 359 毫秒
21.
The medical records of 38 horses with puncture wounds of the navicular bursa were reviewed. Only 12 horses had a satisfactory outcome (breeding or riding). Of the remaining 26 horses, 19 were euthanized, five were sold due to persistent severe lameness, one died, and one was lost to long-term follow-up. Different combinations of conservative management prior to surgical debridement and drainage of the navicular bursa were unsuccessful in resolving the condition. Horses that were treated surgically within 1 week of the injury and had a hind leg affected had the best chance of a satisfactory outcome. Additional wound debridement was necessary in 15 horses after initial surgical treatment. The most common complications encountered were navicular bone osteomyelitis and sepsis of the deep digital flexor tendon. Thirteen of 14 horses that had rupture of the deep digital flexor tendon and subluxation of the distal interphalangeal joint had an unsatisfactory outcome. One mare subsequently developed ankylosis of the distal interphalangeal joint and was a useful brood mare. Two horses that had biaxial palmar digital neurectomy because of persistent lameness were later euthanized because of navicular bone fracture and rupture of the deep digital flexor tendon. Results from limited numbers of bacterial cultures and antibiotic sensitivities suggest that penicillin and an aminoglycoside antibiotic should be used as initial antibiotic therapy. Immediate surgical debridement and appropriate antibiotic treatment are recommended as the minimum therapy for penetrating wounds of the navicular bursa in horses.  相似文献   
22.
Thirteen mixed-breed beef bulls, 1 to 4 years old, were used to determine the effect of live and dead filarial nematodes, Setaria labiatopapillosa, placed in the vaginal cavity of the testes. When dead worms were used, granulomatous lesions developed on the tunica vaginalis parietalis in 7 of 8 testes. The lesions were similar to those seen in some clinical cases of periorchitis. Similar lesions developed in 5 of 6 testes after live worms were implanted in the vaginal cavity of the testes and tetramisole (8 mg/kg) was injected subcutaneously 6 days after implantation. When live worms were implanted and tetramisole was not given, lesions developed in 3 of 6 testes. It was concluded that the granulomatous reaction was a local response to dead or killed S labiatopapillosa.  相似文献   
23.
24.
25.
26.
27.
To optimize mechanical inoculation of test plants as part of the regulated post-entry quarantine testing of stolon- and tuber-forming Solanum spp. (including potato), nine test plant species have been screened for their ability to detect 22 potato-infecting viruses. These included all the common mechanically transmissible potato viruses and most of the viruses found in potato incidentally. The symptoms observed after mechanical inoculation are shown for each combination of test plant species and virus. Under given conditions, Nicotiana occidentalis -P1 and Nicotiana hesperis -67A were found to detect reliably 20 and 18 out of 22 viruses respectively. These and former results on the seed-transmissible viruses and Andean potato mottle virus demonstrate that these Nicotiana species are very suitable for post-entry quarantine testing. Addition of either Chenopodium amaranticolor or Chenopodium quinoa to these two species may slightly extend the range of viruses. Therefore, using C. amaranticolor / C. quinoa , N. hesperis -67A and N. occidentalis -P1 for the biological screening of imported Solanum spp. will improve both the efficiency and the quality of post-entry quarantine testing.  相似文献   
28.
Abstract  The potential utility of pelvic fin rays as ageing structures was evaluated for southern US muskellunge Esox masquinongy Mitchill populations by comparing age estimates among three readers and against cleithrum estimates, and by comparing observed length changes of tagged fish with changes predicted from growth equations based on pelvic fin ray age estimates. Mean coefficient of variation in age estimates among all readers and between the two readers with prior ageing experience was 17.8% and 5.6%, respectively. Exact and within 1-year agreement rates between pelvic fin rays and cleithra were 76% and 100%, respectively. Mean (± 2 SE) estimated absolute error between observed and predicted length changes for 13 tagged muskellunge was 30 ± 14 mm. This evaluation indicated that pelvic fin rays may prove to be a useful, non-lethal method for ageing muskellunge in southern US waters. Validation studies are still needed to ensure that growth rings form consistently throughout fish's life span.  相似文献   
29.
30.
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