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   62538篇
  免费   2834篇
  国内免费   42篇
林业   2516篇
农学   1645篇
基础科学   429篇
  6150篇
综合类   14758篇
农作物   2461篇
水产渔业   2346篇
畜牧兽医   31050篇
园艺   643篇
植物保护   3416篇
  2017年   553篇
  2016年   536篇
  2014年   540篇
  2013年   1863篇
  2012年   1203篇
  2011年   1438篇
  2010年   913篇
  2009年   877篇
  2008年   1427篇
  2007年   1389篇
  2006年   1371篇
  2005年   1386篇
  2004年   1318篇
  2003年   1391篇
  2002年   1354篇
  2001年   1493篇
  2000年   1473篇
  1999年   1206篇
  1998年   531篇
  1997年   538篇
  1995年   596篇
  1994年   573篇
  1993年   561篇
  1992年   1309篇
  1991年   1395篇
  1990年   1449篇
  1989年   1488篇
  1988年   1399篇
  1987年   1356篇
  1986年   1400篇
  1985年   1373篇
  1984年   1150篇
  1983年   1005篇
  1982年   718篇
  1981年   688篇
  1980年   644篇
  1979年   1127篇
  1978年   916篇
  1977年   819篇
  1976年   768篇
  1975年   860篇
  1974年   1126篇
  1973年   1063篇
  1972年   1128篇
  1971年   1080篇
  1970年   1022篇
  1969年   874篇
  1968年   710篇
  1967年   844篇
  1966年   693篇
排序方式: 共有10000条查询结果,搜索用时 12 毫秒
971.
972.
973.
974.
975.
Cytogenetic and histological studies were carried out on an intersex horse which was diagnosed clinically as a cryptorchid. Surgery confirmed the horse to be a bilateral abdominal cryptorchid and histological examination revealed ovarian tissue associated with the left epididymis. Chromosome analysis of cultured cells from testicular tissue, ovarian tissue and skin revealed 64-XX and 64-XY make-up, the left gonad containing a greater preponderance of XX cells over XY cells. The external characteristics and behaviour of the horse were indistinguishable from that of a "routine" cryptorchid. Other cases of equine intersexes are reviewed and theories for the discrepancies between genetic, gonadal and phenotypic sex are discussed.  相似文献   
976.
Two experimental groups and series were compared (leghorns and broilers as well as two age groups of broilers) for their adaptive responses to repeated noise application. The noise was 100 dB and applied daily 30 minutes. The reference for comparison was the plasma-11-hydroxycorticosteroid concentration (11-OHKS). The results differed somewhat from those obtained earlier from one first short-time noise application, in that the rise in plasma glucocorticosteroid concentrations dropped from 431 to 210 per cent of the initial values in adult leghorns exposed to repeated noise stress over seven days. Adult broilers, however, did not exhibit any difference in the magnitude of rise of 11-OHKS concentrations by comparison between first and seven days of repeated stress. The initial values, however, were reached earlier by repeated noise application.  相似文献   
977.
978.
The results of antimicrobial susceptibility testing on 262 strains of Pasteurella multocida and 141 strains of Pasteurella haemolytica isolated from cattle and swine from 1971 to 1974 were analyzed for patterns of resistance to streptomycin, penicillin, tetracycline, and chloramphenicol, using a modified Kirby-Bauer procedure. Resistance was recorded for 80.5% of the isolants of P multocida and 92.2% of those of P haemolytica. Resistance to streptomycin was most frequent, followed by resistance to penicillin and tetracycline. Most cultures of P multocida and P haemolytica were susceptible to chloramphenicol. There were 9 patterns of resistance with the aforementioned antibiotics. The combinations, streptomycin and penicillin and streptomycin and tetracycline, each accounted for approximately 10% of the resistance patterns of P multocida. Approximately half of the 14 isolants of P haemolytica were resistant to the combination of streptomycin, penicillin, and tetracycline. These observations underscore the need for antimicrobial susceptibility testing of clinical isolants of P multocida and P haemolytica.  相似文献   
979.
980.
Two dogs with cloudy aqueous humor due to accumulation of lipid and lipoprotein had concurrent hyperlipemia and anterior uveitis. In 1 dog, serum and aqueous humor had similar lipoprotein electrophoretic patterns, and in the other dog, the patterns were different. The therapeutic approach included symptomatic treatment of the uveitis and reduction of dietary fat intake. Clearing of fat from aqueous humor followed control of the uveitis.  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