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   196505篇
  免费   11282篇
  国内免费   701篇
林业   7708篇
农学   6048篇
基础科学   1517篇
  23271篇
综合类   36687篇
农作物   7393篇
水产渔业   9502篇
畜牧兽医   100312篇
园艺   2629篇
植物保护   13421篇
  2019年   1809篇
  2018年   2601篇
  2017年   2956篇
  2016年   2702篇
  2015年   2491篇
  2014年   2910篇
  2013年   7273篇
  2012年   5627篇
  2011年   6965篇
  2010年   4522篇
  2009年   4423篇
  2008年   6600篇
  2007年   6322篇
  2006年   5970篇
  2005年   5601篇
  2004年   5351篇
  2003年   5331篇
  2002年   5170篇
  2001年   5963篇
  2000年   5864篇
  1999年   4733篇
  1998年   1943篇
  1997年   1904篇
  1995年   2192篇
  1994年   1976篇
  1993年   1899篇
  1992年   3935篇
  1991年   4227篇
  1990年   4262篇
  1989年   4195篇
  1988年   3844篇
  1987年   3991篇
  1986年   4114篇
  1985年   3862篇
  1984年   3302篇
  1983年   2918篇
  1982年   1991篇
  1981年   1874篇
  1979年   2944篇
  1978年   2419篇
  1977年   2045篇
  1976年   1913篇
  1975年   2020篇
  1974年   2683篇
  1973年   2694篇
  1972年   2632篇
  1971年   2410篇
  1970年   2254篇
  1969年   2101篇
  1967年   1798篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
In human medicine it has been shown that the bromocresol green (BCG) dye-binding method for the determination of serum albumin is not entirely specific, the dye reacting also with certain human serum globulins. This causes over-estimation of albumin when reaction times are prolonged beyond 30 seconds.In the present study, serum albumin values obtained from three animal species by the immediate, i.e. less than 30 seconds, BCG reaction were compared with those by the 10-minute BCG reaction. Albumin-depleted sera were prepared using an affinity chromatography technique and their reactions and those of purified gamma globulin preparations with the dye were studied.In cattle, sheep and horses, serum albumin values obtained by the 10-minute reaction were higher than those obtained by the immediate BCG reaction, the differences being statistically significant. Purified gamma globulin did not react with the BCG dye after 10 minutes, but other globulins did. There were differences between the species in the magnitude of the reaction of their globulins with BCG dye.  相似文献   
992.
Cysts found in the liver of a horse which had never been out of New Zealand were used to infect two dogs which were slaughtered 35 days after infection. Large numbers of Echinococcus granulosus were recovered. These cestodes were compared with mature dog-sheep cestodes, using light and scanning electron microscopy and identified as the dog-horse strain of E.granulosus.  相似文献   
993.
A series of 10 farm trials was conducted in which the lambing performance of ewes immunised against polyandroalbumin was compared with that of untreated ewes in the same flock. The trials show that polyandroalbumin treatment is a reliable method of increasing lambing and tailing percentages in New Zealand flocks. An average of 39 extra lambs born per 100 ewes tupped was achieved on farms where ewes were given two treatments about four weeks apart and rams were introduced 18-26 days after the second dose. On farms where rams were introduced less than 12 days after this booster injection an average of 19 extra lambs born per 100 ewes tupped resulted. On farms where rams were introduced at 18-26 days post booster injection an average of 35 extra lambs were tailed for every 100 ewes tupped. The response for immunization increased in direct relation to the liveweight of the ewes at tupping.  相似文献   
994.
995.
The cleistogamous species Collomia grandiflora produces dimorphic cross-incompatible flowers on a single plant. The open or chasmogamous flower has smaller, flask-shaped stigmatic papillae, larger pollen grains, longer styles, and faster pollen tube growth rates down the style than the closed or cleistogamous flower. In intermorph crosses, pollen tube growth rates are greatly decreased and fertilization does not occur.  相似文献   
996.
997.
998.
999.
1000.
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