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   839165篇
  免费   98410篇
  国内免费   427篇
  2018年   7544篇
  2016年   10633篇
  2015年   15729篇
  2014年   17826篇
  2013年   24479篇
  2012年   28035篇
  2011年   27503篇
  2010年   18501篇
  2009年   17040篇
  2008年   24706篇
  2007年   25124篇
  2006年   23662篇
  2005年   22446篇
  2004年   22272篇
  2003年   21352篇
  2002年   20607篇
  2001年   35347篇
  2000年   35679篇
  1999年   28783篇
  1998年   11111篇
  1997年   11652篇
  1996年   11261篇
  1995年   10622篇
  1994年   10429篇
  1993年   10235篇
  1992年   24037篇
  1991年   23304篇
  1990年   22886篇
  1989年   22259篇
  1988年   20472篇
  1987年   20142篇
  1986年   18487篇
  1985年   18651篇
  1984年   15484篇
  1983年   13526篇
  1982年   10835篇
  1981年   9646篇
  1980年   9183篇
  1979年   14933篇
  1978年   11976篇
  1977年   10859篇
  1976年   10234篇
  1975年   11145篇
  1974年   11992篇
  1973年   11744篇
  1972年   10549篇
  1971年   9773篇
  1970年   8414篇
  1969年   8038篇
  1968年   7199篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
994.
995.
996.
997.
998.
Antigenic change on the surface of immature oocytes of Ascaris occurred during passage through the oviduct. Using immunodiffusion and immunoelectrophoretic techniques we examined the possible relationship between the antigenic change of immature oocytes and the junctional fluid (JF) which is present in the fertilization chamber. From the immunodiffusion it was found that the anti-immature oocyte serum (A-I serum) had more immunoprecipitation arcs than did the anti-mature oocyte serum (A-M serum) when reacted against the junctional fluid. This indicated that A-I serum contained more immunoglobulins that reacted with junctional fluid than did the A-M serum. This result was substantiated by using immunoelectrophoretic analysis and two dimension crossed immunoelectrophoresis. Our results suggest that during the migration toward the oviduct-uterine junction the immature oocytes might shed surface proteins into the luminal fluid. Alternatively, the membrane surface of mature oocytes may be altered by the interaction with the substances present in the junctional fluid.  相似文献   
999.
1000.
A total of 764 breeding soundness examinations was conducted on beef bulls utilizing the method of examination and criteria for classifying bulls of the Society for Theriogenology. In addition to this examination each bull was subjected to scrotal circumference measurement and to weighing. Classification of the bulls according to breeding soundness potentials was as follows: 88% of the bulls were satisfactory potential breeders, 8% of the bulls were questionable potential breeders and 4% of the bulls were unsatisfactory potential breeders. The proportions of bulls in each classification; satisfactory, questionable, or unsatisfactory; were not different among the four breeds evaluated. The majority of bulls evaluated in this study were between 14 and 36 months of age and weighed between 900 and 1500 pounds. For the ages and weights evaluated, scrotal circumference measurement variances were not closely related to age and weight differences. There was a tendency shown for “Questionable” and “Unsatisfactory Potential Breeders” to have smaller scrotal circumference measurements. The study indicates that Angus, Charolais, Horned Hereford and Polled Hereford bulls of breeding ages and weights should have scrotal circumference measurements of at least 32 centimeters in order to be classified as “Satisfactory Potential Breeders”.  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