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   964219篇
  免费   108839篇
  国内免费   673篇
  1073731篇
  2018年   7911篇
  2016年   11196篇
  2015年   15537篇
  2014年   18300篇
  2013年   25729篇
  2012年   29089篇
  2011年   29698篇
  2010年   20199篇
  2009年   18910篇
  2008年   26929篇
  2007年   27658篇
  2006年   26094篇
  2005年   25029篇
  2004年   24816篇
  2003年   24082篇
  2002年   23375篇
  2001年   42149篇
  2000年   42439篇
  1999年   33912篇
  1998年   12512篇
  1997年   13115篇
  1996年   12599篇
  1995年   11870篇
  1994年   11695篇
  1993年   11481篇
  1992年   28465篇
  1991年   27716篇
  1990年   27396篇
  1989年   26658篇
  1988年   24616篇
  1987年   24063篇
  1986年   22037篇
  1985年   22325篇
  1984年   18426篇
  1983年   16047篇
  1982年   12477篇
  1981年   11172篇
  1980年   10641篇
  1979年   17636篇
  1978年   14051篇
  1977年   12776篇
  1976年   12196篇
  1975年   13335篇
  1974年   14394篇
  1973年   14210篇
  1972年   12649篇
  1971年   11769篇
  1970年   10149篇
  1969年   9522篇
  1968年   8711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.
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   
998.
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