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   847522篇
  免费   90614篇
  国内免费   915篇
  2018年   7989篇
  2016年   10748篇
  2015年   14799篇
  2014年   17237篇
  2013年   24606篇
  2012年   28596篇
  2011年   29572篇
  2010年   19324篇
  2009年   17176篇
  2008年   25941篇
  2007年   27100篇
  2006年   25375篇
  2005年   24137篇
  2004年   24068篇
  2003年   22939篇
  2002年   22328篇
  2001年   33550篇
  2000年   33650篇
  1999年   26890篇
  1998年   10189篇
  1997年   10357篇
  1996年   9856篇
  1995年   9381篇
  1994年   9047篇
  1993年   9036篇
  1992年   22710篇
  1991年   22362篇
  1990年   22180篇
  1989年   21574篇
  1988年   20164篇
  1987年   18998篇
  1986年   17917篇
  1985年   18252篇
  1984年   15314篇
  1983年   13208篇
  1982年   10254篇
  1981年   9319篇
  1980年   8628篇
  1979年   14442篇
  1978年   11560篇
  1977年   10630篇
  1976年   10022篇
  1975年   11307篇
  1974年   12191篇
  1973年   11941篇
  1972年   10927篇
  1971年   10009篇
  1970年   8546篇
  1969年   8480篇
  1968年   7865篇
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
991.
992.
The anti-DNP response to DNP-BGG is substantially suppressed in guinea pigs sensitized to DNCB. The degree of antibody suppression varies with the mode of skin sensitization and with the degree of conjugation of the challenging immunogen. Suppression of the anti-HSA response was also induced by the prior injection of CFA.  相似文献   
993.
994.
995.
996.
997.
The ergosterol and lecithin absorption IR-spectra were studied in a nonpolar anhydrous medium. The thermodynamical and spectral characteristics of dimeric associates and the enthalpy value for trimeric associates of this sterol are determined. Thermodynamical and spectral parameters of ergosterol intermolecular associates with lecithin in a nonpolar anhydrous medium are found. It is established that the intermolecular interaction of lecithin with ergosterol occurs according to the mechanism of hydrogen bond. A conclusion is drawn that the presence of binary bonds and methyl groups in the cyclic and aliphatic parts of the sterol molecule affects greatly the structure of the model membrane and its strength. It is shown that under conditions of the experiment the oxygen of the phosphate group contributes to formation of the molecular associates of lecithin with sterols and not that of the carbonyl group. The obtained experimental data may be at use when studying structural disturbances of native membranes in norm and with different pathologies.  相似文献   
998.
999.
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   
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