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   335183篇
  免费   22734篇
  国内免费   1142篇
  359059篇
  2018年   14124篇
  2017年   12955篇
  2016年   10659篇
  2015年   4222篇
  2014年   4844篇
  2013年   6824篇
  2012年   11280篇
  2011年   20366篇
  2010年   17055篇
  2009年   12731篇
  2008年   16389篇
  2007年   18118篇
  2006年   6954篇
  2005年   6892篇
  2004年   7245篇
  2003年   7129篇
  2002年   6753篇
  2001年   12250篇
  2000年   12112篇
  1999年   9166篇
  1998年   2676篇
  1997年   2764篇
  1996年   2701篇
  1995年   2476篇
  1994年   2425篇
  1993年   2343篇
  1992年   7193篇
  1991年   7015篇
  1990年   7064篇
  1989年   6848篇
  1988年   6372篇
  1987年   6022篇
  1986年   5353篇
  1985年   5661篇
  1984年   4468篇
  1983年   3877篇
  1982年   2671篇
  1981年   2493篇
  1980年   2304篇
  1979年   4107篇
  1978年   3134篇
  1977年   2881篇
  1976年   2826篇
  1975年   3273篇
  1974年   3496篇
  1973年   3524篇
  1972年   3298篇
  1971年   3106篇
  1970年   2535篇
  1969年   2299篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
Comparative tissue ascorbic acid studies in fishes   总被引:1,自引:0,他引:1  
Comparative tissue ascorbic acid levels in four species of major carp viz., Labeo rohila, L. calbasu, Cirrhina tnrigala and Catla catla , were investigated. The ascorbic acid level was found to be the highest in the spleen in the four species studied (range 430–380 μg/g) followed by the anterior (adrenal) kidney, gonads, liver, renal kidney, brain and/or eye. Heart and blood had the lowest levels (range 26–18 μg/ml) amongst the tissues studied. Overall tissue ascorbic acid levels were the highest in L. rohita and the lowest in C. mrigala . Investigation on seasonal variations in blood and kidney ascorbic acid levels of Notopterus notopterus revealed peak levels in spring (February-April) and the lowest levels in the postspawning period (August-September).  相似文献   
73.
74.
Irradiation conditions in which laboratory animals were kept in experimental laboratories of Chernobyl and Kiev after the accident at the Chernobyl A.P.S. are described. The data are presented on the spectral structural and activity of radionuclides in the diet as well as in the organs and tissues of the animals. The radiation loads have been estimated with regard to an external gamma component and the internal one contributed by the incorporated radionuclides. It has been shown that radiation doses received by the animals during their lifetime due to these contributions do not exceed units of cGy.  相似文献   
75.
76.
77.
Identification of serotonin and dopamine in M. salmonis was conducted by means of some fluorometric methods. The presence of negligible amount of a serotonin-like component and substance close in its spectral characteristics to dopamine was shown.  相似文献   
78.
The effects of corticotropin-releasing hormone (CRH) injected into the dorsal neostriatum on the open-field and shuttle-box behavior were studied in rats with high (Koltushi high avoidance, KHA) and low (Koltushi low avoidance, KLA) capability for avoidance learning. The effects of this hormone on the behavior of these rat strains were different. In KLA rats with passive strategy of behavior the CRH injection led to a rapid locomotor activation in the open field, while the rats with active behavioral strategy (KHA) reacted to the injection by a significant decrease in locomotion and change for the passive mode of behavior. The same CRH effects on locomotion were obtained in the shuttle-box experiments. Moreover, in the KLA rats the neurohormone injection resulted in an improvement of avoidance learning in contrast to the KHA rats, in which CRH substantially impaired avoidance learning. The obtained evidence is discussed in terms of the important role of striatal CRH in the choice of behavioral strategy in stress.  相似文献   
79.
IN addition to its well known antiviral activity, interferon has recently been shown to inhibit the multiplication of tumour and mammalian cells in cell culture1–6. We report here the inhibition by interferon of DNA synthesis induced in mouse spleen lymphocytes by the non-viral stimuli phytohaemagglutinin (PHA) and allogeneic lymphocytes. These findings are in accord with our contention that interferon affects cell function and, furthermore, they suggest that by acting on lymphocytes, interferon plays a role in the immunological response of the host.  相似文献   
80.
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