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   336682篇
  免费   22902篇
  国内免费   1065篇
  2018年   14170篇
  2017年   12997篇
  2016年   10715篇
  2015年   4308篇
  2014年   4938篇
  2013年   6955篇
  2012年   11453篇
  2011年   20522篇
  2010年   17133篇
  2009年   12774篇
  2008年   16444篇
  2007年   18170篇
  2006年   7018篇
  2005年   6931篇
  2004年   7281篇
  2003年   7168篇
  2002年   6787篇
  2001年   12275篇
  2000年   12129篇
  1999年   9180篇
  1998年   2687篇
  1997年   2785篇
  1996年   2726篇
  1995年   2490篇
  1994年   2441篇
  1993年   2358篇
  1992年   7210篇
  1991年   7021篇
  1990年   7082篇
  1989年   6854篇
  1988年   6377篇
  1987年   6027篇
  1986年   5356篇
  1985年   5667篇
  1984年   4472篇
  1983年   3884篇
  1982年   2676篇
  1981年   2500篇
  1980年   2313篇
  1979年   4119篇
  1978年   3144篇
  1977年   2886篇
  1976年   2835篇
  1975年   3279篇
  1974年   3500篇
  1973年   3529篇
  1972年   3302篇
  1971年   3111篇
  1970年   2538篇
  1969年   2302篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
92.
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   
93.
94.
95.
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   
96.
97.
98.
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   
99.
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   
100.
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   
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