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   86181篇
  免费   4924篇
  国内免费   9篇
  2023年   501篇
  2021年   1099篇
  2020年   958篇
  2019年   962篇
  2018年   2342篇
  2017年   2066篇
  2016年   2814篇
  2015年   3734篇
  2014年   3818篇
  2013年   5062篇
  2012年   5883篇
  2011年   5234篇
  2010年   3400篇
  2009年   2572篇
  2008年   4137篇
  2007年   3905篇
  2006年   3843篇
  2005年   3236篇
  2004年   3232篇
  2003年   2857篇
  2002年   2641篇
  2001年   2068篇
  2000年   1928篇
  1999年   1483篇
  1998年   706篇
  1997年   495篇
  1996年   534篇
  1995年   476篇
  1992年   923篇
  1991年   845篇
  1990年   839篇
  1989年   900篇
  1988年   739篇
  1987年   768篇
  1986年   702篇
  1985年   778篇
  1984年   637篇
  1983年   555篇
  1979年   676篇
  1978年   491篇
  1977年   494篇
  1975年   589篇
  1974年   627篇
  1973年   604篇
  1972年   553篇
  1971年   492篇
  1970年   536篇
  1969年   613篇
  1968年   584篇
  1967年   484篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
The oscillations of the free fatty acid concentration in the serum and white (epididymal) adipose tissue, of triglycerides in the serum and liver, of total serum, liver and adrenal cholesterol and of serum phospholipids were studied at 3-hour intervals for a period of 24 hours in fed male Wistar rats and in animals fasted for 24 hours (both adapted to an illumination regimen of 12 hours' light and 12 hours' darkness. The rhythm--studied by means of the cosinor analysis--was present in most of the given parameters; it was not recorded in the liver triglycerides and serum phospholipids of fasted rats and in the adrenal cholesterol of fed animals. Apart from the circadian rhythm, many parameters distinctly displayed an ultradian rhythm, mainly an approximately 12-hour period. In general, one day's starvation did not significantly affect the course of the circadian oscillations of the given indicators of rat lipid metabolism.  相似文献   
92.
93.
94.
95.
96.
97.
Six peripheral blood lymphoid fractions (total lymphocytes, non-T, T, Tar (autologous rosette-forming T cells/precursor), T mu (helper), and T gamma (suppressor) lymphocytes) isolated through rosetting procedures were examined for the presence of ferritin by a direct immunofluorescence technique. Although ferritin was present in all lymphoid fractions studied, a significantly higher proportion of ferritin-containing cells were detected in the T-cell fraction than in the non-T-cell fraction, (mean +/- SD = 7.9 +/- 1.6% and 5.0 +/- 1.2%, respectively). T mu- and T gamma-cell fractions showed a twofold increase in the number of ferritin-positive cells (14.1 +/- 1.4% and 15.4 +/- 2.6%, respectively), as compared with Tar (7.0 +/- 0.9%)-and total lymphocyte (6.9 +/- 1.3%)-cell fractions. These results indicate that ferritin is preferentially distributed in T mu and T gamma lymphocytes and may constitute the basis for explaining some of the roles exercised by these cells in the control of other biological systems.  相似文献   
98.
99.
Comparative mineral and hormonal analyses were made on tissue culture derived truncated leaf syndrome and wild type oil palm seedlings. Mineral analysis confirmed that Boron, Zinc and chlorophyll levels were significantly lower in truncated leaf syndrome leaves than those of wild type. Hormonal analysis also revealed various cytokinin derivatives such as trans-zeatin, trans-zeatin riboside, trans-zeatin O-glucoside and trans-zeatin riboside 5??mono phosphate were significantly higher in truncated leaf syndrome leaves compared to wild type leaves. Brassinolide level was also significantly higher in truncated leaf syndrome leaves than those of the wild type. These observations suggest that the truncated leaf syndrome abnormality could be associated to high cytokinin and brassinosteroid production which affects the uptake of Boron and Zinc.  相似文献   
100.
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