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   84622篇
  免费   4949篇
  国内免费   14篇
  2023年   483篇
  2021年   1051篇
  2020年   909篇
  2019年   886篇
  2018年   2267篇
  2017年   2001篇
  2016年   2746篇
  2015年   3632篇
  2014年   3725篇
  2013年   4862篇
  2012年   5743篇
  2011年   5043篇
  2010年   3302篇
  2009年   2456篇
  2008年   4087篇
  2007年   3844篇
  2006年   3823篇
  2005年   3211篇
  2004年   3179篇
  2003年   2853篇
  2002年   2602篇
  2001年   2063篇
  2000年   1915篇
  1999年   1485篇
  1998年   664篇
  1996年   533篇
  1995年   482篇
  1992年   929篇
  1991年   856篇
  1990年   832篇
  1989年   905篇
  1988年   749篇
  1987年   760篇
  1986年   705篇
  1985年   766篇
  1984年   643篇
  1983年   552篇
  1982年   473篇
  1979年   677篇
  1978年   505篇
  1977年   507篇
  1975年   591篇
  1974年   641篇
  1973年   608篇
  1972年   555篇
  1971年   504篇
  1970年   544篇
  1969年   619篇
  1968年   580篇
  1967年   487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