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   3285篇
  免费   196篇
  2023年   16篇
  2022年   22篇
  2021年   91篇
  2020年   41篇
  2019年   75篇
  2018年   110篇
  2017年   116篇
  2016年   166篇
  2015年   170篇
  2014年   221篇
  2013年   245篇
  2012年   292篇
  2011年   305篇
  2010年   199篇
  2009年   115篇
  2008年   222篇
  2007年   191篇
  2006年   157篇
  2005年   181篇
  2004年   117篇
  2003年   128篇
  2002年   85篇
  2001年   15篇
  2000年   11篇
  1999年   15篇
  1998年   17篇
  1997年   15篇
  1996年   5篇
  1995年   14篇
  1994年   12篇
  1993年   11篇
  1992年   13篇
  1991年   6篇
  1989年   8篇
  1988年   8篇
  1987年   4篇
  1985年   4篇
  1983年   3篇
  1981年   3篇
  1980年   4篇
  1979年   4篇
  1975年   2篇
  1974年   2篇
  1973年   5篇
  1972年   3篇
  1971年   2篇
  1969年   3篇
  1968年   4篇
  1965年   3篇
  1954年   2篇
排序方式: 共有3481条查询结果,搜索用时 19 毫秒
1.
2.
3.
DNA base composition of Gram-positive cocci   总被引:10,自引:0,他引:10  
  相似文献   
4.
Plant material is a rich source of valuable compounds such as flavanones. Their different forms influence bioavailability and biological activity, causing problems with the selection of plant material for specific purposes. The purpose of this research was to determine selected flavanone (eriodictyol, naringenin, liquiritigenin, and hesperetin) enantiomer contents in free form and bonded to glycosides by an RP‐UHPLC‐ESI‐MS/MS method. Different parts (stems, leaves, and flowers) of goldenrod (Solidago virgaurea L.), lucerne (Medicago sativa L.), and phacelia (Phacelia tanacetifolia Benth.) were used. The highest content of eriodictyol was found in goldenrod flowers (13.1 μg/g), where it occurred mainly as the (S)‐enantiomer, and the greatest proportion of the total amount was bonded to glycosides. The richest source of naringenin was found to be lucerne leaves (4.7 μg/g), where it was mainly bonded to glycosides and with the (S)‐enantiomer as the dominant form. Liquiritigenin was determined only in lucerne, where the flowers contained the highest amount (1.2 μg/g), with the (R)‐enantiomer as dominant aglycone form and the (S)‐enantiomer as the dominant glycosylated form. The highest hesperetin content was determined in phacelia leaves (0.38 μg/g), where it was present in the form of a glycoside and only as the (S)‐enantiomer. A comparison of the different analyte forms occurring in different plant parts was performed for the first time.  相似文献   
5.
6.
It has been shown that both IAA and ethylene application inhibit flower induction in the short-day plant Pharbitis nil. However application of IAA has elevated ethylene production in this plant, as well. Strong enhancement of ethylene production is also correlated with the night-break effect, which completely inhibits flowering. In order to determine what the role of IAA and ethylene is in the photoperiodic flower induction in Pharbitis nil, we measured changes in their levels during inductive and non-inductive photoperiods, and the effects of ethylene biosynthesis and action inhibitors on inhibition of flowering by IAA. Our results have shown that the inhibitory effect of IAA on Pharbitis nil flowering is not physiological but is connected with its effect on ethylene biosynthesis.  相似文献   
7.
8.
Mazanec, K. (J. E. Purkyne University, Brno, Czechoslovakia), M. Kocur, and T. Martinec. Electron microscopy of ultrathin sections of Sporosarcina ureae. J. Bacteriol. 90:808-816. 1965.-Ultrathin sections of Sporosarcina ureae cells were studied by means of electron microscopy. The cell wall consists of several layers and is 340 A thick. The cytoplasm is of globular structure and includes ribosomelike structures, occasional mesosomes, and inclusions not precisely identifiable. The nuclear area has various shapes and is formed by filaments 10 to 20 A thick which proceed in various directions. Cell division occurs similarly to that of sarcinate. Both synchronic and asynchronic cell division was observed. The spores of S. ureae consist of an outer coat having several layers, a cortex, a spore wall, and cytoplasm. The results of the present investigation substantiate our previous suggestion that S. ureae should be transferred from the family Micrococcaceae to the family Bacillaceae.  相似文献   
9.
Chromaffin cells both recently isolated or in culture present a high-affinity adenosine transporter with a Km value of 1 microM. When cells were exposed to nerve growth factor (NGF; 10 ng/ml), the adenosine transporter affinity decreased to 3 microM. This value was maintained from 3 days after plating to the end of the culture period. A change in the transport capacity was observed, with a significant increase (approximately 200-260%) in NGF-cultured cells throughout the period studied.  相似文献   
10.
Polytetrafluoroethylene (PTFE) membranes of different porosity were used for lipase from Rhizopus immobilization. The immobilized enzyme applied to sunflower oil hydrolysis achieved the activity of 1228 U/m2 of the membrane area and the half-life time was calculated to be 7 days.  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