全文获取类型
收费全文 | 1087篇 |
免费 | 82篇 |
国内免费 | 54篇 |
出版年
2022年 | 9篇 |
2021年 | 15篇 |
2020年 | 12篇 |
2019年 | 12篇 |
2018年 | 12篇 |
2017年 | 12篇 |
2016年 | 24篇 |
2015年 | 18篇 |
2014年 | 26篇 |
2013年 | 46篇 |
2012年 | 43篇 |
2011年 | 38篇 |
2010年 | 44篇 |
2009年 | 49篇 |
2008年 | 60篇 |
2007年 | 38篇 |
2006年 | 45篇 |
2005年 | 35篇 |
2004年 | 27篇 |
2003年 | 24篇 |
2002年 | 31篇 |
2001年 | 31篇 |
2000年 | 27篇 |
1999年 | 18篇 |
1998年 | 28篇 |
1997年 | 18篇 |
1996年 | 15篇 |
1995年 | 17篇 |
1994年 | 19篇 |
1993年 | 13篇 |
1992年 | 16篇 |
1991年 | 20篇 |
1990年 | 9篇 |
1989年 | 11篇 |
1988年 | 14篇 |
1987年 | 13篇 |
1986年 | 11篇 |
1985年 | 22篇 |
1983年 | 13篇 |
1979年 | 13篇 |
1976年 | 10篇 |
1958年 | 17篇 |
1957年 | 14篇 |
1956年 | 28篇 |
1955年 | 14篇 |
1954年 | 13篇 |
1953年 | 20篇 |
1952年 | 13篇 |
1951年 | 15篇 |
1950年 | 14篇 |
排序方式: 共有1223条查询结果,搜索用时 15 毫秒
1.
2.
In vitro pathogenicity tests demonstrated that Hirschmanniella caudacrena is pathogenic to Ceratophyllum demersum (coontail). Symptoms were chlorotic tissue, deformed stems, and, finally, death of the plant. Inoculum densities of 500 nematodes per 5-cm-long cutting in a test tube containing 50 ml of water resulted in death and decay of some of the cuttings within 8 weeks; 100 nematodes killed the plants in 12 weeks, and 50 and 25 nematodes killed them in 16 weeks. The lowest inoculum level of 10 nematodes did not seriously affect the plants at 16 weeks when the experiment was terminated. A second test conducted outdoors in glass jars containing 3 liters of water and two cuttings weighing a total of 15 g fresh weight showed damage, but results were not statistically significant. Hydrilla verticillata inoculated with H. caudacrena was not affected seriously. 相似文献
3.
J. I. Smith N. J. Smart M. Misawa W. G. W. Kurz S. G. Tallevi F. DiCosmo 《Plant cell reports》1987,6(2):142-145
Vanadyl sulphate (10–500 mg/l), when added to cell suspension cultures of Catharanthus roseus stimulated increased intracellular accumulation of catharanthine and ajmalicine. This response was demonstrated in both flask and fermenter (30 litre) systems. The response varied, and depended upon cell line, concentration of vanadyl sulphate and the stage of the growth phase at which the cells were treated. This process has the potential to increase the yield and reduce the production time for commercially useful secondary plant metabolites.Abbreviations Ajm
ajmalicine
- Cath
catharanthine
- CAS
ceric ammonium sulphate
- VOSO4
vanadyl sulphate
- FW
fresh weight
- n.d.
not detected 相似文献
4.
ANDRÉ PICARD JEAN-CLAUDE LABBÉ GÉRARD PEAUCELLIER FRANÇOISE LE BOUFFANT CHRISTIAN LE PEUCH MARCEL DOREE 《Development, growth & differentiation》1987,29(1):93-103
Many studies suggest that MPF activation depends on protein phosphorylation or that MPF is itself a protein kinase. In the present report, cyclic variations of MPF activity have been correlated in vivo with changes in the extent of protein phosphorylation or in vitro with changes of a major protein kinase during the first cell cycles of fertilized starfish eggs. This cycling protein kinase neither requires cAMP nor Ca2+ . Neither colchicine nor aphidicoline, which inhibits cleavage and chromosome replication respectively, was found to suppress the synchronous and cyclic variations of both MPF and protein kinase activities. Protein synthesis was found to be required for both MPF and protein kinase activities to reappear after their simultaneous drop at the time of mitotic or meiotic cleavages. Production of either MPF or protein kinase activities is not the immediate result of protein synthesis since there is a delay at each cell cycle between the time when protein synthesis is required and the time when both MPF and protein kinase activities are produced. This suggests that both MPF and protein kinase activities might involve some post-translational modification of a precursor protein synthesized during the preceeding cell cycle. 相似文献
5.
A polyclonal antiserum and monoclonal antibodies have been prepared to purified pollen exines of Calocedrus decurrens Florin. The location of the antigen is in the exine, as shown by light-and electron-microscopic immunocytochemistry. The greatest reduction in antibody binding follows treatment of the exine with chemicals known to alter sporopollenin. These results provide evidence that sporopollenin is antigenic. Exines of ten species of gymnosperms and angiosperms also bound the polyclonal antiserum, indicating similarity of sporopollenin structure. 相似文献
6.
7.
8.
中国平脉树螽属五新种记述:直翅目:螽斯科:树螽亚科 总被引:2,自引:0,他引:2
本文报道中国平脉树螽属5个新种。每个新种皆有详细的形态描述和形态特征图。所有模式标本存于北京农业大学昆虫标本室。 相似文献
9.
10.