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   136篇
  免费   15篇
  151篇
  2017年   2篇
  2015年   2篇
  2014年   5篇
  2013年   5篇
  2012年   3篇
  2011年   2篇
  2010年   5篇
  2009年   3篇
  2008年   7篇
  2007年   2篇
  2006年   6篇
  2005年   2篇
  2004年   2篇
  2001年   2篇
  1999年   2篇
  1998年   11篇
  1997年   3篇
  1996年   5篇
  1995年   2篇
  1993年   2篇
  1992年   6篇
  1991年   2篇
  1990年   2篇
  1989年   3篇
  1988年   3篇
  1987年   4篇
  1984年   3篇
  1982年   1篇
  1981年   1篇
  1980年   1篇
  1979年   2篇
  1977年   1篇
  1975年   3篇
  1974年   1篇
  1971年   1篇
  1969年   1篇
  1966年   1篇
  1964年   1篇
  1962年   1篇
  1960年   1篇
  1958年   1篇
  1957年   2篇
  1955年   4篇
  1954年   8篇
  1953年   5篇
  1952年   2篇
  1951年   5篇
  1950年   3篇
  1949年   2篇
  1948年   4篇
排序方式: 共有151条查询结果,搜索用时 7 毫秒
1.
A range of accessions (182) of wild, semi-cultivated and cultivatedPhaseolus were subjected to attack by two Old World bruchids,Callosobruchus maculatus and Caliosobruchus chinensis and twoNew World bruchids Zabrotes subfasciatus and Acanthoscelidesobtectus. Six different stages in the progression of the brochid-legumeinteraction, at which resistance may occur, are described andassessed. Resistance is shown by: no oviposition; disruptedembryo development; failure of larvae to penetrate the testa;death of larvae within the cotyledon; failure of pupation oradult emergence; reduced fitness of adults. The occurrence ofresistance at each of these stages is discussed in the contextof possible causal mechanisms. The patterns of resistance tothe two pairs of bruchids of different geographical origin isconsidered in relation to co-evolutionary processes Phaseolus, wild species, resistance, bruchids, Callosobruchus maculatus, Callosobruchus chinensis, Zabrotes subfaciatus, Acanthoscelides obtectus  相似文献   
2.
3.
4.
Gold salts and phenylbutazone selectively inhibit the synthesis of PGF and PGE2 respectively. Lowered production of one prostaglandin species is accompanied by an increased production of the other. Selective inhibition by these drugs was observed in the presence of adrenaline, reduced glutathione and copper sulphate under conditions when most anti-inflammatory compounds inhibited PGE2 and PGF syntheses equally. It is postulated that selective inhibitors may have a different mode of action and beneficial effects may be related to the endogenous ratio of PGE to PGF required for normal function.  相似文献   
5.
SIMMONDS  N. W. 《Annals of botany》1960,24(2):212-222
A number of synthetic auxins and auxin-antagonists were appliedin lanolin emulsions to young banana fruits and their effectson fruit development and seed fertility estimated. Auxins stimulatedthe formation of edible pulp in both seedy and parthenocarpicbananas and induced varying degrees of seed sterility. Of theauxin antagonists tried, coumarin (contrary to a mistaken earlierreport) stimulated parthenocarpy and induced seed sterility,three others were not or but slightly active, and thiourea markedlyinhibited parthenocarpy. Study of the relation between sizeof mature fruit and seed content indicates that developing seedsstimulate the growth of pulp and that the amount of stimulationis roughly proportional to the level of parthenocarpy. Fruitdevelopment in the banana seems to fit in with Luckwill's generalscheme of dual hormonal stimulus.  相似文献   
6.
Summary : FT is a tool written in C++, which implements the Fourier analysis method to locate periodicities in aminoacid or DNA sequences. It is provided for free public use on a WWW server with a Java interface. Availability : The server address is http://o2.db. uoa.gr/FT Contact : shamodr@atlas.uoa.gr   相似文献   
7.

Background  

Pseudorabies virus (PRV) is an alphaherpesviruses whose native host is pig. PRV infection mainly causes signs of central nervous system disorder in young pigs, and respiratory system diseases in the adult.  相似文献   
8.
In a variety of tumour systems, individuals carrying progressively growing neoplasms have lymphoid cells with a specific cytotoxic effect on cultured tumour cells from the same individual1–4. Since the sera of tumour-bearing individuals have been shown to prevent tumour cell destruction by immune lymphocytes in vitro2,5–8 and since this serum blocking activity appears early in primary and transplant tumour development5,7, it has been suggested that the appearance of this serum blocking activity might be responsible for the progressive growth of tumours in individuals having cytotoxic lymphocytes. Counteraction of this blocking activity would thus be of primary importance in facilitating the function of an already existing or bolstered cell-mediated immunity. The serum blocking activity might be inhibited in various ways, by preventing the formation of blocking antibody or by interfering with its action (“unblocking”), as demonstrated in Moloney sarcoma regressor sera9. This type of serum also has a therapeutic effect on Moloney sarcomas in vivo10,11, which has been tentatively attributed to its unblocking activity8,9 or, possibly, to a complement-dependent cytotoxicity10. Tumour growth in the Moloney sarcoma system, however, might be due in part to continuous recruitment of neoplastic cells by virus-induced transformation and so the therapeutic effect could be due to a virus-neutralizing serum activity9,10.  相似文献   
9.
The four living genera of Ctenodactylidae (Rodentia) are the only survivors of a flourishing Tertiary group. In this paper, we describe a new Oligocene species from Ulantatal (Chinese Mongolia) that highlights the origins of crown ctenodactylids. This species, Helanshania deserta gen. et sp. nov. , is lophodont and displays semi‐hypsodont teeth, a dental pattern that is somewhat transitional between that of primitive Oligocene ctenodactylids and the later hypsodont genera. We perform here a cladistic assessment of the dental evidence for species produced by the successive radiations of the group. In order to get new data, to decipher homologies for the dental pattern of modern ctenodactylids, and to specify their dental replacement, we describe additional dental material of Ctenodactylus, Massoutiera, and Felovia. The phylogenetic analysis (using PAUP) considered 45 characters (mainly dental) and 31 species. The performed heuristic searches yielded 596 equally most parsimonious trees. Protataromys and Karakoromys are stem ctenodactylids and appear as the earliest offshoots of the Ctenodactylidae clade, which represents a well‐supported family rank. Within this family, the Tataromyinae appear paraphyletic, whereas the Ctenodactylinae sensu lato are a clade including the new taxon Helanshania. As such, a revision of the Tataromyinae is envisaged and a new subfamily is erected (Yindirtemyinae). Amongst the Ctenodactylinae, a tribe Ctenodactylini encompassing the crown ctenodactylines is proposed. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 160 , 531–550.  相似文献   
10.

Background  

Microarray-based pooled DNA experiments that combine the merits of DNA pooling and gene chip technology constitute a pivotal advance in biotechnology. This new technique uses pooled DNA, thereby reducing costs associated with the typing of DNA from numerous individuals. Moreover, use of an oligonucleotide gene chip reduces costs related to processing various DNA segments (e.g., primers, reagents). Thus, the technique provides an overall cost-effective solution for large-scale genomic/genetic research. However, few publicly shared tools are available to systematically analyze the rapidly accumulating volume of whole-genome pooled DNA data.  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