全文获取类型
收费全文 | 1590篇 |
免费 | 65篇 |
专业分类
1655篇 |
出版年
2023年 | 2篇 |
2022年 | 5篇 |
2021年 | 14篇 |
2020年 | 7篇 |
2019年 | 4篇 |
2018年 | 14篇 |
2017年 | 10篇 |
2016年 | 26篇 |
2015年 | 43篇 |
2014年 | 53篇 |
2013年 | 69篇 |
2012年 | 122篇 |
2011年 | 86篇 |
2010年 | 70篇 |
2009年 | 66篇 |
2008年 | 95篇 |
2007年 | 106篇 |
2006年 | 86篇 |
2005年 | 110篇 |
2004年 | 102篇 |
2003年 | 112篇 |
2002年 | 93篇 |
2001年 | 20篇 |
2000年 | 15篇 |
1999年 | 16篇 |
1998年 | 41篇 |
1997年 | 13篇 |
1996年 | 21篇 |
1995年 | 16篇 |
1994年 | 21篇 |
1993年 | 20篇 |
1992年 | 14篇 |
1991年 | 12篇 |
1990年 | 7篇 |
1989年 | 9篇 |
1988年 | 7篇 |
1986年 | 9篇 |
1985年 | 11篇 |
1984年 | 10篇 |
1983年 | 10篇 |
1982年 | 12篇 |
1981年 | 15篇 |
1980年 | 10篇 |
1979年 | 6篇 |
1978年 | 10篇 |
1977年 | 5篇 |
1976年 | 9篇 |
1975年 | 7篇 |
1974年 | 5篇 |
1966年 | 2篇 |
排序方式: 共有1655条查询结果,搜索用时 31 毫秒
1.
2.
3.
4.
Chromosome localization and polymorphism of an oestrogen-inducible gene specifically expressed in some breast cancers 总被引:3,自引:0,他引:3
Summary The BCEI gene codes for a small secreted protein and is expressed in the human mammary tumour cell line MCF7 under oestrogen control and in some breast cancers. We have mapped the gene to chromosome 21 using a panel of somatic hybrid lines, and in situ hybridization has allowed a precise assignment to band 21q223. Two restriction fragment length polymorphisms (RFLP) are described that should be of use in linkage or population studies to test a possible involvement of the BCEI gene in genetic predisposition to breast cancer. This gene should also be a useful marker for the genetic and physical mapping of chromosome 21, and for a better definition of the region involved in the clinical phenotype of Downs syndrome. 相似文献
5.
Khalid M. Chraibi B Jean-Claude Castelle Alain Latche Jean-Paul Roustan Jean Fallot 《Plant cell reports》1992,10(12):617-620
We describe here a liquid culture system for the regeneration of shoots at high frequencies from mature cotyledon tissues of three genotypes of sunflower (Helianthus annuus L.) one of which had previously been found to be recalcitrant to regeneration when cotyledons were cultured on solid medium. Cotyledons were excised from 2-day-old seedlings and incubated in liquid Murashige and Skoog's modified medium supplemented with 5.4 M naphthaleneacetic acid (NAA) and 4.4 M benzylaminopurine (BAP). After two weeks in culture, the whole upper surface of regenerating explants was covered with green shootlets. The percentages of regenerating explants of three genotypes varied between 60 and 70%, and the number of shoots per regenerating explant was highly increased. The shootlets were transferred to solid Murashige and Skoog's medium allowing shoot development, then to rooting medium. Rooted plantlets were successfully acclimatized and gave fertile plants. The role of liquid medium culture in the induction of sunflower regeneration is discussed.Abbreviations BAP
6-benzylaminopurine
- NAA
1-naphthaleneacetic acid
- IAA
indole-3-acetic acid
- IBA
indole-3-butyric acid 相似文献
6.
7.
Cell proliferation has been induced from the cambial zone of a branch of Acacia senegal, kept on the basal Knop and Ball medium in the presence of auxin. Transferred on the more complete nutrient medium of Schenk and Hildebrandt, the colonies gave rise to several cell lines. One of the friable lines, consisting of aggregates of parenchymatous cells, gave a cell suspension culture in an agitated liquid medium which is maintained as a strain of illimited growth. The heterogeneous suspension did not undergo noticeable changes after eight transfers. Aggregates collected on a 1000-m nylon seive were able to grow on a solid medium and gave back a friable callus similar to the initial colonies. 相似文献
8.
Jean-Paul Aeschlimann 《Entomologia Experimentalis et Applicata》1974,17(4):487-492
Résumé Les conditions de l'hibernation sont étudiées chez les trois espèces de Métopiines Chorinaeus funebris Gravenhorst, Triclistus podagricus Gravenhorst et Triclistus pygmaeus Cresson. Ces espèces hibernent à des stades de développement compris entre l'éonymphe et l'adulte non émergé (Tableau I). La durée de l'incubation complémentaire après réactivation par le froid à 2o varie entre 10 et 30 jours en moyenne (Tableaux II, IV et V). Chez T. podagricus et T. pygmaeus, on a observé également des émergences d'adultes avant l'hiver (Tableau III). I1 semble que T. podagricus ne parvienne au stade d'imago hibernant qu'après une baisse de la température d'élevage. Aucune souche dépourvue de diapause n'a pu être créée, mais pour les trois espèces, deux générations annuelles seraient possibles sous conditions contrôlées. Enfin, l'utilisation éventuelle de T. pygmaeus pour une lutte biologique contre Zeiraphera diniana Guénée est évoquée.
Summary The conditions of hibernation have been investigated in the three metopiine species Chorinaeus funebris, Triclistus podagricus and Triclistus pygmaeus, all entomophagous on Zeiraphera diniana Guénée (Lepidoptera, Tortricidae) in the Engadine Valley (Switzerland). The hibernating stages are eonymph, pronymph or unemerged adult inside the host pupae (Table I). The length of the complementary incubation after reactivation at 2o varies between 10–30 days (Tables II, IV and V). A small number of T. podagricus and of T. pygmaeus regularly appear as adults before winter, in rearings of both laboratory and field populations (Table III). It seems that T. podagricus larvae need a reduction in the initial rearing temperature before full development is achieved and the hibernating stage is reached (imago). No strain without diapause could be obtained for any of the three species, but the rearing of two annual generations under controlled conditions is possible in the laboratory. The eventual use of T. pygmaeus as a control agent against Z. diniana is discussed.相似文献
9.
Georges Vauquelin Hilde De Vos Jean-Paul De Backer Guy Ebinger 《Neurochemistry international》1990,17(4)
The antagonist [3H]idazoxan binds with comparable affinity to α2 adrenergic receptors and to phentolamine-displaceable non-stereoselective sites in human frontal cortex membranes. In contrast, idazoxan analogs possessing alkyl and alkoxy substituents at the 2-position of the benzodioxan moiety (i.e. RX 821002: 2-methoxy-1,4-[6,7-3H]benzodioxan-2-yl-2-imidazolin HCl, 43.8 Ci/mmol) possess 300–1200 times lower affinity for the non-stereoselective sites. Their affinity for the α2 receptors is increased as well, resulting in more than a 1000-fold selectivity towards the receptors as compared to the non-stereoselective sites. [3H]RX 821002, the 2-methoxy analog of idazoxan possesses an approx. 10-fold higher affinity for the α2 receptors (KD = 2.8 nM than [3H]idazoxan (KD = 24 nM) and about equal affinity as [3H]rauwolscine (KD = 3.6 nM).[3H]Rauwolscine binds with comparable affinity to α2 receptors and to 5-HT1A receptors, and competition studies indicate that the Ki value of unlabelled RX 821002 for the 5-HT1A receptors (30 nM) is about one order in magnitude above its Ki value for the α2 receptors (4.1 nM). Labelling of the 5-HT1A receptors by [3H]RX 821002 and by [3H]rauwolscine can be prevented by selective masking with 8-OH-DPAT (30 nM) or 5-HT (0.3 μM). Under these conditions, specific binding of [3H]RX 821002 to the α2 receptors represents 84% of total binding (at its KD), as compared to 77% for [3H]rauwolscine and 20% for [3H]idazoxan.[3H]RX 821002 labels the α2 receptors as a single class of non-cooperative sites. Association and dissociation kinetics are very fast at 37°C. Antagonist competition curves are steep with Hill coefficients close to one and the agonist curves can be analysed in terms of two affinity sites, confirming the antagonistic properties of [3H]RX821002. About 60% of the α2 receptors possess high agonist affinity. 相似文献
10.
The present work collects the new names of syntaxa (in the sense of the Code of Phytosociological Nomenclature,Barkman et al. 1986) above subassociation, rank found in the literature received by the Library of the Conservatoire et Jardin botaniques in Geneva. For the year 1992, 658 names have been listed. For each one of them, an appreciation about its validity is given relating to the Code of Phytosociological Nomenclature. Fifteen names are given in addition to the Indexes 1987, 1990 and 1991 (Theurillat & Moravec 1990, 1993, 1994). 相似文献