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   525篇
  免费   51篇
  576篇
  2024年   2篇
  2023年   5篇
  2022年   8篇
  2021年   27篇
  2020年   9篇
  2019年   11篇
  2018年   21篇
  2017年   15篇
  2016年   20篇
  2015年   19篇
  2014年   26篇
  2013年   40篇
  2012年   45篇
  2011年   38篇
  2010年   31篇
  2009年   24篇
  2008年   28篇
  2007年   30篇
  2006年   23篇
  2005年   24篇
  2004年   23篇
  2003年   16篇
  2002年   14篇
  2001年   3篇
  1999年   8篇
  1998年   4篇
  1997年   3篇
  1994年   3篇
  1992年   4篇
  1991年   7篇
  1990年   6篇
  1989年   2篇
  1988年   3篇
  1987年   6篇
  1986年   3篇
  1985年   2篇
  1984年   2篇
  1983年   2篇
  1980年   1篇
  1978年   1篇
  1977年   1篇
  1976年   1篇
  1975年   1篇
  1974年   2篇
  1973年   1篇
  1972年   3篇
  1970年   1篇
  1969年   1篇
  1968年   1篇
  1965年   2篇
排序方式: 共有576条查询结果,搜索用时 15 毫秒
571.
Cis-8-dodecenyl acetate, the sex attractant of the plum fruit moth, Grapholitha funebrana, was evaporated in two plum orchards in West Switzerland during the summer months of 1973 and 1974 at rates of 180 to 900 mg per tree and season. A simple and effective evaporator was developed for this purpose which permitted monitoring of attractant evaporation in the field.From the low numbers of males caught with sex traps and the low resulting plum fruit moth attack, as compared with a third orchard receiving conventional insecticide treatment, it is concluded that communication disruption between sexes by evaporation of sex attractant was effective and that this method may be a feasible way of plum fruit moth control.Additional experiments showed that in this insect, as in other Grapholitha species, addition of a small amount of the trans isomer (3 to 5%) to cis-8-dodecenyl acetate is necessary for best attraction.
Résumé L'attractif sexuel du ver des prunes Grapholitha funebrana Tr. (cis-8-dodécényl-acétate) est évaporé dans deux plantations de pruniers en Suisse romande, au cours de l'été en 1973 et en 1974 à raison de 180 à 900 mg par arbre et par saison. Un diffuseur simple est construit à cet effet; il permet de mesurer directement la quantité de produit libérée dans le verger.Comparativement à une parcelle traitée aux insecticides, les captures de mâles aux pièges sexuels dans les deux parcelles considérées sont très peu nombreuses et l'attaque du ver sur fruits est fortement diminuée. Il est par conséquent indéniable que la diffusion d'attractif a provoqué une interruption du rapprochement des sexes. Cette méthode semble ouvrir une voie nouvelle dans la lutte contre le ver des prunes.Des essais complémentaires montrent que pour cette espèce comme pour d'autres Grapholitha le mélange d'une petite quantité d'isomère trans (3 à 5%) au cis-8-dodécényl-acétate est nécessaire pour obtenir une attractivité optimale.
  相似文献   
572.
The emerging tumor-on-chip (ToC) approaches allow to address biomedical questions out of reach with classical cell culture techniques: in biomimetic 3D hydrogels they partially reconstitute ex vivo the complexity of the tumor microenvironment and the cellular dynamics involving multiple cell types (cancer cells, immune cells, fibroblasts, etc.). However, a clear bottleneck is the extraction and interpretation of the rich biological information contained, sometime hidden, in the cell co-culture videos. In this work, we develop and apply novel video analysis algorithms to automatically measure the cytotoxic effects on human cancer cells (lung and breast) induced either by doxorubicin chemotherapy drug or by autologous tumor-infiltrating cytotoxic T lymphocytes (CTL). A live fluorescent dye (red) is used to selectively pre-stain the cancer cells before co-cultures and a live fluorescent reporter for caspase activity (green) is used to monitor apoptotic cell death. The here described open-source computational method, named STAMP (spatiotemporal apoptosis mapper), extracts the temporal kinetics and the spatial maps of cancer death, by localizing and tracking cancer cells in the red channel, and by counting the red to green transition signals, over 2–3 days. The robustness and versatility of the method is demonstrated by its application to different cell models and co-culture combinations. Noteworthy, this approach reveals the strong contribution of primary cancer-associated fibroblasts (CAFs) to breast cancer chemo-resistance, proving to be a powerful strategy to investigate intercellular cross-talks and drug resistance mechanisms. Moreover, we defined a new parameter, the ‘potential of death induction’, which is computed in time and in space to quantify the impact of dying cells on neighbor cells. We found that, contrary to natural death, cancer death induced by chemotherapy or by CTL is transmissible, in that it promotes the death of nearby cancer cells, suggesting the release of diffusible factors which amplify the initial cytotoxic stimulus.  相似文献   
573.
We describe the effects of products of mononuclear phagocytes on the secretory activity of chondrocytes. The primary confluent cultures of rabbit articular chondrocytes were exposed to standard medium alone or enriched with conditioned medium obtained from cultures of rabbit peritoneal macrophages, the mouse macrophage cell line P388D1 or human blood mononuclear cells. Four markers of release were assessed, the neutral proteinases plasminogen activator and collagenase, the acid hydrolase beta-glucuronidase and prostaglandin E2, and the kinetics of their changes were monitored. Chondrocytes that were cultured in standard medium secreted large amounts of plasminogen activator, some beta-glucuronidase, but no collagenase, and released only minor amounts of prostaglandin E2. The addition of conditioned medium from rabbit macrophages induced a rapid release of large quantities of prostaglandin E2 and an abundant secretion of collagenase, while abolishing or strongly decreasing plasminogen activator secretion. In addition, beta-glucuronidase secretion was markedly enhanced. The decrease in secretion of plasminogen activator appeared to reflect a diminished production, since no evidence was found for the generation of inhibitors or for an accelerated extracellular breakdown of the enzyme. Conditioned media of the mouse and human mononuclear cells influenced the secretory activities of rabbit articular chondrocytes in a similar way, suggesting that the factor (or factors) acting on chondrocytes is produced by a variety of macrophages, and that its action is not species-restricted. The time course and concentration-dependence of the effects observed indicate that the secretion of plasminogen activator and collagenase are influenced in a strictly reciprocal fashion by the macrophage products. The release of prostaglandin E2 paralleled that of collagenase.  相似文献   
574.
Interleukin-8, a chemotactic and inflammatory cytokine.   总被引:22,自引:0,他引:22  
Interleukin-8 (IL-8) belongs to a family of small, structurally related cytokines similar to platelet factor 4. It is produced by phagocytes and mesenchymal cells exposed to inflammatory stimuli (e.g., interleukin-1 or tumor necrosis factor) and activates neutrophils inducing chemotaxis, exocytosis and the respiratory burst. In vivo, IL-8 elicits a massive neutrophil accumulation at the site of injection. Five neutrophil-activating cytokines similar to IL-8 in structure and function have been identified recently. IL-8 and the related cytokines are produced in several tissues upon infection, inflammation, ischemia, trauma etc., and are thought to be the main cause of local neutrophil accumulation.  相似文献   
575.
Formyl-methionyl-leucyl-phenylalanine (fMLP) and 1-oleoyl-2-acetyl-glycerol (OAG) are synergistic stimuli of the respiratory burst of neutrophils. Simultaneous exposure to both agents greatly enhanced superoxide production, both in rate and extent. OAG potentiated the response to fMLP also in Ca++ -free medium. Pretreatment of the neutrophils with fMLP drastically shortened the lag of superoxide production in response to OAG. Our findings lead to the following conclusions: (i) Protein kinase C is likely to be involved in the activation of the NADPH oxidase by fMLP; (ii) OAG appears to be utilized as an intermediate in the activation process; (iii) prestimulation of the cells with fMLP facilitates the response to OAG.  相似文献   
576.
The effectiveness of an insect growth regulator (IGR) of the juvenile hormone type (Ro 10-3108/018) was tested in field trials in 1976 against summer fruit tortrix (Adoxophyes orana F.v.R., Lepidoptera: Tortricidae) and other orchard pests. The orchards were sprayed in spring at the beginning of the last larval stage of the hibernated generation of the summer fruit tortrix.Numerous deformations were observed in larvae, pupae and adults, collected 1 to 3 weeks after treatment. The emergence of moths reared from exposed larvae and the reproduction of emerged adults were considerably reduced. In well-isolated orchards, the flight of moths of the treated generation was low, but in less isolated ones reinfestation from elsewhere was observed. The population of the next generation, which was studied in fifteen apple and two pear orchards in Switzerland and in the Netherlands, decreased markedly in well-isolated orchards. Moreover, fruit damage was no greater than that following a classical spraying programme.The advantages and disadvantages of the application of these specific insecticides in integrated control programmes are discussed.
Résume L'efficacité des régulateurs de croissance d'insectes (RCI), analogues de l'hormone juvénile, a été testée en plein champ contre capua (Adoxophyes orana) et contre d'autres ravageurs des vergers du pommier. Les traitements ont été appliqués au début du dernier stade de la génération hivernante de cette tordeuse.De nombreuses malformations ont pu être observées sur des individus de capua récoltés 1 à 3 semaines après le traitement, aussi bien au stade larvaire que pupal et adulte. Le taux d'éclosion des papillons issus de larves traitées et le potentiel de reproduction de ces imagos éclos ont été fortement réduits.L'effet sur la dynamique de la population du ravageur de la génération suivant l'application des RCI a également été étudié dans 15 vergers de pommiers et 2 vergers de poiriers en Suisse et aux Pays-Bas. Le vol des papillons de la génération traitée et la population larvaire de la génération d'été ont été fortement réduits dans les vergers bien isolés. D'autre part les dégâts sur fruits restent en général faibles.Les avantages et les répercussions de l'utilisation de ces insecticides plus spécifiques dans la lutte intégrée, sont discutés.
  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