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排序方式: 共有236条查询结果,搜索用时 15 毫秒
101.
Mosquito larvicidal activity of transgenic Anabaena strain PCC 7120 expressing combinations of genes from Bacillus thuringiensis subsp. israelensis. 总被引:3,自引:0,他引:3 下载免费PDF全文
W Xiaoqiang S J Vennison L Huirong E Ben-Dov A Zaritsky S Boussiba 《Applied microbiology》1997,63(12):4971-4974
Various combinations of the genes cryIVA (cry4A), cryIVD (cry11A), and p20 from Bacillus thuringiensis subsp. israelensis were introduced into the nitrogen-fixing cyanobacterium Anabaena sp. strain PCC 7120 by means of Escherichia coli-Anabaena shuttle vector pRL488p and were expressed under control of two tandem strong promoters, a cyanobacterial promoter (PpsbA) and an E. coli T7 promoter (PA1). Two of the clones carrying cryIVA plus cryIVD, one with p20 and one without p20, displayed toxicity against third-instar larvae of Aedes aegypti at levels greater than any level previously reported for transgenic cyanobacteria. 相似文献
102.
The larvicidal activity of Bacillus thuringiensis var. israelensis against mosquitoes and the blackfly is included in parasporal crystalline bodies which are produced during sporulation. Following ingestion, the crystals are solubilized in the larval midgut and induce death within a short time; the spores germinate in the dead larvae and complete a growth cycle. The fate of the spores in surviving live larvae was elucidated by using a nonlarvicidal B. thuringiensis var. israelensis mutant. When introduced as the only food source, spores of this mutant support development to the adult stage of newly hatched Aedes aegypti larvae at a rate directly related to spore concentration. The conclusion that spores of B. thuringiensis var. israelensis are digested in the larval gut was substantiated by following the incorporation of [35S]methionine-labeled spores into larval tissues. 相似文献
103.
Nina Raver Mohammed Taouis Sami Dridi Michel Derouet Jean Simon Boaz Robinzon Jean Djiane Arieh Gertler 《Protein expression and purification》1998,14(3):403-408
Prokaryotic expression vector pMON3401 encoding full size A(−1) chicken leptin (AF012727) was prepared by PCR of previously described cDNA.Escherichia colicells transformed with this vector overexpressed large amounts of chicken leptin upon induction with nalidixic acid. The expressed protein found in the inclusion bodies was refolded and purified to homogeneity on a Q-Sepharose column, yielding two electrophoretically pure fractions (leptin-1 and leptin-2), eluted from the column by 100 and 125 mM NaCl. Both fractions showed a single band of the expected molecular mass of 16 kDa and were composed of over 95% of monomeric protein. The biological activity of both fractions, resulting from proper renaturation, was further evidenced by their ability to stimulate proliferation of leptin-sensitive BAF/3 cells transfected with a long form of human leptin–receptor construct and by lowering the food intake of starved chicken following intravenal or intraperitoneal injections. 相似文献
104.
105.
S. Boussiba X-Q. Wu E. Ben-Dov A. Zarka A. Zaritsky 《Journal of applied phycology》2000,12(3-5):461-467
Classical biological control is the most successfuland promising way to replace chemical pesticides. Thesubspecies israelensis of Bacillusthuringiensis (Bti) is a safe and efficient agent tocontrol mosquito larvae and hence mosquito-bornediseases. One approach to overcome the low efficacyand short half-life in nature of current formulationsof Bti is by expressing the toxin genes in recombinantcyanobacteria as a delivery system. Attempts toexpress Bti toxin in cyanoabcteria have been carriedout during the last ten years. Toxicities of thetransgenic strains were however very low, even underregulation of strong promoters, too low to beeffective in vivo. Two Bti Cry proteins haverecently been co-expressed in the filamentousnitrogen-fixing cyanobacterium Anabaena PCC7120, resulting in clones with the highest toxicitiesand stabilities ever reached so far. However, toobtain a long-lasting preparation, it would be usefulto express Bti toxin genes in cyanobacterial strainsisolated from nature. This approach requiresdevelopment of a system for effective transformationinto such strains. Releasing such recombinant strainsto open environments is still a major obstacle inexploiting this biotechnology. 相似文献
106.
Collective cell migration plays a major role in embryonic morphogenesis, tissue remodeling, wound repair and cancer invasion. Despite many decades of extensive investigations, only few analytical tools have been developed to enhance the biological understanding of this important phenomenon. Here we present a novel quantitative approach to analyze long term kinetics of bright field time-lapse wound healing. Fully-automated spatiotemporal measures and visualization of cells' motility and implicit morphology were proven to be sound, repetitive and highly informative compared to single-cell tracking analysis. We study cellular collective migration induced by tyrosine kinase-growth factor signaling (Met-Hepatocyte Growth Factor/Scatter Factor (HGF/SF)). Our quantitative approach is applied to demonstrate that collective migration of the adenocarcinoma cell lines is characterized by simple morpho-kinetics. HGF/SF induces complex morpho-kinetic coordinated collective migration: cells at the front move faster and are more spread than those further away from the wound edge. As the wound heals, distant cells gradually accelerate and enhance spread and elongation -resembling the epithelial to mesenchymal transition (EMT), and then the cells become more spread and maintain higher velocity than cells located closer to the wound. Finally, upon wound closure, front cells halt, shrink and round up (resembling mesenchymal to epithelial transition (MET) phenotype) while distant cells undergo the same process gradually. Met inhibition experiments further validate that Met signaling dramatically alters the morpho-kinetic dynamics of the healing wound. Machine-learning classification was applied to demonstrate the generalization of our findings, revealing even subtle changes in motility patterns induced by Met-inhibition. It is concluded that activation of Met-signaling induces an elaborated model in which cells lead a coordinated increased motility along with gradual differentiation-based collective cell motility dynamics. Our quantitative phenotypes may guide future investigation on the molecular and cellular mechanisms of tyrosine kinase-induced coordinate cell motility and morphogenesis in metastasis. 相似文献
107.
Figueiredo D Gertler A Cabello G Decuypere E Buyse J Dridi S 《Cell and tissue research》2007,329(1):91-101
Heat shock protein (HSP)-70 is expressed in normal and stressed cells but is highly stress-inducible. Although leptin has
long been suggested to be involved in the regulation of stress response, its interaction with the HSP-70 gene is still unknown,
under both unstressed and stressed conditions. The present study has aimed to investigate the effect of leptin on HSP-70 gene
expression in normal chicken liver, hypothalamus, and muscle. Continuous infusion of recombinant chicken leptin (8 μg/kg per
hour) at a constant rate of 3 ml/h for 6 h in 3-week-old broiler chickens significantly (P < 0.05) decreased food intake and HSP-70 mRNA levels in liver and hypothalamus, but not in muscle. In an attempt to discriminate
between the effect of leptin and of leptin-reduced food intake on HSP-70 gene expression, we also evaluated the effect of
food deprivation on the same cellular responses in two broiler chicken lines genetically selected for low (LL) or high (FL)
abdominal fat pad size. Food deprivation for 16 h did not affect HSP-70 gene expression in any of the studied tissues indicating
that the effect of leptin was independent of the inhibition of food intake. Regardless of the nutritional status, HSP-70 mRNA
levels were significantly (P < 0.05) higher in the hypothalamus of FL compared with LL chickens consistent with higher mRNA levels for hypothalamic corticotropin-releasing
factor. To assess, whether the effects of leptin were direct or indirect, we carried out in vitro studies. Leptin treatments
did not affect HSP-70 mRNA levels in a leghorn male hepatoma cell line or quail myoblast cell line suggesting that the effect
of leptin on HSP-70 gene expression is mediated through the central nervous system. Furthermore, HSP-70 gene expression was
gender-dependent with significantly (P < 0.05) higher levels in male than in female chickens.
This work was supported by a research grant (G.0402.05) from the FWO-Flanders (Belgium). No conflicts of interest would prejudice
impartiality. 相似文献
108.
Isaac R. Galatzer-Levy Yael Ankri Sara Freedman Yossi Israeli-Shalev Pablo Roitman Moran Gilad Arieh Y. Shalev 《PloS one》2013,8(8)
Context
Uncovering heterogeneities in the progression of early PTSD symptoms can improve our understanding of the disorder''s pathogenesis and prophylaxis.Objectives
To describe discrete symptom trajectories and examine their relevance for preventive interventions.Design
Latent Growth Mixture Modeling (LGMM) of data from a randomized controlled study of early treatment. LGMM identifies latent longitudinal trajectories by exploring discrete mixture distributions underlying observable data.Setting
Hadassah Hospital unselectively receives trauma survivors from Jerusalem and vicinity.Participants
Adult survivors of potentially traumatic events consecutively admitted to the hospital''s emergency department (ED) were assessed ten days and one-, five-, nine- and fifteen months after ED admission. Participants with data at ten days and at least two additional assessments (n = 957) were included; 125 received cognitive behavioral therapy (CBT) between one and nine months.Approach
We used LGMM to identify latent parameters of symptom progression and tested the effect of CBT on these parameters. CBT consisted of 12 weekly sessions of either cognitive therapy (n = 41) or prolonged exposure (PE, n = 49), starting 29.8±5.7 days after ED admission, or delayed PE (n = 35) starting at 151.8±42.4 days. CBT effectively reduced PTSD symptoms in the entire sample.Main Outcome Measure
Latent trajectories of PTSD symptoms; effects of CBT on these trajectories.Results
Three trajectories were identified: Rapid Remitting (rapid decrease in symptoms from 1- to 5-months; 56% of the sample), Slow Remitting (progressive decrease in symptoms over 15 months; 27%) and Non-Remitting (persistently elevated symptoms; 17%). CBT accelerated the recovery of the Slow Remitting class but did not affect the other classes.Conclusions
The early course of PTSD symptoms is characterized by distinct and diverging response patterns that are centrally relevant to understanding the disorder and preventing its occurrence. Studies of the pathogenesis of PTSD may benefit from using clustered symptom trajectories as their dependent variables. 相似文献109.
HIV-associated neurologic disorders are a mounting problem despite the advent of highly active antiretroviral therapy. To address mechanisms of HIV-associated neurologic disorders, we used an SIV pigtailed macaque model to study innate immune responses in brain that suppress viral replication during acute infection. We previously reported that during acute infection in brain, noncanonical type I IFN signaling occurs, where IFN-β mRNA is induced while IFN-α is simultaneously suppressed. Two downstream IFN-stimulated genes, MxA and TRAIL, also show differential expression patterns. In this study, we show that differential signaling is due to interactions between macrophages and astrocytes. Astrocytes produce high levels of CCL2 upon SIV infection, which binds to CCR2 receptors on macrophages, leading to a selective suppression of IFN-α and the IFN-stimulated gene TRAIL while simultaneously inducing IFN-β and MxA. The interactions between chemokine and cytokine pathways are a novel finding that may specifically occur in the CNS. 相似文献
110.