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排序方式: 共有371条查询结果,搜索用时 15 毫秒
31.
Fei‐Xue Fu Mark E. Warner Yaohong Zhang Yuanyuan Feng David A. Hutchins 《Journal of phycology》2007,43(3):485-496
Little is known about the combined impacts of future CO2 and temperature increases on the growth and physiology of marine picocyanobacteria. We incubated Synechococcus and Prochlorococcus under present‐day (380 ppm) or predicted year‐2100 CO2 levels (750 ppm), and under normal versus elevated temperatures (+4°C) in semicontinuous cultures. Increased temperature stimulated the cell division rates of Synechococcus but not Prochlorococcus. Doubled CO2 combined with elevated temperature increased maximum chl a–normalized photosynthetic rates of Synechococcus four times relative to controls. Temperature also altered other photosynthetic parameters (α, Φmax, Ek, and ) in Synechococcus, but these changes were not observed for Prochlorococcus. Both increased CO2 and temperature raised the phycobilin and chl a content of Synechococcus, while only elevated temperature increased divinyl chl a in Prochlorococcus. Cellular carbon (C) and nitrogen (N) quotas, but not phosphorus (P) quotas, increased with elevated CO2 in Synechococcus, leading to ~20% higher C:P and N:P ratios. In contrast, Prochlorococcus elemental composition remained unaffected by CO2, but cell volume and elemental quotas doubled with increasing temperature while maintaining constant stoichiometry. Synechococcus showed a much greater response to CO2 and temperature increases for most parameters measured, compared with Prochlorococcus. Our results suggest that global change could influence the dominance of Synechococcus and Prochlorococcus ecotypes, with likely effects on oligotrophic food‐web structure. However, individual picocyanobacteria strains may respond quite differently to future CO2 and temperature increases, and caution is needed when generalizing their responses to global change in the ocean. 相似文献
32.
Oberholzer A John T Kohl B Gust T Müller RD La Face D Hutchins B Zreiqat H Ertel W Schulze-Tanzil G 《Cell and tissue research》2007,328(2):383-390
Gene transfer into cultured chondrocytes by using adenoviral vectors has potential applications in treating cartilage disorders.
The present study was undertaken to compare and optimize two chondrocyte culture conditions for adenoviral transduction efficacy
by using primary human articular chondrocytes cultivated either directly in a monolayer condition or as outgrowths from alginate-stored
chondrocyte cultures. Isolated primary chondrocytes from human articular cartilage were either immediately transduced with
an EGFP (enhanced green fluorescent protein)-gene-bearing adenoviral vector (1,000 and 3,000 virus particles/cell) or cultured
in alginate before transduction. Immunohistochemistry and flow cytometric analysis were employed to determine the expression
of extracellular matrix proteins and of the αvβ5 integrin receptor involved in adenoviral cell entry. Monolayer chondrocytes
exhibited moderate transduction rates (mean 22.2% and 46.9% EGFP-positive cells at 1,000 and 3,000 virus particles/cell by
72 h post-transduction), whereas alginate-derived chondrocytes revealed significantly higher transduction efficacies (95.7%
and 99%). Both monolayer and alginate-derived chondrocytes expressed αvβ5 integrin, type II collagen and cartilage proteoglycans.
The mean fluorescence intensity of type II collagen was significantly higher in the alginate-derived chondrocytes, whereas
that of αvβ5 integrin was higher in the monolayer chondrocytes. Our results indicate that transduction efficacy is independent
of αvβ5 integrin expression levels in chondrocytes. Moreover, adenoviral transduction of alginate-derived chondrocytes is
more efficient than that for monolayer chondrocytes and may be a suitable tool to achieve sufficient numbers of transduced
and differentiated chondrocytes for experimental applications and cartilage repair.
Dr. Gundula Schulze-Tanzil is supported by a grant awarded by the Rahel Hirsh Foundation from the Charité Medical Schools
Berlin. The study was supported by a grant from the Deutsche Arthrosehilfe e.V. 相似文献
33.
Liu D Brockman JM Dass B Hutchins LN Singh P McCarrey JR MacDonald CC Graber JH 《Nucleic acids research》2007,35(1):234-246
Gene expression and processing during mouse male germ cell maturation (spermatogenesis) is highly specialized. Previous reports have suggested that there is a high incidence of alternative 3′-processing in male germ cell mRNAs, including reduced usage of the canonical polyadenylation signal, AAUAAA. We used EST libraries generated from mouse testicular cells to identify 3′-processing sites used at various stages of spermatogenesis (spermatogonia, spermatocytes and round spermatids) and testicular somatic Sertoli cells. We assessed differences in 3′-processing characteristics in the testicular samples, compared to control sets of widely used 3′-processing sites. Using a new method for comparison of degenerate regulatory elements between sequence samples, we identified significant changes in the use of putative 3′-processing regulatory sequence elements in all spermatogenic cell types. In addition, we observed a trend towards truncated 3′-untranslated regions (3′-UTRs), with the most significant differences apparent in round spermatids. In contrast, Sertoli cells displayed a much smaller trend towards 3′-UTR truncation and no significant difference in 3′-processing regulatory sequences. Finally, we identified a number of genes encoding mRNAs that were specifically subject to alternative 3′-processing during meiosis and postmeiotic development. Our results highlight developmental differences in polyadenylation site choice and in the elements that likely control them during spermatogenesis. 相似文献
34.
Zheng QH Gao M Mock BH Wang S Hara T Nazih R Miller MA Receveur TJ Lopshire JC Groh WJ Zipes DP Hutchins GD DeGrado TR 《Bioorganic & medicinal chemistry letters》2007,17(8):2220-2224
The high-affinity choline transporter (CHT1) system is an attractive target for the development of positron emission tomography (PET) biomarkers to probe brain, cardiac, and cancer diseases. An efficient and convenient synthesis of new radiolabeled CHT1 inhibitors [(11)C]hemicholinium-3 and [(18)F]hemicholinium-3 by solid-phase extraction (SPE) technique using a cation-exchange CM Sep-Pak cartridge has been well developed. The preliminary evaluation of both tracers through biodistribution studies in 9L-glioma rats has been performed, and the uptakes in the heart and tumor were observed, while very low brain uptake was seen. 相似文献
35.
Derivative of plant phenolic compound inhibits the type III secretion system of Dickeya dadantii via HrpX/HrpY two‐component signal transduction and Rsm systems
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36.
McGuigan C Madela K Aljarah M Gilles A Battina SK Ramamurty CV Srinivas Rao C Vernachio J Hutchins J Hall A Kolykhalov A Henson G Chamberlain S 《Bioorganic & medicinal chemistry letters》2011,21(19):6007-6012
We have previously reported the power of combining a 5'-phosphoramidate ProTide, phosphate pro-drug, motif with a 6-methoxy purine pro-drug entity to generate highly potent anti-HCV agents, leading to agents in clinical trial. We herein extend this work with the disclosure that a variety of alternative 6-substituents are tolerated. Several compounds exceed the potency of the prior 6-methoxy leads, and in almost every case the ProTide is several orders of magnitude more potent than the parent nucleoside. We also demonstrate that these agents act as pro-drugs of 2'-C-methyl guanosine monophosphate. We have also reported the novel use of hepatocyte cell lysate as an ex vivo model for ProTide metabolism. 相似文献
37.
Li Q Woods KW Wang W Lin NH Claiborne A Gu WZ Cohen J Stoll VS Hutchins C Frost D Rosenberg SH Sham HL 《Bioorganic & medicinal chemistry letters》2005,15(8):2033-2039
Beginning with the structure of tipifarnib (1), a series of inhibitors of FTase have been synthesized by transposition of the D-ring to the imidazole and subsequent modification of the 2-quinolone motif. The compounds in the new series may be achiral and have structural features that allow for analogs that are difficult or impossible to make in the tertiary carbon-based tipifarnib series. The most potent compound (4d) is 4 times more active in vitro against FTase than tipifarnib. 相似文献
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40.
Hutchins AS Artis D Hendrich BD Bird AP Scott P Reiner SL 《Journal of immunology (Baltimore, Md. : 1950)》2005,175(9):5606-5610
Immunity often depends on proper cell fate choice by helper T lymphocytes. A naive cell, with minimal expression of IFN-gamma and IL-4, must give rise to progeny expressing high levels of either one, but not both, of those cytokines to defend against protozoan and helminthic pathogens, respectively. In the present study, we show that inactivation of the Mbd2 gene, which links DNA methylation and repressed chromatin, results in enhanced resistance to the protozoan parasite Leishmania major but impaired immunity to the intestinal helminth Trichuris muris. Helper T cells from methyl CpG-binding domain protein-2-deficient mice exhibit exuberant patterns of cytokine expression despite appropriate silencing of genes encoding the lineage-specifying factors T-bet and GATA-3. These results suggest that gene silencing can facilitate the ability of a progenitor cell to give rise to appropriately differentiated daughter cells in vivo. These findings also point to novel pathways that could participate in genetic control of resistance to infection and autoimmunity. 相似文献