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排序方式: 共有360条查询结果,搜索用时 125 毫秒
11.
12.
Denise C.O.F. Valdetaro Thomas C. Harrington Leonardo S.S. Oliveira Lúcio M.S. Guimarães Douglas L. McNew Lucas V.A. Pimenta Rivadalve C. Gonçalves Daniel A. Schurt Acelino C. Alfenas 《Fungal biology》2019,123(2):170-182
Ceratocystis fimbriata Ellis & Halsted recently was recorded causing seed and seedling blight on Carapa guianensis Aubl. (andiroba), a tree species native to the Amazon Rainforest and prized for its valuable timber and medicinal seed oil. C. fimbriata more commonly causes wilt type diseases in woody hosts, especially on non-native host trees. However, on andiroba the disease occurs on seedlings and seeds, affecting the species regeneration. We studied 73 isolates of C. fimbriata on andiroba from three regions of the Amazon Basin to see if they represented natural or introduced populations. Analysis of ITS rDNA sequences and phylogenetic analysis of mating type genes revealed new haplotypes of C. fimbriata from the Latin American Clade that were closely related to other Brazilian populations of the fungus. In mating experiments, andiroba isolates were inter-fertile with tester strains of C. fimbriata from Brazil and elsewhere, confirming that they belong to a single biological species. Using microsatellite markers, 14 genotypes and populations with intermediate levels of genetic variability were found, suggesting that the fungus is indigenous to the Amazon Basin. Inoculation tests indicated that the andiroba isolates are host-specialized on andiroba, supporting the proposition of the special form C. fimbriata f. sp. carapa. 相似文献
13.
Pimenta Larissa Langsdorff Lima Gustavo Pereira Biondi Michel Vaz Marcelo Gomes Marçal Vieira de Freitas Coelho Flávia 《Aquatic Ecology》2022,56(3):543-553
Aquatic Ecology - In epiphytic associations, cyanobacteria form the periphyton with phytoplanktonic algae and with aquatic macrophytes. In this study, we found homocytous and heterocytous... 相似文献
14.
HENRY SILVERMAN BABIKER AHMED SAMAR AJEILET SUMAIA AL‐FADIL SUHAIL AL‐AMAD HADIR EL‐DESSOUKY IBRAHIM EL‐GENDY MOHAMED EL‐GUINDI MUSTAFA EL‐NIMEIRI RANA MUZAFFAR AZZA SALEH 《Developing world bioethics》2010,10(2):70-77
To help ensure the ethical conduct of research, many have recommended educational efforts in research ethics to investigators and members of research ethics committees (RECs). One type of education activity involves multi‐day workshops in research ethics. To be effective, such workshops should contain the appropriate content and teaching techniques geared towards the learning styles of the targeted audiences. To ensure consistency in content and quality, we describe the development of a curriculum guide, core competencies and associated learning objectives and activities to help educators organize research ethics workshops in their respective institutions. The curriculum guide is divided into modular units to enable planners to develop workshops of different lengths and choose content materials that match the needs, abilities, and prior experiences of the target audiences. The content material in the curriculum guide is relevant for audiences in the Middle East, because individuals from the Middle East who participated in a Certificate Program in research ethics selected and developed the training materials (e.g., articles, powerpoint slides, case studies, protocols). Also, many of the activities incorporate active‐learning methods, consisting of group work activities analyzing case studies and reviewing protocols. The development of such a workshop training curriculum guide represents a sustainable educational resource to enhance research ethics capacity in the Middle East. 相似文献
15.
Chen VC Chao L Pimenta DC Bledsoe G Juliano L Chao J 《The Journal of biological chemistry》2001,276(2):1276-1284
Kallistatin is a heparin-binding serine proteinase inhibitor (serpin), which specifically inhibits human tissue kallikrein by forming a covalent complex. The inhibitory activity of kallistatin is blocked upon its binding to heparin. In this study we attempted to locate the heparin-binding site of kallistatin using synthetic peptides derived from its surface regions and by site-directed mutagenesis of basic residues in these surface regions. Two synthetic peptides, containing clusters of positive-charged residues, one derived from the F helix and the other from the region encompassing the H helix and C2 sheet of kallistatin, were used to assess their heparin binding activity. Competition assay analysis showed that the peptide derived from the H helix and C2 sheet displayed higher and specific heparin binding activity. The basic residues in both regions were substituted to generate three kallistatin double mutants K187A/K188A (mutations in the F helix) and K307A/R308A and K312A/K313A (mutations in the region between the H helix and C2 sheet), using a kallistatin P1Arg variant as a scaffold. Analysis of these mutants by heparin-affinity chromatography showed that the heparin binding capacity of the variant K187A/K188A was not altered, whereas the binding capacity of K307A/R308A and K312A/K313A mutants was markedly reduced. Titration analysis with heparin showed that the K312A/K313A mutant has the highest dissociation constant. Like kallistatin, the binding activity of K187A/K188A to tissue kallikrein was blocked by heparin, whereas K307A/R308A and K312A/K313A retained significant binding and inhibitory activities in the presence of heparin. These results indicate that the basic residues, particularly Lys(312)-Lys(313), in the region between the H helix and C2 sheet of kallistatin, comprise a major heparin-binding site responsible for its heparin-suppressed tissue kallikrein binding. 相似文献
16.
HlyD has a single transmembrane domain (residues 59-80) and a large periplasmic domain, and is essential for the secretion
of haemolysin from Escherichia coli. Using an antibody raised against HlyD, the protein was localised to the cell envelope by immunofluorescence and to the cytoplasmic
membrane by sucrose gradient analysis. We have examined the stability of this protein in the presence and absence of other
putative components of the translocator, HlyB and TolC. HlyD is normally highly stable but in the absence of TolC, the steady-state
level of HlyD is greatly reduced and the protein has a half-life at 37° C of 36 min. In the absence of HlyB, HlyD is also
unstable and specific degradation products are detected, which co-fractionate with the inner membrane, indicating in this
case limited cleavage at specific sites. However, the effect of removing both HlyB and TolC is not additive. On the contrary,
in the absence of both HlyB and TolC the half-life of HlyD is approximately 110 min. This result shows that in the presence
of HlyB removal of TolC renders HlyD more unstable than it is in the absence of both HlyB and TolC. This suggests that the
presence of HlyB induces a structural change in HlyD. In addition, HlyB itself appears to be less stable in the absence of
HlyD. These results are consistent with an interaction between HlyD/TolC and HlyB/HlyD. A derivative of HlyD, HlyD22, lacking
the 40 N-terminal residues of HlyD assembles into the inner membrane displaying the same stability with and without HlyB as
wild type HlyD does. This N-terminal region therefore appears to play no role in stable localisation but is involved in secretion,
since HlyD22 is completely secretion defective. Modification of the C-terminus on the other hand completely destabilised the
molecule and HlyD was not detectable in the envelope. Secretion of active haemolysin is limited to a brief period during mid
to late exponential phase. In contrast, HlyD is apparently synthesised constitutively throughout the growth phase, demonstrating
that the production of this component of the translocator is not the limiting factor for growth phase-dependent secretion.
Received: 10 July 1998 / Accepted: 19 October 1998 相似文献
17.
Entamoeba histolytica Schaudinn, 1903 and Entamoeba dispar Brumpt. 1925 are two of eight species of Entamoeba that sometimes inhabit the human colon. The former is an invasive organism capable of causing life-threatening intestinal and extra-intestinal disease: the latter appears not to be invasive. Because the two species, when viewed by light microscopy appear morphologically similar, they were long regarded as a single species. However, recent biochemical. immunological, and genetic studies provided convincing evidence that they belong to separate species. Our ultrastructural studies revealed distinct differences in at least two features of the trophozoites. 1) The cell surfaces of the trophozoites of each species differ with regard to structures exposed on the surface, and the distribution and arrangement of intra-membranous proteins. 2) The phagocytosis of bacteria differs in respect to the formation of the phagocytic vacuoles. Loose vacuoles containing several bacteria were seen in E. histolytica whereas tight vacuoles containing a single bacterium were observed in E. dispar. Furthermore, bacteria were found only within vacuoles in E. histolytica; in E. dispar, bacteria were found within vacuoles and some were found free in the cytoplasm. 相似文献
18.
19.
Binz PA Abdi F Affolter M Allard L Barblan J Bhardwaj S Bienvenut WV Bulet P Burgess J Carrette O Corthals G Delalande F Diemer H Favreau P Giuliano E Gueguen Y Guillaume E Hahner S Man P Michalet S Neri D Noukakis D Palagi P Paroutaud P Pimenta DC Quadroni M Resemann A Richert S Rybak J Sanchez JC Scherl A Scheurer S Schweiger Hufnagel U Siethoff C Suckau D van Dorsselaer A Wagner Redeker W Walter N Stöcklin R 《Proteomics》2003,3(8):1562-1566
After the success of the mass spectrometry (MS) round table that was held at the first Swiss Proteomics Society congress (SPS'01) in Geneva, the SPS has organized a proteomics application exercise and allocated a full session at the SPS'02 congress. The main objective was to encourage the exchange of expertise in protein identification, with a focus on the use of mass spectrometry, and to create a bridge between the users' questions and the instrument providers' solutions. Two samples were sent to fifteen interested labs, including academic groups and MS hardware providers. Participants were asked to identify and partially characterize the samples. They consisted of a complex mixture of peptide/proteins (sample A) and an almost pure recombinant peptide carrying post-translational modifications (sample B). Sample A was an extract of snake venom from the species Bothrops jararaca. Sample B was a recombinant and modified peptide derived from the shrimp Penaeus vannamei penaeidin 3a. The eight labs that returned results reported the use of a wide range of MS instrumentation and techniques. They mentioned a variety of time and manpower allocations. The origin of sample A was generally identified together with a number of database protein entries. The difficulty of the sample identification lay in the incomplete knowledge of the Bothrops species genome sequence and is discussed. Sample B was generally and correctly identified as penaeidin. However, only one group reported the full primary structure. Interestingly, the approaches were again varied and are discussed in the text. 相似文献
20.
Phylogenetic tests of the hypothesis of block duplication of homologous genes on human chromosomes 6, 9, and 1 总被引:8,自引:1,他引:7
There are 10 gene families that have members on both human chromosome 6
(6p21.3, the location of the human major histocompatibility complex [MHC])
and human chromosome 9 (mostly 9q33-34). Six of these families also have
members on mouse chromosome 17 (the mouse MHC chromosome) and mouse
chromosome 2. In addition, four of these families have members on human
chromosome 1 (1q21-25 and 1p13), and two of these have members on mouse
chromosome 1. One hypothesis to explain these patterns is that members of
the 10 gene families of human chromosomes 6 and 9 were duplicated
simultaneously as a result of polyploidization or duplication of a
chromosome segment ("block duplication"). A subsequent block duplication
has been proposed to account for the presence of representatives of four of
these families on human chromosome 1. Phylogenetic analyses of the 9 gene
families for which data were available decisively rejected the hypothesis
of block duplication as an overall explanation of these patterns. Three to
five of the genes on human chromosomes 6 and 9 probably duplicated
simultaneously early in vertebrate history, prior to the divergence of
jawed and jawless vertebrates, and shortly after that, all four of the
genes on chromosomes 1 and 9 probably duplicated as a block. However, the
other genes duplicated at different times scattered over at least 1.6
billion years. Since the occurrence of these clusters of related genes
cannot be explained by block duplication, one alternative explanation is
that they cluster together because of shared functional characteristics
relating to expression patterns.
相似文献