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221.
222.
Consider a ligand-gated channel with n agonist binding sites which can undergo desensitization. We present a theoretical experimental procedure for pinpointing
the principal receptor state from which there is a transition to the desensitized state. The method is based on the observation
that the dependence of the slope of the time constant of desensitization vs agonist concentration, at low concentrations,
represents the state from which desensitization occurs. In those receptors where desensitization occurs from the open state
(or the one immediately preceding it), the method also enables us to determine the number of binding sites. 相似文献
223.
224.
Evolutionary history of the COII/tRNALys intergenic 9 base pair deletion in human mitochondrial DNAs from the Pacific 总被引:14,自引:2,他引:12
Redd AJ; Takezaki N; Sherry ST; McGarvey ST; Sofro AS; Stoneking M 《Molecular biology and evolution》1995,12(4):604-615
Length changes in human mitochondrial DNA (mtDNA) are potentially useful
markers for inferring the evolutionary history of populations. One such
length change is a nine base pair (9-bp) deletion that is located in the
intergenic region between the COII gene and the Lysine tRNA gene
(COII/tRNALys intergenic region). This deletion has been used as a genetic
marker to trace descent from peoples of East Asian origin. A geographic
cline of the deletion frequency across modern Pacific Islander populations
suggests that the deletion may be useful for tracing prehistoric Polynesian
origins and affinities. Mitochondrial DNA sequence variation within two
variable segments of the control region (CR) permits a number of inferences
regarding the evolutionary history of the 9-bp deletion that cannot be
determined from frequency data alone. We obtained CR sequences from 74
mtDNAs with the 9-bp deletion from Indonesia, coastal Papua New Guinea
(PNG), and American Samoa. Phylogenetic and pairwise distribution analysis
of these CR sequences pooled with previously published CR sequences reveals
that the deletion arose independently in Africa and Asia and suggests
possible multiple origins of the deletion in Asia. A clinal increase of the
frequency of the 9-bp deletion across the three Pacific populations is
associated with a decrease in CR sequence diversity, consistent with
founder events. Furthermore, analysis of pairwise difference distributions
indicates an expansion time of proto-Polynesians that began 5,500 yr ago
from Southeast Asia. These results are consistent with the express train
model of Polynesian origins.
相似文献
225.
Marcos VH Rambo Humberto R Gamba Gustavo B Borba Joaquim M Maia Carlos AS Ramos 《Biomedical engineering online》2010,9(1):46
Background
The results of an in vivo study on the "ratio method" used in electronic foramen locators (EFL) are presented. EFLs are becoming widely used in the determination of the working length (WL) during the root canal treatment. The WL is the distance from a coronal reference point to the point at which canal preparation and filling should terminate. The "ratio method" was assessed by many clinicians with the aim of determining its ability to locate the apical foramen (AF). Nevertheless, in vivo studies to assess the method itself and to explain why the "ratio method" is able to locate the apical foramen and is unable to determine intermediate distances were not published so far. 相似文献226.
C. SOLIANI J. RONDAN‐DUEÑAS M. B. CHIAPPERO M. MARTÍNEZ E. GARCÍA DA ROSA C. N. GARDENAL 《Medical and veterinary entomology》2010,24(3):316-323
Aedes aegypti (L.) (Diptera: Culicidae), the main vector of yellow fever and dengue viruses, was eradicated from Argentina between 1955 and 1963, but reinvaded the country in 1986. In Uruguay, the species was reintroduced in 1997. In this study we used highly polymorphic inter‐simple sequence repeats (ISSR) markers to analyse the genetic structure of Ae. aegypti populations from Uruguay and northeastern Argentina to identify possible colonization patterns of the vector. Overall genetic differentiation among populations was high (FST = 0.106) and showed no correlation with geographic distance, which is consistent with the short time since the reintroduction of the species in the area. Differentiation between pairs of Argentine populations (FST 0.072 to 0.221) was on average higher than between Uruguayan populations (FST?0.044 to 0.116). Bayesian estimation of population structure defined four genetic clusters and most populations were admixtures of two of them: Mercedes and Treinta y Tres (Uruguay) were mixtures of clusters 1 and 3; Salto (Uruguay) and Paraná (Argentina) of clusters 1 and 4; Fray Bentos (Uruguay) of clusters 2 and 3, and Gualeguaychú (Argentina) of clusters 2 and 3. Posadas and Buenos Aires in Argentina were fairly genetically homogeneous. Our results suggest that Ae. aegypti recolonized Uruguay from bordering cities in Argentina via bridges over the Uruguay River and also from Brazil. 相似文献
227.
Nestboxes are known to increase clutch size, enhance breeding success and affect the social mating system of several cavity nesters. Although in recent years various cavity nesters have been studied in nestboxes in South America, the effects of boxes on the biology of the study species are unknown. We evaluated the effects of nestboxes on the breeding biology and social mating system of Southern House Wrens Troglodytes aedon bonariae by comparing birds breeding in nestboxes and tree cavities in two cattle ranches in Buenos Aires Province, Argentina. Southern House Wrens nesting in boxes had higher breeding success but, contrary to studies on the temperate zone, we did not find differences in clutch size between Wrens breeding in nestboxes and tree cavities. The main causes of nest failure in tree cavities were nest predation and flooding of the cavity (70 and 23% of the failures, respectively) while in nestboxes predation and desertion were the most important causes of failure (38 and 34% of the failures, respectively). The social mating system of Southern House Wrens is monogamy with biparental care, and neither was affected by the boxes. Males did not attract secondary females to additional nestboxes; however, nestboxes are safer breeding sites than tree cavities, and females seemed to prefer males with nestboxes on their territory. These results suggest that nest quality alone might be not enough for secondary females to accept polygyny. 相似文献
228.
A. terreus isolates isolated from some bakery products, corn and rice were found to be able to produce territrems. 90% of theA. terreus isolated from bakery products were able to produce territrem A, with a mean of 0.09 ppm, while 80% ofA. terreus isolates produce territrem B with a mean of 0.24 ppm. On the other hand 31.8% of the isolates ofA. terreus from corn were able to produce territrem A with a mean of 0.44 ppm. ConcerningA. terreus isolates from rice, 66.7% were found to produce territrem A, with a mean of 5.28 ppm, and 77.8% of the isolates produced
territrem B with a mean of 1.79 ppm. 相似文献
229.
Richard J Dobson Patricia B Munroe Mark J Caulfield Mansoor AS Saqi 《BMC bioinformatics》2006,7(1):217-9
Background
There has been an explosion in the number of single nucleotide polymorphisms (SNPs) within public databases. In this study we focused on non-synonymous protein coding single nucleotide polymorphisms (nsSNPs), some associated with disease and others which are thought to be neutral. We describe the distribution of both types of nsSNPs using structural and sequence based features and assess the relative value of these attributes as predictors of function using machine learning methods. We also address the common problem of balance within machine learning methods and show the effect of imbalance on nsSNP function prediction. We show that nsSNP function prediction can be significantly improved by 100% undersampling of the majority class. The learnt rules were then applied to make predictions of function on all nsSNPs within Ensembl. 相似文献230.
Wuelton M Monteiro Fernando FA Val André M Siqueira Gabriel P Franca Vanderson S Sampaio Gisely C Melo Anne CG Almeida Marcelo AM Brito Henry M Peixoto Douglas Fuller Quique Bassat Gustavo AS Romero Oliveira Maria Regina F Lacerda Marcus Vinícius G 《Memórias do Instituto Oswaldo Cruz》2014,109(5):553-568