全文获取类型
收费全文 | 509篇 |
免费 | 37篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 10篇 |
2021年 | 18篇 |
2020年 | 14篇 |
2019年 | 17篇 |
2018年 | 32篇 |
2017年 | 18篇 |
2016年 | 23篇 |
2015年 | 30篇 |
2014年 | 35篇 |
2013年 | 43篇 |
2012年 | 44篇 |
2011年 | 33篇 |
2010年 | 27篇 |
2009年 | 24篇 |
2008年 | 30篇 |
2007年 | 18篇 |
2006年 | 19篇 |
2005年 | 15篇 |
2004年 | 15篇 |
2003年 | 14篇 |
2002年 | 9篇 |
2001年 | 10篇 |
2000年 | 9篇 |
1999年 | 10篇 |
1998年 | 2篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1992年 | 1篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有546条查询结果,搜索用时 281 毫秒
411.
Toscanini U Gusmão L Berardi G Gomes V Amorim A Salas A Raimondi E 《American journal of physical anthropology》2011,146(2):188-196
With this study, we aimed to determine the different male ancestral components of two Native American communities from Argentina, namely Toba and Colla. The analysis of 27 Y-chromosome SNPs allowed us to identify seven different haplogroups in both samples. Chromosomes carrying the M3 mutation, which typically defines the Native American haplogroup Q1a3a, were seen most frequently in the Toba community (90%). Conversely, Q1a3a was represented in 34% of the Colla Y-chromosomes, whereas haplogroup R1b1, the main representative of western European populations, exhibited the highest frequency in this population (41%). Different M3 sublineages in the Toba community could be identified by observing point mutations at both DYS385 and M19 loci. A microvariant at DYS385, named 16.1, has been characterized, which helps to further subdivide Q1a3a. It is the first time the M19 mutated allele is described in a population from Argentina. This finding supports the old age of the lineages carrying the M19 mutation, but it contradicts the previous hypothesis that the M19 mutated allele is confined to only two Equatorial-Tucano population groups from the north region of South America. The detection of M19 further south than previously thought allows questioning of the hypothesis that this lineage serves as an example of isolation after colonization. This observation also affirms the strong genetic drift to which Native Americans have been subjected. Moreover, our study illustrates a heterogeneous contribution of Europeans to these populations and supports previous studies showing that most Native American groups were subjected to European admixture that primarily involved immigrant men. 相似文献
412.
dos Santos Rocha PB de Castro Amorim A de Sousa AF do Monte SJ da Mata Sousa LC do Nascimento Nogueira N Neto JM do Nascimento Marreiro D 《Biological trace element research》2011,143(2):603-611
Research has investigated the participation of zinc transport proteins and metallothionein in the metabolism of this mineral.
However, studies about the genetic expression of these proteins in obese patients are scarce. The study determined the expression
of zinc transporter protein codifying genes (ZnT-1, Zip-1 and Zip-3) and of metallothionein in 55 obese women, aged between
20 and 56 years. The assessment of body composition was carried out using anthropometric measurements and bioelectrical impedance.
Zinc intake was obtained by recording diet over a 3-day period, and the nutritional analysis was carried out using NutWin
software version 1.5. The plasmatic and erythrocytary zinc were analyzed by atomic absorption spectrophotometry (λ = 213. 9 nm). The determination of mRNA expression of the zinc transporter proteins and metallothionein was carried out using
blood, using the RT-PCR method. The mean values of body mass index were 37.9 ± 5.5 kg/m2. The average intake of zinc was 9.4 ± 2.3 mg/day. The analysis of the zinc plasma concentrations showed values of 58.4 ± 10.9 μg/dL.
The mean values of zinc in the erythroytes were 38.7 ± 9.1 μg/g Hb. The metallothionein gene had a higher expression in the
blood, when compared to zinc transporters ZnT-1, Zip-1, and Zip-3 (p = 0.01). The study shows that there are alterations in the biochemical parameters of zinc in obese patients assessed, as
well as higher expression of the codifying gene metallothionein, when compared to the investigated zinc transporters. 相似文献
413.
Amorim HV Lopes ML de Castro Oliveira JV Buckeridge MS Goldman GH 《Applied microbiology and biotechnology》2011,91(5):1267-1275
Bioethanol (fuel alcohol) has been produced by industrial alcoholic fermentation processes in Brazil since the beginning of
the twentieth century. Currently, 432 mills and distilleries crush about 625 million tons of sugarcane per crop, producing
about 27 billion liters of ethanol and 38.7 million tons of sugar. The production of bioethanol from sugarcane represents
a major large-scale technology capable of producing biofuel efficiently and economically, providing viable substitutes to
gasoline. The combination of immobilization of CO2 by sugarcane crops by photosynthesis into biomass together with alcoholic fermentation of this biomass has allowed production
of a clean and high-quality liquid fuel that contains 93% of the original energy found in sugar. Over the last 30 years, several
innovations have been introduced to Brazilian alcohol distilleries resulting in the improvement of plant efficiency and economic
competitiveness. Currently, the main scientific challenges are to develop new technologies for bioethanol production from
first and second generation feedstocks that exhibit positive energy balances and appropriately meet environmental sustainability
criteria. This review focuses on these aspects and provides special emphasis on the selection of new yeast strains, genetic
breeding, and recombinant DNA technology, as applied to bioethanol production processes. 相似文献
414.
Andreia A Santos Célia C Lopes Jorge R Ribeiro Liliana R Martins Joana C Santos Irina F Amorim Fátima Gärtner Augusto J Matos 《BMC veterinary research》2013,9(1):1-11
Background
Although several histopathological and clinical features of canine mammary gland tumours have been widely studied from a prognostic standpoint, considerable variations in tumour individual biologic behaviour difficult the definition of accurate prognostic factors. It has been suggested that the malignant behaviour of tumours is the end result of several alterations in cellular physiology that culminate in tumour growth and spread. Accordingly, the aim of this study was to determine, using a multivariable model, the independent prognostic value of several immunohistochemically detected tumour-associated molecules, such as MMP-9 and uPA in stromal cells and Ki-67, TIMP-2 and VEGF in cancer cells.Results
Eighty-five female dogs affected by spontaneous malignant mammary neoplasias were followed up for a 2-year post-operative period. In univariate analysis, tumour characteristics such as size, mode of growth, regional lymph node metastases, tumour cell MIB-1 LI and MMP-9 and uPA expressions in tumour-adjacent fibroblasts, were associated with both survival and disease-free intervals. Histological type and grade were related with overall survival while VEGF and TIMP-2 were not significantly associated with none of the outcome parameters. In multivariable analysis, only a MIB-1 labelling index higher than 40% and a stromal expression of MMP-9 higher than 50% retained significant relationships with poor overall and disease-free survival.Conclusions
The results of this study indicate that MMP-9 and Ki-67 are independent prognostic markers of canine malignant mammary tumours. Furthermore, the high stromal expressions of uPA and MMP-9 in aggressive tumours suggest that these molecules are potential therapeutic targets in the post-operative treatment of canine mammary cancer. 相似文献415.
416.
417.
Barbosa TP Sousa SC Amorim FM Rodrigues YK de Assis PA Caldas JP Oliveira MR Vasconcellos ML 《Bioorganic & medicinal chemistry》2011,19(14):4250-4256
The chalcone-like series 1a-1g was efficiently synthesized from Morita-Baylis-Hillman reaction (52-74% yields). Compounds 1a-1g were designed by molecular hybridization based on the anti-inflammatory drug methyl salicylate (3) and the antileishmanial moiety of the Morita-Baylis-Hillman adducts 2a-2g. The 1a-1g compounds were much more actives than precursor series 2a-2g, for example, IC(50)=7.65 μM on Leishmania amazonensis and 10.14 μM on Leishmania chagasi (compound 1c) when compared to IC(50)=50.08 μM on L. amazonensis and 82.29 μM on L. chagasi (compound 2c). The IC(50) values of compound 3 (228.49 μM on L. amazonensis and 261.45 μM on L. chagasi) and acryloyl salicylate 4 (108.50 μM on L. amazonensis and 118.83 μM on L. chagasi) were determined here, by the first time, on Leishmania. 相似文献
418.
Current proteomics technology is limited in resolving the proteome complexity of biological systems. The main issue at stake is to increase throughput and spectra quality so that spatiotemporal dimensions, population parameters and the complexity of protein modifications on a quantitative scale can be considered. MS-based proteomics and protein arrays are the main players in large-scale proteome analysis and an integration of these two methodologies is powerful but presently not sufficient for detailed quantitative and spatiotemporal proteome characterization. Improvements of instrumentation for MS-based proteomics have been achieved recently resulting in data sets of approximately one million spectra which is a large step in the right direction. The corresponding raw data range from 50 to 100?Gb and are frequently made available. Multidimensional LC-MS data sets have been demonstrated to identify and quantitate 2000-8000 proteins from whole cell extracts. The analysis of the resulting data sets requires several steps from raw data processing, to database-dependent search, statistical evaluation of the search result, quantitative algorithms and statistical analysis of quantitative data. A large number of software tools have been proposed for the above-mentioned tasks. However, it is not the aim of this review to cover all software tools, but rather discuss common data analysis strategies used by various algorithms for each of the above-mentioned steps in a non-redundant approach and to argue that there are still some areas which need improvements. 相似文献
419.
Myrcia thomasii, a new species from the Atlantic Forest of southern Bahia, is described and illustrated. The new species is similar to M. micropetala, but differs in having the inflorescence and basal bracts puberulent, lanceolate bracts at the base of flowers, longer calyx lobes and petals, and a 3-locular ovary. 相似文献
420.