全文获取类型
收费全文 | 584篇 |
免费 | 39篇 |
专业分类
623篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 12篇 |
2021年 | 20篇 |
2020年 | 15篇 |
2019年 | 17篇 |
2018年 | 33篇 |
2017年 | 18篇 |
2016年 | 25篇 |
2015年 | 37篇 |
2014年 | 41篇 |
2013年 | 49篇 |
2012年 | 45篇 |
2011年 | 33篇 |
2010年 | 29篇 |
2009年 | 25篇 |
2008年 | 33篇 |
2007年 | 20篇 |
2006年 | 20篇 |
2005年 | 17篇 |
2004年 | 17篇 |
2003年 | 15篇 |
2002年 | 14篇 |
2001年 | 11篇 |
2000年 | 11篇 |
1999年 | 12篇 |
1998年 | 7篇 |
1997年 | 5篇 |
1996年 | 4篇 |
1995年 | 5篇 |
1994年 | 2篇 |
1992年 | 1篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1977年 | 2篇 |
1972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623条查询结果,搜索用时 15 毫秒
81.
Nadine Correia Santos Patrício Soares Costa Liliana Amorim Pedro Silva Moreira Pedro Cunha Jorge Cotter Nuno Sousa 《PloS one》2015,10(4)
Here we focus on factor analysis from a best practices point of view, by investigating the factor structure of neuropsychological tests and using the results obtained to illustrate on choosing a reasonable solution. The sample (n=1051 individuals) was randomly divided into two groups: one for exploratory factor analysis (EFA) and principal component analysis (PCA), to investigate the number of factors underlying the neurocognitive variables; the second to test the “best fit” model via confirmatory factor analysis (CFA). For the exploratory step, three extraction (maximum likelihood, principal axis factoring and principal components) and two rotation (orthogonal and oblique) methods were used. The analysis methodology allowed exploring how different cognitive/psychological tests correlated/discriminated between dimensions, indicating that to capture latent structures in similar sample sizes and measures, with approximately normal data distribution, reflective models with oblimin rotation might prove the most adequate. 相似文献
82.
Rodrigues AP Amorim CA Costa SH Matos MH Santos RR Lucci CM Báo SN Ohashi OM Figueiredo JR 《Animal reproduction science》2004,84(1-2):211-227
The caprine ovary is a rich source of potentially viable immature oocytes enclosed in preantral follicles (PF). Previous experiments showed that these oocytes can be successfully cryopreserved in ovarian tissue of several species. However, until now, no information about the caprine PF cryopreservation is available in the literature. The aim of the present research was to evaluate the structural and ultrastructural characteristics of caprine PF after treatment and cryopreservation of ovarian tissue with 1.5 and 3 M dimethylsulphoxide (DMSO) and propanediol (PROH). One fragment of ovarian tissue was immediately fixed for histological examination and ultrastructural analysis, after slaughter (control). Four fragments were equilibrated at 20 degrees C/20 min in 1.8 ml of minimum essential medium (MEM) containing 1.5 or 3 M DMSO or PROH for the toxicity test, and the other four fragments were slowly frozen in each cryoprotectant at the concentrations previously described. After toxicity test and freezing/thawing procedures, the ovarian fragments were fixed for histological examination. The results showed that after toxicity test and cryopreservation of ovarian tissue using both cryoprotectants, the percentage of normal PF was less (P < 0.05) as compared with the control group. The present study revealed that the percentage of normal PF after toxicity test and cryopreservation in 1.5 M DSMO was significantly greater (P < 0.05) as compared with results obtained with 3 M DMSO or 1.5 and 3 M PROH. This result was confirmed by transmission electron microscopy, which showed that the PF were preserved in a higher quality state with 1.5 M DMSO. In conclusion, the present study demonstrated that caprine PF can be cryopreserved in ovarian tissue using 1.5 M DMSO. 相似文献
83.
During a survey of mucoralean fungi from a Cerrado reserve (Brazilian savanna) some isolates of a Mucor-like fungus were isolated from soil plates. Characterization based on morphological, physiological and molecular data from translation elongation factor (EF-1α), 28S (D1/D2) and ITS1-5.8S-ITS2 rDNA sequences was made. The isolates produce lateral branches bearing multispored sporangiola in addition to the multispored sporangia and a uniformly septate mycelium as the main differentiating characteristics. To our surprise this fungus possesses two EF-1α genes 1.4 and 1.5 kb long. Evidence from the analyzed datasets supports the delimitation of a new genus and the inclusion of Mucor fuscus based on 28S and ITS rDNA data. 相似文献
84.
A.G. Tempone S.E. Treiger Borborema H.F. de Andrade Jr. N.C. de Amorim Gualda . Yogi C. Salerno Carvalho D. Bachiega F.N. Lupo S.V. Bonotto D.C.H. Fischer 《Phytomedicine》2005,12(5):382-390
Leishmaniasis and Chagas disease afflict the poorest countries in the world. The Brazilian flora represents a rich source for the screening of potential antiparasitic compounds. In this work, we tested the total alkaloid and ethanol extracts of nine different plants from Brazilian families which produce isoquinoline alkaloids, to determine their in vitro antiparasitic effect against L. chagasi and T. cruzi parasites. Promastigotes of L. chagasi were shown to be susceptible only to the total alkaloid extracts of A. crassiflora (EC50 value = 24.89 microg/ml), A. coriacea (EC50 value = 41.60 microg/ml), C. ovalifolia (EC50 value = 63.88 microg/ml) and G. australis (EC50 value = 37.88 microg/ml). Except for the G. australis total alkaloids, all the three extracts presented a considerable activity when tested against intracellular amastigotes. The most effective alkaloid extracts were those from A. crassiflora and C. ovalifolia, which reduced the number of infected macrophages at 25 microg/ml by 86.1% and 89.8%, respectively. Among the 18 tested extracts, 16 showed anti-Trypanosoma activity. Eight extracts (A. crassiflora, A. coriacea, C. ovalifolia, D. furfuracea, D. lanceolata, S. guianensis, X. emarginata and G. australis) were the most effective against the trypomastigotes, killing approximately 100% of the parasites at the maximal concentration of 100 microg/ml. Cytotoxicity against mammalian cells was evaluated for all extracts, but potential ones showed little or no cytotoxicity and a considerable antiparasitic effect, including D. furfuracea, D. lanceolata, G. australis, S. guianensis and X. emarginata. Plants are a rich source of natural compounds, and a powerful tool for the development of new arsenals for the therapy of protozoan diseases. 相似文献
85.
Dutra BK Fernandes FA Oliveira GT 《Comparative biochemistry and physiology. Toxicology & pharmacology : CBP》2008,147(2):179-188
The present study investigated the effects of carbofuran on the energy metabolism (levels of glycogen, total proteins, total lipids, triglycerides, and lipoperoxidation), Na+/K+ATPase activity, and reproductive parameters (formation of couples, ovigerous females, and mean number of eggs) in the freshwater amphipods Hyalella pleoacuta and Hyalella curvispina. These crustaceans live in limnetic environments of the plateau (H. pleoacuta) and coastal plain (H. curvispina) of the state of Rio Grande do Sul in southern Brazil. The animals were collected in the winter of 2006 in the Vale das Trutas (28 degrees 47'00'S-49 degrees 50'53'W) in the Municipality of S?o José dos Ausentes, and in Gentil Lagoon (29 degrees 56'30'S, 50 degrees 07'50'W) in the Municipality of Tramandaí. In the laboratory, the amphipods were kept submerged in aquariums under controlled conditions of photoperiod (12 h light: 12 h dark), temperature (23 degrees C+/-1), and constant oxygenation. Animals were exposed to carbofuran at a dose of 5 or 50 microg/L for a period of 7 days. At the end of this period, the animals were immediately frozen for determination of the biochemical parameters, lipoperoxidation levels (TBARS), and enzyme Na+/K+ATPase activity. During each day of culture, several reproductive parameters were observed. Statistical analysis (ANOVA) revealed that carbofuran induces significant decreases in glycogen, proteins, lipids, triglycerides, and Na+/K+ATPase, as well as a significant increase in lipoperoxidation levels. Studies of all the biochemical parameters seem to be quite promising, in order to assess and predict the effects of toxicants on non-target organisms. The results also suggest that the reproductive parameters (formation of couples, ovigerous females and mean number of eggs) may provide sensitive criteria for assessing ecotoxicological effects. Furthermore, H. pleoacuta and H. curvispina are suitable organisms for use in toxicity tests, and we suggest that they are sensitive species that could be used in monitoring studies. 相似文献
86.
Fabrízio Siqueira Boniolo Raphael Cardoso Rodrigues Edson Oliveira Delatorre Mauricio Moura da Silveira Victor Martín Quintana Flores Marília Amorim Berbert-Molina 《Current microbiology》2009,59(6):593-599
In this study, the effect of glycine betaine as osmoprotectant compound for Gluconacetobacter diazotrophicus PAL5 was evaluated by kinetic growth parameters. Batch fermentation assays were performed employing media supplemented with
different sodium chloride concentrations to simulate saline stress conditions. Salt concentrations of 50–300 mM led to decreased
cell concentrations, while the maximum specific growth rates and cell productivities were reduced at concentrations above
100-mM NaCl. Salt inhibition was mainly observed in media with 200- and 300-mM NaCl, in which drastic changes in cell morphology
were also noted. The addition of glycine betaine to the media showed to be efficient to counteract the salt inhibitory effect
by increasing some fermentation parameters. However, the osmoprotectant was not able to revert the polymorphism promoted by
higher salt concentrations. 相似文献
87.
Lorrany dos Santos Franco Paloma Oliveira Vidal Jaime Henrique Amorim 《Journal of biomedical science》2017,24(1):88
Background
The arboviruses Zika virus (ZIKV) and Dengue virus (DENV) have important epidemiological impact in Brazil and other tropical regions of the world. Recently, it was shown that previous humoral immunity to DENV enhances ZIKV replication in vitro, which may lead to more severe forms of the disease. Thus, traditional approaches of vaccine development aiming to control viral infection through neutralizing antibodies may induce cross-reactive enhancing antibodies. In contrast, cellular immune response was shown to be capable of controlling DENV infection independently of antibodies. The aim of the present study was to design a flavivirus NS5 protein capable of inducing a cellular immune response against DENV and ZIKV.Methods
A consensus sequence of ZIKV NS5 protein was designed among isolates from various continents. Epitopes were predicted for the most prevalent alleles of class I and II HLA in the Brazilian population. Then, this epitopes were analyzed with regard to their conservation, population coverage and distribution along the whole antigen.Results
Nineteen epitopes predicted to be more reactive (percentile rank <1) and 100% conserved among ZIKV and DENV serotypes were selected. The distribution of such epitopes along the protein was shown on a three-dimensional model and population coverage was calculated for different regions of the world. The designed protein was predicted to be stable and the distribution of selected epitopes was shown to be homogeneous along domains. The population coverage of selected epitopes was higher than 50% for most of tropical areas of the world.Conclusion
Such results indicate that the proposed antigen has the potential to induce protective cellular immune response to ZIKV and DENV in different human populations of the world.88.
Transgenic cotton expressing Cry10Aa toxin confers high resistance to the cotton boll weevil 下载免费PDF全文
Thuanne Pires Ribeiro Fabricio Barbosa Monteiro Arraes Isabela Tristan Lourenço‐Tessutti Marilia Santos Silva Maria Eugênia Lisei‐de‐Sá Wagner Alexandre Lucena Leonardo Lima Pepino Macedo Janaina Nascimento Lima Regina Maria Santos Amorim Sinara Artico Márcio Alves‐Ferreira Maria Cristina Mattar Silva Maria Fatima Grossi‐de‐Sa 《Plant biotechnology journal》2017,15(8):997-1009
89.
Bertolonia alternifolia and B. bullata, two new endemic species of Melastomataceae from the Atlantic Forest biome of the southern region of Bahia state, Brazil, are described and illustrated based on recent
botanical explorations and literature records. The main diagnostic characteristics that distinguish B. alternifolia are alternate leaves with cordate bases, and anthers with terminal-dorsal pores and unappendaged connectives. B. bullata can be identified by having leaves bullate on the adaxial surface, foveolate on the abaxial surface and bases cordate to
cordate-lobate, calyx lobes with entire to slightly undulate margins, and stamens dorsally appendaged. Both species are classified
as Critically Endangered (CR) and Endangered (EN) respectively. 相似文献
90.
Raquel O. Vasconcelos Joseph A. Sisneros M. Clara P. Amorim Paulo J. Fonseca 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2011,197(9):903-913
A novel form of auditory plasticity for enhanced detection of social signals was described in a teleost fish, Porichthys notatus (Batrachoididae, Porichthyinae). The seasonal onset of male calling coincides with inshore migration from deep waters by
both sexes and increased female sensitivity to dominant frequencies of male calls. The closely related Lusitanian toadfish,
Halobatrachus didactylus, (Batrachoididae, Halophryninae) also breeds seasonally and relies on acoustic communication to find mates but, instead,
both sexes stay in estuaries and show vocal activity throughout the year. We investigated whether the sensitivity of the inner
ear saccule of H. didactylus is seasonally plastic and sexually dimorphic. We recorded evoked potentials from populations of saccular hair cells from
non-reproductive and reproductive males and females in response to 15–945 Hz tones. Saccular hair cells were most sensitive
at 15–205 Hz (thresholds between 111 and 118 dB re. 1 μPa). Both sexes showed identical hearing sensitivity and no differences
were found across seasons. The saccule was well suited to detect conspecific vocalizations and low frequencies that overlapped
with lateral line sensitivity. We showed that the saccule in H. didactylus has major importance in acoustic communication throughout the year and that significant sensory differences may exist between
the two batrachoidid subfamilies. 相似文献