全文获取类型
收费全文 | 3074篇 |
免费 | 172篇 |
国内免费 | 1篇 |
出版年
2023年 | 27篇 |
2022年 | 59篇 |
2021年 | 106篇 |
2020年 | 66篇 |
2019年 | 88篇 |
2018年 | 113篇 |
2017年 | 97篇 |
2016年 | 134篇 |
2015年 | 196篇 |
2014年 | 174篇 |
2013年 | 234篇 |
2012年 | 249篇 |
2011年 | 228篇 |
2010年 | 154篇 |
2009年 | 153篇 |
2008年 | 190篇 |
2007年 | 169篇 |
2006年 | 148篇 |
2005年 | 145篇 |
2004年 | 123篇 |
2003年 | 98篇 |
2002年 | 85篇 |
2001年 | 31篇 |
2000年 | 19篇 |
1999年 | 29篇 |
1998年 | 18篇 |
1997年 | 12篇 |
1996年 | 10篇 |
1995年 | 7篇 |
1994年 | 8篇 |
1993年 | 4篇 |
1992年 | 6篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1965年 | 1篇 |
排序方式: 共有3247条查询结果,搜索用时 31 毫秒
41.
Rafael Piovezan Stéfany Larissa Rosa Matheus Luca Rocha Thiago Salomão de Azevedo Cláudio José Von Zuben 《Journal of vector ecology》2013,38(2):317-325
Because of the high adaptive capacity of mosquitoes, studies that focus on transitional environments become very important, such as those in rural areas, which are considered as bridges between wild diseases and human populations of urban areas. In this study, a survey of the existing species of mosquitoes was performed in an Atlantic Forest area of the city of Santa Bárbara d'Oeste, São Paulo state, Brazil, using traps for immatures and analyzing the frequency and distribution of these insects over the sampling months. Five mosquito species were found: Aedes albopictus (the most frequent species), Aedes aegypti, Aedes fluviatilis, Culex quinquefasciatus, and Toxorhynchites theobaldi. The 4,524 eggs collected in ovitraps showed the presence of the tribe Aedini. Aedes aegypti and Ae. albopictus were identified after larval hatching in the laboratory, with different spatial distributions: the first of which coincides with the area of greatest diversity calculated using the Simpson index, while the second does not. The association of ecological analysis of spatial diversity with simple methods of data collection enables the identification of possible epidemiological risk situations and is a strategy that may be implemented to monitor ecological processes resulting from the interaction among different species of mosquitoes. 相似文献
42.
43.
Guilherme Loss-Morais Andreia Carina Turchetto-Zolet Matheus Etges Alexandro Cagliari Ana Paula K?rbes Felipe dos Santos Maraschin Márcia Margis-Pinheiro Rogério Margis 《Genetics and molecular biology》2013,36(1):74-86
Ribosome-inactivating proteins (RIPs) are enzymes that inhibit protein synthesis after depurination of a specific adenine in rRNA. The RIP family members are classified as type I RIPs that contain an RNA-N-glycosidase domain and type II RIPs that contain a lectin domain (B chain) in addition to the glycosidase domain (A chain). In this work, we identified 30 new plant RIPs and characterized 18 Ricinus communis RIPs. Phylogenetic and functional divergence analyses indicated that the emergence of type I and II RIPs probably occurred before the monocot/eudicot split. We also report the expression profiles of 18 castor bean genes, including those for ricin and agglutinin, in five seed stages as assessed by quantitative PCR. Ricin and agglutinin were the most expressed RIPs in developing seeds although eight other RIPs were also expressed. All of the RIP genes were most highly expressed in the stages in which the endosperm was fully expanded. Although the reason for the large expansion of RIP genes in castor beans remains to be established, the differential expression patterns of the type I and type II members reinforce the existence of biological functions other than defense against predators and herbivory. 相似文献
44.
Albert Flexas Jaume Rosselló Julia F. Christensen Marcos Nadal Antonio Olivera La Rosa Enric Munar 《PloS one》2013,8(11)
We examined the influence of affective priming on the appreciation of abstract artworks using an evaluative priming task. Facial primes (showing happiness, disgust or no emotion) were presented under brief (Stimulus Onset Asynchrony, SOA = 20ms) and extended (SOA = 300ms) conditions. Differences in aesthetic liking for abstract paintings depending on the emotion expressed in the preceding primes provided a measure of the priming effect. The results showed that, for the extended SOA, artworks were liked more when preceded by happiness primes and less when preceded by disgust primes. Facial expressions of happiness, though not of disgust, exerted similar effects in the brief SOA condition. Subjective measures and a forced-choice task revealed no evidence of prime awareness in the suboptimal condition. Our results are congruent with findings showing that the affective transfer elicited by priming biases evaluative judgments, extending previous research to the domain of aesthetic appreciation. 相似文献
45.
Matheus Balduíno Goncalves dos Reis Letícia Correa Manjolin Claudia do Carmo Maquiaveli Osvaldo Andrade Santos-Filho Edson Roberto da Silva 《PloS one》2013,8(11)
Epigallocatechin-3-gallate (EGCG), a dietary polyphenol (flavanol) from green tea, possesses leishmanicidal and antitrypanosomal activity. Mitochondrial damage was observed in Leishmania treated with EGCG, and it contributed to the lethal effect. However, the molecular target has not been defined. In this study, EGCG, (+)-catechin and (−)-epicatechin were tested against recombinant arginase from Leishmania amazonensis (ARG-L) and rat liver arginase (ARG-1). The compounds inhibit ARG-L and ARG-1 but are more active against the parasite enzyme. Enzyme kinetics reveal that EGCG is a mixed inhibitor of the ARG-L while (+)-catechin and (−)-epicatechin are competitive inhibitors. The most potent arginase inhibitor is (+)-catechin (IC50 = 0.8 µM) followed by (−)-epicatechin (IC50 = 1.8 µM), gallic acid (IC50 = 2.2 µM) and EGCG (IC50 = 3.8 µM). Docking analyses showed different modes of interaction of the compounds with the active sites of ARG-L and ARG-1. Due to the low IC50 values obtained for ARG-L, flavanols can be used as a supplement for leishmaniasis treatment. 相似文献
46.
47.
Dong Wook Han Natalia Tapia Marcos J. Araúzo-Bravo Kyung Tae Lim Kee Pyo Kim Kinarm Ko Hoon Taek Lee Hans R. Sch?ler 《PloS one》2013,8(6)
Epiblast stem cells (EpiSCs) and embryonic stem cells (ESCs) differ in their in vivo differentiation potential. While ESCs form teratomas and efficiently contribute to the development of chimeras, EpiSCs form teratomas but very rarely chimeras. In contrast to their differentiation potential, the reprogramming potential of EpiSCs has not yet been investigated. Here we demonstrate that the epiblast-derived pluripotent stem cells EpiSCs and P19 embryonal carcinoma cells (ECCs) exhibit a lower reprogramming potential than ESCs and F9 ECCs. In addition, we show that the low reprogramming ability is due to the lower levels of Sox2 in epiblast-derived stem cells. Consistent with this observation, overexpression of Sox2 enhances reprogramming efficiency. In summary, these findings suggest that a low reprogramming potential is a general feature of epiblast-derived stem cells and that the Sox2 level is a determinant of the cellular reprogramming potential. 相似文献
48.
Adriana S. Azevedo Ant?nio J. S. Gon?alves Marcia Archer Marcos S. Freire Ricardo Galler Ada M. B. Alves 《PloS one》2013,8(3)
The dengue envelope glycoprotein (E) is the major component of virion surface and its ectodomain is composed of domains I, II and III. This protein is the main target for the development of a dengue vaccine with induction of neutralizing antibodies. In the present work, we tested two different vaccination strategies, with combined immunizations in a prime/booster regimen or simultaneous inoculation with a DNA vaccine (pE1D2) and a chimeric yellow fever/dengue 2 virus (YF17D-D2). The pE1D2 DNA vaccine encodes the ectodomain of the envelope DENV2 protein fused to t-PA signal peptide, while the YF17D-D2 was constructed by replacing the prM and E genes from the 17D yellow fever vaccine virus by those from DENV2. Balb/c mice were inoculated with these two vaccines by different prime/booster or simultaneous immunization protocols and most of them induced a synergistic effect on the elicited immune response, mainly in neutralizing antibody production. Furthermore, combined immunization remarkably increased protection against a lethal dose of DENV2, when compared to each vaccine administered alone. Results also revealed that immunization with the DNA vaccine, regardless of the combination with the chimeric virus, induced a robust cell immune response, with production of IFN-γ by CD8+ T lymphocytes. 相似文献
49.
This paper presents a new method of analysis by which structural similarities between brain data and linguistic data can be assessed at the semantic level. It shows how to measure the strength of these structural similarities and so determine the relatively better fit of the brain data with one semantic model over another. The first model is derived from WordNet, a lexical database of English compiled by language experts. The second is given by the corpus-based statistical technique of latent semantic analysis (LSA), which detects relations between words that are latent or hidden in text. The brain data are drawn from experiments in which statements about the geography of Europe were presented auditorily to participants who were asked to determine their truth or falsity while electroencephalographic (EEG) recordings were made. The theoretical framework for the analysis of the brain and semantic data derives from axiomatizations of theories such as the theory of differences in utility preference. Using brain-data samples from individual trials time-locked to the presentation of each word, ordinal relations of similarity differences are computed for the brain data and for the linguistic data. In each case those relations that are invariant with respect to the brain and linguistic data, and are correlated with sufficient statistical strength, amount to structural similarities between the brain and linguistic data. Results show that many more statistically significant structural similarities can be found between the brain data and the WordNet-derived data than the LSA-derived data. The work reported here is placed within the context of other recent studies of semantics and the brain. The main contribution of this paper is the new method it presents for the study of semantics and the brain and the focus it permits on networks of relations detected in brain data and represented by a semantic model. 相似文献
50.
David N. Gumieiro Bruna P. M. Rafacho Andrea F. Gon?alves Priscila P. Santos Paula S. Azevedo Leonardo A. M. Zornoff Gilberto J. C. Pereira Luiz S. Matsubara Sergio A. R. Paiva Marcos F. Minicucci 《PloS one》2013,8(2)