全文获取类型
收费全文 | 798篇 |
免费 | 52篇 |
出版年
2024年 | 2篇 |
2023年 | 9篇 |
2022年 | 9篇 |
2021年 | 25篇 |
2020年 | 21篇 |
2019年 | 18篇 |
2018年 | 30篇 |
2017年 | 23篇 |
2016年 | 28篇 |
2015年 | 43篇 |
2014年 | 54篇 |
2013年 | 56篇 |
2012年 | 56篇 |
2011年 | 64篇 |
2010年 | 41篇 |
2009年 | 26篇 |
2008年 | 30篇 |
2007年 | 33篇 |
2006年 | 23篇 |
2005年 | 27篇 |
2004年 | 35篇 |
2003年 | 24篇 |
2002年 | 19篇 |
2001年 | 24篇 |
2000年 | 18篇 |
1999年 | 13篇 |
1998年 | 9篇 |
1997年 | 8篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 13篇 |
1991年 | 2篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 8篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1970年 | 2篇 |
1969年 | 1篇 |
1967年 | 1篇 |
1963年 | 1篇 |
1903年 | 1篇 |
排序方式: 共有850条查询结果,搜索用时 15 毫秒
101.
Canada N Meireles CS Mezo M González-Warleta M Correia da Costa JM Sreekumar C Hill DE Miska KB Dubey JP 《The Journal of parasitology》2004,90(4):863-864
Neospora caninum was isolated from the brain of a 6-mo-old aborted bovine fetus from Galicia, Spain. The fetal brain homogenate was inoculated intraperitoneally into cortisonized mice. The peritoneal exudate from the infected mice, along with mouse sarcoma cells (Tg180), was inoculated into a second group of mice, and parasites were harvested from the peritoneal exudate. The parasites were adapted to in vitro growth in Vero monolayers. The tachyzoites from the peritoneal exudate reacted positively with anti-N. caninum antibodies and not with anti-Toxoplasma gondii antibodies on indirect fluorescent antibody test. The tachyzoites were lethal to interferon gamma gene knock out (KO) mice and could be identified immunohistochemically in the tissues. The identity of the parasite was also confirmed by polymerase chain reaction amplification of N. caninum-specific fragments. The sequences of the amplified gene 5 fragments (GenBank AY494944) were found to be identical to that of an Austrian isolate of N. caninum but not to that of NC-1. This is the first isolation of viable N. caninum from Spain. 相似文献
102.
Glaucio Valdameri Tatiana Herrerias Eva Gunilla Skare Carnieri Silvia Maria Suter Correia Cadena Glaucia Regina Martinez Maria Eliane Merlin Rocha 《Chemico-biological interactions》2010,188(1):52-58
Flavonoids are a large group of polyphenolic compounds that have received considerable attention because of their biological and physiological importance. The flavone (2-phenyl-4H-1-benzopyran-4one) used in this work is found in some cereal grains and generates several biological activities, including: apoptosis induction, cell cycle arrest, caspase activation and inhibition of tumor cell proliferation. However, its effects on the hepatic mitochondrial metabolism are still unknown. We evaluated the effect of flavone on the metabolism of mitochondria isolated from rat liver. Polarographic experiments using 200 μmol L?1 flavone and rat liver mitochondria oxidizing glutamate or succinate indicated that both substrates underwent: (i) reduction of state 3 respiration; (ii) stimulation of state 4 respiration; (iii) reduction of the respiratory control coefficient; and (iv) reduction of the ADP/O ratio. An analysis of the activity of enzymatic complexes in the respiratory chain showed that flavone acts between complexes I and III. Flavone reduced the membrane electric potential at doses of 100, 150 and 200 μmol L?1. Flavone at certain doses (75–200 μmol L?1) reduced mitochondrial swelling in the presence of valinomycin and KNO3, suggesting that flavone could induce changes in mitochondrial membrane properties. These results demonstrate that the inhibition of mitochondrial enzymes in the respiratory chain coupled with the effects on membrane properties are promoted by the core structure of flavones, and these effects may be in part responsible for the cytotoxic effects of flavones. 相似文献
103.
The chemistry of black seabream Spondyliosoma cantharus otoliths from three main fishery grounds (Olhão, Sagres and Sesimbra) located along c. 400 km of the Portuguese south and west coasts was examined. Element:Ca ratios were determined in whole otoliths and otolith cores of young adult specimens of 2–3 years of age. Using the data from whole otoliths, it was possible to discriminate among S. cantharus from the three fishing grounds with an average accuracy of 91%. Differences among fishing grounds were significant for all element:Ca ratios, and otoliths from Sagres had significantly higher levels of all ratios compared to the other fishing grounds. In contrast, the chemical composition of the otolith core, representative of the larval stage, showed limited variation among the fishing grounds, with an average discrimination accuracy of only 44%, although the Mg:Ca ratio of the otolith cores was also significantly higher for the Sagres samples. The data suggest that larval stages experienced a homogenous environment consistent with an offshore oceanic spawning. Juveniles appeared to display local residency on the inshore fishing grounds, areas probably characterized by greater environmental heterogeneity. Spondyliosoma cantharus population structure is consistent with distinct local population units that share a spawning ground providing recruits to different coastal fishery areas. 相似文献
104.
Gregório Miguel Ferreira de Camargo Diercles Francisco Cardoso Fernanda Maria Monsalves Gil Patrícia Dias da Silva Fonseca Larissa Zetouni Camila Urbano Braz Ana Claudia de Freitas Fábio Ricardo Pablos de Souza Rusbel Raul Aspilcueta-Borquis Fernando Baldi Lucia Galv?o de Albuquerque Luciana Correia de Almeida Regitano Humberto Tonhati 《Molecular biology reports》2012,39(12):10105-10109
Protein JY-1 is a bovine oocyte-specific protein that regulates granulosa cell function and is involved in early embryonic development, influencing the chance of pregnancy. This study investigated molecular markers for the JY-1 gene. Seven SNPs were identified in exon 3 of the gene. The positions of the SNPs in the exon and the respective substitutions are: 163 (T/C), 281 (T/C), 321 (T/C), 532 (T/C), 652 (A/G), 679 (T/C), and 722 (G/C) (GenBank: JN592587 and JF262042.2). SNP 163 is located in a coding region and causes a proline-to-leucine substitution. The other SNPs are located in the 3′UTR region. SNPs 163, 281, 321, and 679 were genotyped in 297 Nellore heifers and the haplotypes were constructed. The haplotypes of JY-1 were not correlated with the traits studied at 5?%. 相似文献
105.
In this work the presence of broad-host-plasmids in an estuary in Portugal has been investigated. Pseudomonas putida KT2442 was used as model recipient bacteria in biparental matings with tetracycline and mercury to select for resistance phenotypes. As a result, 7 transconjugants were shown to carry broad-host-plasmids from the IncP-1 group, as seen by PCR amplification of the trfA gene. Sequence analysis confirmed the isolation of 4 plasmids from β-1 subgroup and 3 assigned to the recently described ε subgroup. To our knowledge this is the first report concerning the detection and isolation of IncP-1β and ε plasmids in estuarine waters. Moreover it is shown that, even though the retrieved plasmids are phylogenetically close to previously characterized plasmids, such as pB10 and pKJK5, respectively, they constitute new molecular variants. 相似文献
106.
Sandra Correia Ana Estefânia Cunha Lígia Salgueiro Jorge M. Canhoto 《Plant Cell, Tissue and Organ Culture》2012,109(1):143-152
Somatic embryogenesis induction and somatic embryo development of the solanaceous tamarillo tree were previously established
and successfully used for plant regeneration from different explants and varieties. Somatic embryogenesis was induced in Murashige
and Skoog medium containing 2,4-dichlorophenoxyacetic acid (2,4-D) or picloram and high sucrose concentrations (0.25 M). The
embryogenic tissues were transferred to an auxin-free medium, with reduced sucrose levels, to permit embryo development and
conversion into plantlets. This two-step protocol is often impaired by an ineffective transition from the proembryogenic masses
to embryo development. In this work, attempts to optimize the somatic embryogenesis system of tamarillo by improving the quality
of somatic embryo and embryo conversion were carried out. The results showed that the presence of a high number of abnormal
somatic embryos did not significantly inhibit plant conversion, hence indicating that shoot apical meristem development was
not affected in abnormal somatic embryos. It was also shown that the manipulation of sucrose concentration in the development
medium (0.11 M) and dark conditions before conversion increased the number of morphologically normal somatic embryos. The
comparison between mature cotyledonary zygotic and somatic embryos showed an inefficient accumulation of storage compounds,
mainly lipids, in somatic embryos. These reduced levels of lipid storage could be responsible for the abnormal patterns of
embryo development found in tamarillo somatic embryos. 相似文献
107.
Moura A Jové T Ploy MC Henriques I Correia A 《Applied and environmental microbiology》2012,78(15):5413-5416
The diversity of gene cassette promoters in class 1 integrons was investigated in 47 strains isolated from wastewaters. The weak PcW and PcH1 variants predominated, suggesting that, similar to clinical environments, high rates of gene cassette recombination, rather than high expression of gene cassettes, have been preferentially selected in wastewaters. 相似文献
108.
Santos AL Oliveira V Baptista I Henriques I Gomes NC Almeida A Correia A Cunha A 《Applied and environmental microbiology》2012,78(6):2066-2069
The effects of UV radiation (UVR) on estuarine bacterioneuston and bacterioplankton were assessed in microcosm experiments. Bacterial abundance and DNA synthesis were more affected in bacterioplankton. Protein synthesis was more inhibited in bacterioneuston. Community analysis indicated that UVR has the potential to select resistant bacteria (e.g., Gammaproteobacteria), particularly abundant in bacterioneuston. 相似文献
109.
Santana AB Lucas SD Gonçalves LM Correia HF Cardote TA Guedes RC Iley J Moreira R 《Bioorganic & medicinal chemistry letters》2012,22(12):3993-3997
The synthesis, inhibitory activity and mode of action of oxazolidine-2,4-diones against porcine pancreatic elastase, here used as a model for human neutrophil elastase, are reported. The nature of N-substitution at the oxazolidine-2,4-dione scaffold has large effect on the inhibitory potency against elastase. N-Acyl and N-sulfonyloxazolidine-2,4-diones emerged as potent pseudo-irreversible inhibitors, displaying high second-order rate constants for PPE inactivation. The title compounds were also shown to be potent inhibitors of human neutrophil elastase (HNE) and proteinase-3, and weak inhibitors of human cathepsin G. The results herein presented show that the oxazolidine-2,4-diones represent a new promising class of serine protease inhibitors. 相似文献
110.
Leite Ferreira BJ Duarte MG Gil MH Fernandes MH Nunes Correia R 《Journal of applied biomaterials & functional materials》2012,10(2):e92-e98
Purpose: The formation of a calcium phosphate layer on the surface of bone tissue engineering biomaterials is crucial for their integration in bone. Simulated biological fluids used to study the in vitro formation of those layers do not usually contain important organic components present in vivo-notably proteins. In this work the influence of bovine serum albumin on the mineralization process of poly(methylmethacrylate)-based composite was studied in vitro. Methods: The effect of protein on calcium phosphate formation was followed by ion concentration analyses (ICP), x-ray diffraction (XRD), and scanning electron microscopy coupled with x-ray energy dispersive spectroscopy (SEM-EDS). Results and Conclusions: The results showed the precipitation of a calcium phosphate layer on the surface of composites immersed in SBF and SBFA. Further transformation and crystallization of this layer, initially amorphous, appears to be influenced by the presence of albumin. 相似文献