全文获取类型
收费全文 | 363篇 |
免费 | 60篇 |
专业分类
423篇 |
出版年
2023年 | 2篇 |
2021年 | 4篇 |
2020年 | 11篇 |
2019年 | 6篇 |
2018年 | 7篇 |
2017年 | 11篇 |
2016年 | 12篇 |
2015年 | 12篇 |
2014年 | 16篇 |
2013年 | 25篇 |
2012年 | 23篇 |
2011年 | 19篇 |
2010年 | 18篇 |
2009年 | 11篇 |
2008年 | 24篇 |
2007年 | 14篇 |
2006年 | 15篇 |
2005年 | 11篇 |
2004年 | 13篇 |
2003年 | 17篇 |
2002年 | 7篇 |
2001年 | 13篇 |
2000年 | 15篇 |
1999年 | 14篇 |
1998年 | 9篇 |
1997年 | 9篇 |
1996年 | 6篇 |
1995年 | 6篇 |
1994年 | 12篇 |
1993年 | 6篇 |
1992年 | 4篇 |
1991年 | 7篇 |
1990年 | 8篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1975年 | 4篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1971年 | 1篇 |
1969年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有423条查询结果,搜索用时 15 毫秒
351.
352.
353.
D. CardosoA.Z.M. Salem F.D. ProvenzaR. Rojo L.M. CamachoD.G. Satterlee 《Animal Feed Science and Technology》2011,163(1):52-58
We assessed the effects of cereal type (corn-based, CB or rice-based, RB) and housing system (floor, F, or cage, C) on the performance of two Japanese quail genotypes (non-selected, JAP, and a Jumbo variety, JUM) in two, 2 × 2 factorially designed, experiments. In Exp. 1, during the 15-d experimental period, there were 4 experimental groups: JAP quail fed the CB diet, JAP-CB; JAP quail fed the RB diet, JAP-RB; JUM quail fed the CB diet, JUM-CB; JUM quail fed the RB diet, JUM-RB. Quail in each of the 4 groups (42 quail/group) were housed in 7 pens, each with 6 birds. In Exp. 2, there were also 4 experimental groups (42 quail/group, 7 pens, each with 6 birds) examined during a 19-d experimental period under two different rearing systems: JAP-F, JUM-F, JAP-CF and JUM-C. Genotype did not affect dry matter feed intake (DMI) in Exp. 1, but both JAP and JUM quail consumed more (P<0.001) of the CB than RB diets. Average daily gain (ADG) was similarly higher (P<0.001) in JAP-CB and JUM-CB quail compared to the other 2 treatment groups. Feed conversion (FC) differed (P<0.001) as follows (best to worst): JUM-CB > JAP-CB = JAP-RB = JUM-RB. Final BW was similarly higher (P<0.001) in the JUM-CB, and JAP-CB groups compared to the JAP-RB and JUM-RB, groups and carcass yield (CY, P<0.001) differed as follows: JUM-RB = JUM-CB = JAP-RB > JAP-CB. In Exp. 2, DMI was similarly higher (P<0.05) in the JAP-C, JUM-F, and JUM-C groups compared to JAP-F quail and ADG was notably higher (P=0.07) in JUM-F quail than the other 3 groups. Regardless of housing system, FC was better (P=0.04) in JUM quail. Although final BW was higher (P<0.05) in F- than C-housed quail, CY was greater (P<0.01) in caged birds. Final BW and CY were unaffected by quail genome and its interaction with housing system. With a few exceptions, better performance was generally observed in quail fed diets containing corn regardless of genotype (Exp. 1), while C-reared JUM quail generally outperformed the other genotype × housing system groups (Exp. 2). 相似文献
354.
Phylogenetic relationships and taxonomic ranking of pipizine flower flies (Diptera: Syrphidae) with implications for the evolution of aphidophagy 下载免费PDF全文
Ximo Mengual Gunilla Ståhls Santos Rojo 《Cladistics : the international journal of the Willi Hennig Society》2015,31(5):491-508
The taxonomic rank and phylogenetic relationships of the pipizine flower flies (Diptera: Syrphidae: Pipizini) were estimated based on DNA sequence data from three gene regions (COI, 28S and 18S) and 111 adult morphological characters. Pipizini has been treated as a member of the subfamily Eristalinae based on diagnostic adult morphological characteristics, while the larval feeding mode and morphology is shared with members of the subfamily Syrphinae. We analysed each dataset, both separately and combined, in a total evidence approach under maximum parsimony and maximum likelihood. To evaluate the influence of different alignment strategies of rDNA 28S and 18S genes on the resulting topologies, we compared the topologies inferred from a multiple alignment using fast Fourier transform (MAFFT) program with those topologies resulting from aligning the secondary structure of these rDNA genes. Total evidence analyses resolved pipizines as a sister group of the subfamily Syrphinae. Although the structural alignment and the MAFFT alignment differed in the inferred relationships of some clades and taxa, there was congruence in the placement of pipizines. The homogeneous morphology of the Pipizini clade in combination with their unique combination of characters among the Syrphidae suggest a change of rank to subfamily. Thus, we propose to divide Syrphidae into four subfamilies, including the subfamily Pipizinae stat. rev. 相似文献
355.
ángel Juan García-Yagüe Patricia Rada Ana I. Rojo Isabel Lastres-Becker Antonio Cuadrado 《The Journal of biological chemistry》2013,288(8):5506-5517
Orphan receptor Nurr1 participates in the acquisition and maintenance of the dopaminergic cell phenotype, modulation of inflammation, and cytoprotection, but little is known about its regulation. In this study, we report that Nurr1 contains a bipartite nuclear localization signal (NLS) within its DNA binding domain and two leucine-rich nuclear export signals (NES) in its ligand binding domain. Together, these signals regulate Nurr1 shuttling in and out of the nucleus. Immunofluorescence and immunoblot analysis revealed that Nurr1 is mostly nuclear. A Nurr1 mutant lacking the NLS failed to enter the nucleus. The Nurr1 NLS sequence, when fused to green fluorescent protein, led to nuclear accumulation of this chimeric protein, indicating that this sequence was sufficient to direct nuclear localization of Nurr1. Furthermore, two NES were characterized in the ligand binding domain, whose deletion caused Nurr1 to accumulate predominantly in the nucleus. The Nurr1 NES was sensitive to CRM1 and could function as an independent export signal when fused to green fluorescent protein. Sodium arsenite, an agent that induces oxidative stress, promoted nuclear export of ectopically expressed Nurr1 in HEK293T cells, and the antioxidant N-acetylcysteine rescued from this effect. Similarly, in dopaminergic MN9D cells, arsenite induced the export of endogenous Nurr1, resulting in the loss of expression of Nurr1-dependent genes. This study illustrates that Nurr1 shuttling between the cytosol and nucleus is controlled by specific nuclear import and export signals and that oxidative stress can unbalance the distribution of Nurr1 to favor its cytosolic accumulation. 相似文献
356.
Naiara Rojo Gorka Gallastegui Luis Gurtubay Astrid Barona Ana Elías 《Bioprocess and biosystems engineering》2013,36(4):389-397
The bacteriostatic properties of carbon disulphide (CS2) hamper its biodegradation in conventional biofilters. The response of four biofilters operating in downflow mode and reverse-flow mode was compared in a laboratory-scale plant treating CS2 under sudden short-term changes in operating conditions. A process shutdown for 24 h, an inlet concentration increase and an interruption of the inlet air humidification for 48 h at an empty bed residence time (EBRT) of 240 s did not impact significantly on biodegradation performance, regardless of flow mode. Nevertheless, a reduction in the EBRT to 60 s resulted in a significant decrease in removal efficiency in all the biofilters. The CS2 degradation profile showed that the reverse-flow mode strategy rendered a more homogenous distribution of biomass along the bed height. The benefits of the reverse-flow mode were demonstrated even when the unidirectional flow mode was re-established. 相似文献
357.
Effects of ribosome-inactivating proteins on Escherichia coli and Agrobacterium tumefaciens translation systems. 总被引:2,自引:0,他引:2 下载免费PDF全文
T Girbs L Barbieri M Ferreras F J Arias M A Rojo R Iglesias C Alegre C Escarmis F Stirpe 《Journal of bacteriology》1993,175(20):6721-6724
The effects of 30 type 1 and of 2 (ricin and volkensin) type 2 ribosome-inactivating proteins (RIPs) on Escherichia coli and Agrobacterium tumefaciens cell-free translation systems were compared with the effects on a rabbit reticulocyte translation system. The depurinating activity of RIPs on E. coli ribosomes was also evaluated. Only six type 1 RIPs inhibited endogenous mRNA-directed translational activity of E. coli lysates, with submicromolar 50% inhibitory concentrations. Four RIPs had similar activities on poly(U)-directed phenylalanine polymerization by E. coli ribosomes, and three RIPs inhibited poly(U)-directed polyphenylalanine synthesis by A. tumefaciens ribosomes, with submicromolar 50% inhibitory concentrations. 相似文献
358.
Cloning and expression of the ponB gene, encoding penicillin-binding protein 1B of Escherichia coli, in heterologous systems. 下载免费PDF全文
A fragment from the ponB region of the Escherichia coli chromosome comprising the promoterless sequence encoding penicillin-binding protein 1B (PBP 1B) has been cloned in a broad-host-range expression vector under the control of the kanamycin resistance gene promoter present in the vector. The hybrid plasmid (pJP3) was used to transform appropriate strains of Salmonella typhimurium, Pseudomonas putida, and Pseudomonas aeruginosa. In all instances, the coding sequence was expressed in the heterologous hosts, yielding a product with electrophoretic mobility, protease accessibility, membrane location, and beta-lactam-binding properties identical to those of native PBP 1B in E. coli. These results indicated that PBP 1B of E. coli is compatible with the cytoplasmic membrane environment of unrelated bacterial species and support the idea that interspecific transfer of mutated alleles of genes coding for PBPs could potentially be an efficient spreading mechanism for intrinsic resistance to beta-lactams. 相似文献
359.
Javier H. Rojo Daniel E. Figueroa Claudia C. Boy 《Environmental Biology of Fishes》2018,101(7):1149-1160
The population of Galaxias maculatus studied here, Arroyo Negro (54° S), is located at the southern extreme of the species distribution. This is the first work on growth and other life history traits of a Fueguian diadromous population based on otoliths study. This species is part of the native fish fauna of Patagonia. Furthermore, studies on the growth and reproduction of G. maculatus in South America mostly refer to freshwater populations of Andean-Patagonian lakes and rivers (about 41° S). Size cohorts were studied; age and growth parameters were estimated, the latter using the VBGM. Four size cohorts were established, and 3+ was determined as maximum age class. No differences were found in growth curves between males and females. The 1+ age class was by far not only the most numerous in the population but also the most represented in the reproductive population. The relation between mean TL and latitude was positive (r?=?0.62) for South American populations; however, further studies are needed to determine whether it is this population’s life strategy, the local adaptation of a peripheral population or countergradient growth. The results are interpreted in the context of the information available for other populations, and provide important information about the plasticity in life history traits of this species. 相似文献
360.
Evelina G. Ferrer María V. Salinas María J. Correa Luciana Naso Daniel A. Barrio Susana B. Etcheverry Luis Lezama Teófilo Rojo Patricia A. M. Williams 《Journal of biological inorganic chemistry》2006,11(6):791-801
The development of new vanadium derivatives with organic ligands, which improve the beneficial actions (insulin-mimetic, antitumoral) and decrease the toxic effects, is of great interest. A good candidate for the generation of a new vanadium compound is the flavonoid quercetin because of its own anticarcinogenic effect. The complex [VO(Quer)2EtOH]
n
(QuerVO) has been synthesized and characterized by means of different spectroscopic techniques (UV–vis, Fourier transform IR, electron paramagnetic resonance) and its magnetic and stability properties. The inhibitory effect on bovine alkaline phosphatase (ALP) activity has been tested for the free ligand, the complex as well as for the vanadyl(IV) (comparative purposes). The biological activity of the complex on the proliferation of two osteoblast-like cells in culture, a normal one (MC3T3E1) and a tumoral one (UMR106), has been compared with that of the vanadyl(IV) cation and quercetin. The differentiation osteoblast markers ALP specific activity and collagen synthesis have been also tested. In addition, the effect of QuerVO on the activation of the extracellular regulated kinase (ERK) pathway is reported. The bone antitumoral effect of quercetin alone was established with the cell proliferation assays (it inhibits the proliferation of the tumoral cells and does not exert any effect on the normal osteoblasts). Moreover, the complex exerts osteogenic effects since it stimulates the type I collagen production and is a weak inhibitory agent upon ALP activity. Finally, QuerVO stimulated the ERK phosphorylation in a dose–response manner and this activation seems to be involved as one of the possible mechanisms for the biological effects of the complex. 相似文献