全文获取类型
收费全文 | 2057篇 |
免费 | 141篇 |
国内免费 | 1篇 |
出版年
2022年 | 13篇 |
2021年 | 31篇 |
2020年 | 8篇 |
2019年 | 11篇 |
2018年 | 17篇 |
2017年 | 17篇 |
2016年 | 41篇 |
2015年 | 55篇 |
2014年 | 85篇 |
2013年 | 101篇 |
2012年 | 122篇 |
2011年 | 114篇 |
2010年 | 82篇 |
2009年 | 69篇 |
2008年 | 119篇 |
2007年 | 102篇 |
2006年 | 95篇 |
2005年 | 105篇 |
2004年 | 76篇 |
2003年 | 121篇 |
2002年 | 89篇 |
2001年 | 31篇 |
2000年 | 28篇 |
1999年 | 33篇 |
1998年 | 44篇 |
1997年 | 24篇 |
1996年 | 33篇 |
1995年 | 31篇 |
1994年 | 24篇 |
1993年 | 34篇 |
1992年 | 36篇 |
1991年 | 26篇 |
1990年 | 27篇 |
1989年 | 26篇 |
1988年 | 14篇 |
1987年 | 22篇 |
1986年 | 12篇 |
1985年 | 29篇 |
1984年 | 22篇 |
1983年 | 14篇 |
1982年 | 24篇 |
1981年 | 15篇 |
1980年 | 22篇 |
1979年 | 25篇 |
1978年 | 11篇 |
1977年 | 14篇 |
1976年 | 12篇 |
1975年 | 9篇 |
1974年 | 12篇 |
1973年 | 11篇 |
排序方式: 共有2199条查询结果,搜索用时 15 毫秒
111.
Georges Ona-Nguema Cédric Carteret Omar Benali Mustapha Abdelmoula Jean-Marie Génin Frédéric Jorand 《Geomicrobiology journal》2013,30(2):79-90
The formation of hydroxysulphate green rust 2, a Fe(II-III) compound commonly found during corrosion processes of iron-based materials in seawater, has not yet been reported in bacterial cultures. Here we used Shewanella putrefaciens, a dissimilatory iron-reducing bacterium to anaerobically catalyze the transformation of a ferric oxyhydroxide, lepidocrocite (γ-FeOOH), into Fe(II) in the presence of various sulphate concentrations. Biotransformation assays of γ-FeOOH were performed with formate as the electron donor under a variety of concentrations. The results showed that the competitive formation of hydroxycarbonate green rust 1 (GR1(CO3 2?)) and hydroxysulphate green rust 2 (GR2(SO4 2 ?)) depended upon the relative ratio (R) of bicarbonate and sulphate concentrations. When R ≥ 0.17, GR1(CO3 2 ?) only was formed whereas when R < 0.17, a mixture of GR2(SO4 2 ?) and GR1(CO3 2 ?) was obtained. These results demonstrated that the hydroxysulphate GR2 can originate from the microbial reduction of γ-FeOOH and confirmed the preference for carbonate over sulphate during green rust precipitation. The solid phases were characterized by X-ray diffraction, transmission Mössbauer spectroscopy and scanning electron microscopy. Diffuse reflectance infrared Fourier transform spectroscopy confirmed the presence of intercalated carbonate and sulphate in green rust's structure. This study sheds light on the influence of dissimilatory iron-reducing bacteria on microbiologically influenced corrosion. 相似文献
112.
Lumeng Ye Steven Ballet Falk Hildebrand Georges Laus Karel Guillemyn Jeroen Raes Sandra Matthijs José Martins Pierre Cornelis 《Biometals》2013,26(4):561-575
The structure of a pyoverdine produced by Pseudomonas putida, W15Oct28, was elucidated by combining mass spectrometric methods and bioinformatics by the analysis of non-ribosomal peptide synthetase genes present in the newly sequenced genome. The only form of pyoverdine produced by P. putida W15Oct28 is characterized to contain α-ketoglutaric acid as acyl side chain, a dihydropyoverdine chromophore, and a 12 amino acid peptide chain. The peptide chain is unique among all pyoverdines produced by Pseudomonas subspecies strains. It was characterized as –l-Asp-l-Ala-d-AOHOrn-l-Thr-Gly-c[l-Thr(O-)-l-Hse-d-Hya-l-Ser-l-Orn-l-Hse-l-Ser-O-]. The chemical formula and the detected and calculated molecular weight of this pyoverdine are: C65H93N17O32, detected mass 1624.6404 Da, calculated mass 1624.6245. Additionally, pyoverdine structures from both literature reports and bioinformatics prediction of the genome sequenced P. putida strains are summarized allowing us to propose a scheme based on pyoverdines structures as tool for the phylogeny of P. putida. This study shows the strength of the combination of in silico analysis together with analytical data and literature mining in determining the structure of secondary metabolites such as peptidic siderophores. 相似文献
113.
Apostolos K. Makrygiannis Evangelos Pavlakis Petros Petrou Evgenia Kalogeraki Georges Chalepakis 《Histochemistry and cell biology》2013,140(5):595-601
The Fras1/Frem family of extracellular matrix proteins consists of Fras1 and its structurally related proteins, Frem1 (Fras1-related extracellular matrix protein 1), Frem2 and Frem3. These are co-localized in embryonic epithelial basement membranes (BMs), where they contribute to epithelial–mesenchymal adhesion. Although Fras1 localization pattern in epithelial BMs has been well defined, it has not yet been comprehensively studied in the central nervous system. Here, we demonstrate the immunohistochemical profile of Fras1 in the developing mouse brain and reveal an exclusively meningeal BM protein deposition. Interestingly, Fras1 displays a segmental localization pattern, which is restricted to certain regions of the meningeal BM. Frem2 protein displays a similar localization pattern, while Frem3 is rather uniformly distributed throughout the meningeal BM. Fras1 and Frem2 proteins are detected in regions of the BM that underlie organizing centers, such as the roof plate (RP) of diencephalon, midbrain and hindbrain, and the RP-derived structures of telencephalon (choroid plexus and hem). Organizing centers exert their activity via the production of bioactive molecules, which are potential Fras1 ligands. The restricted pattern of Fras1 and Frem2 proteins indicates a molecular compartmentalization of the meningeal BM that could reflect, yet unspecified, functional and structural differences. 相似文献
114.
Sarah Berry Wouter Coppieters Stephen Davis Alayna Burrett Natalie Thomas David Palmer Van Kelly Vladimir Obolonkin Kathryn Sanders Richard Spelman Michel Georges Klaus Lehnert Russell Snell 《PloS one》2013,8(3)
The aim of this study was to determine a genetic basis for IgA concentration in milk of Bos taurus. We used a Holstein-Friesian x Jersey F2 crossbred pedigree to undertake a genome-wide search for QTL influencing IgA concentration and yield in colostrum and milk. We identified a single genome-wide significant QTL on chromosome 16, maximising at 4.8 Mbp. The polymeric immunoglobulin receptor gene (PIGR) was within the confidence interval of the QTL. In addition, mRNA expression analysis revealed a liver PIGR expression QTL mapping to the same locus as the IgA quantitative trait locus. Sequencing and subsequent genotyping of the PIGR gene revealed three divergent haplotypes that explained the variance of both the IgA QTL and the PIGR expression QTL. Genetic selection based on these markers will facilitate the production of bovine herds producing milk with higher concentrations of IgA. 相似文献
115.
Are variations of direct and indirect plant interactions along a climatic gradient dependent on species’ strategies? An experiment on tree seedlings
下载免费PDF全文
![点击此处可从《Oikos》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Emmanuel Defossez Benoît Courbaud Olivier Lasbouygues Katja Schiffers Georges Kunstler 《Oikos》2016,125(5):708-717
Investigating how interactions among plants depend on environmental conditions is key to understand and predict plant communities’ response to climate change. However, while many studies have shown how direct interactions change along climatic gradients, indirect interactions have received far less attention. In this study, we aim at contributing to a more complete understanding of how biotic interactions are modulated by climatic conditions. We investigated both direct and indirect effects of adult tree canopy and ground vegetation on seedling growth and survival in five tree species in the French Alps. To explore the effect of environmental conditions, the experiment was carried out at 10 sites along a climatic gradient closely related to temperature. While seedling growth was little affected by direct and indirect interactions, seedling survival showed significant patterns across multiple species. Ground vegetation had a strong direct competitive effect on seedling survival under warmer conditions. This effect decreased or shifted to facilitation at lower temperatures. While the confidence intervals were wider for the effect of adult canopy, it displayed the same pattern. The monitoring of micro‐environmental conditions revealed that competition by ground vegetation in warmer sites could be related to reduced water availability; and weak facilitation by adult canopy in colder sites to protection against frost. For a cold‐intolerant and shade‐tolerant species (Fagus sylvatica), adult canopy indirectly facilitated seedling survival by suppressing ground vegetation at high temperature sites. The other more cold tolerant species did not show this indirect effect (Pinus uncinata, Larix decidua and Abies alba). Our results support the widely observed pattern of stronger direct competition in more productive climates. However, for shade tolerant species, the effect of direct competition may be buffered by tree canopies reducing the competition of ground vegetation, resulting in an opposite trend for indirect interactions across the climatic gradient. 相似文献
116.
Mark C. Vanderwel Hongcheng Zeng John P. Caspersen Georges Kunstler Jeremy W. Lichstein 《Ecology letters》2016,19(4):414-423
Ecologists have limited understanding of how geographic variation in forest biomass arises from differences in growth and mortality at continental to global scales. Using forest inventories from across North America, we partitioned continental‐scale variation in biomass growth and mortality rates of 49 tree species groups into (1) species‐independent spatial effects and (2) inherent differences in demographic performance among species. Spatial factors that were separable from species composition explained 83% and 51% of the respective variation in growth and mortality. Moderate additional variation in mortality (26%) was attributable to differences in species composition. Age‐dependent biomass models showed that variation in forest biomass can be explained primarily by spatial gradients in growth that were unrelated to species composition. Species‐dependent patterns of mortality explained additional variation in biomass, with forests supporting less biomass when dominated by species that are highly susceptible to competition (e.g. Populus spp.) or to biotic disturbances (e.g. Abies balsamea). 相似文献
117.
Zhu Yaling Zhou Zhimin Huang Tao Zhang Zhen Li Wanbo Ling Ziqi Jiang Tao Yang Jiawen Yang Siyu Xiao Yanyuan Charlier Carole Georges Michel Yang Bin Huang Lusheng 《中国科学:生命科学英文版》2022,65(8):1517-1534
Science China Life Sciences - The limited knowledge of genomic noncoding and regulatory regions has restricted our ability to decipher the genetic mechanisms underlying complex traits in pigs. In... 相似文献
118.
Overlapping and divergent localization of Frem1 and Fras1 and its functional implications during mouse embryonic development 总被引:1,自引:0,他引:1
Frem1 belongs to a family of structurally related extracellular matrix proteins of which Fras1 is the founding member. Mutations in Fras1 and Frem1 have been identified in mouse models for Fraser syndrome, which display a strikingly similar embryonic skin blistering phenotype due to impaired dermal-epidermal adhesion. Here we show that Frem1 originates from both epithelial and mesenchymal cells, in contrast to Fras1 that is exclusively derived from epithelia. However, both proteins are localized in an absolutely overlapping fashion in diverse epithelial basement membranes. At the ultrastructural level, Frem1 exhibits a clustered arrangement in the sublamina densa coinciding with fibrillar structures reminiscent of anchoring fibrils. Furthermore, in addition to its extracellular deposition, around E16, Frem1 displays an intracellular distribution in distinct epidermal cell types such as the periderm layer and basal keratinocytes. Since periderm cells are known to participate in temporary epithelial fusions like embryonic eyelid closure, defective function of Frem1 in these cells could provide a molecular explanation for the "eyes open at birth" phenotype, a feature unique for Frem1 deficient mouse mutants. Finally, we demonstrate loss of Frem1 localization in the basement membrane but not in periderm cells in the skin of Fras1(-/-) embryos. Taken together, our findings indicate that besides a cooperative function with Fras1 in embryonic basement membranes, Frem1 can also act independently in processes related to epidermal differentiation. 相似文献
119.
De Leeuw F Zhang T Wauquier C Huez G Kruys V Gueydan C 《Experimental cell research》2007,313(20):4130-4144
The cold-inducible RNA-binding protein (CIRP) is a nuclear 18-kDa protein consisting of an amino-terminal RNA Recognition Motif (RRM) and a carboxyl-terminal domain containing several RGG motifs. First characterized for its overexpression upon cold shock, CIRP is also induced by stresses such as UV irradiation and hypoxia. Here, we investigated the expression as well as the subcellular localization of CIRP in response to other stress conditions. We demonstrate that oxidative stress leads to the migration of CIRP to stress granules (SGs) without alteration of expression. Stress granules are dynamic cytoplasmic foci at which stalled translation initiation complexes accumulate in cells subjected to environmental stress. Relocalization of CIRP into SGs also occurs upon other cytoplasmic stresses (osmotic pressure or heat shock) as well as in response to stresses of the endoplasmic reticulum. CIRP migration into SGs is independent from TIA-1 which has been previously reported to be a general mediator of SG formation, thereby suggesting the existence of multiple pathways leading to SG formation. Moreover, deletion mutants revealed that both RGG and RRM domains can independently promote CIRP migration into SGs. However, the methylation of arginine residues in the RGG domain is necessary for CIRP to exit the nucleus to be further recruited into SGs. By RNA-tethering experiments, we also show that CIRP down-regulates mRNA translation and that this activity is carried by the carboxyl-terminal RG-enriched domain. Altogether, our findings further reveal the diversity of mechanisms by which CIRP is regulated by environmental stresses and provide new insights into CIRP cytoplasmic function. 相似文献
120.
Hamelin M Sayd T Chambon C Bouix J Bibé B Milenkovic D Leveziel H Georges M Clop A Marinova P Laville E 《Proteomics》2007,7(2):271-280
Fiber-type distribution is known to vary widely within and between muscles according to differences in muscle functions. 2-DE and MALDI-MS were used to investigate the molecular basis of muscle fiber type-related variability. We compared four lamb skeletal muscles with heterogeneous fiber-type composition that are relatively rich in fast-twitch fiber types, i.e., the semimembranosus, vastus medialis, longissimus dorsi, and tensor fasciae latae (TL). Our results clearly showed that none of the glycolytic metabolism enzymes detected, including TL which was most strongly glycolytic, made intermuscular differentiation possible. Muscle differentiation was based on the differential expression of proteins involved in oxidative metabolism, including not only citric acid cycle enzymes but also other classes of proteins with functions related to oxidative metabolism, oxidative stress, and probably to higher protein turnover. Detected proteins were involved in transport (carbonate dehydratase, myoglobin, fatty acid-binding protein), repair of misfolding damage (heat shock protein (HSP) 60 kDa, HSP-27 kDa, alpha-crystallin beta subunit, DJ1, stress-induced phosphoprotein), detoxification or degradation of impaired proteins (GST-Pi, aldehyde dehydrogenase, peroxiredoxin, ubiquitin), and protein synthesis (tRNA-synthetase). The fractionating method led to the detection of proteins involved in different functions related to oxidative metabolism that have not previously been shown concomitancy. 相似文献