全文获取类型
收费全文 | 1707篇 |
免费 | 73篇 |
出版年
2022年 | 5篇 |
2021年 | 16篇 |
2020年 | 8篇 |
2019年 | 8篇 |
2018年 | 16篇 |
2017年 | 11篇 |
2016年 | 27篇 |
2015年 | 45篇 |
2014年 | 62篇 |
2013年 | 80篇 |
2012年 | 128篇 |
2011年 | 95篇 |
2010年 | 74篇 |
2009年 | 71篇 |
2008年 | 98篇 |
2007年 | 111篇 |
2006年 | 89篇 |
2005年 | 115篇 |
2004年 | 103篇 |
2003年 | 115篇 |
2002年 | 91篇 |
2001年 | 20篇 |
2000年 | 20篇 |
1999年 | 21篇 |
1998年 | 42篇 |
1997年 | 15篇 |
1996年 | 21篇 |
1995年 | 20篇 |
1994年 | 22篇 |
1993年 | 21篇 |
1992年 | 15篇 |
1991年 | 15篇 |
1990年 | 7篇 |
1989年 | 11篇 |
1988年 | 7篇 |
1986年 | 9篇 |
1985年 | 11篇 |
1984年 | 15篇 |
1983年 | 12篇 |
1982年 | 15篇 |
1981年 | 15篇 |
1980年 | 10篇 |
1979年 | 7篇 |
1978年 | 10篇 |
1977年 | 5篇 |
1976年 | 9篇 |
1975年 | 7篇 |
1974年 | 9篇 |
1970年 | 3篇 |
1966年 | 3篇 |
排序方式: 共有1780条查询结果,搜索用时 187 毫秒
991.
In this paper, we develop a dynamic stock model and scenario analysis involving a bottom‐up approach to analyze copper demand in China from 2005 to 2050 based on government and related sectoral policies. The results show that in the short‐term, China's copper industry cannot achieve a completely circular economy without additional measures. Aggregate and per capita copper demand are both set to increase substantially, especially in infrastructure, transportation, and buildings. Between 2016 and 2050, total copper demand will increase almost threefold. Copper use in buildings will stabilize before 2050, but the copper stock in infrastructure and transportation will not yet have reached saturation in 2050. The continuous growth of copper stock implies that secondary copper will be able to cover just over 50% of demand in 2050, at best, even with an assumed recycling rate of 90%. Finally, future copper demand depends largely on the lifetime of applications. There is therefore an urgent need to prolong the service life of end‐use products to reduce the amount of materials used, especially in large‐scale applications in buildings and infrastructure. 相似文献
992.
Chuan-Ming Xie Dongping Wei Lili Zhao Sylvie Marchetto Lin Mei Jean-Paul Borg Yi Sun 《The Journal of cell biology》2015,209(5):721-738
SAG/RBX2 is the RING (really interesting new gene) component of Cullin-RING ligase, which is required for its activity. An organ-specific role of SAG in tumorigenesis is unknown. We recently showed that Sag/Rbx2, upon lung-targeted deletion, suppressed KrasG12D-induced tumorigenesis via inactivating NF-κB and mammalian target of rapamycin pathways. In contrast, we report here that, upon skin-targeted deletion, Sag significantly accelerated KrasG12D-induced papillomagenesis. In KrasG12D-expressing primary keratinocytes, Sag deletion promotes proliferation by inhibiting autophagy and senescence, by inactivating the Ras–Erk pathway, and by blocking reactive oxygen species (ROS) generation. This is achieved by accumulation of Erbin to block Ras activation of Raf and Nrf2 to scavenge ROS and can be rescued by knockdown of Nrf2 or Erbin. Simultaneous one-allele deletion of the Erbin-encoding gene Erbb2ip partially rescued the phenotypes. Finally, we characterized Erbin as a novel substrate of SAG-βTrCP E3 ligase. By degrading Erbin and Nrf2, Sag activates the Ras–Raf pathway and causes ROS accumulation to trigger autophagy and senescence, eventually delaying KrasG12D-induced papillomagenesis and thus acting as a skin-specific tumor suppressor. 相似文献
993.
Jean-Paul Lema?tre Amandine Duroux Romain Pimpie Jean-Marie Duez Marie-Louise Milat 《Applied and environmental microbiology》2015,81(6):2117-2124
The detection of Listeria monocytogenes from food is currently carried out using a double enrichment. For the ISO methodology, this double enrichment is performed using half-Fraser and Fraser broths, in which the overgrowth of L. innocua can occur in samples where both species are present. In this study, we analyzed the induction of phages and phage tails of Listeria spp. in these media and in two brain heart infusion (BHI) broths (BHIM [bioMérieux] and BHIK [Biokar]) to identify putative effectors. It appears that Na2HPO4 at concentrations ranging from 1 to 40 g/liter with an initial pH of 7.5 can induce phage or phage tail production of Listeria spp., especially with 10 g/liter of Na2HPO4 and a pH of 7.5, conditions present in half-Fraser and Fraser broths. Exposure to LiCl in BHIM (18 to 21 g/liter) can also induce phage and phage tail release, but in half-Fraser and Fraser broths, the concentration of LiCl is much lower (3 g/liter). Low phage titers were induced by acriflavine and/or nalidixic acid. We also show that the production of phages and phage tails can occur in half-Fraser and Fraser broths. This study points out that induction of phages and phage tails could be triggered by compounds present in enrichment media. This could lead to a false-negative result for the detection of L. monocytogenes in food products. 相似文献
994.
Patrick von Aderkas Caroline Teyssier Jean-Paul Charpentier Markus Gutmann Luc Paques Claire Le Metté Kevin Ader Philippe Label Lisheng Kong Marie-Anne Lelu-Walter 《Annals of botany》2015,115(4):605-615
Background and Aims In conifers, mature somatic embryos and zygotic embryos appear to resemble one another physiologically and morphologically. However, phenotypes of cloned conifer embryos can be strongly influenced by a number of in vitro factors and in some instances clonal variation can exceed that found in nature. This study examines whether zygotic embryos that develop within light-opaque cones differ from somatic embryos developing in dark/light conditions in vitro. Embryogenesis in larch is well understood both in situ and in vitro and thus provides a suitable system for addressing this question.Methods Features of somatic and zygotic embryos of hybrid larch, Larix × marschlinsii, were quantified, including cotyledon numbers, protein concentration and phenol chemistry. Somatic embryos were placed either in light or darkness for the entire maturation period. Embryos at different developmental stages were embedded and sectioned for histological analysis.Key Results Light, and to a lesser degree abscisic acid (ABA), influenced accumulation of protein and phenolic compounds in somatic and zygotic embryos. Dark-grown mature somatic embryos had more protein (91·77 ± 11·26 µg protein mg–1 f.wt) than either dark-grown zygotic embryos (62·40 ± 5·58) or light-grown somatic embryos (58·15 ± 10·02). Zygotic embryos never accumulated phenolic compounds at any stage, whereas somatic embryos stored phenolic compounds in the embryonal root caps and suspensors. Light induced the production of quercetrin (261·13 ± 9·2 µg g–1 d.wt) in somatic embryos. Mature zygotic embryos that were removed from seeds and placed on medium in light rapidly accumulated phenolics in the embryonal root cap and hypocotyl. Delaying germination with ABA delayed phenolic compound accumulation, restricting it to the embryonal root cap.Conclusions In larch embryos, light has a negative effect on protein accumulation, but a positive effect on phenol accumulation. Light did not affect morphogenesis, e.g. cotyledon number. Somatic embryos produced different amounts of phenolics, such as quercetrin, depending on light conditions. The greatest difference was seen in the embryonal root cap in all embryo types and conditions. 相似文献
995.
Meriem Bennabi Richard Delorme José Oliveira Catherine Fortier Mohamed Lajnef Wahid Boukouaci Jean-Paul Feugeas Fran?ois Marzais Alexandru Gaman Dominique Charron Bijan Ghaleh Rajagopal Krishnamoorthy Marion Leboyer Ryad Tamouza 《PloS one》2015,10(9)
Introduction
In autism spectrum disorders (ASD), complex gene-environment interactions contribute to disease onset and progress. Given that gastro-intestinal dysfunctions are common in ASD, we postulated involvement of microbial dysbiosis in ASD and investigated, under a case-control design, the influence of DNA polymorphisms in the CLEC7A gene that encodes a pivotal fungal sensor, Dectin-1.Material and methods
DNAs from 478 ASD patients and 351 healthy controls (HC) were analyzed for the CLEC7A rs16910631G/A and rs2078178 A/G single nucleotide polymorphisms (SNPs). Differences in the distribution of allele, genotype and haplotype by Chi-square testing and nonparametric analysis by Kruskal-Wallis/Mann–Whitney tests, where appropriate, were performed. The free statistical package R.2.13 software was used for the statistical analysis.Results
We found that the CLEC7A rs2078178 G allele and GG genotype were more prevalent in HC as compared to ASD but failed to reach statistical significance for the latter (pc = 0.01, 0.06 respectively). However, after phenotype-based stratification, the CLEC7A rs2078178 G allele and GG genotype were found to be significantly more frequent in the Asperger group as compared to other ASD subsets (pc = 0.02, 0.01), a finding reinforced by haplotype analysis (rs2078178/rs16910631 G-G/G-G) (pc = 0.002). Further, intellectual quotient (IQ)-based stratification of ASD patients revealed that IQ values increase linearly along the CLEC7A rs2078178 AA, AG and GG genotypes (p = 0.05) and in a recessive manner (GG vs. AA+AG p = 0.02), further confirmed by haplotype distribution (CLEC7A rs2078178-16910631; A-G/A-G, A-G/G-G and G-G/G-G, p = 0.02, G-G/G-G vs. others, p = 0.01).Conclusion
Our data suggest that the genetic diversity of CLEC7A gene influences the ASD phenotype by behaving as a disease specifier and imply that the genetic control of innate immune response could determine the ASD phenotype. 相似文献996.
Jér?me Le Chenadec Daniel Scott-Algara Stéphane Blanche Céline Didier Thomas Montange Jean-Paul Viard Catherine Dollfus Véronique Avettand-Fenoel Christine Rouzioux Josiane Warszawski Florence Buseyne 《PloS one》2015,10(12)
The ANRS-EP38-IMMIP study aimed to provide a detailed assessment of the immune status of perinatally infected youths living in France. We studied Gag-specific CD4 and CD8 T-cell proliferation and the association between the proliferation of these cells, demographic factors and HIV disease history. We included 93 youths aged between 15 and 24 years who had been perinatally infected with HIV. Sixty-nine had undergone valid CFSE-based T-cell proliferation assays. Gag-specific proliferation of CD4 and CD8 T cells was detected in 12 (16%) and 30 (38%) patients, respectively. The Gag-specific proliferation of CD4 and CD8 T cells was more frequently observed in black patients than in patients from other ethnic groups (CD4: 32% vs. 4%, P = 0.001; CD8: 55% vs. 26%, P = 0.02). Among aviremic patients, the duration of viral suppression was shorter in CD8 responders than in CD8 nonresponders (medians: 54 vs. 20 months, P = 0.04). Among viremic patients, CD8 responders had significantly lower plasma HIV RNA levels than CD8 nonresponders (2.7 vs. 3.7 log10 HIV-RNA copies/ml, P = 0.02). In multivariate analyses including sex and HIV-1 subtype as covariables, Gag-specific CD4 T-cell proliferation was associated only with ethnicity, whereas Gag-specific CD8 T-cell proliferation was associated with both ethnicity and the duration of viral suppression. Both CD4 and CD8 responders reached their nadir CD4 T-cell percentages at younger ages than their nonresponder counterparts (6 vs. 8 years, P = 0.04 for both CD4 and CD8 T-cell proliferation). However, these associations were not significant in multivariate analysis. In conclusion, after at least 15 years of HIV infection, Gag-specific T-cell proliferation was found to be more frequent in black youths than in patients of other ethnic groups, despite all the patients being born in the same country, with similar access to care. 相似文献
997.
Jelle T. C. Schrauwen Antonios Karanasos Nienke S. van Ditzhuijzen Jean-Paul Aben Antonius F. W. van der Steen Jolanda J. Wentzel Frank J. H. Gijsen 《PloS one》2015,10(12)
Introduction
Wall shear stress (WSS) plays a key role in the onset and progression of atherosclerosis in human coronary arteries. Especially sites with low and oscillating WSS near bifurcations have a higher propensity to develop atherosclerosis. WSS computations in coronary bifurcations can be performed in angiography-based 3D reconstructions. It is essential to evaluate how reconstruction errors influence WSS computations in mildly-diseased coronary bifurcations. In mildly-diseased lesions WSS could potentially provide more insight in plaque progression.Materials Methods
Four Plexiglas phantom models of coronary bifurcations were imaged with bi-plane angiography. The lumens were segmented by two clinically experienced readers. Based on the segmentations 3D models were generated. This resulted in three models per phantom: one gold-standard from the phantom model itself, and one from each reader. Steady-state and transient simulations were performed with computational fluid dynamics to compute the WSS. A similarity index and a noninferiority test were used to compare the WSS in the phantoms and their reconstructions. The margin for this test was based on the resolution constraints of angiography.Results
The reconstruction errors were similar to previously reported data; in seven out of eight reconstructions less than 0.10 mm. WSS in the regions proximal and far distal of the stenosis showed a good agreement. However, the low WSS areas directly distal of the stenosis showed some disagreement between the phantoms and the readers. This was due to small deviations in the reconstruction of the stenosis that caused differences in the resulting jet, and consequently the size and location of the low WSS area.Discussion
This study showed that WSS can accurately be computed within angiography-based 3D reconstructions of coronary arteries with early stage atherosclerosis. Qualitatively, there was a good agreement between the phantoms and the readers. Quantitatively, the low WSS regions directly distal to the stenosis were sensitive to small reconstruction errors. 相似文献998.
Janna C. Welleweerd Bastiaan G. L. Nelissen Dave Koole Jean-Paul P. M. de Vries Frans L. Moll Gerard Pasterkamp Aryan Vink Gert Jan de Borst 《PloS one》2015,10(1)
Introduction
Extracranial carotid artery aneurysms (ECAA) are rare but may be accompanied with significant morbidity. Previous studies mostly focused on diagnostic imaging and treatment. In contrast, the pathophysiological mechanisms and natural course of ECAA are largely unknown. Understanding the pathophysiological background may add to prediction of risk for adverse outcome and need for surgical exclusion. The aim of this study was to investigate the histopathological characteristics of ECAA in patients who underwent complete surgical ECAA resection.Material and Methods
From March 2004 till June 2013, 13 patients were treated with open ECAA repair. During surgery the aneurysm sac was resected and processed for standardized histological analysis. Sections were stained with routine hematoxylin and eosin and special stains to detect elastin, collagen, different types of inflammatory cells, vascular smooth muscle cells and endothelial cells.Results
Histopathological characterization revealed two distinct categories: dissection (abrupt interruption of the media; n = 3) and degeneration (general loss of elastin fibers in the media; n = 10). In the degenerative samples the elastin fibers in the media were fragmented and were partly absent. Inflammatory cells were observed in the vessel wall of the aneurysms.Conclusion
Histological analysis in this small sample size revealed dissection and degeneration as the two distinct underlying mechanisms in ECAA formation. 相似文献999.
Nicolas Jullien Catherine Roche Thierry Brue Dominique Figarella-Branger Thomas Graillon Anne Barlier Jean-Paul Herman 《PloS one》2015,10(3)
To test the role of wtPIT-1 (PITWT) or PIT-1 (R271W) (PIT271) in somatolactotroph cells, we established, using inducible lentiviral vectors, sublines of GH4C1 somatotroph cells that allow the blockade of the expression of endogenous PIT-1 and/or the expression of PITWT or PIT271, a dominant negative mutant of PIT-1 responsible for Combined Pituitary Hormone Deficiency in patients. Blocking expression of endogenous PIT-1 induced a marked decrease of cell proliferation. Overexpressing PITWT twofold led also to a dose-dependent decrease of cell proliferation that was accompanied by cell death. Expression of PIT271 induced a strong dose-dependent decrease of cell proliferation accompanied by a very pronounced cell death. These actions of PIT271 are independent of its interaction/competition with endogenous PIT-1, as they were unchanged when expression of endogenous PIT-1 was blocked. All these actions are specific for somatolactotroph cells, and could not be observed in heterologous cells. Cell death induced by PITWT or by PIT271 was accompanied by DNA fragmentation, but was not inhibited by inhibitors of caspases, autophagy or necrosis, suggesting that this cell death is a caspase-independent apoptosis. Altogether, our results indicate that under normal conditions PIT-1 is important for the maintenance of cell proliferation, while when expressed at supra-normal levels it induces cell death. Through this dual action, PIT-1 may play a role in the expansion/regression cycles of pituitary lactotroph population during and after lactation. Our results also demonstrate that the so-called “dominant-negative” action of PIT271 is independent of its competition with PIT-1 or a blockade of the actions of the latter, and are actions specific to this mutant variant of PIT-1. 相似文献
1000.
Leplé JC Dauwe R Morreel K Storme V Lapierre C Pollet B Naumann A Kang KY Kim H Ruel K Lefèbvre A Joseleau JP Grima-Pettenati J De Rycke R Andersson-Gunnerås S Erban A Fehrle I Petit-Conil M Kopka J Polle A Messens E Sundberg B Mansfield SD Ralph J Pilate G Boerjan W 《The Plant cell》2007,19(11):3669-3691