全文获取类型
收费全文 | 1968篇 |
免费 | 132篇 |
专业分类
2100篇 |
出版年
2023年 | 15篇 |
2022年 | 29篇 |
2021年 | 41篇 |
2020年 | 26篇 |
2019年 | 35篇 |
2018年 | 38篇 |
2017年 | 32篇 |
2016年 | 61篇 |
2015年 | 101篇 |
2014年 | 107篇 |
2013年 | 120篇 |
2012年 | 142篇 |
2011年 | 135篇 |
2010年 | 80篇 |
2009年 | 86篇 |
2008年 | 117篇 |
2007年 | 111篇 |
2006年 | 98篇 |
2005年 | 93篇 |
2004年 | 80篇 |
2003年 | 79篇 |
2002年 | 75篇 |
2001年 | 28篇 |
2000年 | 18篇 |
1999年 | 24篇 |
1998年 | 25篇 |
1997年 | 13篇 |
1996年 | 11篇 |
1995年 | 11篇 |
1994年 | 14篇 |
1993年 | 13篇 |
1992年 | 17篇 |
1990年 | 15篇 |
1989年 | 14篇 |
1988年 | 9篇 |
1986年 | 8篇 |
1985年 | 14篇 |
1984年 | 16篇 |
1982年 | 7篇 |
1981年 | 8篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1978年 | 9篇 |
1977年 | 11篇 |
1976年 | 5篇 |
1970年 | 6篇 |
1965年 | 5篇 |
1964年 | 8篇 |
1960年 | 4篇 |
1955年 | 5篇 |
排序方式: 共有2100条查询结果,搜索用时 0 毫秒
21.
Nils Pilotte Marina Papaiakovou Jessica R. Grant Lou Ann Bierwert Stacey Llewellyn James S. McCarthy Steven A. Williams 《PLoS neglected tropical diseases》2016,10(3)
BackgroundThe soil transmitted helminths are a group of parasitic worms responsible for extensive morbidity in many of the world’s most economically depressed locations. With growing emphasis on disease mapping and eradication, the availability of accurate and cost-effective diagnostic measures is of paramount importance to global control and elimination efforts. While real-time PCR-based molecular detection assays have shown great promise, to date, these assays have utilized sub-optimal targets. By performing next-generation sequencing-based repeat analyses, we have identified high copy-number, non-coding DNA sequences from a series of soil transmitted pathogens. We have used these repetitive DNA elements as targets in the development of novel, multi-parallel, PCR-based diagnostic assays.Conclusions/SignificanceThe utilization of next-generation sequencing-based repeat DNA analysis methodologies for the identification of molecular diagnostic targets has the ability to improve assay species-specificity and limits of detection. By exploiting such high copy-number repeat sequences, the assays described here will facilitate soil transmitted helminth diagnostic efforts. We recommend similar analyses when designing PCR-based diagnostic tests for the detection of other eukaryotic pathogens. 相似文献
22.
23.
Tobias Ruck Stefanie Bock Steffen Pfeuffer Christina B.Schroeter Derya Cengiz Paul Marciniak Maren Lindner Alexander Herrmann Marie Liebmann Stjepana Kovac Lukas Gola Leoni Rolfes Marc Pawlitzki Nils Opel Tim Hahn Udo Dannlowski Thomas Pap Felix Luessi Julian A.Schreiber Bernhard Wünsch Tanja Kuhlmann Guiscard Seebohm Bjrn Tackenberg Patricia Seja Frank Dring Erhard Wischmeyer Achmet Imam Chasan Johannes Roth Luisa Klotz Gerd Meyer zu Hrste Heinz Wiendl Tobias Marschall Stefan Floess Jochen Huehn Thomas Budde Tobias Bopp Stefan Bittner Sven G.Meuth 《Cell research》2022,32(1):72-88
It remains largely unclear how thymocytes translate relative differences in T cell receptor (TCR) signal strength into distinct developmental programs that driv... 相似文献
24.
Vicky G. Kastbjerg Dennis S. Nielsen Nils Arneborg Lone Gram 《Applied and environmental microbiology》2009,75(13):4550-4556
Listeria monocytogenes has a remarkable ability to survive and persist in food production environments. The purpose of the present study was to determine if cells in a population of L. monocytogenes differ in sensitivity to disinfection agents as this could be a factor explaining persistence of the bacterium. In situ analyses of Listeria monocytogenes single cells were performed during exposure to different concentrations of the disinfectant Incimaxx DES to study a possible population subdivision. Bacterial survival was quantified with plate counting and disinfection stress at the single-cell level by measuring intracellular pH (pHi) over time by fluorescence ratio imaging microscopy. pHi values were initially 7 to 7.5 and decreased in both attached and planktonic L. monocytogenes cells during exposure to sublethal and lethal concentrations of Incimaxx DES. The response of the bacterial population was homogenous; hence, subpopulations were not detected. However, pregrowth with NaCl protected the planktonic bacterial cells during disinfection with Incimaxx (0.0015%) since pHi was higher (6 to 6.5) for the bacterial population pregrown with NaCl than for cells grown without NaCl (pHi 5 to 5.5) (P < 0.05). The protective effect of NaCl was reflected by viable-cell counts at a higher concentration of Incimaxx (0.0031%), where the salt-grown population survived better than the population grown without NaCl (P < 0.05). NaCl protected attached cells through drying but not during disinfection. This study indicates that a population of L. monocytogenes cells, whether planktonic or attached, is homogenous with respect to sensitivity to an acidic disinfectant studied on the single-cell level. Hence a major subpopulation more tolerant to disinfectants, and hence more persistent, does not appear to be present.Listeria monocytogenes is a food-borne, human pathogen that has a remarkable ability to colonize food-processing environments (5, 16, 20, 21, 26, 29). Some L. monocytogenes strains can persist for years in food-processing plants (11, 14, 20, 27), and specific molecular subtypes can repeatedly be isolated from the processing environment (29) despite being very infrequent in the outdoor environment (9). This ability to persist has, hitherto, not been linked to any specific genetic or phenotypic trait.It has been suggested that persistent L. monocytogenes strains may be more tolerant or resistant to cleaning and especially disinfectants used in the food industry. Aase et al. (1) found increased tolerance to both benzalkonium chloride and ethidium bromide in L. monocytogenes isolates that had persisted for more than 4 years; however, other studies have not been able to link persistence and tolerance to disinfectants (6, 10, 11, 13). We recently compared disinfection sensitivities of persistent and presumed nonpersistent L. monocytogenes strains using viable-cell counts and did not find the latter group more sensitive to the two disinfectants Triquart SUPER and Incimaxx DES than persistent strains (13). However, we found that for all subtypes of L. monocytogenes, growth with NaCl increased the tolerance of planktonic L. monocytogenes cells to Incimaxx DES, whereas spot-inoculated, dried L. monocytogenes cells were not protected by NaCl against disinfection.There is no doubt that L. monocytogenes will be completely inactivated at the disinfectant concentrations recommended for use in the food industry; however, the efficiency of the disinfectant is very much influenced by the presence of organic material being inactivated by the presence of food debris. Hence, it is likely that the bacterial cell in a food production environment may be exposed to concentrations at a sublethal level. It is currently not known if treatment with a sublethal concentration of disinfectant affects the entire bacterial population or only attacks a fraction of the cell population, leaving another fraction of cells unaffected. In case of the latter, some bacterial cells may be able to survive the disinfection treatment. The potential presence of such tolerant subpopulations could, ultimately, ensure that the genome is propagated, leading to persistence.The presence of a more tolerant subpopulation can be determined on the single-cell level. Flow cytometry is a rapid method useable for measurements at the single-cell resolution (22); however, it cannot monitor the same single cells over time. Optical microscopy combined with microfluidic devices that allow measurement of growth of single cells is a useful technique (2), and in situ analyses of the physiological condition of single cells by the fluorescence ratio imaging microscopy (FRIM) technique represents another elegant approach (25). FRIM enables studies of dynamic changes with high sensitivity and on the single-cell level in important physiological parameters: e.g., intracellular pH (pHi). Listeria maintains its pHi within a narrow range of 7.6 to 8 at extracellular pH (pHex) values of 5.0 to 8.0 (4, 25) and at pHex 4.0 with the presence of glucose (23). It is believed that viable cells need to maintain a transmembrane pH gradient with their pHi above the pHex, and failure to maintain pHi homeostasis indicates that the bacterial cell is severely stressed and ultimately leads to loss of cell viability. FRIM has been used to determine the pHi of L. monocytogenes after exposure to osmotic and acid stress (7, 23). Also, the dissipation of the pH gradient in L. monocytogenes after exposure to different bacteriocins has been determined with FRIM (4, 12). Hornbæk et al. (12) found that treatment with subinhibitory concentrations of leucocin and nisin gave rise to two subpopulations: one consisting of cells with a dissipated pH gradient (ΔpH) and the other consisting of cells that maintained ΔpH, which could indicate phenotypic heterogeneity.The aim of the present study was to investigate the physiological effects of the disinfectant Incimaxx DES at sublethal and lethal concentrations on single cells and the population level of a persistent L. monocytogenes strain to study a possible subdivision of sensitivity in the population. We also addressed the potential protective effect of NaCl against disinfection and compared sensitivities in a population of planktonic and attached bacteria. We applied the in situ technique FRIM and compared the pHi measurements with the traditional viable-cell-count method.(Part of the results have been presented at a poster session at the 95th International Association for Food Protection annual meeting in Columbus, OH, 3 to 6 August 2008.) 相似文献
25.
Artem Pankin Chiara Campoli Xue Dong Benjamin Kilian Rajiv Sharma Axel Himmelbach Reena Saini Seth J Davis Nils Stein Korbinian Schneeberger Maria von Korff 《Genetics》2014,198(1):383-396
Phytochromes play an important role in light signaling and photoperiodic control of flowering time in plants. Here we propose that the red/far-red light photoreceptor HvPHYTOCHROME C (HvPHYC), carrying a mutation in a conserved region of the GAF domain, is a candidate underlying the early maturity 5 locus in barley (Hordeum vulgare L.). We fine mapped the gene using a mapping-by-sequencing approach applied on the whole-exome capture data from bulked early flowering segregants derived from a backcross of the Bowman(eam5) introgression line. We demonstrate that eam5 disrupts circadian expression of clock genes. Moreover, it interacts with the major photoperiod response gene Ppd-H1 to accelerate flowering under noninductive short days. Our results suggest that HvPHYC participates in transmission of light signals to the circadian clock and thus modulates light-dependent processes such as photoperiodic regulation of flowering. 相似文献
26.
Madhurima Dhara Antonio Yarzagaray Yvonne Schwarz Soumyajit Dutta Chad Grabner Paanteha K. Moghadam Anneka Bost Claudia Schirra Jens Rettig Kerstin Reim Nils Brose Ralf Mohrmann Dieter Bruns 《The Journal of cell biology》2014,204(7):1123-1140
ComplexinII (CpxII) and SynaptotagminI (SytI) have been implicated in regulating the function of SNARE proteins in exocytosis, but their precise mode of action and potential interplay have remained unknown. In this paper, we show that CpxII increases Ca2+-triggered vesicle exocytosis and accelerates its secretory rates, providing two independent, but synergistic, functions to enhance synchronous secretion. Specifically, we demonstrate that the C-terminal domain of CpxII increases the pool of primed vesicles by hindering premature exocytosis at submicromolar Ca2+ concentrations, whereas the N-terminal domain shortens the secretory delay and accelerates the kinetics of Ca2+-triggered exocytosis by increasing the Ca2+ affinity of synchronous secretion. With its C terminus, CpxII attenuates fluctuations of the early fusion pore and slows its expansion but is functionally antagonized by SytI, enabling rapid transmitter discharge from single vesicles. Thus, our results illustrate how key features of CpxII, SytI, and their interplay transform the constitutively active SNARE-mediated fusion mechanism into a highly synchronized, Ca2+-triggered release apparatus. 相似文献
27.
Barley grain maturation and germination: metabolic pathway and regulatory network commonalities and differences highlighted by new MapMan/PageMan profiling tools 总被引:4,自引:0,他引:4 下载免费PDF全文
Sreenivasulu N Usadel B Winter A Radchuk V Scholz U Stein N Weschke W Strickert M Close TJ Stitt M Graner A Wobus U 《Plant physiology》2008,146(4):1738-1758
28.
29.
30.
Claudia Pogoreutz Nils Rädecker Anny Cárdenas Astrid Gärdes Christian R. Voolstra Christian Wild 《Global Change Biology》2017,23(9):3838-3848
The disruption of the coral–algae symbiosis (coral bleaching) due to rising sea surface temperatures has become an unprecedented global threat to coral reefs. Despite decades of research, our ability to manage mass bleaching events remains hampered by an incomplete mechanistic understanding of the processes involved. In this study, we induced a coral bleaching phenotype in the absence of heat and light stress by adding sugars. The sugar addition resulted in coral symbiotic breakdown accompanied by a fourfold increase of coral‐associated microbial nitrogen fixation. Concomitantly, increased N:P ratios by the coral host and algal symbionts suggest excess availability of nitrogen and a disruption of the nitrogen limitation within the coral holobiont. As nitrogen fixation is similarly stimulated in ocean warming scenarios, here we propose a refined coral bleaching model integrating the cascading effects of stimulated microbial nitrogen fixation. This model highlights the putative role of nitrogen‐fixing microbes in coral holobiont functioning and breakdown. 相似文献