全文获取类型
收费全文 | 1003篇 |
免费 | 110篇 |
国内免费 | 1篇 |
出版年
2022年 | 4篇 |
2021年 | 22篇 |
2020年 | 16篇 |
2019年 | 19篇 |
2018年 | 39篇 |
2017年 | 34篇 |
2016年 | 38篇 |
2015年 | 65篇 |
2014年 | 86篇 |
2013年 | 68篇 |
2012年 | 83篇 |
2011年 | 63篇 |
2010年 | 54篇 |
2009年 | 36篇 |
2008年 | 39篇 |
2007年 | 58篇 |
2006年 | 50篇 |
2005年 | 44篇 |
2004年 | 47篇 |
2003年 | 43篇 |
2002年 | 46篇 |
2001年 | 14篇 |
2000年 | 11篇 |
1999年 | 11篇 |
1998年 | 13篇 |
1997年 | 9篇 |
1996年 | 8篇 |
1995年 | 8篇 |
1994年 | 12篇 |
1993年 | 7篇 |
1992年 | 7篇 |
1991年 | 6篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1984年 | 3篇 |
1983年 | 6篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1972年 | 2篇 |
1967年 | 1篇 |
1962年 | 1篇 |
1951年 | 1篇 |
1950年 | 3篇 |
1939年 | 1篇 |
排序方式: 共有1114条查询结果,搜索用时 15 毫秒
101.
102.
103.
Ying Wang Anni B. Hougaard Wilhelm Paulander Leif H. Skibsted Hanne Ingmer Mogens L. Andersen 《Applied and environmental microbiology》2015,81(18):6393-6398
Detection of free radicals in biological systems is challenging due to their short half-lives. We have applied electron spin resonance (ESR) spectroscopy combined with spin traps using the probes PBN (N-tert-butyl-α-phenylnitrone) and DMPO (5,5-dimethyl-1-pyrroline N-oxide) to assess free radical formation in the human pathogen Staphylococcus aureus treated with a bactericidal antibiotic, vancomycin or ciprofloxacin. While we were unable to detect ESR signals in bacterial cells, hydroxyl radicals were observed in the supernatant of bacterial cell cultures. Surprisingly, the strongest signal was detected in broth medium without bacterial cells present and it was mitigated by iron chelation or by addition of catalase, which catalyzes the decomposition of hydrogen peroxide to water and oxygen. This suggests that the signal originates from hydroxyl radicals formed by the Fenton reaction, in which iron is oxidized by hydrogen peroxide. Previously, hydroxyl radicals have been proposed to be generated within bacterial cells in response to bactericidal antibiotics. We found that when S. aureus was exposed to vancomycin or ciprofloxacin, hydroxyl radical formation in the broth was indeed increased compared to the level seen with untreated bacterial cells. However, S. aureus cells express catalase, and the antibiotic-mediated increase in hydroxyl radical formation was correlated with reduced katA expression and catalase activity in the presence of either antibiotic. Therefore, our results show that in S. aureus, bactericidal antibiotics modulate catalase expression, which in turn influences the formation of free radicals in the surrounding broth medium. If similar regulation is found in other bacterial species, it might explain why bactericidal antibiotics are perceived as inducing formation of free radicals. 相似文献
104.
105.
Jeong Jin Ahn Ji-Hoon Kim Youngjoo Kim Ji Young Hong Gi Won Kim Seung Yong Hwang 《Analytical biochemistry》2015
Locked nucleic acid (LNA) is a modified RNA nucleotide that can be incorporated at specific positions to generate probes with the desired length, melting temperature (TM), and specificity. Here, we describe a method of multiplex genotyping based on dramatic shifts in the TM of a single dual-labeled LNA probe. Using this method, two varieties of the hairtail fish Trichiurus lepturus can be distinguished from each other, as well as from Trichiurus japonicus, based on a 1- to 2-bp difference in a fragment of mitochondrial cytochrome oxidase subunit 1. The shift in TM was 15 °C for a 1-bp mismatch and 27 °C for a 2-bp mismatch, indicating remarkable specificity. We anticipate that the method will be widely useful in applications such as species identification that require accurate, multiplex, and efficient detection of DNA polymorphisms. 相似文献
106.
David?E. Koser Emad Moeendarbary Janina Hanne Stefanie Kuerten Kristian Franze 《Biophysical journal》2015,108(9):2137-2147
Mechanical signaling plays an important role in cell physiology and pathology. Many cell types, including neurons and glial cells, respond to the mechanical properties of their environment. Yet, for spinal cord tissue, data on tissue stiffness are sparse. To investigate the regional and direction-dependent mechanical properties of spinal cord tissue at a spatial resolution relevant to individual cells, we conducted atomic force microscopy (AFM) indentation and tensile measurements on acutely isolated mouse spinal cord tissue sectioned along the three major anatomical planes, and correlated local mechanical properties with the underlying cellular structures. Stiffness maps revealed that gray matter is significantly stiffer than white matter irrespective of directionality (transverse, coronal, and sagittal planes) and force direction (compression or tension) (Kg= ∼130 Pa vs. Kw= ∼70 Pa); both matters stiffened with increasing strain. When all data were pooled for each plane, gray matter behaved like an isotropic material under compression; however, subregions of the gray matter were rather heterogeneous and anisotropic. For example, in sagittal sections the dorsal horn was significantly stiffer than the ventral horn. In contrast, white matter behaved transversely isotropic, with the elastic stiffness along the craniocaudal (i.e., longitudinal) axis being lower than perpendicular to it. The stiffness distributions we found under compression strongly correlated with the orientation of axons, the areas of cell nuclei, and cellular in plane proximity. Based on these morphological parameters, we developed a phenomenological model to estimate local mechanical properties of central nervous system (CNS) tissue. Our study may thus ultimately help predicting local tissue stiffness, and hence cell behavior in response to mechanical signaling under physiological and pathological conditions, purely based on histological data. 相似文献
107.
Kristof Moonens Imke Van den Broeck Maia De Kerpel Francine Deboeck Hanne Raymaekers Han Remaut Henri De Greve 《The Journal of biological chemistry》2015,290(13):8409-8419
Enterotoxigenic Escherichia coli (ETEC) strains are important causes of intestinal disease in humans and lead to severe production losses in animal farming. A range of fimbrial adhesins in ETEC strains determines host and tissue tropism. ETEC strains expressing F4 fimbriae are associated with neonatal and post-weaning diarrhea in piglets. Three naturally occurring variants of F4 fimbriae (F4ab, F4ac, and F4ad) exist that differ in the primary sequence of their major adhesive subunit FaeG, and each features a related yet distinct receptor binding profile. Here the x-ray structure of FaeGad bound to lactose provides the first structural insight into the receptor specificity and mode of binding by the poly-adhesive F4 fimbriae. A small D′-D″-α1-α2 subdomain grafted on the immunoglobulin-like core of FaeG hosts the carbohydrate binding site. Two short amino acid stretches Phe150–Glu152 and Val166–Glu170 of FaeGad bind the terminal galactose in the lactosyl unit and provide affinity and specificity to the interaction. A hemagglutination-based assay with E. coli expressing mutant F4ad fimbriae confirmed the elucidated co-complex structure. Interestingly, the crucial D′-α1 loop that borders the FaeGad binding site adopts a different conformation in the two other FaeG variants and hints at a heterogeneous binding pocket among the FaeG serotypes. 相似文献
108.
Won Gi Yoo Sanghyun Lee Myoung-Ro Lee Mi-Ran Yun Taesoo Kwon Dae-Won Kim 《Bioinformation》2015,11(1):17-20
The increase in prevalence of antimicrobial resistance makes the search for new antibiotic agents imperative. Antimicrobial
peptides (AMPs) from natural resources have been recognized as suitable tools to combat antibiotic-resistant bacteria. The liver
fluke Clonorchis sinensis living in germ-filled environments could be a good source of antimicrobials. Here, we report the use of a
rational protocol that combines AMP predictions based on their physicochemical properties and their in vivo stability to discover
AMP candidates from the entire genome of C. sinensis. To screen AMP candidates, in silico analyses based on the physicochemical
properties of known AMPs, such as length, charge, isoelectric point, and in vitro and in vivo aggregation values were performed. To
enhance their in vivo stability, proteins having proteolytic cleavage sites were excluded. As a consequence, four high-activity, highstability
peptides were identified. These peptides could be potential starting materials for the development of new AMPs via
structural modification and optimization. Thus, this study proposes a refined computational method to develop new AMPs and
identifies four AMP candidates, which could serve as templates for further development of peptide antibiotics. 相似文献
109.
110.
Minky Son Chanin Park Seul Gi Kwon Woo Young Bang Sam Woong Kim Chul Wook Kim Keun Woo Lee 《BMC structural biology》2015,15(1):1