全文获取类型
收费全文 | 434篇 |
免费 | 49篇 |
国内免费 | 9篇 |
出版年
2019年 | 6篇 |
2018年 | 9篇 |
2017年 | 2篇 |
2016年 | 7篇 |
2015年 | 15篇 |
2014年 | 19篇 |
2013年 | 21篇 |
2012年 | 18篇 |
2011年 | 25篇 |
2010年 | 22篇 |
2009年 | 20篇 |
2008年 | 11篇 |
2007年 | 19篇 |
2006年 | 14篇 |
2005年 | 15篇 |
2004年 | 14篇 |
2003年 | 14篇 |
2002年 | 8篇 |
2001年 | 14篇 |
2000年 | 7篇 |
1999年 | 8篇 |
1998年 | 13篇 |
1997年 | 7篇 |
1996年 | 6篇 |
1995年 | 4篇 |
1994年 | 15篇 |
1993年 | 7篇 |
1992年 | 7篇 |
1991年 | 8篇 |
1990年 | 12篇 |
1989年 | 8篇 |
1988年 | 7篇 |
1987年 | 13篇 |
1986年 | 11篇 |
1985年 | 8篇 |
1984年 | 8篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1981年 | 3篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1977年 | 11篇 |
1976年 | 6篇 |
1975年 | 6篇 |
1974年 | 4篇 |
1973年 | 4篇 |
1971年 | 3篇 |
1969年 | 2篇 |
1955年 | 1篇 |
1954年 | 2篇 |
排序方式: 共有492条查询结果,搜索用时 15 毫秒
51.
Haijun Liu Hao Zhang Jeremy D. King Nathan R. Wolf Mindy Prado Michael L. Gross Robert E. Blankenship 《BBA》2014
The orange carotenoid protein (OCP), a member of the family of blue light photoactive proteins, is required for efficient photoprotection in many cyanobacteria. Photoexcitation of the carotenoid in the OCP results in structural changes within the chromophore and the protein to give an active red form of OCP that is required for phycobilisome binding and consequent fluorescence quenching. We characterized the light-dependent structural changes by mass spectrometry-based carboxyl footprinting and found that an α helix in the N-terminal extension of OCP plays a key role in this photoactivation process. Although this helix is located on and associates with the outside of the β-sheet core in the C-terminal domain of OCP in the dark, photoinduced changes in the domain structure disrupt this interaction. We propose that this mechanism couples light-dependent carotenoid conformational changes to global protein conformational dynamics in favor of functional phycobilisome binding, and is an essential part of the OCP photocycle. 相似文献
52.
Intraguild (IG) predation is an important factor influencing community structure, yet factors allowing coexistence of IG predator
and IG prey are not well understood. The existence of spatial refuges for IG prey has recently been noted for their importance
in allowing coexistence. However, reduction in basal prey availability might lead IG prey to leave spatial refuges for greater
access to prey, leading to increased IG predation and fewer opportunities for coexistence. We determined how the availability
of prey affected space-use patterns of bobcats (Lynx rufus, IG prey) in relation to coyote space-use patterns (Canis latrans, IG predators). We located animals from fall 2007 to spring 2009 and estimated bobcat home ranges and core areas seasonally.
For each bobcat relocation, we determined intensity of coyote use, distance to water, small mammal biomass, and mean small
mammal biomass of the home range during the season the location was collected. We built generalized linear mixed models and
used Akaike Information Criteria to determine which factors best predicted bobcat space use. Coyote intensity was a primary
determinant of bobcat core area location. In bobcat home ranges with abundant prey, core areas occurred where coyote use was
low, but shifted to areas intensively used by coyotes when prey declined. High spatial variability in basal prey abundance
allowed some bobcats to avoid coyotes while at the same time others were forced into more risky areas. Our results suggest
that multiple behavioral strategies associated with spatial variation in basal prey abundance likely allow IG prey and IG
predators to coexist. 相似文献
53.
Background
Heliobacterium modesticaldum is a gram-positive nitrogen-fixing phototrophic bacterium that can grow either photoheterotrophically or chemotrophically but not photoautotrophically. Surprisingly, this organism is lacking only one gene for the complete reverse tricarboxylic acid (rTCA) cycle required for autotrophic carbon fixation. Along with the genomic information reported recently, we use multiple experimental approaches in this report to address questions regarding energy metabolic pathways in darkness, CO2 fixation, sugar assimilation and acetate metabolism. 相似文献54.
The complete genome sequence of Roseobacter denitrificans reveals a mixotrophic rather than photosynthetic metabolism
下载免费PDF全文
![点击此处可从《Journal of bacteriology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
55.
Pigment analysis of "Candidatus Chlorothrix halophila," a green filamentous anoxygenic phototrophic bacterium
下载免费PDF全文
![点击此处可从《Journal of bacteriology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Olson TL van de Meene AM Francis JN Pierson BK Blankenship RE 《Journal of bacteriology》2007,189(11):4187-4195
The pigment composition of "Candidatus Chlorothrix halophila," a filamentous anoxygenic phototrophic bacterium found in Baja California Sur, Mexico, was determined. Previous work showed that bacteriochlorophyll c (BChl c) was the major pigment in "Ca. Chlorothrix halophila," but it was not clear if this bacterium also contains BChl a (J. A. Klappenbach and B. K. Pierson, Arch. Microbiol. 181:17-25, 2004). Here we show that in addition to BChl c, a small amount of a pigment that is spectrally indistinguishable from BChl a is present in cell extracts of "Ca. Chlorothrix halophila." Nevertheless, the BChl a-like pigment from "Ca. Chlorothrix halophila" has a different molecular weight and a different high-performance liquid chromatography elution time than BChl a from other photosynthetic bacteria. Based on mass spectrometry and other spectroscopic analysis, we determined that the BChl a-like pigment in "Ca. Chlorothrix halophila" contains a tetrahydrogeranylgeraniol tail rather than the phytol tail that is present in BChl a. The carotenoids and major BChl c homologs in "Ca. Chlorothrix halophila" were also identified. BChls c were found to be farnesol esterified and geranylgeraniol esterified. 相似文献
56.
Blankenship JW Dawson PE 《Protein science : a publication of the Protein Society》2007,16(7):1249-1256
Proteins adopt complex folds in nature that typically avoid conformations that are knotted or “threaded” through closed loops. Is this the result of fundamental barriers to folding, or have proteins simply evolved to avoid threaded conformations? Organic synthesis has been used in supramolecular chemistry to install topological links in small molecules. By following these principles, we now show that it is possible to assemble a topologically linked protein complex by threading a linear protein through a cyclic protein to form a [2]pseudo‐rotaxane. Subsequent ring closure using native chemical ligation cyclizes the linear protein, forming a [2]heterocatenane. Although the kinetics of protein threading are slower than the folding kinetics of the native protein, threading appears to be a highly efficient process. 相似文献
57.
CA Kalva-Filho EZ Campos VL Andrade ASR Silva AM Zagatto MCS Lima M Papoti 《Biology of sport / Institute of Sport》2015,32(4):333-337
The aims of the present study were to investigate the relationship of aerobic and anaerobic parameters with 400 m performance, and establish which variable better explains long distance performance in swimming. Twenty-two swimmers (19.1±1.5 years, height 173.9±10.0 cm, body mass 71.2±10.2 kg; 76.6±5.3% of 400 m world record) underwent a lactate minimum test to determine lactate minimum speed (LMS) (i.e., aerobic capacity index). Moreover, the swimmers performed a 400 m maximal effort to determine mean speed (S400m), peak oxygen uptake () and total anaerobic contribution (CANA). The CANA was assumed as the sum of alactic and lactic contributions. Physiological parameters of 400 m were determined using the backward extrapolation technique ( and alactic contributions of CANA) and blood lactate concentration analysis (lactic anaerobic contributions of CANA). The Pearson correlation test and backward multiple regression analysis were used to verify the possible correlations between the physiological indices (predictor factors) and S400m (independent variable) (p < 0.05). Values are presented as mean ± standard deviation. Significant correlations were observed between S400m (1.4±0.1 m·s-1) and LMS (1.3±0.1 m·s-1; r = 0.80), (4.5±3.9 L·min-1; r = 0.72) and CANA (4.7±1.5 L·O2; r= 0.44). The best model constructed using multiple regression analysis demonstrated that LMS and explained 85% of the 400 m performance variance. When backward multiple regression analysis was performed, CANA lost significance. Thus, the results demonstrated that both aerobic parameters (capacity and power) can be used to predict 400 m swimming performance. 相似文献
58.
Polyana C Tizioto Jeremy F Taylor Jared E Decker Caio F Gromboni Mauricio A Mudadu Robert D Schnabel Luiz L Coutinho Gerson B Mour?o Priscila SN Oliveira Marcela M Souza James M Reecy Renata T Nassu Flavia A Bressani Patricia Tholon Tad S Sonstegard Mauricio M Alencar Rymer R Tullio Ana RA Nogueira Luciana CA Regitano 《遗传、选种与进化》2015,47(1)
59.
60.
A limiting factor for photosynthetic organisms is their light-harvesting efficiency, that is the efficiency of their conversion of light energy to chemical energy. Small modifications or variations of chlorophylls allow photosynthetic organisms to harvest sunlight at different wavelengths. Oxygenic photosynthetic organisms usually utilize only the visible portion of the solar spectrum. The cyanobacterium Acaryochloris marina carries out oxygenic photosynthesis but contains mostly chlorophyll d and only traces of chlorophyll a. Chlorophyll d provides a potential selective advantage because it enables Acaryochloris to use infrared light (700-750 nm) that is not absorbed by chlorophyll a. Recently, an even more red-shifted chlorophyll termed chlorophyll f has been reported. Here, we discuss using modified chlorophylls to extend the spectral region of light that drives photosynthetic organisms. 相似文献