全文获取类型
收费全文 | 2477篇 |
免费 | 172篇 |
专业分类
2649篇 |
出版年
2024年 | 3篇 |
2023年 | 21篇 |
2022年 | 39篇 |
2021年 | 86篇 |
2020年 | 50篇 |
2019年 | 58篇 |
2018年 | 77篇 |
2017年 | 51篇 |
2016年 | 104篇 |
2015年 | 160篇 |
2014年 | 208篇 |
2013年 | 212篇 |
2012年 | 244篇 |
2011年 | 248篇 |
2010年 | 149篇 |
2009年 | 123篇 |
2008年 | 161篇 |
2007年 | 145篇 |
2006年 | 108篇 |
2005年 | 106篇 |
2004年 | 82篇 |
2003年 | 75篇 |
2002年 | 67篇 |
2001年 | 13篇 |
2000年 | 6篇 |
1999年 | 14篇 |
1998年 | 13篇 |
1997年 | 6篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1984年 | 1篇 |
1977年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有2649条查询结果,搜索用时 0 毫秒
1.
Fiddler crabs (Uca spp., Decapoda: Ocypodidae) are commonly found forming large aggregations in intertidal zones, where they perform rhythmic waving displays with their greatly enlarged claws. While performing these displays, fiddler crabs often synchronize their behavior with neighboring males, forming the only known synchronized visual courtship displays involving reflected light and moving body parts. Despite being one of the most conspicuous aspects of fiddler crab behavior, little is known about the mechanisms underlying synchronization of male displays. In this study we develop a spatially explicit model of fiddler crab waving displays using coupled logistic map equations. We explored two alternative models in which males either direct their attention at random angles or preferentially toward neighbors. Our results indicate that synchronization is possible over a fairly large region of parameter space. Moreover, our model was capable of generating local synchronization neighborhoods, as commonly observed in fiddler crabs under natural conditions. 相似文献
2.
3.
Sabrina Nickel Farnusch Kaschani Tom Colby Renier A.L. van der Hoorn Markus Kaiser 《Bioorganic & medicinal chemistry》2012,20(2):601-606
Activity-based protein profiling represents a powerful methodology to probe the activity state of enzymes under various physiological conditions. Here we present the development of a para-nitrophenol phosphonate activity-based probe with structural similarities to the potent agrochemical paraoxon. We demonstrate that this probes labels distinct serine hydrolases with the carboxylesterase CXE12 as the predominant target in Arabidopsis thaliana. The designed probe features a distinct labeling pattern and therefore represents a promising chemical tool to investigate physiological roles of selected serine hydrolases such as CXE12 in plant biology. 相似文献
4.
5.
6.
Sabrina Piombo Gode B. Calleja Bong Yul Yoo Byron F. Johnson 《Cell biochemistry and biophysics》1998,29(3):263-279
Distributions of rupture sites of fission yeast cells ruptured by glass beads have been related to a new morphometric analysis.
As shown previously (Johnson et al.,Cell Biophysics, 1995), ruptures were not randomly distributed nor was their distribution dictated by geometry, rather, ruptures at the extensile
end were related to cell length just as the rate of extension is related to cell length. The extension patterns of early log,
mid-log, late log, and stationary phase cells from suspension cultures were found to approximate the linear growth patterns
of Kubitschek and Clay (1986). The median length of cells was found to decline through the log phase in an unbalanced manner. 相似文献
7.
The rheological properties of aqueous solutions of hydroxyethyl guar gum, a synthetic derivative of guar gum, have been studied under continuous and oscillatory shear flow conditions. Data obtained from both experimental techniques were satisfactorily fitted according to Cross-type models. The effect of polymer concentration, molecular weight and temperature on the rheological behavior of hydroxyethyl guar gum systems have been investigated and discussed in terms of rheological parameters like the zero-shear viscosity η0 and the characteristic times λ and λ′. 相似文献
8.
Mateusz Okrutniak Irena M. Grześ Anna K. Kucharska Filip Turza Małgorzata Zimocha Sabrina Kerdiane Patryk Jabłoński 《Entomological Science》2023,26(3):e12549
In ants, workers of different sizes may perform various tasks, even in so-called monomorphic species with relatively low body size variation. However, it is unclear if the body size diversity of monomorphic workers correlates with task efficiency, especially in stressful contingencies. Here we tested if the body size variation of workers corresponds with its efficiency in transferring pupae. Transferring brood is a pre-set behavioral response to stress, e.g. suboptimal temperature. Here we applied a laboratory experiment simulating nest damage. The study was performed on the common garden ant (Lasius niger (Linnaeus, 1758)) – a species with no distinct worker subcastes. The efficiency of workers was measured as the latency of transferring pupae from a lit part of the experimental colony to a darkened part, while the body size diversity was expressed as the within-colony coefficient of variation in head width. We did not find any significant correlation between efficiency and body size variation. Summarizing the existing studies and the present results, we propose the hypothesis that the body size diversity of L. niger may have implications for workers’ division of labor but not for their task efficiency in a stressful contingency. 相似文献
9.
Zhuqing Mao Nicolai Müller Sabrina Borusak David Schleheck Bernhard Schink 《Environmental microbiology》2023,25(11):2068-2074
Phosphite is a stable phosphorus compound that, together with phosphate, made up a substantial part of the total phosphorus content of the prebiotic Earth's crust. Oxidation of phosphite to phosphate releases electrons at an unusually low redox potential (−690 mV at pH 7.0). Numerous aerobic and anaerobic bacteria use phosphite as a phosphorus source and oxidise it to phosphate for synthesis of nucleotides and other phosphorus-containing cell constituents. Only two pure cultures of strictly anaerobic bacteria have been isolated so far that use phosphite as an electron donor in their energy metabolism, the Gram-positive Phosphitispora fastidiosa and the Gram-negative Desulfotignum phosphitoxidans. The key enzyme of this metabolism is an NAD+-dependent phosphite dehydrogenase enzyme that phosphorylates AMP to ADP. These phosphorylating phosphite dehydrogenases were found to be related to nucleoside diphosphate sugar epimerases. The produced NADH is channelled into autotrophic CO2 fixation via the Wood-Ljungdahl (CO-DH) pathway, thus allowing for nearly complete assimilation of the substrate electrons into bacterial biomass. This extremely efficient type of electron flow connects energy and carbon metabolism directly through NADH and might have been important in the early evolution of life when phosphite was easily available on Earth. 相似文献
10.
Pedro F. P. Brandão-Dias Daniel M. C. Hallack Elise D. Snyder Jennifer L. Tank Diogo Bolster Sabrina Volponi Arial J. Shogren Gary A. Lamberti Kyle Bibby Scott P. Egan 《Molecular ecology resources》2023,23(4):756-770
Environmental DNA (eDNA) analysis is a powerful tool for remote detection of target organisms. However, obtaining quantitative and longitudinal information from eDNA data is challenging, requiring a deep understanding of eDNA ecology. Notably, if the various size components of eDNA decay at different rates, and we can separate them within a sample, their changing proportions could be used to obtain longitudinal dynamics information on targets. To test this possibility, we conducted an aquatic mesocosm experiment in which we separated fish-derived eDNA components using sequential filtration to evaluate the decay rate and changing proportion of various eDNA particle sizes over time. We then fit four alternative mathematical decay models to the data, building towards a predictive framework to interpret eDNA data from various particle sizes. We found that medium-sized particles (1–10 μm) decayed more slowly than other size classes (i.e., <1 and > 10 μm), and thus made up an increasing proportion of eDNA particles over time. We also observed distinct eDNA particle size distribution (PSD) between our Common carp and Rainbow trout samples, suggesting that target-specific assays are required to determine starting eDNA PSDs. Additionally, we found evidence that different sizes of eDNA particles do not decay independently, with particle size conversion replenishing smaller particles over time. Nonetheless, a parsimonious mathematical model where particle sizes decay independently best explained the data. Given these results, we suggest a framework to discern target distance and abundance with eDNA data by applying sequential filtration, which theoretically has both metabarcoding and single-target applications. 相似文献