全文获取类型
收费全文 | 610篇 |
免费 | 42篇 |
国内免费 | 9篇 |
出版年
2023年 | 3篇 |
2022年 | 4篇 |
2021年 | 10篇 |
2020年 | 10篇 |
2019年 | 9篇 |
2018年 | 9篇 |
2017年 | 17篇 |
2016年 | 9篇 |
2015年 | 23篇 |
2014年 | 21篇 |
2013年 | 20篇 |
2012年 | 22篇 |
2011年 | 16篇 |
2010年 | 24篇 |
2009年 | 21篇 |
2008年 | 30篇 |
2007年 | 14篇 |
2006年 | 20篇 |
2005年 | 11篇 |
2004年 | 17篇 |
2003年 | 14篇 |
2002年 | 13篇 |
2001年 | 14篇 |
2000年 | 8篇 |
1999年 | 16篇 |
1998年 | 8篇 |
1997年 | 9篇 |
1996年 | 13篇 |
1995年 | 4篇 |
1994年 | 5篇 |
1992年 | 9篇 |
1991年 | 3篇 |
1989年 | 3篇 |
1986年 | 3篇 |
1984年 | 6篇 |
1983年 | 6篇 |
1980年 | 3篇 |
1978年 | 6篇 |
1974年 | 3篇 |
1972年 | 3篇 |
1959年 | 7篇 |
1958年 | 23篇 |
1957年 | 26篇 |
1956年 | 26篇 |
1955年 | 22篇 |
1954年 | 22篇 |
1953年 | 13篇 |
1952年 | 13篇 |
1951年 | 10篇 |
1950年 | 9篇 |
排序方式: 共有661条查询结果,搜索用时 31 毫秒
71.
72.
Spatially resolved characterization of biogenic manganese oxide production within a bacterial biofilm 总被引:3,自引:0,他引:3
Toner B Fakra S Villalobos M Warwick T Sposito G 《Applied and environmental microbiology》2005,71(3):1300-1310
Pseudomonas putida strain MnB1, a biofilm-forming bacterial culture, was used as a model for the study of bacterial Mn oxidation in freshwater and soil environments. The oxidation of aqueous Mn+2 [Mn+2(aq)] by P. putida was characterized by spatially and temporally resolving the oxidation state of Mn in the presence of a bacterial biofilm, using scanning transmission X-ray microscopy (STXM) combined with near-edge X-ray absorption fine structure (NEXAFS) spectroscopy at the Mn L2,3 absorption edges. Subsamples were collected from growth flasks containing 0.1 and 1 mM total Mn at 16, 24, 36, and 48 h after inoculation. Immediately after collection, the unprocessed hydrated subsamples were imaged at a 40-nm resolution. Manganese NEXAFS spectra were extracted from X-ray energy sequences of STXM images (stacks) and fit with linear combinations of well-characterized reference spectra to obtain quantitative relative abundances of Mn(II), Mn(III), and Mn(IV). Careful consideration was given to uncertainty in the normalization of the reference spectra, choice of reference compounds, and chemical changes due to radiation damage. The STXM results confirm that Mn+2(aq) was removed from solution by P. putida and was concentrated as Mn(III) and Mn(IV) immediately adjacent to the bacterial cells. The Mn precipitates were completely enveloped by bacterial biofilm material. The distribution of Mn oxidation states was spatially heterogeneous within and between the clusters of bacterial cells. Scanning transmission X-ray microscopy is a promising tool for advancing the study of hydrated interfaces between minerals and bacteria, particularly in cases where the structure of bacterial biofilms needs to be maintained. 相似文献
73.
74.
75.
The broad fish tapeworm, Diphyllobothrium latum, is an exotic species in both Chile and Argentina, and until now, its copepod host has remained unknown in South American waters. The objective of this study was to identify calanoid copepod species that may be intermediate hosts for D. latum in Lake Panguipulli, Chile. In this lake, the highest levels of infection by this tapeworm occur in the introduced rainbow trout, Oncorhynchus mykiss. Of the 2 calanoid copepods found in Lake Panguipulli, Diaptomus diabolicus and Boeckella gracilipes, only D. diabolicus became infected on experimental exposure to coracidia. Prevalence (mean intensity) of experimental infection in adult copepods was 73.2% (2.8 procercoids per host). Diaptomus diabolicus has been demonstrated to be a new intermediate host; this is the first record of a copepod host for D. latum in South America. 相似文献
76.
77.
Orozco A Villalobos P Valverde-R C 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》2002,131(2):387-395
We here analyzed the effect of a mild hyperosmotic challenge on the activities of deiodinases type I (D1) and II (D2) in the trout liver, and D1 in kidney and gill, two organs involved in osmoregulation. FW-adapted immature rainbow trout were transferred to 5 per thousand SW and killed 0.5, 1, 2, 4, 8 12, 24 and 48 h post-transfer (PT). Fish maintained in FW served as controls. Hepatic, renal and branchial D1 and hepatic D2 activities were assessed as well as circulating levels of T(3), T(4) and cortisol. Hyperosmotic challenge elicited significant and sustained decreases in kidney D1 and liver D2 activities at 8 h PT, which returned to control values at 48 h PT. In contrast, liver and gill D1 activities exhibited no significant change throughout the study. Also, significant increases in circulating T(4) at 2-4 and 48 h PT were observed. Circulating T(3) remained unmodified until 24-48 h PT, when it rose sharply. Simultaneously, cortisol showed a trend towards increase during the initial 4 h PT, which attained significance at 48 h PT. The present findings demonstrate that a mild hypertonic challenge is sufficient to elicit responses in the trout thyroidal axis. Hormonal changes in the circulatory compartment are in accordance with those previously described for migratory salmonids. A novel aspect of our findings is the organ-specific differential response exhibited by ORD-enzymes when trout are exposed to a mildly different osmotic environment. Our findings further establish the uniqueness of fish thyroid physiology, and can be of value in further understanding the evolutionary aspects of this ORD family of deiodinases. 相似文献
78.
79.
Lipoteichoic acid is an important microbe-associated molecular pattern of Lactobacillus rhamnosus GG
Claes Ingmar JJ Segers Marijke E Verhoeven Tine LA Dusselier Michiel Sels Bert F De Keersmaecker Sigrid CJ Vanderleyden Jos Lebeer Sarah 《Microbial cell factories》2012,11(1):1-8