全文获取类型
收费全文 | 226篇 |
免费 | 20篇 |
出版年
2021年 | 4篇 |
2020年 | 2篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2017年 | 3篇 |
2016年 | 10篇 |
2015年 | 9篇 |
2014年 | 4篇 |
2013年 | 17篇 |
2012年 | 17篇 |
2011年 | 19篇 |
2010年 | 9篇 |
2009年 | 3篇 |
2008年 | 8篇 |
2007年 | 13篇 |
2006年 | 12篇 |
2005年 | 10篇 |
2003年 | 9篇 |
2002年 | 13篇 |
2001年 | 5篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1993年 | 1篇 |
1991年 | 4篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 6篇 |
1985年 | 1篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1956年 | 1篇 |
1929年 | 1篇 |
排序方式: 共有246条查询结果,搜索用时 15 毫秒
71.
72.
Natacha?Ryckelynck Hilmar?A.?StecherIII Clare?E.?ReimersEmail author 《Biogeochemistry》2005,76(1):113-139
Seafloor fuel cells made with graphite electrodes generate electricity by promoting electron transfer in response to a natural
voltage difference (−0.7 to −0.8 V) between anoxic sediments and overlying oxic seawater. Geochemical impacts of a seafloor
fuel cell on sediment solids and porewaters were examined to identify the anodic mechanisms and substrates available for current
production. In an estuarine environment with little dissolved sulfide, solid-phase acid volatile sulfide and Cr2+-reducible sulfur minerals decreased significantly toward the anode after 7 months of nearly continuous energy harvesting.
Porewater iron and sulfate increased by millimolar amounts. Scanning electron microscope images showed a biofilm overcoating
the anode, and electron microprobe analyses revealed accumulations of sulfur, iron, silicon and phosphorus at the electrode
surface. Sulfur deposition was also observed on a laboratory fuel cell anode used to generate electricity with only dissolved
sulfide as an electron donor. Moreover, current densities and voltages displayed by these purely chemical cells were similar
to the values measured with field devices. These results indicate that electron transfer to seafloor fuel cells can readily
result in the oxidation of dissolved and solid-phase forms of reduced sulfur producing mainly S0 which deposits at the electrode surface. This oxidation product is consistent with the observed enrichment of bacteria most
closely related to Desulfobulbus/Desulfocapsa genera within the anode biofilm, and its presence is proposed to promote a localized biogeochemical cycle whereby biofilm
bacteria regenerate sulfate and sulfide. This electron-shuttling mechanism may co-occur while these or other bacteria use
the anode directly as a terminal electron acceptor. 相似文献
73.
Efficient class I major histocompatibility complex down-regulation by simian immunodeficiency virus Nef is associated with a strong selective advantage in infected rhesus macaques 下载免费PDF全文
Substitution of Y223F disrupts the ability of simian immunodeficiency virus (SIV) Nef to down-modulate major histocompatibility complex (MHC) class I from the cell surface but has no effect on other Nef functions, such as down-regulation of CD4, CD28, and CD3 cell surface expression or stimulation of viral replication and enhancement of virion infectivity. Inoculation of three rhesus macaques with the SIVmac239 Y223F-Nef variant revealed that this point mutation consistently reverts and that Nef activity in MHC class I down-modulation is fully restored within 4 weeks after infection. Our results demonstrate a strong selective pressure for a tyrosine at amino acid position 223 in SIV Nef, and they constitute evidence that Nef-mediated MHC class I down-regulation provides a selective advantage for viral replication in vivo. 相似文献
74.
Inducible nitric oxide synthase expression before and after eradication of Helicobacter pylori in different forms of gastritis 总被引:5,自引:0,他引:5
Antos D Enders G Rieder G Stolte M Bayerdörffer E Hatz RA 《FEMS immunology and medical microbiology》2001,30(2):127-131
An increased expression of inducible nitric oxide synthase (iNOS) has been observed in the inflamed human gastric mucosa as well as in some tumors. This observation suggests a pathobiological role of elevated NO production. The purpose of this study was to compare the immunohistochemical iNOS expression in the different kinds of gastritis before and after the eradication of Helicobacter pylori. We performed iNOS and H. pylori immunohistochemical staining and counted iNOS positive cells. We detected elevated expression of iNOS around sites infected with H. pylori. iNOS expression in chemical gastritis was strongly elevated in mucosal glands. After treatment, we found a significant difference in iNOS expression in patients with classical H. pylori-induced antrum predominant gastritis and in patients with active autoimmune gastritis. In the special case of progressed gastritis with intestinal metaplasia we found persistence of intestinal metaplasia, and we could not find a significant difference in the number of positive iNOS cells before and after treatment. The persistence of IM as a possibly precancerous lesion is probably at least in the antrum a source of continuous iNOS induction even after H. pylori eradication. 相似文献
75.
76.
Holger Schmidt Trutz Heinemann Judith Elster Marija Djukic Stefan Harscher Katja Neubieser Hilmar Prange Andreas Kastrup Veit Rohde 《BMC neurology》2011,11(1):77
Background
Decompressive hemicraniectomy is a life-saving procedure for patients with malignant middle cerebral artery infarctions. However, the neuropsychological sequelae in such patients have up to now received little attention. In this study we not only describe neuropsychological deficits but also the quality of life and the extent of depression and other psychiatric symptoms in patients after complete media infarction of the non-speech dominant hemisphere. 相似文献77.
Wall CE Vinyard CJ Williams SH Gapeyev V Liu X Lapp H German RZ 《Integrative and comparative biology》2011,51(2):215-223
The Feeding Experiments End-user Database (FEED) is a research tool developed by the Mammalian Feeding Working Group at the National Evolutionary Synthesis Center that permits synthetic, evolutionary analyses of the physiology of mammalian feeding. The tasks of the Working Group are to compile physiologic data sets into a uniform digital format stored at a central source, develop a standardized terminology for describing and organizing the data, and carry out a set of novel analyses using FEED. FEED contains raw physiologic data linked to extensive metadata. It serves as an archive for a large number of existing data sets and a repository for future data sets. The metadata are stored as text and images that describe experimental protocols, research subjects, and anatomical information. The metadata incorporate controlled vocabularies to allow consistent use of the terms used to describe and organize the physiologic data. The planned analyses address long-standing questions concerning the phylogenetic distribution of phenotypes involving muscle anatomy and feeding physiology among mammals, the presence and nature of motor pattern conservation in the mammalian feeding muscles, and the extent to which suckling constrains the evolution of feeding behavior in adult mammals. We expect FEED to be a growing digital archive that will facilitate new research into understanding the evolution of feeding anatomy. 相似文献
78.
79.
80.
Identification and optimization of tetrahydro-2H-3-benzazepin-2-ones as squalene synthase inhibitors
Griebenow N Flessner T Buchmueller A Raabe M Bischoff H Kolkhof P 《Bioorganic & medicinal chemistry letters》2011,21(8):2554-2558
Novel squalene synthase inhibitors are disclosed. SAR and pharmacological profile of selected compounds are discussed. 相似文献