全文获取类型
收费全文 | 270篇 |
免费 | 20篇 |
出版年
2021年 | 4篇 |
2019年 | 1篇 |
2018年 | 3篇 |
2017年 | 3篇 |
2016年 | 5篇 |
2015年 | 11篇 |
2014年 | 6篇 |
2013年 | 1篇 |
2012年 | 4篇 |
2011年 | 8篇 |
2010年 | 7篇 |
2009年 | 6篇 |
2008年 | 7篇 |
2007年 | 6篇 |
2006年 | 10篇 |
2005年 | 5篇 |
2004年 | 6篇 |
2003年 | 2篇 |
2002年 | 6篇 |
2001年 | 12篇 |
2000年 | 13篇 |
1999年 | 6篇 |
1998年 | 19篇 |
1997年 | 10篇 |
1996年 | 8篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 8篇 |
1991年 | 3篇 |
1990年 | 9篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1985年 | 9篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1982年 | 8篇 |
1981年 | 1篇 |
1979年 | 5篇 |
1978年 | 2篇 |
1977年 | 8篇 |
1976年 | 8篇 |
1975年 | 5篇 |
1974年 | 4篇 |
1973年 | 2篇 |
1972年 | 3篇 |
1971年 | 1篇 |
排序方式: 共有290条查询结果,搜索用时 15 毫秒
211.
Plant cell vacuoles may have storage or lytic functions, but biochemical markers specific for the tonoplasts of functionally distinct vacuoles are poorly defined. Here, we use antipeptide antibodies specific for the tonoplast intrinsic proteins alpha-TIP, gamma-TIP, and delta-TIP in confocal immunofluorescence experiments to test the hypothesis that different TIP isoforms may define different vacuole functions. Organelles labeled with these antibodies were also labeled with antipyrophosphatase antibodies, demonstrating that regardless of their size, they had the expected characteristics of vacuoles. Our results demonstrate that the storage vacuole tonoplast contains delta-TIP, protein storage vacuoles containing seed-type storage proteins are marked by alpha- and delta- or alpha- and delta- plus gamma-TIP, whereas vacuoles storing vegetative storage proteins and pigments are marked by delta-TIP alone or delta- plus gamma-TIP. In contrast, those marked by gamma-TIP alone have characteristics of lytic vacuoles, and results from other researchers indicate that alpha-TIP alone is a marker for autophagic vacuoles. In root tips, relatively undifferentiated cells that contain vacuoles labeled separately for each of the three TIPs have been identified. These results argue that plant cells have the ability to generate and maintain three separate vacuole organelles, with each being marked by a different TIP, and that the functional diversity of the vacuolar system may be generated from different combinations of the three basic types. 相似文献
212.
Harriëtte Riese Tanja GM Vrijkotte Piet Meijer Cees Kluft Eco JC de Geus 《BMC cardiovascular disorders》2002,2(1):9-12
Background
Serum C-reactive protein (CRP) has been identified in prospective epidemiological research as an independent risk marker for cardiovascular disease. In this paper, short-term biological variation of CRP is documented and a strategy to test the reliability of a single CRP sample is proposed. 相似文献213.
Onion (Allium cepa) is an important horticulture crop because of its value as a food with a long shelf life being a relatively non-perishable product. It is very helpful to understand the growth response of the seeded onion crop to conduct appropriate field practices in attaining the highest or optimum yields. A three year field experiment was conducted using a variety of onion Valcatorce INTA, in a randomized block design with five replicates. Treatments were two plant densities and three rates of N application. The bulb growth followed a classical sigmoid curve. During the rapid growing period, the crop had the greatest leaf area (LA) with at least six leaves per plant. Increasing plant density increased yield in kg/ha, but decreased bulb size. Defoliating 40 to 60% of the LA had a significant impact on bulb production only at early growth stages. Late in the growing period, the remaining LA was apparently large enough for producing sufficient amounts of metabolites to feed new leaves, increasing their photosynthesis efficiency for the benefit of bulb production. 相似文献
214.
215.
Jin-Oh You Dariela Almeda George JC Ye Debra T Auguste 《Journal of biological engineering》2010,4(1):15
For years, the field of drug delivery has focused on (1) controlling the release of a therapeutic and (2) targeting the therapeutic
to a specific cell type. These research endeavors have concentrated mainly on the development of new degradable polymers and
molecule-labeled drug delivery vehicles. Recent interest in biomaterials that respond to their environment have opened new
methods to trigger the release of drugs and localize the therapeutic within a particular site. These novel biomaterials, usually
termed "smart" or "intelligent", are able to deliver a therapeutic agent based on either environmental cues or a remote stimulus.
Stimuli-responsive materials could potentially elicit a therapeutically effective dose without adverse side effects. Polymers
responding to different stimuli, such as pH, light, temperature, ultrasound, magnetism, or biomolecules have been investigated
as potential drug delivery vehicles. This review describes the most recent advances in "smart" drug delivery systems that
respond to one or multiple stimuli. 相似文献
216.
Caroline B Michielse Ringo van Wijk Linda Reijnen Ben JC Cornelissen Martijn Rep 《Genome biology》2009,10(1):R4-18
Background
Fusarium oxysporum f. sp. lycopersici is the causal agent of vascular wilt disease in tomato. In order to gain more insight into the molecular processes in F. oxysporum necessary for pathogenesis and to uncover the genes involved, we used Agrobacterium-mediated insertional mutagenesis to generate 10,290 transformants and screened the transformants for loss or reduction of pathogenicity. 相似文献217.
218.
219.
The hermaphroditic Mangrove Killifish, Kryptolebias marmoratus, is the world''s only vertebrate that routinely self-fertilizes. As such, highly inbred and presumably isogenic “clonal” lineages of this androdioecious species have long been maintained in several laboratories and used in a wide variety of experiments that require genetically uniform vertebrate specimens. Here we conduct a genetic inventory of essentially all laboratory stocks of the Mangrove Killifish held worldwide. At 32 microsatellite loci, these stocks proved to show extensive interline differentiation as well as some intraline variation, much of which can be attributed to post-origin de novo mutations and/or to the segregation of polymorphisms from wild progenitors. Our genetic findings also document that many of the surveyed laboratory strains are not what they have been labeled, apparently due to the rather frequent mishandling or unintended mixing of various laboratory stocks over the years. Our genetic inventory should help to clarify much of this confusion about the clonal identities and genetic relationships of laboratory lines, and thereby help to rejuvenate interest in K. marmoratus as a reliable vertebrate model for experimental research that requires or can capitalize upon “clonal” replicate specimens. 相似文献
220.
The evolution of reproductive and genomic diversity in ray-finned fishes: insights from phylogeny and comparative analysis 总被引:1,自引:0,他引:1
Collectively, ray-finned fishes (Actinopterygii) display far more diversity in many reproductive and genomic features than any other major vertebrate group. Recent large-scale comparative phylogenetic analyses have begun to reveal the evolutionary patterns and putative causes for much of this diversity. Several such recent studies have offered clues to how different reproductive syndromes evolved in these fishes, as well as possible physiological and genomic triggers. In many cases, repeated independent origins of complex reproductive strategies have been uncovered, probably reflecting convergent selection operating on common suites of underlying genes and hormonal controls. For example, phylogenetic analyses have uncovered multiple origins and predominant transitional pathways in the evolution of alternative male reproductive tactics, modes of parental care and mechanisms of sex determination. They have also shown that sexual selection in these fishes is repeatedly associated with particular reproductive strategies. Collectively, studies on reproductive and genomic diversity across the Actinopterygii illustrate both the strengths and the limitations of comparative phylogenetic approaches on large taxonomic scales. 相似文献