全文获取类型
收费全文 | 129篇 |
免费 | 0篇 |
专业分类
系统科学 | 1篇 |
现状及发展 | 57篇 |
研究方法 | 7篇 |
综合类 | 62篇 |
自然研究 | 2篇 |
出版年
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 1篇 |
2013年 | 2篇 |
2012年 | 8篇 |
2011年 | 6篇 |
2009年 | 2篇 |
2008年 | 4篇 |
2007年 | 9篇 |
2006年 | 3篇 |
2005年 | 9篇 |
2004年 | 3篇 |
2003年 | 1篇 |
2002年 | 3篇 |
2001年 | 1篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1998年 | 1篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1992年 | 3篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 4篇 |
1985年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1974年 | 4篇 |
1973年 | 2篇 |
1972年 | 3篇 |
1971年 | 6篇 |
1970年 | 10篇 |
1969年 | 3篇 |
1968年 | 1篇 |
1967年 | 2篇 |
1966年 | 2篇 |
1965年 | 1篇 |
1961年 | 1篇 |
1958年 | 1篇 |
1947年 | 2篇 |
排序方式: 共有129条查询结果,搜索用时 15 毫秒
21.
22.
Summary The spectral sensitivity of 3 species of planktonic Rotatoria (Asplanchna priodonta, Polyarthra remata, Filinia longiseta) were measured by means of the positive phototactic reaction.Asplanchna andPolyarthra both have a broad maximum sensitivity range around 540 nm and a near maximum at 440 nm. In the UV direction (to 360 nm) the spectral sensitivity increases. In contrast,Filinia has only a maximum of 460 nm in the visible spectrum, but behaves similarly to the other species in the UV region. The ecological significance of these results is discussed, as well as their bearing on a possible dermal light sense. 相似文献
23.
X M Yin K Wang A Gross Y Zhao S Zinkel B Klocke K A Roth S J Korsmeyer 《Nature》1999,400(6747):886-891
The protein Bid is a participant in the pathway that leads to cell death (apoptosis), mediating the release of cytochrome c from mitochondria in response to signals from 'death' receptors known as TNFR1/Fas on the cell surface. It is a member of the proapoptotic Bcd-2 family and is activated as a result of its cleavage by caspase 8, one of a family of proteolytic cell-death proteins. To investigate the role of Bid in vivo, we have generated mice deficient for Bid. We find that when these mice are injected with an antibody directed against Fas, they nearly all survive, whereas wild-type mice die from hepatocellular apoptosis and haemorrhagic necrosis. About half of the Bid-deficient animals had no apparent liver injury and showed no evidence of activation of the effector caspases 3 and 7, although the initiator caspase 8 had been activated. Other Bid-deficient mice survived with only moderate damage: all three caspases (8 and 37) were activated but their cell nuclei were intact and no mitochondrial cytochrome c was released. We also investigated the effects of Bid deficiency in cultured cells treated with anti-Fas antibody (hepatocytes and thymocytes) or with TNFalpha. (fibroblasts). In these Bid-/- cells, mitochondrial dysfunction was delayed, cytochrome c was not released, effector caspase activity was reduced and the cleavage of apoptosis substrates was altered. This loss-of-function model indicates that Bid is a critical substrate in vivo for signalling by death-receptor agonists, which mediates a mitochondrial amplification loop that is essential for the apoptosis of selected cells. 相似文献
24.
Monolayers on crystalline surfaces often form complex structures with physical and chemical properties that differ strongly from those of their bulk phases. Such hetero-epitactic overlayers are currently used in nanotechnology and understanding their growth mechanism is important for the development of new materials and devices. In comparison with crystals, quasicrystalline surfaces exhibit much larger structural and chemical complexity leading, for example, to unusual frictional, catalytical or optical properties. Deposition of thin films on such substrates can lead to structures that may have typical quasicrystalline properties. Recent experiments have indeed showed 5-fold symmetries in the diffraction pattern of metallic layers adsorbed on quasicrystals. Here we report a real-space investigation of the phase behaviour of a colloidal monolayer interacting with a quasicrystalline decagonal substrate created by interfering five laser beams. We find a pseudomorphic phase that shows both crystalline and quasicrystalline structural properties. It can be described by an archimedean-like tiling consisting of alternating rows of square and triangular tiles. The calculated diffraction pattern of this phase is in agreement with recent observations of copper adsorbed on icosahedral Al(70)Pd(21)Mn(9) surfaces. In addition to establishing a link between archimedean tilings and quasicrystals, our experiments allow us to investigate in real space how single-element monolayers can form commensurate structures on quasicrystalline surfaces. 相似文献
25.
Wheeler DA Srinivasan M Egholm M Shen Y Chen L McGuire A He W Chen YJ Makhijani V Roth GT Gomes X Tartaro K Niazi F Turcotte CL Irzyk GP Lupski JR Chinault C Song XZ Liu Y Yuan Y Nazareth L Qin X Muzny DM Margulies M Weinstock GM Gibbs RA Rothberg JM 《Nature》2008,452(7189):872-876
The association of genetic variation with disease and drug response, and improvements in nucleic acid technologies, have given great optimism for the impact of 'genomic medicine'. However, the formidable size of the diploid human genome, approximately 6 gigabases, has prevented the routine application of sequencing methods to deciphering complete individual human genomes. To realize the full potential of genomics for human health, this limitation must be overcome. Here we report the DNA sequence of a diploid genome of a single individual, James D. Watson, sequenced to 7.4-fold redundancy in two months using massively parallel sequencing in picolitre-size reaction vessels. This sequence was completed in two months at approximately one-hundredth of the cost of traditional capillary electrophoresis methods. Comparison of the sequence to the reference genome led to the identification of 3.3 million single nucleotide polymorphisms, of which 10,654 cause amino-acid substitution within the coding sequence. In addition, we accurately identified small-scale (2-40,000 base pair (bp)) insertion and deletion polymorphism as well as copy number variation resulting in the large-scale gain and loss of chromosomal segments ranging from 26,000 to 1.5 million base pairs. Overall, these results agree well with recent results of sequencing of a single individual by traditional methods. However, in addition to being faster and significantly less expensive, this sequencing technology avoids the arbitrary loss of genomic sequences inherent in random shotgun sequencing by bacterial cloning because it amplifies DNA in a cell-free system. As a result, we further demonstrate the acquisition of novel human sequence, including novel genes not previously identified by traditional genomic sequencing. This is the first genome sequenced by next-generation technologies. Therefore it is a pilot for the future challenges of 'personalized genome sequencing'. 相似文献
26.
The role of peroxisomes in aging 总被引:2,自引:0,他引:2
27.
E. F. Roth Jr J. C. McKitrick F. Herz 《Cellular and molecular life sciences : CMLS》1989,45(5):478-480
Summary In vitro culture systems are often contaminated by bacteria and fungi. It is therefore often necessary to supplement culture media with agents such as penicillin/streptomycin, gentamycin or amphotericin B. The latter cannot be used in the in vitro culture of erythrocytic stages ofP. falciparum, and thus anti-fungal agents have not been regularly used in this system. We describe the prophylactic use of 5-fluorocytosine (5-FC) and ketoconazole (KTZ) in tissue cultures at concentrations up to 300 and 10 g/ml respectively which have no effect on the growth ofP. falciparum (FCR-3 strain). A melanoma cell line (C32) and a line of uterine carcinoma (C41) were also unaffected by similar concentrations of 5-FC and KTZ. When dissolved in complete culture medium (RPMI 1640) with 10% human plasma, the minimum inhibitory concentration of 5-FC for a susceptible strain ofCandida remained below 2 g/ml. These experiments suggest that 5-FC (at 50 g/ml) alone or in combination with KTZ (at 1 g/ml) is a useful addition to the armamentarium of antimicrobials available to the tissue culture biologist for a variety of cell culture systems. 相似文献
28.
J. M. Goldbach J. Roth B. Störr E. Zeisberger 《Cellular and molecular life sciences : CMLS》1996,52(8):774-777
Tumor necrosis factor (TNF) was repeatedly microinfused into the lateral ventricle of guinea pig brains at a dose of 200 ng, 4 times within 150 min, at intervals of 3 days. In comparison to guinea pigs infused with solvent according to the same time schedule, the animals responded to TNF with pronounced fevers. The quantity of the fever response was the same after each of the 4 microinfusions of TNF. Three days after the last infusion of TNF or solvent all animals received an intramuscular injection of bacterial lipopolysaccharide (LPS). The fever in response to LPS was the same in both groups. Thus, the reported development of tolerance to repeated systemic administration of TNF1–3 does not develop inside the blood-brain barrier. Also, the febrile response to LPS is not influenced by repeated central pre-treatment with TNF, whereas repeated peripheral treatment does have an effect. 相似文献
29.
30.