全文获取类型
收费全文 | 714篇 |
免费 | 1篇 |
专业分类
化学工业 | 3篇 |
矿业工程 | 1篇 |
能源动力 | 1篇 |
轻工业 | 3篇 |
无线电 | 2篇 |
一般工业技术 | 1篇 |
冶金工业 | 703篇 |
原子能技术 | 1篇 |
出版年
2020年 | 1篇 |
2019年 | 1篇 |
2016年 | 2篇 |
2015年 | 1篇 |
2013年 | 1篇 |
2011年 | 3篇 |
2008年 | 1篇 |
2007年 | 2篇 |
1999年 | 16篇 |
1998年 | 210篇 |
1997年 | 133篇 |
1996年 | 78篇 |
1995年 | 49篇 |
1994年 | 33篇 |
1993年 | 44篇 |
1992年 | 11篇 |
1991年 | 7篇 |
1990年 | 5篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 12篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1983年 | 1篇 |
1982年 | 7篇 |
1981年 | 6篇 |
1980年 | 15篇 |
1978年 | 2篇 |
1977年 | 18篇 |
1976年 | 43篇 |
1975年 | 2篇 |
排序方式: 共有715条查询结果,搜索用时 0 毫秒
101.
102.
103.
A mating type-linked gene cluster expressed in Chlamydomonas zygotes participates in the uniparental inheritance of the chloroplast genome 总被引:1,自引:0,他引:1
A characteristic feature of early zygote development in Chlamydomonas is the selective degradation of chloroplast DNA from the mating type minus parent. The zygote-specific gene cluster ezy-1 is linked to the mating type locus and is transcribed almost immediately upon zygote formation. We show here that the acidic Ezy-1 polypeptide is rapidly transported to both the plus and minus chloroplasts, where it interacts with each chloroplast nucleoid. Expression of ezy-1 is selectively inhibited when plus, but not minus, gametes are briefly ultraviolet irradiated just prior to mating, a treatment known to disrupt the uniparental inheritance of chloroplast traits. We propose that the Ezy-1 polypeptide participates in the destruction of the minus chloroplast DNA in zygotes and thus the uniparental inheritance of chloroplast traits. The ezy-1 gene represents a valuable molecular probe for dissecting mechanisms underlying organelle inheritance. 相似文献
104.
Fura-2 and its lipid analogue, FFP-18, were used to measure changes in cytosolic free Ca2+ concentration within human neutrophils. Whereas fura-2 was employed to monitor cytosolic Ca2+ increases throughout the cytosol, FFP-18 was used to monitor Ca2+ changes only near the membrane. This latter probe was incorporated into the plasma membrane as its acetoxymethyl ester (FFP-18-AM) but as de-esterification was catalysed by cytosolic esterases, the Ca(2+)-sensing probe (FFP-18 acid) accumulated on the inner face of membrane. The fluorescence of esterified probe on the extracellularly facing membrane leaflet was quenched by the membrane-impermeant ion Ni2+. Under these conditions, near membrane Ca2+ changes which resulted from the release of Ca2+ from intracellular stores was possible by conventional ratio fluorescence measurement of FFP-18. From the timing of arrival of Ca2+ at the plasma membrane, it was proposed that there were two Ca2+ storage sites, liberated by different stimuli, one close to the plasma membrane and the other more distant. In order to discover whether organelles within the neutrophil had distributions which correlate with the Ca2+ release sites, fluorescent dyes for structures within the cytosol were employed. We have previously shown that the location of the intracellular membrane stain, DiOC6 (3) corresponds to the distant Ca2+ release site. Here a second stain, BODIPY-C5 ceramide, has also been used and is shown to stain a peripheral region of the neutrophil, in a similar pattern to the near membrane Ca2+ storage site. These data therefore raise the question of whether these stains mark the organelles in neutrophils which are the two Ca2+ storage and release sites. 相似文献
105.
The paper reports 7 cases of dimorphic anemia, development of Addison-Biermer disease in preexisting chronic posthemorrhagic anemia. The authors consider some diagnostic and therapeutic aspects. It is thought valid to discontinue iron preparations prior to vitamin B12 therapy and to start them again upon the arising reticulocytic crisis. 相似文献
106.
107.
EV Karpenko AN Shul'ga NS Shcheglova SA Eliseev RI Vil'danova-Martsishin AA Turovski? 《Canadian Metallurgical Quarterly》1996,58(5):18-24
Pseudomonas species S-27 was grown on various substrates. It was established that the Pseudomonas species S-27 strain can produce biosurfactants of ramnolipid nature decreasing the surface and interfacial tension to 29.2 and 0.05 mN/m. respectively, as well as a biopolymer stabilizing the emulsions with hydrocarbons and oils. The biosurfactant and bioemulsifier synthesis is shown to depend of the substrate nature. 相似文献
108.
MIu Shchelkanov NG Iaroslavtseva AN Iudin VF Eremin NS Pyzhova IuA Semiletov AV Abélian LP Titov EV Karamov 《Canadian Metallurgical Quarterly》1998,32(4):717-728
This article reviews the existing knowledge base concerning the biology of spinal fusion, with the understanding that the focus is weighted toward posterolateral lumbar spinal fusion because of a relative paucity of biologic information on healing of other types of fusions. The discussion focuses first on the basic science of spinal fusion healing from the standpoint of animal modeling. Next, the discussion centers on the multitude of local factors that can affect fusion healing. Finally, the numerous systemic factors known to affect fusion healing are discussed. 相似文献
109.
AM Baranov SS Vetchinin EV Baranova SF Biketov EA Svetoch 《Canadian Metallurgical Quarterly》1998,45(6):1163-1168
The monoclonal antibodies (MAbs) against lipopolysaccharide of virulent strain of Legionella pneumophila serogroup 1 were produced. Three most productive hybrid clones (5F4, 5F10 and 2C9) were selected from fusions of mouse myeloma cells with spleen cells from BALB/c mice, immunized with bacterial outer membrane antigens. All generated clones were IgG-secreting. The MAbs had narrow strain specificity and showed no cross-reactions with other unrelated bacterial species. These antibodies were tested in sandwich ELISA. The results suggest that the MAbs could be used for diagnostic purposes. 相似文献
110.
BACKGROUND: Because of the success of secondary prevention of coronary events by intense risk factor modification, a more precise measure of atherosclerosis in youth would have great clinical value both in the design of clinical trials for the demonstration of the usefulness of coronary disease prevention early in life and in guiding therapy. Identification of calcium in coronary arteries by electron beam tomography has been associated with severity of atherosclerosis in adults. METHODS AND RESULTS: Twenty-nine youths 11 to 23 years old with familial hypercholesterolemia (average LDL cholesterol, 5.95 mmol/L) underwent electron beam tomography as well as comprehensive risk factor assessment with measurement of total cholesterol, triglycerides, HDL cholesterol, lipoprotein (a), apolipoprotein E phenotype, blood pressure, body mass index, and history of tobacco use. Significant coronary calcium was identified in 7 of 29 subjects. Increased body mass index was significantly associated with the presence of coronary calcium (25.3 versus 20.6 kg/m2, P<0.03). No other risk factors were associated with the presence of coronary calcium. CONCLUSIONS: Coronary calcium, uncommonly identified before the fourth decade, was found in a significant percentage of adolescents and young adults with familial hypercholesterolemia. Overweight may increase the likelihood of coronary calcium being present in individuals already at high risk. 相似文献