全文获取类型
收费全文 | 1798篇 |
免费 | 170篇 |
国内免费 | 2篇 |
出版年
2023年 | 9篇 |
2022年 | 13篇 |
2021年 | 35篇 |
2020年 | 19篇 |
2019年 | 19篇 |
2018年 | 27篇 |
2017年 | 22篇 |
2016年 | 44篇 |
2015年 | 74篇 |
2014年 | 78篇 |
2013年 | 98篇 |
2012年 | 125篇 |
2011年 | 117篇 |
2010年 | 73篇 |
2009年 | 82篇 |
2008年 | 119篇 |
2007年 | 111篇 |
2006年 | 93篇 |
2005年 | 99篇 |
2004年 | 87篇 |
2003年 | 85篇 |
2002年 | 92篇 |
2001年 | 21篇 |
2000年 | 19篇 |
1999年 | 23篇 |
1998年 | 25篇 |
1997年 | 17篇 |
1996年 | 11篇 |
1995年 | 12篇 |
1994年 | 8篇 |
1993年 | 8篇 |
1992年 | 17篇 |
1991年 | 12篇 |
1990年 | 17篇 |
1988年 | 13篇 |
1986年 | 7篇 |
1985年 | 10篇 |
1984年 | 13篇 |
1983年 | 12篇 |
1982年 | 15篇 |
1981年 | 10篇 |
1979年 | 7篇 |
1976年 | 7篇 |
1974年 | 14篇 |
1972年 | 7篇 |
1971年 | 6篇 |
1970年 | 6篇 |
1969年 | 6篇 |
1967年 | 7篇 |
1966年 | 6篇 |
排序方式: 共有1970条查询结果,搜索用时 15 毫秒
11.
The hydrolysis of bradykinin and its higher homologues by angiotensin-converting enzyme has been investigated by using an automated ninhydrin technique. The results show an inverse relationship of hydrolysis rate with size and charge of the peptide, which parallels the inactivation in the pulmonary circulation and offers an explanation for the selectivity of metabolism of these kinins by the lungs. 相似文献
12.
J. Frederic 《Chromosoma》1969,28(2):199-210
The basic principle of the technique is the analysis of photomicrographs (light microscope) with a system of closed television chain. By suitable settings of the video scanning (e.g. black and white level, contrast) it is possible to bring out some particular structures of chromosomes, by a kind of optical density selection. — Chromosomes in mitosis and meiosis from different species (man, rat, sloth) have been studied up to now; all of them show a similar inner organization. The double spiralization of each chromatid appears clearly. Each chromonema contains a more or less dense heap of fine loops; these appear to be made of a folded fibril of 200–300 Å thickness. In less condensed zones of the chromonema, e.g. in uncoiled parts, four filaments arranged in two more or less twisted pairs are clearly distinguishable; these filaments seem to correspond to 1/8 chromatid. From our first investigations it seems that the inner fibrils of the chromosomes are organized according to one of the DuPraw's models (combined transverse and longitudinal folding with quaternary coiling). — Some arguments are proposed and discussed as to explain how it is possible to reach such a high resolution with a conventional light microscope.
Recherches effectuées avec l'aide du Fonds de la Recherche Scientifique Médicale (Belgique). 相似文献
Recherches effectuées avec l'aide du Fonds de la Recherche Scientifique Médicale (Belgique). 相似文献
13.
14.
15.
Sans résuméRecherches effectuées avec l'appui du Fonds de la Recherche Scientifique Médicale et du Fonds de la Recherche Fondamentale Collective (Belgique). 相似文献
16.
Atherton, John G. (University of Southern California, Los Angeles), Sotiros G. Chaparas, Martha Cremer, and Irving Gordon. Mechanism of polykaryocytosis associated with noncytopathic infection by measles virus. J. Bacteriol. 90:213-219. 1965.-Infection with a measles virus variant resulted not only in formation of polykaryocytes (PK) but also in formation of multicellular immunofluorescent foci (IFF) in which no cytopathic effect could be detected. The ratio of IFF to PK changed from 27 to 4 during the first passage and remained 4 after a second passage. PK were plaques. Plaque assay was linear in the presence of IFF. To investigate the mechanism of PK formation, radioautography was done on cells pulse-labeled with tritiated thymidine before virus multiplication began. The results showed that PK were formed by fusion; there were no PK whose nuclei contained no label, and the proportion of labeled nuclei (32%) and distribution of grain counts was the same in PK as in uninvolved cells, ruling out nuclear replication without concomitant cytoplasmic membrane formation as the mechanism of formation of these PK. Early in PK development, neutral red uptake was markedly increased ("red" plaques). As PK matured, hyperchromicity disappeared ("white" plaques). This sequence provided an index of rate of evolution of PK. Rate of PK maturation was more rapid at 37 than at 32 C. 相似文献
17.
Jill E. Cremer 《The Biochemical journal》1967,104(1):212-222
1. The rate of appearance of 14CO2 from [6-14C]glucose and [3-14C]pyruvate was measured. Pyruvate is oxidized to carbon dioxide twice as fast as glucose, although the oxygen uptake is almost the same with each substrate. 2. The presence of 30μm-2,4-dinitrophenol increases the output of 14CO2 from [6-14C]glucose sixfold whereas the oxygen uptake is not quite doubled. Similar results are obtained with 0·1m-potassium chloride. The stimulating action of these two agents on the output of 14CO2 from [3-14C]pyruvate is much less than on that from [6-14C]glucose. 3. The effects of oligomycin, ouabain and triethyltin on the respiration of control and stimulated brain-cortex slices were studied. Triethyltin (1·3μm) inhibited the oxidation of [6-14C]glucose more than 70%, but did not inhibit the oxidation of[3-14C]pyruvate. [3-14C]pyruvate. 4. The production of lactic acid by brain-cortex slices incubated with glucose is twice as great as that with pyruvate. Lactic acid increases two and a half times in the presence of either triethyltin or oligomycin when the substrate is glucose, but is no different from the control when the substrate is pyruvate. 5. With kidney slices the production of lactic acid from glucose is very low. It is increased by oligomycin but not by triethyltin. 6. The results are discussed in terms of the oxidation of the extramitochondrial NADH2 produced during glycolysis. 相似文献
18.
19.
20.
Previous studies have shown that certain specific leaf mRNAs exhibit a diurnal rhythmicity in their quantity in higher plants. To determine whether this situation is restricted to a few mRNAs, or affects a large number, we have used in vitro translation and two-dimensional polyacrylamide gel electrophoresis to analyze the mRNA complement in leaves of Sinapis alba at different times during an 8-hour/16-hour day/night cycle. A method for the visual analysis of two-dimensional polyacrylamide gel electrophoresis was also developed. This method selected, at each sampling time, spots that were significant. It then selected, between two sampling times, intensity changes that were significant at the 0.02 confidence level. During a day/night cycle, complex rhythmic changes affected about 10% of the mRNAs. Nineteen different rhythm patterns were found. These 19 patterns fell into four main classes: mRNAs that increase during the light period and decrease during the dark, mRNAs that increase and then decrease during the light period, mRNAs that decrease during the light period and increase during the dark period, and mRNAs that increase and then decrease during the dark period. 相似文献