全文获取类型
收费全文 | 12173篇 |
免费 | 1254篇 |
国内免费 | 4篇 |
出版年
2023年 | 81篇 |
2022年 | 115篇 |
2021年 | 243篇 |
2020年 | 202篇 |
2019年 | 228篇 |
2018年 | 239篇 |
2017年 | 278篇 |
2016年 | 442篇 |
2015年 | 684篇 |
2014年 | 715篇 |
2013年 | 812篇 |
2012年 | 952篇 |
2011年 | 874篇 |
2010年 | 645篇 |
2009年 | 562篇 |
2008年 | 700篇 |
2007年 | 616篇 |
2006年 | 561篇 |
2005年 | 604篇 |
2004年 | 566篇 |
2003年 | 550篇 |
2002年 | 496篇 |
2001年 | 110篇 |
2000年 | 98篇 |
1999年 | 127篇 |
1998年 | 129篇 |
1997年 | 98篇 |
1996年 | 98篇 |
1995年 | 84篇 |
1994年 | 76篇 |
1993年 | 71篇 |
1992年 | 75篇 |
1991年 | 55篇 |
1990年 | 68篇 |
1989年 | 63篇 |
1988年 | 57篇 |
1987年 | 55篇 |
1986年 | 53篇 |
1985年 | 38篇 |
1984年 | 71篇 |
1983年 | 49篇 |
1982年 | 56篇 |
1981年 | 59篇 |
1980年 | 49篇 |
1979年 | 50篇 |
1978年 | 39篇 |
1977年 | 43篇 |
1976年 | 42篇 |
1975年 | 40篇 |
1974年 | 33篇 |
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
91.
The cystine-containing peptides of horse growth hormone were isolated and their amino acid sequences determined. Four unique half-cystine residues occur in two peptides, one containing 11 and the other, at the C-terminus of the protein, 15 amino acids. These sequences are compared with published data on growth hormones from other species. 相似文献
92.
Summary In vitro,Phoma liliana could not be distinguished from the later-describedP. ehretiae and two incidental isolates fromMangifera andChrysanthemum. Starting from the principle of the classification in the Deuteromycetes, our conclusion is that we must speak of one and the same form-species, which can be found on different plants. 相似文献
93.
The strainCandida utilis T 20 adapted to a high concentration of ethionine, excretes considerable amounts of methionine in a synthetic medium, about 40 times as much as the original non-adapted strain. At the same time, the amount of methionine in yeast cells incrncreased, predominantly in the pool (9 times as much as in the control). This ability to produce greater amounts of methionine in the pool or to excrete it into the medium is not permanent, since after 5 passages on agar with ut ethionine the amount of methionine was practically not increased as compared with the original non-adapted strain. An increase in free methionine and of methionine excreted into the medium was found on cultivating the strain in a molasses-containing medium, too. 相似文献
94.
The de-repression of thiamine biosynthesis by adenosine. A tool for investigating this biosynthetic pathway 总被引:6,自引:3,他引:3
1. Growth of Salmonella typhimurium LT2 in the presence of adenosine was shown to cause enormous synthesis of thiamine in washed-cell suspensions. 2. Evidence that this was due to de-repression and not an accumulation of precursors was obtained by using a mutant blocked in the biosynthesis of the thiazole moiety, which showed a similarly large synthesis of the pyrimidine of thiamine. 3. The specific requirements for a source of energy, nitrogen and sulphur were investigated, and indicated new synthesis in this system. 相似文献
95.
96.
97.
98.
Factors Controlling the Production of Lysogenic Cultures of B. megatherium 总被引:1,自引:1,他引:0
下载免费PDF全文
![点击此处可从《The Journal of general physiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
John H. Northrop with the technical assistance of Marie King 《The Journal of general physiology》1961,44(5):859-867
(1) The proportion of infected B. megatherium cells which develop lysogenic colonies depends on the number and kind of infecting virus particles and on the culture medium in which the cells are growing. (2) Cells infected with 100 or more T virus particles (from megatherium 899) in yeast extract peptone disintegrate, produce very few virus particles, and less than one lysogenic colony per 107 infected cells. Cells infected with one or a few particles produce 500 to 1000 virus particles each and about 30 lysogenic colonies per 107 infected colonies. (3) T phage obtained from lysogenic magatherium KM cultures produces many more lysogenic cells than does the original megatherium 899 virus. (4) Cells infected with megatherium 899 T virus in peptone medium and then transferred to asparagine medium give rise to 106 lysogenic colonies per 107 infected cells and this transformation will occur even after the infected cells have been in peptone for 60 to 90 minutes and are beginning to produce virus particles. (5) Continued growth of KM strain with either C or T virus from megatherium 899 for several hundred generations in the steady state apparatus results in a lysogenic strain which produces several different types of virus. 相似文献
99.
Titration and Neutralization of Poliovirus in Micro Tissue Culture Under Increased Carbon Dioxide 总被引:5,自引:3,他引:2
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Modification of the micro tissue culture technique, including incubation under increased CO(2), resulted in prolongation of the viability of the cells. As a consequence, satisfactory titrations of poliovirus and of poliovirus antiserum have been achieved by the micro method. The technique offers a number of advantages over conventional methods. 相似文献
100.
R. C. Newell 《Journal of Zoology》1967,151(1):299-311
In Newell & Northcroft (1967) evidence was presented which showed that the metabolism of certain intertidal invertebrates at rest does not vary greatly with temperature change. The following work was undertaken to determine whether temperature-independent metabolism could be demonstrated in suspensions of mitochondria extracted from poikilotherm tissue and whether it could be inferred that there was any difference in the ability of poikilotherms from different habitats to adjust toshort-term temperature change.
It was found that the rate of reaction/temperature curve of mitochondria isolated from the skate Raia had a flattened region below 10°C but above this the rate of oxidation of succinate and pyruvate increased regularly with temperature. The curve for intertidal forms had a gradual slope extending as high as 20°C in the mussel Mytilus edulis while in the terrestrial snail Helix aspersa the gradual slope reached 27.5°C after which the rate of oxidation of substrate increased sharply before declining towards higher temperatures. Finally, the curve for mitochondria isolated from the desert locust Schistocerca gregaria showed a gradual slope up to 35°C after which a sharp increase in the rate of oxidation of substrate occurred. Thus the extent of the gradual slope corresponds with the normal environmental temperature range to which the tissues of the poikilotherms are subjected and the general form of the R-T curve is such that rapid fluctuations within the normal environmental temperature range have relatively little effect on the rate of mitochondrial activity. 相似文献
It was found that the rate of reaction/temperature curve of mitochondria isolated from the skate Raia had a flattened region below 10°C but above this the rate of oxidation of succinate and pyruvate increased regularly with temperature. The curve for intertidal forms had a gradual slope extending as high as 20°C in the mussel Mytilus edulis while in the terrestrial snail Helix aspersa the gradual slope reached 27.5°C after which the rate of oxidation of substrate increased sharply before declining towards higher temperatures. Finally, the curve for mitochondria isolated from the desert locust Schistocerca gregaria showed a gradual slope up to 35°C after which a sharp increase in the rate of oxidation of substrate occurred. Thus the extent of the gradual slope corresponds with the normal environmental temperature range to which the tissues of the poikilotherms are subjected and the general form of the R-T curve is such that rapid fluctuations within the normal environmental temperature range have relatively little effect on the rate of mitochondrial activity. 相似文献