全文获取类型
收费全文 | 4913篇 |
免费 | 428篇 |
出版年
2022年 | 30篇 |
2021年 | 65篇 |
2020年 | 50篇 |
2019年 | 42篇 |
2018年 | 70篇 |
2017年 | 55篇 |
2016年 | 115篇 |
2015年 | 170篇 |
2014年 | 186篇 |
2013年 | 276篇 |
2012年 | 341篇 |
2011年 | 362篇 |
2010年 | 218篇 |
2009年 | 214篇 |
2008年 | 297篇 |
2007年 | 293篇 |
2006年 | 289篇 |
2005年 | 253篇 |
2004年 | 245篇 |
2003年 | 254篇 |
2002年 | 256篇 |
2001年 | 57篇 |
2000年 | 45篇 |
1999年 | 58篇 |
1998年 | 68篇 |
1997年 | 46篇 |
1996年 | 44篇 |
1995年 | 43篇 |
1994年 | 40篇 |
1993年 | 35篇 |
1992年 | 43篇 |
1991年 | 36篇 |
1990年 | 37篇 |
1989年 | 32篇 |
1988年 | 27篇 |
1987年 | 34篇 |
1985年 | 26篇 |
1984年 | 27篇 |
1983年 | 27篇 |
1982年 | 24篇 |
1981年 | 27篇 |
1980年 | 17篇 |
1979年 | 30篇 |
1978年 | 20篇 |
1977年 | 17篇 |
1976年 | 26篇 |
1975年 | 17篇 |
1974年 | 26篇 |
1973年 | 19篇 |
1972年 | 19篇 |
排序方式: 共有5341条查询结果,搜索用时 93 毫秒
41.
42.
J. Dennis Pollack Norman L. Somerson Laurence B. Senterfit 《Journal of bacteriology》1969,97(2):612-619
Mycoplasma pneumoniae harvested from media which had become acid lost the ability both to induce formation of tetrazolium reduction inhibition antibody and to act as antigens in immunodiffusion against human convalescent-phase sera. Incorporation of N-tris(hydroxymethyl)-2-aminoethane sulfonic acid and N-2-hydroxyethylpiperazine-N'-2-ethane sulfonic acid buffers into a new medium containing PPLO Serum Fraction instead of horse serum delayed the pH decline. Tris(hydroxymethyl)aminomethane, triethanolamine, and 3,6-endomethylene-1,2,3,6-tetrahydrophthalic acid buffers inhibited growth. Mycoplasmas obtained from buffered cultures retained antigenicity as measured by immunodiffusion and could stimulate tetrazolium reduction inhibition antibody formation in animals. 相似文献
43.
Measurement of the weight of individual virus particles from untreated and antibody-treated populations was made by quantitative electron microscopy. The weight of antibody bound depended on the concentration of antibody in solution. One population of viruses exposed to an antibody concentration which resulted in 95% inhibition of hemagglutination showed a mass increase of 55%, corresponding to an absolute increase of 9.0 x 10-17 g in the median value. Another population, whose hemagglutination inhibition assay was 64%, showed a 39% increase in mass corresponding to an absolute median increase of 7.3 x 10-17 g. The larger viruses in each population bound a greater absolute amount of antibody than did the smaller ones, but the latter bound relatively more antibody in proportion to their mass. No cross-reactivity was found between the antibody to influenza A/PR8 and the influenza strain B/LEE. Influenza A/PR8 controls exposed to nonspecific gamma-globulin displayed a significant weight loss, at least in part owing to loss from the core, as judged from the electron micrographs. 相似文献
44.
45.
46.
47.
1. The relative amounts of incorporation in vivo of l-lysine, and in one experiment l-arginine, into different histone fractions from Krebs ascites and a lymphoma ascites cells of mice and a `solid' tumour and liver of rats have been determined. 2. No marked differences in the incorporations of the amino acids into the fractions F1, F2a, F2b and F3 from the tumours were generally observed, although in some experiments there was a greater incorporation into fraction F2b, which could be decreased by further purification. 3. In the tumours the incorporations into all cell protein fractions obtained were approximately the same, indicating that the amount of incorporation was that required for the increase of cell mass. 4. In rat liver, the incorporations into fractions F1, F2a and F3 were not greatly different. That into fraction F2b was variable. The incorporation into the histone fractions was much less than that into the acid-insoluble nuclear residue, indicating that considerable turnover of amino acids in the latter occurs. 5. The decrease in radioactivity of labelled histone and acid-insoluble nuclear protein in vivo during several days confirmed the relatively small turnover of the histone fraction. The time taken for liver whole histone to lose half its radioactivity was about 1 week. A histone fraction of slower metabolism was also detected. 6. It is concluded that no appreciable turnover of protein occurs in any one histone fraction, the somewhat higher values obtained in certain cases being associated with acidic impurities. The apparently high rate of incorporation into histone of resting liver is discussed in relation to recent evidence on DNA metabolism of resting liver. 相似文献
48.
Plasmid origin of replication of herpesvirus papio: DNA sequence and enhancer function. 总被引:4,自引:2,他引:2
下载免费PDF全文
![点击此处可从《Journal of virology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
D D Loeb N S Sung R L Pesano C J Sexton C Hutchison rd J S Pagano 《Journal of virology》1990,64(6):2876-2883
49.
50.
Mutational analysis of human immunodeficiency virus type 1 protease suggests functional homology with aspartic proteinases. 总被引:15,自引:13,他引:2
下载免费PDF全文
![点击此处可从《Journal of virology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
D D Loeb C A Hutchison rd M H Edgell W G Farmerie R Swanstrom 《Journal of virology》1989,63(1):111-121
Processing of the retroviral gag and pol gene products is mediated by a viral protease. Bacterial expression systems have been developed which permit genetic analysis of the human immunodeficiency virus type 1 protease as measured by cleavage of the pol protein precursor. Deletion analysis of the pol reading frame locates the sequences required to encode a protein with appropriate proteolytic activity near the left end of the pol reading frame but largely outside the gag-pol overlap region, which is at the extreme left end of pol. Most missense mutations within an 11-amino-acid domain highly conserved among retroviral proteases and with sequence similarity to the active site of aspartic proteinases abolish appropriate processing, suggesting that the retrovirus proteases share a catalytic mechanism with aspartic proteinases. Substitution of the amino acids flanking the scissile bond at three of the processing sites encoded by pol demonstrates distinct sequence requirements for cleavage at these different sites. The inclusion of a charged amino acid at the processing site blocks cleavage. A subset of these substitutions also inhibits processing at the nonmutated sites. 相似文献