全文获取类型
收费全文 | 12252篇 |
免费 | 913篇 |
国内免费 | 24篇 |
出版年
2023年 | 71篇 |
2022年 | 105篇 |
2021年 | 347篇 |
2020年 | 263篇 |
2019年 | 308篇 |
2018年 | 422篇 |
2017年 | 360篇 |
2016年 | 482篇 |
2015年 | 604篇 |
2014年 | 717篇 |
2013年 | 837篇 |
2012年 | 955篇 |
2011年 | 852篇 |
2010年 | 514篇 |
2009年 | 471篇 |
2008年 | 591篇 |
2007年 | 592篇 |
2006年 | 509篇 |
2005年 | 459篇 |
2004年 | 432篇 |
2003年 | 377篇 |
2002年 | 383篇 |
2001年 | 251篇 |
2000年 | 206篇 |
1999年 | 193篇 |
1998年 | 99篇 |
1997年 | 90篇 |
1996年 | 65篇 |
1995年 | 86篇 |
1994年 | 71篇 |
1993年 | 51篇 |
1992年 | 110篇 |
1991年 | 104篇 |
1990年 | 88篇 |
1989年 | 81篇 |
1988年 | 80篇 |
1987年 | 74篇 |
1986年 | 57篇 |
1985年 | 66篇 |
1984年 | 49篇 |
1983年 | 53篇 |
1982年 | 54篇 |
1981年 | 44篇 |
1980年 | 34篇 |
1979年 | 41篇 |
1978年 | 51篇 |
1977年 | 36篇 |
1976年 | 31篇 |
1974年 | 43篇 |
1968年 | 35篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
101.
Sphaerotilus natans required calcium for the production of sheaths and probably requires calcium for growth as well, though at a lower concentration. Neither strontium nor barium substituted for calcium. S. natans grew attached to the culture vessels of the continuous-flow apparatus even when no sheaths were produced. Tentative evidence showed that the requirement for calcium is shared by the manganese-oxidizing species S. discophorus. 相似文献
102.
Growth-promoting Activity of Spent Sulfite Liquor for Sphaerotilus natans Growing in a Continuous-Flow Apparatus 下载免费PDF全文
The calcium in ammonia-base spent sulfite liquor, unlike that in calcium-base spent liquor, is not available for growth of Sphaerotilus natans. It has not been possible to obtain a mixed slime with Sphaerotilus as the dominant organism in a continuous-flow apparatus fed spent sulfite liquor. 相似文献
103.
Dias FF 《Applied microbiology》1967,15(6):1512-1513
104.
Utilization of Inorganic Nitrogen Compounds by Sphaerotilus natans Growing in a Continuous-Flow Apparatus 总被引:3,自引:3,他引:0 下载免费PDF全文
Sphaerotilus natans was grown, attached, in a continuous-flow apparatus with inorganic nitrogen compounds (NH4Cl, NaNO2, or NaNO3) as the only sources of nitrogen. The growth rate with NH4+-containing medium did not differ from that with media containing glutamate or Casitone as the nitrogen source. 相似文献
105.
J. ŘeŘÁbek 《Biologia Plantarum》1967,9(4):285-291
Exeised roots ofSolanum laciniatum Ait. grown in vitro in a liquid medium will form the typical rich white callus with a high water content. Its formation is made possible by the presence of 2,4-dichlorophenoxyacetic acid and niyo-inositol in the nutrient medium. Choline, ascorbic acid, riboflavin, calcium pantothenate and biotin are inactive. A mixture of thiamine, pyridoxine and nicotinic acid will induce only slight proliferation. 相似文献
106.
Summary Eight newSalmonella types are described.S. houten, 43; Z4, Z23 :−, was isolated from a frog,S.tuindorp, 43: Z4, Z32: −,S. vleuten, 44: fg: −,S.zeist, 18: Z10: Z6, andS.soesterberg. 21: Z4, Z23: −, were isolated from lizards.
S. kralingen (8), 20: y: Z6, was isolated from peanuts andS. assen, 21: a: −, was isolated from a swine. All these strains were isolated in the Netherlands.
S.mim, 13, 22: a: 1,6, was isolated from a rat in Ghana. 相似文献
107.
Adolf Češka 《Folia Geobotanica》1966,1(3):93-100
Various possibilities of usingSörensen's coefficient of floristic similarity in plant sociology are summarized. A new formula (11), derived from that bySörensen and based on constancy values, is suggested in order to calculate the mean floristic similarity within a set of relevés. 相似文献
108.
Adolf Češka 《Folia Geobotanica》1966,1(2):93-100
Various possibilities of usingSörensen’s coefficient of floristic similarity in plant sociology are summarized. A new formula (11). derived from that bySörensen and based on constancy values, is suggested in order to calculate the mean floristic similarity within a set of relevés. 相似文献
109.
110.
Out of 12,472 strains ofSalmonella isolated in the Netherlands in 1962, 1365, or 10.94%, were found to be resistant to tetracycline or chloramphenicol or to both. Compared with the findings of the preceding years (1958/59:2.08%, 1960:1.29%, 1961:3.96%) this is a considerable increase. Of these 1365 strains, 1285, or 94.1%, were resistant to tetracycline and 46, or 3.4%, were resistant to chloramphenicol. The remaining 34 strains, or 2.5%, were resistant to both drugs.Among allSalmonella strains isolated in 1962, 5517 belonged to the speciesS. typhi murium. Of these, 1203 or 21.8%, were resistant to tetracycline. The resistance rates of strains originating from human patients, calves, pigs, other animals and other materials were 24.4%, 37.1%, 15.0%, 8.0% and 5.7% respectively.Factors which may possibly have contributed to the greatly increased frequency of drug resistance inS. typhi murium are: (1) the rapid spread of the use of tetracycline for therapeutic, prophylactic and nutritive purposes, and (2) the possibility of an episome-mediated transfer of drug resistance from relatively harmless intestinal bacteria, such asE. coli, toS. typhi murium. 相似文献