全文获取类型
收费全文 | 731篇 |
免费 | 37篇 |
国内免费 | 4篇 |
出版年
2024年 | 2篇 |
2023年 | 6篇 |
2022年 | 15篇 |
2021年 | 34篇 |
2020年 | 11篇 |
2019年 | 40篇 |
2018年 | 36篇 |
2017年 | 13篇 |
2016年 | 29篇 |
2015年 | 37篇 |
2014年 | 41篇 |
2013年 | 35篇 |
2012年 | 50篇 |
2011年 | 57篇 |
2010年 | 36篇 |
2009年 | 26篇 |
2008年 | 28篇 |
2007年 | 41篇 |
2006年 | 28篇 |
2005年 | 26篇 |
2004年 | 25篇 |
2003年 | 18篇 |
2002年 | 15篇 |
2001年 | 16篇 |
2000年 | 9篇 |
1999年 | 6篇 |
1998年 | 4篇 |
1996年 | 7篇 |
1995年 | 6篇 |
1994年 | 7篇 |
1993年 | 6篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 7篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1972年 | 3篇 |
1971年 | 3篇 |
1966年 | 2篇 |
1962年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有772条查询结果,搜索用时 31 毫秒
661.
Summary Native plants of Iraq have shown considerable variation in their ability to accumulate mineral elements. Halophytes such asSeidlitzia rosmarinus andHalocnemum strobilaceum indicate very high soil sodium contents, and others high magnesium and sulphate contents.
Selectivity in the uptake and accumulation of mineral elements was exhibited by many native plants. Surprisingly high or low
concentrations of particular elements were found in certain species in comparison with other species collected from the same
site and at the same time. Magnesium and sulphate concentrations were as high as 5.80 and 12.16 per cent, respectively, when
the concentrations in other species growing on the same site were as low as 0.59 and 1.29 per cent respectively. Selectivity
was also indicated by the ability of certain species to accumulate a specific element from soils with high or low concentration
of that element. 相似文献
662.
663.
664.
665.
666.
Ayadi Habib; Abid Olfa; Elloumi Jannet; Bouain Abderrahmen; Sime-Ngando Telesphore 《Journal of plankton research》2004,26(6):669-679
The structure and ecophysiological characteristics of phytoplanktonassemblages were studied for 10 months in two lagoons of differentsalinity (40 and 90) in the saltern of Sfax (Tunisia), in relationto environmental factors. These assemblages were largely dominatedby diatoms and dinoflagellates, which accounted for >90%of total abundance. A principal components analysis clearlydifferentiated the observations made in the two lagoons, thedominant correlate being the salinity. Euryhaline species andparticularly diatoms developed preferentially in the less salinelagoon, and were largely replaced by stenohaline species representedby dinoflagellates, which were dominant in the more saline lagoon.Calculation of the pigment diversity index and the species diversityindex showed that the phytoplankton assemblages studied werepermanently in a juvenile stage, as the species restructuringrelated to environmental constraints did not allow them to reachthe climax stage at any given time in their development. Despitethe heavy constraint imposed by the salinity, it is evidentthat other environmental factors, e.g. temperature, play a rolein the regulation of the planktonic communities. Finally, thedifference in the size distribution of the total microbial biomass,estimated by the assay of particulate proteins, showed thatthere was a significant change in the community structure andthe planktonic trophic networks, in parallel with the increasein salinity. 相似文献
667.
668.
669.
670.
Moncef Nasri Abdelhafidh Dhouib Fathi Zorguani Habib Kriaa Radouan Ellouz 《Biotechnology letters》1989,11(12):865-870
Summary Lysine production by immobilizedCorynebacterium sp cells in alginate gel beads was investigated in flasks. ImmobilizedCorynebacterium sp cells exhibited a slightly greater lysine production than free cells and accumulated 60 g/l of L-lysine at maximum, when cultured for 120h in a medium containing 200g/l glucose as carbon source. Several factors, such as inoculum size, incubation time and alginate gel concentration were examined in order to improve lysine production by immobilized growing cells. 相似文献